ctdb-vacuum: change full db traverse vacuuming to fill delete queue

[Samba.git] / ctdb / server / ctdb_vacuum.c

/*
   ctdb vacuuming events

   Copyright (C) Ronnie Sahlberg  2009
   Copyright (C) Michael Adam 2010-2013
   Copyright (C) Stefan Metzmacher 2010-2011

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, see <http://www.gnu.org/licenses/>.
*/

#include "includes.h"
#include "tdb.h"
#include "system/network.h"
#include "system/filesys.h"
#include "system/dir.h"
#include "../include/ctdb_private.h"
#include "db_wrap.h"
#include "lib/util/dlinklist.h"
#include "../include/ctdb_private.h"
#include "../common/rb_tree.h"

#define TIMELIMIT() timeval_current_ofs(10, 0)

enum vacuum_child_status { VACUUM_RUNNING, VACUUM_OK, VACUUM_ERROR, VACUUM_TIMEOUT};

struct ctdb_vacuum_child_context {
        struct ctdb_vacuum_child_context *next, *prev;
        struct ctdb_vacuum_handle *vacuum_handle;
        /* fd child writes status to */
        int fd[2];
        pid_t child_pid;
        enum vacuum_child_status status;
        struct timeval start_time;
};

struct ctdb_vacuum_handle {
        struct ctdb_db_context *ctdb_db;
        struct ctdb_vacuum_child_context *child_ctx;
        uint32_t fast_path_count;
};


/*  a list of records to possibly delete */
struct vacuum_data {
        uint32_t vacuum_limit;
        uint32_t repack_limit;
        struct ctdb_context *ctdb;
        struct ctdb_db_context *ctdb_db;
        struct tdb_context *dest_db;
        trbt_tree_t *delete_list;
        uint32_t delete_count;
        struct ctdb_marshall_buffer **vacuum_fetch_list;
        struct timeval start;
        bool traverse_error;
        bool vacuum;
        uint32_t total;
        uint32_t vacuumed;
        uint32_t copied;
        uint32_t fast_added_to_vacuum_fetch_list;
        uint32_t fast_added_to_delete_list;
        uint32_t fast_deleted;
        uint32_t fast_skipped;
        uint32_t fast_error;
        uint32_t fast_total;
        uint32_t full_scheduled;
        uint32_t full_skipped;
        uint32_t full_error;
        uint32_t full_total;
        uint32_t delete_left;
        uint32_t delete_remote_error;
        uint32_t delete_local_error;
        uint32_t delete_deleted;
        uint32_t delete_skipped;
};

/* this structure contains the information for one record to be deleted */
struct delete_record_data {
        struct ctdb_context *ctdb;
        struct ctdb_db_context *ctdb_db;
        struct ctdb_ltdb_header hdr;
        TDB_DATA key;
        uint8_t keydata[1];
};

struct delete_records_list {
        struct ctdb_marshall_buffer *records;
        struct vacuum_data *vdata;
};

static int insert_record_into_delete_queue(struct ctdb_db_context *ctdb_db,
                                           const struct ctdb_ltdb_header *hdr,
                                           TDB_DATA key);

/**
 * Store key and header in a tree, indexed by the key hash.
 */
static int insert_delete_record_data_into_tree(struct ctdb_context *ctdb,
                                               struct ctdb_db_context *ctdb_db,
                                               trbt_tree_t *tree,
                                               const struct ctdb_ltdb_header *hdr,
                                               TDB_DATA key)
{
        struct delete_record_data *dd;
        uint32_t hash;
        size_t len;

        len = offsetof(struct delete_record_data, keydata) + key.dsize;

        dd = (struct delete_record_data *)talloc_size(tree, len);
        if (dd == NULL) {
                DEBUG(DEBUG_ERR,(__location__ " Out of memory\n"));
                return -1;
        }
        talloc_set_name_const(dd, "struct delete_record_data");

        dd->ctdb      = ctdb;
        dd->ctdb_db   = ctdb_db;
        dd->key.dsize = key.dsize;
        dd->key.dptr  = dd->keydata;
        memcpy(dd->keydata, key.dptr, key.dsize);

        dd->hdr = *hdr;

        hash = ctdb_hash(&key);

        trbt_insert32(tree, hash, dd);

        return 0;
}

static int add_record_to_delete_list(struct vacuum_data *vdata, TDB_DATA key,
                                     struct ctdb_ltdb_header *hdr)
{
        struct ctdb_context *ctdb = vdata->ctdb;
        struct ctdb_db_context *ctdb_db = vdata->ctdb_db;
        uint32_t hash;
        int ret;

        hash = ctdb_hash(&key);

        if (trbt_lookup32(vdata->delete_list, hash)) {
                DEBUG(DEBUG_INFO, (__location__ " Hash collision when vacuuming, skipping this record.\n"));
                return 0;
        }

        ret = insert_delete_record_data_into_tree(ctdb, ctdb_db,
                                                  vdata->delete_list,
                                                  hdr, key);
        if (ret != 0) {
                return -1;
        }

        vdata->delete_count++;

        return 0;
}

/**
 * Add a record to the list of records to be sent
 * to their lmaster with VACUUM_FETCH.
 */
static int add_record_to_vacuum_fetch_list(struct vacuum_data *vdata,
                                           TDB_DATA key)
{
        struct ctdb_context *ctdb = vdata->ctdb;
        struct ctdb_rec_data *rec;
        uint32_t lmaster;
        size_t old_size;
        struct ctdb_marshall_buffer *vfl;

        lmaster = ctdb_lmaster(ctdb, &key);

        vfl = vdata->vacuum_fetch_list[lmaster];

        rec = ctdb_marshall_record(vfl, ctdb->pnn, key, NULL, tdb_null);
        if (rec == NULL) {
                DEBUG(DEBUG_ERR,(__location__ " Out of memory\n"));
                vdata->traverse_error = true;
                return -1;
        }

        old_size = talloc_get_size(vfl);
        vfl = talloc_realloc_size(NULL, vfl, old_size + rec->length);
        if (vfl == NULL) {
                DEBUG(DEBUG_ERR,(__location__ " Failed to expand\n"));
                vdata->traverse_error = true;
                return -1;
        }
        vdata->vacuum_fetch_list[lmaster] = vfl;

        vfl->count++;
        memcpy(old_size+(uint8_t *)vfl, rec, rec->length);
        talloc_free(rec);

        vdata->total++;

        return 0;
}


static void ctdb_vacuum_event(struct event_context *ev, struct timed_event *te,
                              struct timeval t, void *private_data);

static int vacuum_record_parser(TDB_DATA key, TDB_DATA data, void *private_data)
{
        struct ctdb_ltdb_header *header =
                (struct ctdb_ltdb_header *)private_data;

        if (data.dsize != sizeof(struct ctdb_ltdb_header)) {
                return -1;
        }

        *header = *(struct ctdb_ltdb_header *)data.dptr;

        return 0;
}

/*
 * traverse function for gathering the records that can be deleted
 */
static int vacuum_traverse(struct tdb_context *tdb, TDB_DATA key, TDB_DATA data,
                           void *private_data)
{
        struct vacuum_data *vdata = talloc_get_type(private_data,
                                                    struct vacuum_data);
        struct ctdb_context *ctdb = vdata->ctdb;
        struct ctdb_db_context *ctdb_db = vdata->ctdb_db;
        uint32_t lmaster;
        struct ctdb_ltdb_header *hdr;
        int res = 0;

        vdata->full_total++;

        lmaster = ctdb_lmaster(ctdb, &key);
        if (lmaster >= ctdb->num_nodes) {
                vdata->full_error++;
                DEBUG(DEBUG_CRIT, (__location__
                                   " lmaster[%u] >= ctdb->num_nodes[%u] for key"
                                   " with hash[%u]!\n",
                                   (unsigned)lmaster,
                                   (unsigned)ctdb->num_nodes,
                                   (unsigned)ctdb_hash(&key)));
                return -1;
        }

        if (data.dsize != sizeof(struct ctdb_ltdb_header)) {
                /* it is not a deleted record */
                vdata->full_skipped++;
                return 0;
        }

        hdr = (struct ctdb_ltdb_header *)data.dptr;

        if (hdr->dmaster != ctdb->pnn) {
                vdata->full_skipped++;
                return 0;
        }

