storage/mozStorageConnection.h

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
   2  * vim: sw=2 ts=2 et lcs=trail\:.,tab\:>~ :
   3  * This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef mozilla_storage_Connection_h
   8 #define mozilla_storage_Connection_h
   9
  10 #include "nsCOMPtr.h"
  11 #include "mozilla/Atomics.h"
  12 #include "mozilla/Mutex.h"
  13 #include "nsProxyRelease.h"
  14 #include "nsThreadUtils.h"
  15 #include "nsIInterfaceRequestor.h"
  16
  17 #include "nsDataHashtable.h"
  18 #include "mozIStorageProgressHandler.h"
  19 #include "SQLiteMutex.h"
  20 #include "mozIStorageConnection.h"
  21 #include "mozStorageService.h"
  22 #include "mozIStorageAsyncConnection.h"
  23 #include "mozIStorageCompletionCallback.h"
  24
  25 #include "mozilla/Attributes.h"
  26
  27 #include "sqlite3.h"
  28
  29 class nsIFile;
  30 class nsIFileURL;
  31 class nsIEventTarget;
  32 class nsIThread;
  33
  34 namespace mozilla {
  35 namespace storage {
  36
  37 class Connection final : public mozIStorageConnection,
  38                          public nsIInterfaceRequestor {
  39  public:
  40   NS_DECL_THREADSAFE_ISUPPORTS
  41   NS_DECL_MOZISTORAGEASYNCCONNECTION
  42   NS_DECL_MOZISTORAGECONNECTION
  43   NS_DECL_NSIINTERFACEREQUESTOR
  44
  45   /**
  46    * Indicates if a database operation is synchronous or asynchronous.
  47    *
  48    * - Async operations may be called from any thread for all connections.
  49    * - Sync operations may be called from any thread for sync connections, and
  50    *   from background threads for async connections.
  51    */
  52   enum ConnectionOperation { ASYNCHRONOUS, SYNCHRONOUS };
  53
  54   /**
  55    * Structure used to describe user functions on the database connection.
  56    */
  57   struct FunctionInfo {
  58     enum FunctionType { SIMPLE, AGGREGATE };
  59
  60     nsCOMPtr<nsISupports> function;
  61     FunctionType type;
  62     int32_t numArgs;
  63   };
  64
  65   /**
  66    * @param aService
  67    *        Pointer to the storage service.  Held onto for the lifetime of the
  68    *        connection.
  69    * @param aFlags
  70    *        The flags to pass to sqlite3_open_v2.
  71    * @param aSupportedOperations
  72    *        The operation types supported on this connection. All connections
  73    *        implement both the async (`mozIStorageAsyncConnection`) and sync
  74    *        (`mozIStorageConnection`) interfaces, but async connections may not
  75    *        call sync operations from the main thread.
  76    * @param aIgnoreLockingMode
  77    *        If |true|, ignore locks in force on the file. Only usable with
  78    *        read-only connections. Defaults to false.
  79    *        Use with extreme caution. If sqlite ignores locks, reads may fail
  80    *        indicating database corruption (the database won't actually be
  81    *        corrupt) or produce wrong results without any indication that has
  82    *        happened.
  83    */
  84   Connection(Service* aService, int aFlags,
  85              ConnectionOperation aSupportedOperations,
  86              bool aIgnoreLockingMode = false);
  87
  88   /**
  89    * Creates the connection to an in-memory database.
  90    */
  91   nsresult initialize();
  92
  93   /**
  94    * Creates the connection to the database.
  95    *
  96    * @param aDatabaseFile
  97    *        The nsIFile of the location of the database to open, or create if it
  98    *        does not exist.
  99    */
 100   nsresult initialize(nsIFile* aDatabaseFile);
 101
 102   /**
 103    * Creates the connection to the database.
 104    *
 105    * @param aFileURL
 106    *        The nsIFileURL of the location of the database to open, or create if
 107    * it does not exist.
 108    */
 109   nsresult initialize(nsIFileURL* aFileURL);
 110
 111   /**
 112    * Same as initialize, but to be used on the async thread.
 113    */
 114   nsresult initializeOnAsyncThread(nsIFile* aStorageFile);
 115
 116   /**
 117    * Fetches runtime status information for this connection.
 118    *
 119    * @param aStatusOption One of the SQLITE_DBSTATUS options defined at
 120    *        http://www.sqlite.org/c3ref/c_dbstatus_options.html
 121    * @param [optional] aMaxValue if provided, will be set to the highest
 122    *        istantaneous value.
 123    * @return the current value for the specified option.
 124    */
 125   int32_t getSqliteRuntimeStatus(int32_t aStatusOption,
 126                                  int32_t* aMaxValue = nullptr);
 127   /**
 128    * Registers/unregisters a commit hook callback.
