xapian-core/common/debuglog.cc

   1 /** @file
   2  * @brief Debug logging macros.
   3  */
   4 /* Copyright (C) 2008,2011,2012,2014,2015,2019 Olly Betts
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
  19  */
  20
  21 #include <config.h>
  22
  23 #ifdef XAPIAN_DEBUG_LOG
  24
  25 #include "debuglog.h"
  26
  27 #include "errno_to_string.h"
  28 #include "str.h"
  29
  30 #include <sys/types.h>
  31 #include "safefcntl.h"
  32 #include "safesysstat.h"
  33 #include "safeunistd.h"
  34
  35 #include <cerrno>
  36 #include <cstdlib> // For getenv().
  37 #include <string>
  38
  39 using namespace std;
  40
  41 DebugLogger xapian_debuglogger_;
  42
  43 DebugLogger::~DebugLogger()
  44 {
  45     LOGLINE(ALWAYS, PACKAGE_STRING": debug log ended");
  46 }
  47
  48 void
  49 DebugLogger::initialise_categories_mask()
  50 {
  51     fd = -2;
  52     const char* f = getenv("XAPIAN_DEBUG_LOG");
  53     int flags = 0;
  54     if (f && *f) {
  55         if (f[0] == '-' && f[1] == '\0') {
  56             // Filename "-" means "log to stderr".
  57             fd = 2;
  58         } else {
  59             string fnm, pid;
  60             while (*f) {
  61                 if (*f == '%') {
  62                     if (f[1] == 'p') {
  63                         // Replace %p in the filename with the process id.
  64                         if (pid.empty()) pid = str(getpid());
  65                         fnm += pid;
  66                         f += 2;
  67                         continue;
  68                     } else if (f[1] == '!') {
  69                         // %! in the filename means we should attempt to ensure
  70                         // that debug output is written to disk so that none is
  71                         // lost if we crash.
  72                         //
  73                         // We use O_DSYNC in preference if available - updating
  74                         // the log file's mtime isn't important.
  75 #if O_DSYNC - 0 != 0
  76                         flags = O_DSYNC;
  77 #elif O_SYNC - 0 != 0
  78                         flags = O_SYNC;
  79 #endif
  80                         f += 2;
  81                         continue;
  82                     }
  83                 }
  84                 fnm += *f++;
  85             }
  86
  87             flags |= O_CREAT|O_WRONLY|O_APPEND|O_CLOEXEC;
  88             fd = open(fnm.c_str(), flags, 0644);
  89             if (fd == -1) {
  90                 // If we failed to open the log file, report to stderr, but
  91                 // don't spew all the log output to stderr too or else the
  92                 // user will probably miss the message about the debug log
  93                 // failing to open!
  94                 fd = 2;
  95                 LOGLINE(ALWAYS, PACKAGE_STRING": Failed to open debug log '"
  96                         << fnm << "' (" << errno_to_string(errno) << ')');
  97                 fd = -2;
  98             }
  99         }
 100
 101         if (fd >= 0) {
 102             const char* v = getenv("XAPIAN_DEBUG_FLAGS");
 103             if (v) {
 104                 bool toggle = (*v == '-');
 105                 if (toggle) ++v;
 106                 categories_mask = 0;
 107                 while (*v) {
 108                     int ch = *v++ - '@';
 109                     if (ch > 0 && ch <= 26) categories_mask |= 1ul << ch;
 110                 }
 111                 if (toggle) categories_mask ^= 0xffffffff;
 112             }
 113         }
 114     }
 115     LOGLINE(ALWAYS, PACKAGE_STRING": debug log started");
 116 }
 117
 118 void
 119 DebugLogger::log_line(debuglog_categories category, const string& msg)
 120 {
 121     if (fd < 0) return;
 122
 123     // Preserve errno over logging calls, so they can safely be added to code
 124     // which expects errno not to change.
 125     int saved_errno = errno;
 126
 127     string line;
 128     line.reserve(9 + indent_level + msg.size());
 129     line = char(category) + '@';
 130     line += ' ';
 131     line += str(getpid());
 132     line.append(indent_level + 1, ' ');
 133     line += msg;
 134     line += '\n';
 135
 136     const char* p = line.data();
 137     size_t to_do = line.size();
 138     while (to_do) {
 139         ssize_t n = write(fd, p, to_do);
 140         if (n < 0) {
 141             // Retry if interrupted by a signal.
 142             if (errno == EINTR) continue;
 143
 144             // Upon other errors, close the log file, moan to stderr, and stop
 145             // logging.
 146             (void)close(fd);
 147             fd = 2;
 148             LOGLINE(ALWAYS, PACKAGE_STRING": Failed to write log output ("
 149                     << errno_to_string(errno) << ')');
 150             fd = -2;
 151             break;
 152         }
 153         p += n;
 154         to_do -= n;
 155     }
 156
 157     errno = saved_errno;
 158 }
 159
 160 #endif // XAPIAN_DEBUG_LOG