        /*
         * Add the record to this process's delete_queue for processing
         * in the subsequent traverse in the fast vacuum run.
         */
        res = insert_record_into_delete_queue(ctdb_db, hdr, key);
        if (res != 0) {
                vdata->full_error++;
        } else {
                vdata->full_scheduled++;
        }

        return 0;
}

/*
 * traverse the tree of records to delete and marshall them into
 * a blob
 */
static int delete_marshall_traverse(void *param, void *data)
{
        struct delete_record_data *dd = talloc_get_type(data, struct delete_record_data);
        struct delete_records_list *recs = talloc_get_type(param, struct delete_records_list);
        struct ctdb_rec_data *rec;
        size_t old_size;

        rec = ctdb_marshall_record(dd, recs->records->db_id, dd->key, &dd->hdr, tdb_null);
        if (rec == NULL) {
                DEBUG(DEBUG_ERR, (__location__ " failed to marshall record\n"));
                return 0;
        }

        old_size = talloc_get_size(recs->records);
        recs->records = talloc_realloc_size(NULL, recs->records, old_size + rec->length);
        if (recs->records == NULL) {
                DEBUG(DEBUG_ERR,(__location__ " Failed to expand\n"));
                return 0;
        }
        recs->records->count++;
        memcpy(old_size+(uint8_t *)(recs->records), rec, rec->length);
        return 0;
}

/**
 * Variant of delete_marshall_traverse() that bumps the
 * RSN of each traversed record in the database.
 *
 * This is needed to ensure that when rolling out our
 * empty record copy before remote deletion, we as the
 * record's dmaster keep a higher RSN than the non-dmaster
 * nodes. This is needed to prevent old copies from
 * resurrection in recoveries.
 */
static int delete_marshall_traverse_first(void *param, void *data)
{
        struct delete_record_data *dd = talloc_get_type(data, struct delete_record_data);
        struct delete_records_list *recs = talloc_get_type(param, struct delete_records_list);
        struct ctdb_db_context *ctdb_db = dd->ctdb_db;
        struct ctdb_context *ctdb = ctdb_db->ctdb;
        struct ctdb_ltdb_header *header;
        TDB_DATA tdb_data, ctdb_data;
        uint32_t lmaster;
        uint32_t hash = ctdb_hash(&(dd->key));
        int res;

        res = tdb_chainlock(ctdb_db->ltdb->tdb, dd->key);
        if (res != 0) {
                DEBUG(DEBUG_ERR,
                      (__location__ " Error getting chainlock on record with "
                       "key hash [0x%08x] on database db[%s].\n",
                       hash, ctdb_db->db_name));
                recs->vdata->delete_skipped++;
                talloc_free(dd);
                return 0;
        }

        /*
         * Verify that the record is still empty, its RSN has not
         * changed and that we are still its lmaster and dmaster.
         */

        tdb_data = tdb_fetch(ctdb_db->ltdb->tdb, dd->key);
        if (tdb_data.dsize < sizeof(struct ctdb_ltdb_header)) {
                DEBUG(DEBUG_INFO, (__location__ ": record with hash [0x%08x] "
                                   "on database db[%s] does not exist or is not"
                                   " a ctdb-record.  skipping.\n",
                                   hash, ctdb_db->db_name));
                goto skip;
        }

        if (tdb_data.dsize > sizeof(struct ctdb_ltdb_header)) {
                DEBUG(DEBUG_INFO, (__location__ ": record with hash [0x%08x] "
                                   "on database db[%s] has been recycled. "
                                   "skipping.\n",
                                   hash, ctdb_db->db_name));
                goto skip;
        }

        header = (struct ctdb_ltdb_header *)tdb_data.dptr;

        if (header->flags & CTDB_REC_RO_FLAGS) {
                DEBUG(DEBUG_INFO, (__location__ ": record with hash [0x%08x] "
                                   "on database db[%s] has read-only flags. "
                                   "skipping.\n",
                                   hash, ctdb_db->db_name));
                goto skip;
        }

        if (header->dmaster != ctdb->pnn) {
                DEBUG(DEBUG_INFO, (__location__ ": record with hash [0x%08x] "
                                   "on database db[%s] has been migrated away. "
                                   "skipping.\n",
                                   hash, ctdb_db->db_name));
                goto skip;
        }

        if (header->rsn != dd->hdr.rsn) {
                DEBUG(DEBUG_INFO, (__location__ ": record with hash [0x%08x] "
                                   "on database db[%s] seems to have been "
                                   "migrated away and back again (with empty "
                                   "data). skipping.\n",
                                   hash, ctdb_db->db_name));
                goto skip;
        }

        lmaster = ctdb_lmaster(ctdb_db->ctdb, &dd->key);

        if (lmaster != ctdb->pnn) {
                DEBUG(DEBUG_INFO, (__location__ ": not lmaster for record in "
                                   "delete list (key hash [0x%08x], db[%s]). "
                                   "Strange! skipping.\n",
                                   hash, ctdb_db->db_name));
                goto skip;
        }

        /*
         * Increment the record's RSN to ensure the dmaster (i.e. the current
         * node) has the highest RSN of the record in the cluster.
         * This is to prevent old record copies from resurrecting in recoveries
         * if something should fail during the deletion process.
         * Note that ctdb_ltdb_store_server() increments the RSN if called
         * on the record's dmaster.
         */

        ctdb_data.dptr = tdb_data.dptr + sizeof(struct ctdb_ltdb_header);
        ctdb_data.dsize = tdb_data.dsize - sizeof(struct ctdb_ltdb_header);

        res = ctdb_ltdb_store(ctdb_db, dd->key, header, ctdb_data);
        if (res != 0) {
                DEBUG(DEBUG_ERR, (__location__ ": Failed to store record with "
                                  "key hash [0x%08x] on database db[%s].\n",
                                  hash, ctdb_db->db_name));
                goto skip;
        }

        tdb_chainunlock(ctdb_db->ltdb->tdb, dd->key);

        goto done;

skip:
        tdb_chainunlock(ctdb_db->ltdb->tdb, dd->key);

        recs->vdata->delete_skipped++;
        talloc_free(dd);
        dd = NULL;

done:
        if (tdb_data.dptr != NULL) {
                free(tdb_data.dptr);
        }

        if (dd == NULL) {
                return 0;
        }

        return delete_marshall_traverse(param, data);
}

/**
 * traverse function for the traversal of the delete_queue,
 * the fast-path vacuuming list.
 *
 *  - If the record has been migrated off the node
 *    or has been revived (filled with data) on the node,
 *    then skip the record.
 *
 *  - If the current node is the record's lmaster and it is
 *    a record that has never been migrated with data, then
 *    delete the record from the local tdb.
 *
 *  - If the current node is the record's lmaster and it has
 *    been migrated with data, then schedule it for the normal
 *    vacuuming procedure (i.e. add it to the delete_list).
 *
 *  - If the current node is NOT the record's lmaster then
 *    add it to the list of records that are to be sent to
 *    the lmaster with the VACUUM_FETCH message.
 */
static int delete_queue_traverse(void *param, void *data)
{
        struct delete_record_data *dd =
                talloc_get_type(data, struct delete_record_data);
        struct vacuum_data *vdata = talloc_get_type(param, struct vacuum_data);
        struct ctdb_db_context *ctdb_db = dd->ctdb_db;
        struct ctdb_context *ctdb = ctdb_db->ctdb; /* or dd->ctdb ??? */
        int res;
        struct ctdb_ltdb_header header;
        uint32_t lmaster;
        uint32_t hash = ctdb_hash(&(dd->key));

        vdata->fast_total++;

        res = tdb_chainlock(ctdb_db->ltdb->tdb, dd->key);
        if (res != 0) {
                DEBUG(DEBUG_ERR,
                      (__location__ " Error getting chainlock on record with "
                       "key hash [0x%08x] on database db[%s].\n",
                       hash, ctdb_db->db_name));
                vdata->fast_error++;
                return 0;
        }

        res = tdb_parse_record(ctdb_db->ltdb->tdb, dd->key,
                               vacuum_record_parser, &header);
        if (res != 0) {
                goto skipped;
        }

        if (header.dmaster != ctdb->pnn) {
                /* The record has been migrated off the node. Skip. */
                goto skipped;
        }

        if (header.rsn != dd->hdr.rsn) {
                /*
                 * The record has been migrated off the node and back again.
                 * But not requeued for deletion. Skip it.
                 */
                goto skipped;
        }