 129    *
 130    * @param aCallbackFn a callback function to be invoked on transactions
 131    *        commit.  Pass nullptr to unregister the current callback.
 132    * @param [optional] aData if provided, will be passed to the callback.
 133    * @see http://sqlite.org/c3ref/commit_hook.html
 134    */
 135   void setCommitHook(int (*aCallbackFn)(void*), void* aData = nullptr) {
 136     MOZ_ASSERT(mDBConn, "A connection must exist at this point");
 137     ::sqlite3_commit_hook(mDBConn, aCallbackFn, aData);
 138   };
 139
 140   /**
 141    * Gets autocommit status.
 142    */
 143   bool getAutocommit() {
 144     return mDBConn && static_cast<bool>(::sqlite3_get_autocommit(mDBConn));
 145   };
 146
 147   /**
 148    * Lazily creates and returns a background execution thread.  In the future,
 149    * the thread may be re-claimed if left idle, so you should call this
 150    * method just before you dispatch and not save the reference.
 151    *
 152    * This must be called from the opener thread.
 153    *
 154    * @return an event target suitable for asynchronous statement execution.
 155    * @note This method will return null once AsyncClose() has been called.
 156    */
 157   nsIEventTarget* getAsyncExecutionTarget();
 158
 159   /**
 160    * Mutex used by asynchronous statements to protect state.  The mutex is
 161    * declared on the connection object because there is no contention between
 162    * asynchronous statements (they are serialized on mAsyncExecutionThread).
 163    * Currently protects:
 164    *  - Connection.mAsyncExecutionThreadShuttingDown
 165    *  - Connection.mConnectionClosed
 166    *  - AsyncExecuteStatements.mCancelRequested
 167    */
 168   Mutex sharedAsyncExecutionMutex;
 169
 170   /**
 171    * Wraps the mutex that SQLite gives us from sqlite3_db_mutex.  This is public
 172    * because we already expose the sqlite3* native connection and proper
 173    * operation of the deadlock detector requires everyone to use the same single
 174    * SQLiteMutex instance for correctness.
 175    */
 176   SQLiteMutex sharedDBMutex;
 177
 178   /**
 179    * References the thread this database was opened on.  This MUST be thread it
 180    * is closed on.
 181    */
 182   const nsCOMPtr<nsIThread> threadOpenedOn;
 183
 184   /**
 185    * Closes the SQLite database, and warns about any non-finalized statements.
 186    */
 187   nsresult internalClose(sqlite3* aDBConn);
 188
 189   /**
 190    * Shuts down the passed-in async thread.
 191    */
 192   void shutdownAsyncThread();
 193
 194   /**
 195    * Obtains the filename of the connection.  Useful for logging.
 196    */
 197   nsCString getFilename();
 198
 199   /**
 200    * Creates an sqlite3 prepared statement object from an SQL string.
 201    *
 202    * @param aNativeConnection
 203    *        The underlying Sqlite connection to prepare the statement with.
 204    * @param aSQL
 205    *        The SQL statement string to compile.
 206    * @param _stmt
 207    *        New sqlite3_stmt object.
 208    * @return the result from sqlite3_prepare_v2.
 209    */
 210   int prepareStatement(sqlite3* aNativeConnection, const nsCString& aSQL,
 211                        sqlite3_stmt** _stmt);
 212
 213   /**
 214    * Performs a sqlite3_step on aStatement, while properly handling
 215    * SQLITE_LOCKED when not on the main thread by waiting until we are notified.
 216    *
 217    * @param aNativeConnection
 218    *        The underlying Sqlite connection to step the statement with.
 219    * @param aStatement
 220    *        A pointer to a sqlite3_stmt object.
 221    * @return the result from sqlite3_step.
 222    */
 223   int stepStatement(sqlite3* aNativeConnection, sqlite3_stmt* aStatement);
 224
 225   /**
 226    * Raw connection transaction management.
 227    *
 228    * @see BeginTransactionAs, CommitTransaction, RollbackTransaction.
 229    */
 230   nsresult beginTransactionInternal(
 231       const SQLiteMutexAutoLock& aProofOfLock, sqlite3* aNativeConnection,
 232       int32_t aTransactionType = TRANSACTION_DEFERRED);
 233   nsresult commitTransactionInternal(const SQLiteMutexAutoLock& aProofOfLock,
 234                                      sqlite3* aNativeConnection);
 235   nsresult rollbackTransactionInternal(const SQLiteMutexAutoLock& aProofOfLock,
 236                                        sqlite3* aNativeConnection);
 237
 238   /**
 239    * Indicates if this database connection is open.
 240    */
 241   inline bool connectionReady() { return mDBConn != nullptr; }
 242
 243   /**
 244    * Indicates if this database connection has an open transaction. Because
 245    * multiple threads can execute statements on the same connection, this method
 246    * requires proof that the caller is holding `sharedDBMutex`.