        /*
         * We are dmaster, and the record has no data, and it has
         * not been migrated after it has been queued for deletion.
         *
         * At this stage, the record could still have been revived locally
         * and last been written with empty data. This can only be
         * fixed with the addition of an active or delete flag. (TODO)
         */

        lmaster = ctdb_lmaster(ctdb_db->ctdb, &dd->key);

        if (lmaster != ctdb->pnn) {
                res = add_record_to_vacuum_fetch_list(vdata, dd->key);

                if (res != 0) {
                        DEBUG(DEBUG_ERR,
                              (__location__ " Error adding record to list "
                               "of records to send to lmaster.\n"));
                        vdata->fast_error++;
                } else {
                        vdata->fast_added_to_vacuum_fetch_list++;
                }
                goto done;
        }

        /* use header->flags or dd->hdr.flags ?? */
        if (dd->hdr.flags & CTDB_REC_FLAG_MIGRATED_WITH_DATA) {
                res = add_record_to_delete_list(vdata, dd->key, &dd->hdr);

                if (res != 0) {
                        DEBUG(DEBUG_ERR,
                              (__location__ " Error adding record to list "
                               "of records for deletion on lmaster.\n"));
                        vdata->fast_error++;
                } else {
                        vdata->fast_added_to_delete_list++;
                }
        } else {
                res = tdb_delete(ctdb_db->ltdb->tdb, dd->key);

                if (res != 0) {
                        DEBUG(DEBUG_ERR,
                              (__location__ " Error deleting record with key "
                               "hash [0x%08x] from local data base db[%s].\n",
                               hash, ctdb_db->db_name));
                        vdata->fast_error++;
                        goto done;
                }

                DEBUG(DEBUG_DEBUG,
                      (__location__ " Deleted record with key hash "
                       "[0x%08x] from local data base db[%s].\n",
                       hash, ctdb_db->db_name));
                vdata->fast_deleted++;
        }

        goto done;

skipped:
        vdata->fast_skipped++;

done:
        tdb_chainunlock(ctdb_db->ltdb->tdb, dd->key);

        return 0;
}

/**
 * Delete the records that we are lmaster and dmaster for and
 * that could be deleted on all other nodes via the TRY_DELETE_RECORDS
 * control.
 */
static int delete_record_traverse(void *param, void *data)
{
        struct delete_record_data *dd =
                talloc_get_type(data, struct delete_record_data);
        struct vacuum_data *vdata = talloc_get_type(param, struct vacuum_data);
        struct ctdb_db_context *ctdb_db = dd->ctdb_db;
        struct ctdb_context *ctdb = ctdb_db->ctdb;
        int res;
        struct ctdb_ltdb_header *header;
        TDB_DATA tdb_data;
        uint32_t lmaster;
        uint32_t hash = ctdb_hash(&(dd->key));

        res = tdb_chainlock(ctdb_db->ltdb->tdb, dd->key);
        if (res != 0) {
                DEBUG(DEBUG_ERR,
                      (__location__ " Error getting chainlock on record with "
                       "key hash [0x%08x] on database db[%s].\n",
                       hash, ctdb_db->db_name));
                vdata->delete_local_error++;
                vdata->delete_left--;
                talloc_free(dd);
                return 0;
        }

        /*
         * Verify that the record is still empty, its RSN has not
         * changed and that we are still its lmaster and dmaster.
         */

        tdb_data = tdb_fetch(ctdb_db->ltdb->tdb, dd->key);
        if (tdb_data.dsize < sizeof(struct ctdb_ltdb_header)) {
                DEBUG(DEBUG_INFO, (__location__ ": record with hash [0x%08x] "
                                   "on database db[%s] does not exist or is not"
                                   " a ctdb-record.  skipping.\n",
                                   hash, ctdb_db->db_name));
                goto skip;
        }

        if (tdb_data.dsize > sizeof(struct ctdb_ltdb_header)) {
                DEBUG(DEBUG_INFO, (__location__ ": record with hash [0x%08x] "
                                   "on database db[%s] has been recycled. "
                                   "skipping.\n",
                                   hash, ctdb_db->db_name));
                goto skip;
        }

        header = (struct ctdb_ltdb_header *)tdb_data.dptr;

        if (header->flags & CTDB_REC_RO_FLAGS) {
                DEBUG(DEBUG_INFO, (__location__ ": record with hash [0x%08x] "
                                   "on database db[%s] has read-only flags. "
                                   "skipping.\n",
                                   hash, ctdb_db->db_name));
                goto skip;
        }

        if (header->dmaster != ctdb->pnn) {
                DEBUG(DEBUG_INFO, (__location__ ": record with hash [0x%08x] "
                                   "on database db[%s] has been migrated away. "
                                   "skipping.\n",
                                   hash, ctdb_db->db_name));
                goto skip;
        }

        if (header->rsn != dd->hdr.rsn + 1) {
                /*
                 * The record has been migrated off the node and back again.
                 * But not requeued for deletion. Skip it.
                 * (Note that the first marshall traverse has bumped the RSN
                 *  on disk.)
                 */
                DEBUG(DEBUG_INFO, (__location__ ": record with hash [0x%08x] "
                                   "on database db[%s] seems to have been "
                                   "migrated away and back again (with empty "
                                   "data). skipping.\n",
                                   hash, ctdb_db->db_name));
                goto skip;
        }

        lmaster = ctdb_lmaster(ctdb_db->ctdb, &dd->key);

        if (lmaster != ctdb->pnn) {
                DEBUG(DEBUG_INFO, (__location__ ": not lmaster for record in "
                                   "delete list (key hash [0x%08x], db[%s]). "
                                   "Strange! skipping.\n",
                                   hash, ctdb_db->db_name));
                goto skip;
        }

        res = tdb_delete(ctdb_db->ltdb->tdb, dd->key);

        if (res != 0) {
                DEBUG(DEBUG_ERR,
                      (__location__ " Error deleting record with key hash "
                       "[0x%08x] from local data base db[%s].\n",
                       hash, ctdb_db->db_name));
                vdata->delete_local_error++;
                goto done;
        }

        DEBUG(DEBUG_DEBUG,
              (__location__ " Deleted record with key hash [0x%08x] from "
               "local data base db[%s].\n", hash, ctdb_db->db_name));

        vdata->delete_deleted++;
        goto done;

skip:
        vdata->delete_skipped++;

done:
        free(tdb_data.dptr);

        tdb_chainunlock(ctdb_db->ltdb->tdb, dd->key);

        talloc_free(dd);
        vdata->delete_left--;

        return 0;
}

/**
 * Fast vacuuming run:
 * Traverse the delete_queue.
 * This fills the same lists as the database traverse.
 */
static void ctdb_vacuum_db_fast(struct ctdb_db_context *ctdb_db,
                                struct vacuum_data *vdata)
{
        uint32_t sum;

        trbt_traversearray32(ctdb_db->delete_queue, 1, delete_queue_traverse, vdata);

        sum = vdata->fast_deleted
            + vdata->fast_skipped
            + vdata->fast_error
            + vdata->fast_added_to_delete_list
            + vdata->fast_added_to_vacuum_fetch_list;

        if (vdata->fast_total != sum) {
                DEBUG(DEBUG_ERR, (__location__ " Inconsistency in fast vacuum "
                      "counts for db[%s]: total[%u] != sum[%u]\n",
                      ctdb_db->db_name, (unsigned)vdata->fast_total,
                      (unsigned)sum));
        }

        if (vdata->fast_total > 0) {
                DEBUG(DEBUG_INFO,
                      (__location__
                       " fast vacuuming delete_queue traverse statistics: "
                       "db[%s] "
                       "total[%u] "
                       "del[%u] "
                       "skp[%u] "
                       "err[%u] "
                       "adl[%u] "
                       "avf[%u]\n",
                       ctdb_db->db_name,
                       (unsigned)vdata->fast_total,
                       (unsigned)vdata->fast_deleted,
                       (unsigned)vdata->fast_skipped,
                       (unsigned)vdata->fast_error,
                       (unsigned)vdata->fast_added_to_delete_list,
                       (unsigned)vdata->fast_added_to_vacuum_fetch_list));
        }

        return;
}

/**
 * Full vacuum run:
 * read-only traverse of the database, looking for records that
 * might be able to be vacuumed.
 *
 * This is not done each time but only every tunable
 * VacuumFastPathCount times.
 */
static int ctdb_vacuum_db_full(struct ctdb_db_context *ctdb_db,
                               struct vacuum_data *vdata)
{
        int ret;