 247    *
 248    * Per the SQLite docs, `sqlite3_get_autocommit` returns 0 if autocommit mode
 249    * is disabled. `BEGIN` disables autocommit mode, and `COMMIT`, `ROLLBACK`, or
 250    * an automatic rollback re-enables it.
 251    */
 252   inline bool transactionInProgress(const SQLiteMutexAutoLock& aProofOfLock) {
 253     return !getAutocommit();
 254   }
 255
 256   /**
 257    * Indicates if this database connection supports the given operation.
 258    *
 259    * @param  aOperationType
 260    *         The operation type, sync or async.
 261    * @return `true` if the operation is supported, `false` otherwise.
 262    */
 263   bool operationSupported(ConnectionOperation aOperationType);
 264
 265   /**
 266    * Thread-aware version of connectionReady, results per caller's thread are:
 267    *  - owner thread: Same as connectionReady().  True means we have a valid,
 268    *    un-closed database connection and it's not going away until you invoke
 269    *    Close() or AsyncClose().
 270    *  - async thread: Returns true at all times because you can't schedule
 271    *    runnables against the async thread after AsyncClose() has been called.
 272    *    Therefore, the connection is still around if your code is running.
 273    *  - any other thread: Race-prone Lies!  If you are main-thread code in
 274    *    mozStorageService iterating over the list of connections, you need to
 275    *    acquire the sharedAsyncExecutionMutex for the connection, invoke
 276    *    connectionReady() while holding it, and then continue to hold it while
 277    *    you do whatever you need to do.  This is because of off-main-thread
 278    *    consumers like dom/cache and IndexedDB and other QuotaManager clients.
 279    */
 280   bool isConnectionReadyOnThisThread();
 281
 282   /**
 283    * True if this connection has inited shutdown.
 284    */
 285   bool isClosing();
 286
 287   /**
 288    * True if the underlying connection is closed.
 289    * Any sqlite resources may be lost when this returns true, so nothing should
 290    * try to use them.
 291    * This locks on sharedAsyncExecutionMutex.
 292    */
 293   bool isClosed();
 294
 295   /**
 296    * Same as isClosed(), but takes a proof-of-lock instead of locking
 297    * internally.
 298    */
 299   bool isClosed(MutexAutoLock& lock);
 300
 301   /**
 302    * True if the async execution thread is alive and able to be used (i.e., it
 303    * is not in the process of shutting down.)
 304    *
 305    * This must be called from the opener thread.
 306    */
 307   bool isAsyncExecutionThreadAvailable();
 308
 309   nsresult initializeClone(Connection* aClone, bool aReadOnly);
 310
 311  private:
 312   ~Connection();
 313   nsresult initializeInternal();
 314   void initializeFailed();
 315
 316   /**
 317    * Sets the database into a closed state so no further actions can be
 318    * performed.
 319    *
 320    * @note mDBConn is set to nullptr in this method.
 321    */
 322   nsresult setClosedState();
 323
 324   /**
 325    * Helper for calls to sqlite3_exec. Reports long delays to Telemetry.
 326    *
 327    * @param aNativeConnection
 328    *        The underlying Sqlite connection to execute the query with.
 329    * @param aSqlString
 330    *        SQL string to execute
 331    * @return the result from sqlite3_exec.
 332    */
 333   int executeSql(sqlite3* aNativeConnection, const char* aSqlString);
 334
 335   /**
 336    * Describes a certain primitive type in the database.
 337    *
 338    * Possible Values Are:
 339    *  INDEX - To check for the existence of an index
 340    *  TABLE - To check for the existence of a table
 341    */
 342   enum DatabaseElementType { INDEX, TABLE };
 343
 344   /**
 345    * Determines if the specified primitive exists.
 346    *
 347    * @param aElementType
 348    *        The type of element to check the existence of
 349    * @param aElementName
 350    *        The name of the element to check for
 351    * @returns true if element exists, false otherwise
 352    */
 353   nsresult databaseElementExists(enum DatabaseElementType aElementType,
 354                                  const nsACString& aElementName, bool* _exists);
 355
 356   bool findFunctionByInstance(nsISupports* aInstance);
 357
 358   static int sProgressHelper(void* aArg);
 359   // Generic progress handler
 360   // Dispatch call to registered progress handler,
 361   // if there is one. Do nothing in other cases.
 362   int progressHandler();
 363
 364   /**
 365    * Like `operationSupported`, but throws (and, in a debug build, asserts) if
 366    * the operation is unsupported.
 367    */
 368   nsresult ensureOperationSupported(ConnectionOperation aOperationType);
 369
 370   sqlite3* mDBConn;
 371   nsCOMPtr<nsIFileURL> mFileURL;
 372   nsCOMPtr<nsIFile> mDatabaseFile;
 373
 374   /**
 375    * The filename that will be reported to telemetry for this connection. By
 376    * default this will be the leaf of the path to the database file.