        ret = tdb_traverse_read(ctdb_db->ltdb->tdb, vacuum_traverse, vdata);
        if (ret == -1 || vdata->traverse_error) {
                DEBUG(DEBUG_ERR, (__location__ " Traverse error in vacuuming "
                                  "'%s'\n", ctdb_db->db_name));
                return -1;
        }

        if (vdata->full_total > 0) {
                DEBUG(DEBUG_INFO,
                      (__location__
                       " full vacuuming db traverse statistics: "
                       "db[%s] "
                       "total[%u] "
                       "skp[%u] "
                       "err[%u] "
                       "sched[%u]\n",
                       ctdb_db->db_name,
                       (unsigned)vdata->full_total,
                       (unsigned)vdata->full_skipped,
                       (unsigned)vdata->full_error,
                       (unsigned)vdata->full_scheduled));
        }

        return 0;
}

/**
 * Process the vacuum fetch lists:
 * For records for which we are not the lmaster, tell the lmaster to
 * fetch the record.
 */
static int ctdb_process_vacuum_fetch_lists(struct ctdb_db_context *ctdb_db,
                                           struct vacuum_data *vdata)
{
        int i;
        struct ctdb_context *ctdb = ctdb_db->ctdb;

        for (i = 0; i < ctdb->num_nodes; i++) {
                TDB_DATA data;
                struct ctdb_marshall_buffer *vfl = vdata->vacuum_fetch_list[i];

                if (ctdb->nodes[i]->pnn == ctdb->pnn) {
                        continue;
                }

                if (vfl->count == 0) {
                        continue;
                }

                DEBUG(DEBUG_INFO, ("Found %u records for lmaster %u in '%s'\n",
                                   vfl->count, ctdb->nodes[i]->pnn,
                                   ctdb_db->db_name));

                data.dsize = talloc_get_size(vfl);
                data.dptr  = (void *)vfl;
                if (ctdb_client_send_message(ctdb, ctdb->nodes[i]->pnn,
                                             CTDB_SRVID_VACUUM_FETCH,
                                             data) != 0)
                {
                        DEBUG(DEBUG_ERR, (__location__ " Failed to send vacuum "
                                          "fetch message to %u\n",
                                          ctdb->nodes[i]->pnn));
                        return -1;
                }
        }

        return 0;
}

/**
 * Process the delete list:
 *
 * This is the last step of vacuuming that consistently deletes
 * those records that have been migrated with data and can hence
 * not be deleted when leaving a node.
 *
 * In this step, the lmaster does the final deletion of those empty
 * records that it is also dmaster for. It has ususally received
 * at least some of these records previously from the former dmasters
 * with the vacuum fetch message.
 *
 * This last step is implemented as a 3-phase process to protect from
 * races leading to data corruption:
 *
 *  1) Send the lmaster's copy to all other active nodes with the
 *     RECEIVE_RECORDS control: The remote nodes store the lmaster's copy.
 *  2) Send the records that could successfully be stored remotely
 *     in step #1 to all active nodes with the TRY_DELETE_RECORDS
 *     control. The remote notes delete their local copy.
 *  3) The lmaster locally deletes its copies of all records that
 *     could successfully be deleted remotely in step #2.
 */
static int ctdb_process_delete_list(struct ctdb_db_context *ctdb_db,
                                    struct vacuum_data *vdata)
{
        int ret, i;
        struct ctdb_context *ctdb = ctdb_db->ctdb;
        struct delete_records_list *recs;
        TDB_DATA indata;
        struct ctdb_node_map *nodemap;
        uint32_t *active_nodes;
        int num_active_nodes;
        TALLOC_CTX *tmp_ctx;

        if (vdata->delete_count == 0) {
                return 0;
        }

        tmp_ctx = talloc_new(vdata);
        if (tmp_ctx == NULL) {
                DEBUG(DEBUG_ERR,(__location__ " Out of memory\n"));
                return 0;
        }

        vdata->delete_left = vdata->delete_count;

        /*
         * get the list of currently active nodes
         */

        ret = ctdb_ctrl_getnodemap(ctdb, TIMELIMIT(),
                                   CTDB_CURRENT_NODE,
                                   tmp_ctx,
                                   &nodemap);
        if (ret != 0) {
                DEBUG(DEBUG_ERR,(__location__ " unable to get node map\n"));
                ret = -1;
                goto done;
        }

        active_nodes = list_of_active_nodes(ctdb, nodemap,
                                            nodemap, /* talloc context */
                                            false /* include self */);
        /* yuck! ;-) */
        num_active_nodes = talloc_get_size(active_nodes)/sizeof(*active_nodes);

        /*
         * Now delete the records all active nodes in a three-phase process:
         * 1) send all active remote nodes the current empty copy with this
         *    node as DMASTER
         * 2) if all nodes could store the new copy,
         *    tell all the active remote nodes to delete all their copy
         * 3) if all remote nodes deleted their record copy, delete it locally
         */

        /*
         * Step 1:
         * Send currently empty record copy to all active nodes for storing.
         */

        recs = talloc_zero(tmp_ctx, struct delete_records_list);
        if (recs == NULL) {
                DEBUG(DEBUG_ERR,(__location__ " Out of memory\n"));
                ret = -1;
                goto done;
        }
        recs->records = (struct ctdb_marshall_buffer *)
                talloc_zero_size(recs,
                                 offsetof(struct ctdb_marshall_buffer, data));
        if (recs->records == NULL) {
                DEBUG(DEBUG_ERR,(__location__ " Out of memory\n"));
                ret = -1;
                goto done;
        }
        recs->records->db_id = ctdb_db->db_id;
        recs->vdata = vdata;

        /*
         * traverse the tree of all records we want to delete and
         * create a blob we can send to the other nodes.
         *
         * We call delete_marshall_traverse_first() to bump the
         * records' RSNs in the database, to ensure we (as dmaster)
         * keep the highest RSN of the records in the cluster.
         */
        trbt_traversearray32(vdata->delete_list, 1,
                             delete_marshall_traverse_first, recs);

        indata.dsize = talloc_get_size(recs->records);
        indata.dptr  = (void *)recs->records;

        for (i = 0; i < num_active_nodes; i++) {
                struct ctdb_marshall_buffer *records;
                struct ctdb_rec_data *rec;
                int32_t res;
                TDB_DATA outdata;

                ret = ctdb_control(ctdb, active_nodes[i], 0,
                                CTDB_CONTROL_RECEIVE_RECORDS, 0,
                                indata, recs, &outdata, &res,
                                NULL, NULL);
                if (ret != 0 || res != 0) {
                        DEBUG(DEBUG_ERR, ("Error storing record copies on "
                                          "node %u: ret[%d] res[%d]\n",
                                          active_nodes[i], ret, res));
                        ret = -1;
                        goto done;
                }

                /*
                 * outdata contains the list of records coming back
                 * from the node: These are the records that the
                 * remote node could not store. We remove these from
                 * the list to process further.
                 */
                records = (struct ctdb_marshall_buffer *)outdata.dptr;
                rec = (struct ctdb_rec_data *)&records->data[0];
                while (records->count-- > 1) {
                        TDB_DATA reckey, recdata;
                        struct ctdb_ltdb_header *rechdr;
                        struct delete_record_data *dd;

                        reckey.dptr = &rec->data[0];
                        reckey.dsize = rec->keylen;
                        recdata.dptr = &rec->data[reckey.dsize];
                        recdata.dsize = rec->datalen;

                        if (recdata.dsize < sizeof(struct ctdb_ltdb_header)) {
                                DEBUG(DEBUG_CRIT,(__location__ " bad ltdb record\n"));
                                ret = -1;
                                goto done;
                        }
                        rechdr = (struct ctdb_ltdb_header *)recdata.dptr;
                        recdata.dptr += sizeof(*rechdr);
                        recdata.dsize -= sizeof(*rechdr);

                        dd = (struct delete_record_data *)trbt_lookup32(
                                        vdata->delete_list,
                                        ctdb_hash(&reckey));
                        if (dd != NULL) {
                                /*
                                 * The other node could not store the record
                                 * copy and it is the first node that failed.
                                 * So we should remove it from the tree and
                                 * update statistics.
                                 */
                                talloc_free(dd);
                                vdata->delete_remote_error++;
                                vdata->delete_left--;
                        }

                        rec = (struct ctdb_rec_data *)(rec->length + (uint8_t *)rec);
                }
        }

        if (vdata->delete_left == 0) {
                goto success;
        }

        /*
         * Step 2:
         * Send the remaining records to all active nodes for deletion.
         *
         * The lmaster's (i.e. our) copies of these records have been stored
         * successfully on the other nodes.
         */

        /*
         * Create a marshall blob from the remaining list of records to delete.
         */

        talloc_free(recs->records);

        recs->records = (struct ctdb_marshall_buffer *)
                talloc_zero_size(recs,
                                 offsetof(struct ctdb_marshall_buffer, data));
        if (recs->records == NULL) {
                DEBUG(DEBUG_ERR,(__location__ " Out of memory\n"));
                ret = -1;
                goto done;
        }
        recs->records->db_id = ctdb_db->db_id;

        trbt_traversearray32(vdata->delete_list, 1,
                             delete_marshall_traverse, recs);

        indata.dsize = talloc_get_size(recs->records);
        indata.dptr  = (void *)recs->records;

        for (i = 0; i < num_active_nodes; i++) {
                struct ctdb_marshall_buffer *records;
                struct ctdb_rec_data *rec;
                int32_t res;
                TDB_DATA outdata;

                ret = ctdb_control(ctdb, active_nodes[i], 0,
                                CTDB_CONTROL_TRY_DELETE_RECORDS, 0,
                                indata, recs, &outdata, &res,
                                NULL, NULL);
                if (ret != 0 || res != 0) {
                        DEBUG(DEBUG_ERR, ("Failed to delete records on "
                                          "node %u: ret[%d] res[%d]\n",
                                          active_nodes[i], ret, res));
                        ret = -1;
                        goto done;
                }

                /*
                 * outdata contains the list of records coming back
                 * from the node: These are the records that the
                 * remote node could not delete. We remove these from
                 * the list to delete locally.
                 */
                records = (struct ctdb_marshall_buffer *)outdata.dptr;
                rec = (struct ctdb_rec_data *)&records->data[0];
                while (records->count-- > 1) {
                        TDB_DATA reckey, recdata;
                        struct ctdb_ltdb_header *rechdr;
                        struct delete_record_data *dd;

                        reckey.dptr = &rec->data[0];
                        reckey.dsize = rec->keylen;
                        recdata.dptr = &rec->data[reckey.dsize];
                        recdata.dsize = rec->datalen;

                        if (recdata.dsize < sizeof(struct ctdb_ltdb_header)) {
                                DEBUG(DEBUG_CRIT,(__location__ " bad ltdb record\n"));
                                ret = -1;
                                goto done;
                        }
                        rechdr = (struct ctdb_ltdb_header *)recdata.dptr;
                        recdata.dptr += sizeof(*rechdr);
                        recdata.dsize -= sizeof(*rechdr);

                        dd = (struct delete_record_data *)trbt_lookup32(
                                        vdata->delete_list,
                                        ctdb_hash(&reckey));
                        if (dd != NULL) {
                                /*
                                 * The other node could not delete the
                                 * record and it is the first node that
                                 * failed. So we should remove it from
                                 * the tree and update statistics.
                                 */
                                talloc_free(dd);
                                vdata->delete_remote_error++;
                                vdata->delete_left--;
                        }

                        rec = (struct ctdb_rec_data *)(rec->length + (uint8_t *)rec);
                }
        }

        if (vdata->delete_left == 0) {
                goto success;
        }

        /*
         * Step 3:
         * Delete the remaining records locally.
         *
         * These records have successfully been deleted on all
         * active remote nodes.
         */

        trbt_traversearray32(vdata->delete_list, 1,
                             delete_record_traverse, vdata);

success:

        if (vdata->delete_count > 0) {
                DEBUG(DEBUG_INFO,
                      (__location__
                       " vacuum delete list statistics: "
                       "db[%s] "
                       "total[%u] "
                       "del[%u] "
                       "skip[%u] "
                       "rem.err[%u] "
                       "loc.err[%u] "
                       "left[%u]\n",
                       ctdb_db->db_name,
                       (unsigned)vdata->delete_count,
                       (unsigned)vdata->delete_deleted,
                       (unsigned)vdata->delete_skipped,
                       (unsigned)vdata->delete_remote_error,
                       (unsigned)vdata->delete_local_error,
                       (unsigned)vdata->delete_left));
        }

        ret = 0;

done:
        talloc_free(tmp_ctx);

        return ret;
}

/**
 * initialize the vacuum_data
 */
static int ctdb_vacuum_init_vacuum_data(struct ctdb_db_context *ctdb_db,
                                        struct vacuum_data *vdata)
{
        int i;
        struct ctdb_context *ctdb = ctdb_db->ctdb;

        vdata->fast_added_to_delete_list = 0;
        vdata->fast_added_to_vacuum_fetch_list = 0;
        vdata->fast_deleted = 0;
        vdata->fast_skipped = 0;
        vdata->fast_error = 0;
        vdata->fast_total = 0;
        vdata->full_scheduled = 0;
        vdata->full_skipped = 0;
        vdata->full_error = 0;
        vdata->full_total = 0;
        vdata->delete_count = 0;
        vdata->delete_left = 0;
        vdata->delete_remote_error = 0;
        vdata->delete_local_error = 0;
        vdata->delete_skipped = 0;
        vdata->delete_deleted = 0;

        /* the list needs to be of length num_nodes */
        vdata->vacuum_fetch_list = talloc_zero_array(vdata,
                                                struct ctdb_marshall_buffer *,
                                                ctdb->num_nodes);
        if (vdata->vacuum_fetch_list == NULL) {
                DEBUG(DEBUG_ERR,(__location__ " Out of memory\n"));
                return -1;
        }
        for (i = 0; i < ctdb->num_nodes; i++) {
                vdata->vacuum_fetch_list[i] = (struct ctdb_marshall_buffer *)
                        talloc_zero_size(vdata->vacuum_fetch_list,
                                         offsetof(struct ctdb_marshall_buffer, data));
                if (vdata->vacuum_fetch_list[i] == NULL) {
                        DEBUG(DEBUG_ERR,(__location__ " Out of memory\n"));
                        return -1;
                }
                vdata->vacuum_fetch_list[i]->db_id = ctdb_db->db_id;
        }

        return 0;
}

/**
 * Vacuum a DB:
 *  - Always do the fast vacuuming run, which traverses
 *    the in-memory delete queue: these records have been
 *    scheduled for deletion.
 *  - Only if explicitly requested, the database is traversed
 *    in order to use the traditional heuristics on empty records
 *    to trigger deletion.
 *    This is done only every VacuumFastPathCount'th vacuuming run.
 *
 * The traverse runs fill two lists:
 *
 * - The delete_list:
 *   This is the list of empty records the current
 *   node is lmaster and dmaster for. These records are later
 *   deleted first on other nodes and then locally.
 *
 *   The fast vacuuming run has a short cut for those records
 *   that have never been migrated with data: these records
 *   are immediately deleted locally, since they have left
 *   no trace on other nodes.
 *
 * - The vacuum_fetch lists
 *   (one for each other lmaster node):
 *   The records in this list are sent for deletion to
 *   their lmaster in a bulk VACUUM_FETCH message.
 *
 *   The lmaster then migrates all these records to itelf
 *   so that they can be vacuumed there.
 *
 * This executes in the child context.
 */
static int ctdb_vacuum_db(struct ctdb_db_context *ctdb_db,
                          struct vacuum_data *vdata,
                          bool full_vacuum_run)
{
        struct ctdb_context *ctdb = ctdb_db->ctdb;
        int ret, pnn;

        DEBUG(DEBUG_INFO, (__location__ " Entering %s vacuum run for db "
                           "%s db_id[0x%08x]\n",
                           full_vacuum_run ? "full" : "fast",
                           ctdb_db->db_name, ctdb_db->db_id));

        ret = ctdb_ctrl_getvnnmap(ctdb, TIMELIMIT(), CTDB_CURRENT_NODE, ctdb, &ctdb->vnn_map);
        if (ret != 0) {
                DEBUG(DEBUG_ERR, ("Unable to get vnnmap from local node\n"));
                return ret;
        }

        pnn = ctdb_ctrl_getpnn(ctdb, TIMELIMIT(), CTDB_CURRENT_NODE);
        if (pnn == -1) {
                DEBUG(DEBUG_ERR, ("Unable to get pnn from local node\n"));
                return -1;
        }

        ctdb->pnn = pnn;

        ret = ctdb_vacuum_init_vacuum_data(ctdb_db, vdata);
        if (ret != 0) {
                return ret;
        }

        if (full_vacuum_run) {
                ret = ctdb_vacuum_db_full(ctdb_db, vdata);
                if (ret != 0) {
                        return ret;
                }
        }

        ctdb_vacuum_db_fast(ctdb_db, vdata);

        ret = ctdb_process_vacuum_fetch_lists(ctdb_db, vdata);
        if (ret != 0) {
                return ret;
        }

        ret = ctdb_process_delete_list(ctdb_db, vdata);
        if (ret != 0) {
                return ret;
        }

        /* this ensures we run our event queue */
        ctdb_ctrl_getpnn(ctdb, TIMELIMIT(), CTDB_CURRENT_NODE);

        return 0;
}


/*
 * traverse function for repacking
 */
static int repack_traverse(struct tdb_context *tdb, TDB_DATA key, TDB_DATA data,
                           void *private_data)
{
        struct vacuum_data *vdata = (struct vacuum_data *)private_data;

        if (vdata->vacuum) {
                uint32_t hash = ctdb_hash(&key);
                struct delete_record_data *kd;
                /*
                 * check if we can ignore this record because it's in the delete_list
                 */
                kd = (struct delete_record_data *)trbt_lookup32(vdata->delete_list, hash);
                /*
                 * there might be hash collisions so we have to compare the keys here to be sure
                 */
                if (kd && kd->key.dsize == key.dsize && memcmp(kd->key.dptr, key.dptr, key.dsize) == 0) {
                        struct ctdb_ltdb_header *hdr = (struct ctdb_ltdb_header *)data.dptr;
                        /*
                         * we have to check if the record hasn't changed in the meantime in order to
                         * savely remove it from the database
                         */
                        if (data.dsize == sizeof(struct ctdb_ltdb_header) &&
                                hdr->dmaster == kd->ctdb->pnn &&
                                ctdb_lmaster(kd->ctdb, &(kd->key)) == kd->ctdb->pnn &&
                                kd->hdr.rsn == hdr->rsn) {
                                vdata->vacuumed++;
                                return 0;
                        }
                }
        }
        if (tdb_store(vdata->dest_db, key, data, TDB_INSERT) != 0) {
                vdata->traverse_error = true;
                return -1;
        }
        vdata->copied++;
        return 0;
}

/*
 * repack a tdb
 */
static int ctdb_repack_tdb(struct tdb_context *tdb, TALLOC_CTX *mem_ctx, struct vacuum_data *vdata)
{
        struct tdb_context *tmp_db;

        if (tdb_transaction_start(tdb) != 0) {
                DEBUG(DEBUG_ERR,(__location__ " Failed to start transaction\n"));
                return -1;
        }

        tmp_db = tdb_open("tmpdb", tdb_hash_size(tdb),
                          TDB_INTERNAL|TDB_DISALLOW_NESTING,
                          O_RDWR|O_CREAT, 0);
        if (tmp_db == NULL) {
                DEBUG(DEBUG_ERR,(__location__ " Failed to create tmp_db\n"));
                tdb_transaction_cancel(tdb);
                return -1;
        }

        vdata->traverse_error = false;
        vdata->dest_db = tmp_db;
        vdata->vacuum = true;
        vdata->vacuumed = 0;
        vdata->copied = 0;

        /*
         * repack and vacuum on-the-fly by not writing the records that are
         * no longer needed
         */
        if (tdb_traverse_read(tdb, repack_traverse, vdata) == -1) {
                DEBUG(DEBUG_ERR,(__location__ " Failed to traverse copying out\n"));
                tdb_transaction_cancel(tdb);
                tdb_close(tmp_db);
                return -1;              
        }

        DEBUG(DEBUG_INFO,(__location__ " %u records vacuumed\n", vdata->vacuumed));
        
        if (vdata->traverse_error) {
                DEBUG(DEBUG_ERR,(__location__ " Error during traversal\n"));
                tdb_transaction_cancel(tdb);
                tdb_close(tmp_db);
                return -1;
        }

        if (tdb_wipe_all(tdb) != 0) {
                DEBUG(DEBUG_ERR,(__location__ " Failed to wipe database\n"));
                tdb_transaction_cancel(tdb);
                tdb_close(tmp_db);
                return -1;
        }

        vdata->traverse_error = false;
        vdata->dest_db = tdb;
        vdata->vacuum = false;
        vdata->copied = 0;

        if (tdb_traverse_read(tmp_db, repack_traverse, vdata) == -1) {
                DEBUG(DEBUG_ERR,(__location__ " Failed to traverse copying back\n"));
                tdb_transaction_cancel(tdb);
                tdb_close(tmp_db);
                return -1;              
        }

        if (vdata->traverse_error) {
                DEBUG(DEBUG_ERR,(__location__ " Error during second traversal\n"));
                tdb_transaction_cancel(tdb);
                tdb_close(tmp_db);
                return -1;
        }

        tdb_close(tmp_db);


        if (tdb_transaction_commit(tdb) != 0) {
                DEBUG(DEBUG_ERR,(__location__ " Failed to commit\n"));
                return -1;
        }
        DEBUG(DEBUG_INFO,(__location__ " %u records copied\n", vdata->copied));

        return 0;
}

/*
 * repack and vaccum a db
 * called from the child context
 */
static int ctdb_vacuum_and_repack_db(struct ctdb_db_context *ctdb_db,
                                     TALLOC_CTX *mem_ctx,
                                     bool full_vacuum_run)
{
        uint32_t repack_limit = ctdb_db->ctdb->tunable.repack_limit;
        uint32_t vacuum_limit = ctdb_db->ctdb->tunable.vacuum_limit;
        const char *name = ctdb_db->db_name;
        int freelist_size = 0;
        struct vacuum_data *vdata;

        vdata = talloc_zero(mem_ctx, struct vacuum_data);
        if (vdata == NULL) {
                DEBUG(DEBUG_ERR,(__location__ " Out of memory\n"));
                return -1;
        }

        vdata->ctdb = ctdb_db->ctdb;
        vdata->vacuum_limit = vacuum_limit;
        vdata->repack_limit = repack_limit;
        vdata->delete_list = trbt_create(vdata, 0);
        vdata->ctdb_db = ctdb_db;
        if (vdata->delete_list == NULL) {
                DEBUG(DEBUG_ERR,(__location__ " Out of memory\n"));
                talloc_free(vdata);
                return -1;
        }

        vdata->start = timeval_current();
 
        /*
         * gather all records that can be deleted in vdata
         */
        if (ctdb_vacuum_db(ctdb_db, vdata, full_vacuum_run) != 0) {
                DEBUG(DEBUG_ERR,(__location__ " Failed to vacuum '%s'\n", name));
        }

        if (repack_limit != 0) {
                freelist_size = tdb_freelist_size(ctdb_db->ltdb->tdb);
                if (freelist_size == -1) {
                        DEBUG(DEBUG_ERR,(__location__ " Failed to get freelist size for '%s'\n", name));
                        talloc_free(vdata);
                        return -1;
                }
        }

        /*
         * decide if a repack is necessary
         */
        if ((repack_limit == 0 || (uint32_t)freelist_size < repack_limit) &&
            vdata->delete_left < vacuum_limit)
        {
                talloc_free(vdata);
                return 0;
        }

        DEBUG(DEBUG_INFO,("Repacking %s with %u freelist entries and %u records to delete\n", 
                        name, freelist_size, vdata->delete_left));

        /*
         * repack and implicitely get rid of the records we can delete
         */
        if (ctdb_repack_tdb(ctdb_db->ltdb->tdb, mem_ctx, vdata) != 0) {
                DEBUG(DEBUG_ERR,(__location__ " Failed to repack '%s'\n", name));
                talloc_free(vdata);
                return -1;
        }
        talloc_free(vdata);

        return 0;
}

static uint32_t get_vacuum_interval(struct ctdb_db_context *ctdb_db)
{
        uint32_t interval = ctdb_db->ctdb->tunable.vacuum_interval;

        return interval;
}

static int vacuum_child_destructor(struct ctdb_vacuum_child_context *child_ctx)
{
        double l = timeval_elapsed(&child_ctx->start_time);
        struct ctdb_db_context *ctdb_db = child_ctx->vacuum_handle->ctdb_db;
        struct ctdb_context *ctdb = ctdb_db->ctdb;

        DEBUG(DEBUG_INFO,("Vacuuming took %.3f seconds for database %s\n", l, ctdb_db->db_name));

        if (child_ctx->child_pid != -1) {
                ctdb_kill(ctdb, child_ctx->child_pid, SIGKILL);
        } else {
                /* Bump the number of successful fast-path runs. */
                child_ctx->vacuum_handle->fast_path_count++;
        }

        DLIST_REMOVE(ctdb->vacuumers, child_ctx);

        event_add_timed(ctdb->ev, child_ctx->vacuum_handle,
                        timeval_current_ofs(get_vacuum_interval(ctdb_db), 0), 
                        ctdb_vacuum_event, child_ctx->vacuum_handle);

        return 0;
}

/*
 * this event is generated when a vacuum child process times out
 */
static void vacuum_child_timeout(struct event_context *ev, struct timed_event *te,
                                         struct timeval t, void *private_data)
{
        struct ctdb_vacuum_child_context *child_ctx = talloc_get_type(private_data, struct ctdb_vacuum_child_context);

        DEBUG(DEBUG_ERR,("Vacuuming child process timed out for db %s\n", child_ctx->vacuum_handle->ctdb_db->db_name));

        child_ctx->status = VACUUM_TIMEOUT;

        talloc_free(child_ctx);
}


/*
 * this event is generated when a vacuum child process has completed
 */
static void vacuum_child_handler(struct event_context *ev, struct fd_event *fde,
                             uint16_t flags, void *private_data)
{
        struct ctdb_vacuum_child_context *child_ctx = talloc_get_type(private_data, struct ctdb_vacuum_child_context);
        char c = 0;
        int ret;

        DEBUG(DEBUG_INFO,("Vacuuming child process %d finished for db %s\n", child_ctx->child_pid, child_ctx->vacuum_handle->ctdb_db->db_name));
        child_ctx->child_pid = -1;

        ret = read(child_ctx->fd[0], &c, 1);
        if (ret != 1 || c != 0) {
                child_ctx->status = VACUUM_ERROR;
                DEBUG(DEBUG_ERR, ("A vacuum child process failed with an error for database %s. ret=%d c=%d\n", child_ctx->vacuum_handle->ctdb_db->db_name, ret, c));
        } else {
                child_ctx->status = VACUUM_OK;
        }

        talloc_free(child_ctx);
}

/*
 * this event is called every time we need to start a new vacuum process
 */
static void
ctdb_vacuum_event(struct event_context *ev, struct timed_event *te,
                               struct timeval t, void *private_data)
{
        struct ctdb_vacuum_handle *vacuum_handle = talloc_get_type(private_data, struct ctdb_vacuum_handle);
        struct ctdb_db_context *ctdb_db = vacuum_handle->ctdb_db;
        struct ctdb_context *ctdb = ctdb_db->ctdb;
        struct ctdb_vacuum_child_context *child_ctx;
        struct tevent_fd *fde;
        int ret;

        /* we dont vacuum if we are in recovery mode, or db frozen */
        if (ctdb->recovery_mode == CTDB_RECOVERY_ACTIVE ||
            ctdb->freeze_mode[ctdb_db->priority] != CTDB_FREEZE_NONE) {
                DEBUG(DEBUG_INFO, ("Not vacuuming %s (%s)\n", ctdb_db->db_name,
                                   ctdb->recovery_mode == CTDB_RECOVERY_ACTIVE ? "in recovery"
                                   : ctdb->freeze_mode[ctdb_db->priority] == CTDB_FREEZE_PENDING
                                   ? "freeze pending"
                                   : "frozen"));
                event_add_timed(ctdb->ev, vacuum_handle,
                        timeval_current_ofs(get_vacuum_interval(ctdb_db), 0),
                        ctdb_vacuum_event, vacuum_handle);
                return;
        }

        child_ctx = talloc(vacuum_handle, struct ctdb_vacuum_child_context);
        if (child_ctx == NULL) {
                DEBUG(DEBUG_CRIT, (__location__ " Failed to allocate child context for vacuuming of %s\n", ctdb_db->db_name));
                ctdb_fatal(ctdb, "Out of memory when crating vacuum child context. Shutting down\n");
        }


        ret = pipe(child_ctx->fd);
        if (ret != 0) {
                talloc_free(child_ctx);
                DEBUG(DEBUG_ERR, ("Failed to create pipe for vacuum child process.\n"));
                event_add_timed(ctdb->ev, vacuum_handle,
                        timeval_current_ofs(get_vacuum_interval(ctdb_db), 0),
                        ctdb_vacuum_event, vacuum_handle);
                return;
        }

        if (vacuum_handle->fast_path_count > ctdb->tunable.vacuum_fast_path_count) {
                vacuum_handle->fast_path_count = 0;
        }

        child_ctx->child_pid = ctdb_fork(ctdb);
        if (child_ctx->child_pid == (pid_t)-1) {
                close(child_ctx->fd[0]);
                close(child_ctx->fd[1]);
                talloc_free(child_ctx);
                DEBUG(DEBUG_ERR, ("Failed to fork vacuum child process.\n"));
                event_add_timed(ctdb->ev, vacuum_handle,
                        timeval_current_ofs(get_vacuum_interval(ctdb_db), 0),
                        ctdb_vacuum_event, vacuum_handle);
                return;
        }


        if (child_ctx->child_pid == 0) {
                char cc = 0;
                bool full_vacuum_run = false;
                close(child_ctx->fd[0]);

                DEBUG(DEBUG_INFO,("Vacuuming child process %d for db %s started\n", getpid(), ctdb_db->db_name));
                ctdb_set_process_name("ctdb_vacuum");
                if (switch_from_server_to_client(ctdb, "vacuum-%s", ctdb_db->db_name) != 0) {
                        DEBUG(DEBUG_CRIT, (__location__ "ERROR: failed to switch vacuum daemon into client mode. Shutting down.\n"));
                        _exit(1);
                }

                /* 
                 * repack the db
                 */
                if ((ctdb->tunable.vacuum_fast_path_count > 0) &&
                    (vacuum_handle->fast_path_count == 0))
                {
                        full_vacuum_run = true;
                }
                cc = ctdb_vacuum_and_repack_db(ctdb_db, child_ctx,
                                               full_vacuum_run);

                write(child_ctx->fd[1], &cc, 1);
                _exit(0);
        }

        set_close_on_exec(child_ctx->fd[0]);
        close(child_ctx->fd[1]);

        child_ctx->status = VACUUM_RUNNING;
        child_ctx->start_time = timeval_current();

        DLIST_ADD(ctdb->vacuumers, child_ctx);
        talloc_set_destructor(child_ctx, vacuum_child_destructor);

        /*
         * Clear the fastpath vacuuming list in the parent.
         */
        talloc_free(ctdb_db->delete_queue);
        ctdb_db->delete_queue = trbt_create(ctdb_db, 0);
        if (ctdb_db->delete_queue == NULL) {
                /* fatal here? ... */
                ctdb_fatal(ctdb, "Out of memory when re-creating vacuum tree "
                                 "in parent context. Shutting down\n");
        }

        event_add_timed(ctdb->ev, child_ctx,
                timeval_current_ofs(ctdb->tunable.vacuum_max_run_time, 0),
                vacuum_child_timeout, child_ctx);

        DEBUG(DEBUG_DEBUG, (__location__ " Created PIPE FD:%d to child vacuum process\n", child_ctx->fd[0]));

        fde = event_add_fd(ctdb->ev, child_ctx, child_ctx->fd[0],
                           EVENT_FD_READ, vacuum_child_handler, child_ctx);
        tevent_fd_set_auto_close(fde);

        vacuum_handle->child_ctx = child_ctx;
        child_ctx->vacuum_handle = vacuum_handle;
}

void ctdb_stop_vacuuming(struct ctdb_context *ctdb)
{
        /* Simply free them all. */
        while (ctdb->vacuumers) {
                DEBUG(DEBUG_INFO, ("Aborting vacuuming for %s (%i)\n",
                           ctdb->vacuumers->vacuum_handle->ctdb_db->db_name,
                           (int)ctdb->vacuumers->child_pid));
                /* vacuum_child_destructor kills it, removes from list */
                talloc_free(ctdb->vacuumers);
        }
}

/* this function initializes the vacuuming context for a database
 * starts the vacuuming events
 */
int ctdb_vacuum_init(struct ctdb_db_context *ctdb_db)
{
        if (ctdb_db->persistent != 0) {
                DEBUG(DEBUG_ERR,("Vacuuming is disabled for persistent database %s\n", ctdb_db->db_name));
                return 0;
        }

        ctdb_db->vacuum_handle = talloc(ctdb_db, struct ctdb_vacuum_handle);
        CTDB_NO_MEMORY(ctdb_db->ctdb, ctdb_db->vacuum_handle);

        ctdb_db->vacuum_handle->ctdb_db         = ctdb_db;
        ctdb_db->vacuum_handle->fast_path_count = 0;

        event_add_timed(ctdb_db->ctdb->ev, ctdb_db->vacuum_handle, 
                        timeval_current_ofs(get_vacuum_interval(ctdb_db), 0), 
                        ctdb_vacuum_event, ctdb_db->vacuum_handle);

        return 0;
}

static void remove_record_from_delete_queue(struct ctdb_db_context *ctdb_db,
                                            const struct ctdb_ltdb_header *hdr,
                                            const TDB_DATA key)
{
        struct delete_record_data *kd;
        uint32_t hash;

        hash = (uint32_t)ctdb_hash(&key);

        DEBUG(DEBUG_DEBUG, (__location__
                            " remove_record_from_delete_queue: "
                            "db[%s] "
                            "db_id[0x%08x] "
                            "key_hash[0x%08x] "
                            "lmaster[%u] "
                            "migrated_with_data[%s]\n",
                             ctdb_db->db_name, ctdb_db->db_id,
                             hash,
                             ctdb_lmaster(ctdb_db->ctdb, &key),
                             hdr->flags & CTDB_REC_FLAG_MIGRATED_WITH_DATA ? "yes" : "no"));

        kd = (struct delete_record_data *)trbt_lookup32(ctdb_db->delete_queue, hash);
        if (kd == NULL) {
                DEBUG(DEBUG_DEBUG, (__location__
                                    " remove_record_from_delete_queue: "
                                    "record not in queue (hash[0x%08x])\n.",
                                    hash));
                return;
        }

        if ((kd->key.dsize != key.dsize) ||
            (memcmp(kd->key.dptr, key.dptr, key.dsize) != 0))
        {
                DEBUG(DEBUG_DEBUG, (__location__
                                    " remove_record_from_delete_queue: "
                                    "hash collision for key with hash[0x%08x] "
                                    "in db[%s] - skipping\n",
                                    hash, ctdb_db->db_name));
                return;
        }

        DEBUG(DEBUG_DEBUG, (__location__
                            " remove_record_from_delete_queue: "
                            "removing key with hash[0x%08x]\n",
                             hash));

        talloc_free(kd);

        return;
}

/**
 * Insert a record into the ctdb_db context's delete queue,
 * handling hash collisions.
 */
static int insert_record_into_delete_queue(struct ctdb_db_context *ctdb_db,
                                           const struct ctdb_ltdb_header *hdr,
                                           TDB_DATA key)
{
        struct delete_record_data *kd;
        uint32_t hash;
        int ret;

        hash = (uint32_t)ctdb_hash(&key);

        DEBUG(DEBUG_INFO, (__location__ " schedule for deletion: db[%s] "
                           "db_id[0x%08x] "
                           "key_hash[0x%08x] "
                           "lmaster[%u] "
                           "migrated_with_data[%s]\n",
                            ctdb_db->db_name, ctdb_db->db_id,
                            hash,
                            ctdb_lmaster(ctdb_db->ctdb, &key),
                            hdr->flags & CTDB_REC_FLAG_MIGRATED_WITH_DATA ? "yes" : "no"));

        kd = (struct delete_record_data *)trbt_lookup32(ctdb_db->delete_queue, hash);
        if (kd != NULL) {
                if ((kd->key.dsize != key.dsize) ||
                    (memcmp(kd->key.dptr, key.dptr, key.dsize) != 0))
                {
                        DEBUG(DEBUG_INFO,
                              (__location__ " schedule for deletion: "
                               "hash collision for key hash [0x%08x]. "
                               "Skipping the record.\n", hash));
                        return 0;
                } else {
                        DEBUG(DEBUG_DEBUG,
                              (__location__ " schedule for deletion: "
                               "updating entry for key with hash [0x%08x].\n",
                               hash));
                }
        }

        ret = insert_delete_record_data_into_tree(ctdb_db->ctdb, ctdb_db,
                                                  ctdb_db->delete_queue,
                                                  hdr, key);
        if (ret != 0) {
                DEBUG(DEBUG_INFO,
                      (__location__ " schedule for deletion: error "
                       "inserting key with hash [0x%08x] into delete queue\n",
                       hash));
                return -1;
        }

        return 0;
}

/**
 * Schedule a record for deletetion.
 * Called from the parent context.
 */
int32_t ctdb_control_schedule_for_deletion(struct ctdb_context *ctdb,
                                           TDB_DATA indata)
{
        struct ctdb_control_schedule_for_deletion *dd;
        struct ctdb_db_context *ctdb_db;
        int ret;
        TDB_DATA key;

        dd = (struct ctdb_control_schedule_for_deletion *)indata.dptr;

        ctdb_db = find_ctdb_db(ctdb, dd->db_id);
        if (ctdb_db == NULL) {
                DEBUG(DEBUG_ERR, (__location__ " Unknown db id 0x%08x\n",
                                  dd->db_id));
                return -1;
        }

        key.dsize = dd->keylen;
        key.dptr = dd->key;

        ret = insert_record_into_delete_queue(ctdb_db, &dd->hdr, key);

        return ret;
}

int32_t ctdb_local_schedule_for_deletion(struct ctdb_db_context *ctdb_db,
                                         const struct ctdb_ltdb_header *hdr,
                                         TDB_DATA key)
{
        int ret;
        struct ctdb_control_schedule_for_deletion *dd;
        TDB_DATA indata;
        int32_t status;

        if (ctdb_db->ctdb->ctdbd_pid == getpid()) {
                /* main daemon - directly queue */
                ret = insert_record_into_delete_queue(ctdb_db, hdr, key);

                return ret;
        }

        /* if we dont have a connection to the daemon we can not send
           a control. For example sometimes from update_record control child
           process.
        */
        if (!ctdb_db->ctdb->can_send_controls) {
                return -1;
        }


        /* child process: send the main daemon a control */
        indata.dsize = offsetof(struct ctdb_control_schedule_for_deletion, key) + key.dsize;
        indata.dptr = talloc_zero_array(ctdb_db, uint8_t, indata.dsize);
        if (indata.dptr == NULL) {
                DEBUG(DEBUG_ERR, (__location__ " out of memory\n"));
                return -1;
        }
        dd = (struct ctdb_control_schedule_for_deletion *)(void *)indata.dptr;
        dd->db_id = ctdb_db->db_id;
        dd->hdr = *hdr;
        dd->keylen = key.dsize;
        memcpy(dd->key, key.dptr, key.dsize);

        ret = ctdb_control(ctdb_db->ctdb,
                           CTDB_CURRENT_NODE,
                           ctdb_db->db_id,
                           CTDB_CONTROL_SCHEDULE_FOR_DELETION,
                           CTDB_CTRL_FLAG_NOREPLY, /* flags */
                           indata,
                           NULL, /* mem_ctx */
                           NULL, /* outdata */
                           &status,
                           NULL, /* timeout : NULL == wait forever */
                           NULL); /* error message */

        talloc_free(indata.dptr);

        if (ret != 0 || status != 0) {
                DEBUG(DEBUG_ERR, (__location__ " Error sending "
                                  "SCHEDULE_FOR_DELETION "
                                  "control.\n"));
                if (status != 0) {
                        ret = -1;
                }
        }

        return ret;
}

void ctdb_local_remove_from_delete_queue(struct ctdb_db_context *ctdb_db,
                                         const struct ctdb_ltdb_header *hdr,
                                         const TDB_DATA key)
{
        if (ctdb_db->ctdb->ctdbd_pid != getpid()) {
                /*
                 * Only remove the record from the delete queue if called
                 * in the main daemon.
                 */
                return;
        }

        remove_record_from_delete_queue(ctdb_db, hdr, key);

        return;
}