 377    */
 378   nsCString mTelemetryFilename;
 379
 380   /**
 381    * Lazily created thread for asynchronous statement execution.  Consumers
 382    * should use getAsyncExecutionTarget rather than directly accessing this
 383    * field.
 384    *
 385    * This must be modified only on the opener thread.
 386    */
 387   nsCOMPtr<nsIThread> mAsyncExecutionThread;
 388
 389   /**
 390    * Set to true by Close() or AsyncClose() prior to shutdown.
 391    *
 392    * If false, we guarantee both that the underlying sqlite3 database
 393    * connection is still open and that getAsyncExecutionTarget() can
 394    * return a thread. Once true, either the sqlite3 database
 395    * connection is being shutdown or it has been
 396    * shutdown. Additionally, once true, getAsyncExecutionTarget()
 397    * returns null.
 398    *
 399    * This variable should be accessed while holding the
 400    * sharedAsyncExecutionMutex.
 401    */
 402   bool mAsyncExecutionThreadShuttingDown;
 403
 404   /**
 405    * Set to true just prior to calling sqlite3_close on the
 406    * connection.
 407    *
 408    * This variable should be accessed while holding the
 409    * sharedAsyncExecutionMutex.
 410    */
 411   bool mConnectionClosed;
 412
 413   /**
 414    * Stores the default behavior for all transactions run on this connection.
 415    */
 416   mozilla::Atomic<int32_t> mDefaultTransactionType;
 417
 418   /**
 419    * Used to trigger cleanup logic only the first time our refcount hits 1.  We
 420    * may trigger a failsafe Close() that invokes SpinningSynchronousClose()
 421    * which invokes AsyncClose() which may bump our refcount back up to 2 (and
 422    * which will then fall back down to 1 again).  It's also possible that the
 423    * Service may bump our refcount back above 1 if getConnections() runs before
 424    * we invoke unregisterConnection().
 425    */
 426   mozilla::Atomic<bool> mDestroying;
 427
 428   /**
 429    * Stores the mapping of a given function by name to its instance.  Access is
 430    * protected by sharedDBMutex.
 431    */
 432   nsDataHashtable<nsCStringHashKey, FunctionInfo> mFunctions;
 433
 434   /**
 435    * Stores the registered progress handler for the database connection.  Access
 436    * is protected by sharedDBMutex.
 437    */
 438   nsCOMPtr<mozIStorageProgressHandler> mProgressHandler;
 439
 440   /**
 441    * Stores the flags we passed to sqlite3_open_v2.
 442    */
 443   const int mFlags;
 444
 445   /**
 446    * Stores whether we should ask sqlite3_open_v2 to ignore locking.
 447    */
 448   const bool mIgnoreLockingMode;
 449
 450   // This is here for two reasons: 1) It's used to make sure that the
 451   // connections do not outlive the service.  2) Our custom collating functions
 452   // call its localeCompareStrings() method.
 453   RefPtr<Service> mStorageService;
 454
 455   /**
 456    * Indicates which operations are supported on this connection.
 457    */
 458   const ConnectionOperation mSupportedOperations;
 459
 460   nsresult synchronousClose();
 461 };
 462
 463 /**
 464  * A Runnable designed to call a mozIStorageCompletionCallback on
 465  * the appropriate thread.
 466  */
 467 class CallbackComplete final : public Runnable {
 468  public:
 469   /**
 470    * @param aValue The result to pass to the callback. It must
 471    *               already be owned by the main thread.
 472    * @param aCallback The callback. It must already be owned by the
 473    *                  main thread.
 474    */
 475   CallbackComplete(nsresult aStatus, nsISupports* aValue,
 476                    already_AddRefed<mozIStorageCompletionCallback> aCallback)
 477       : Runnable("storage::CallbackComplete"),
 478         mStatus(aStatus),
 479         mValue(aValue),
 480         mCallback(aCallback) {}
 481
 482   NS_IMETHOD Run() override {
 483     MOZ_ASSERT(NS_IsMainThread());
 484     nsresult rv = mCallback->Complete(mStatus, mValue);
 485
 486     // Ensure that we release on the main thread
 487     mValue = nullptr;
 488     mCallback = nullptr;
 489     return rv;
 490   }
 491
 492  private:
 493   nsresult mStatus;
 494   nsCOMPtr<nsISupports> mValue;
 495   // This is a RefPtr<T> and not a nsCOMPtr<T> because
 496   // nsCOMP<T> would cause an off-main thread QI, which
 497   // is not a good idea (and crashes XPConnect).
 498   RefPtr<mozIStorageCompletionCallback> mCallback;
 499 };
 500
 501 }  // namespace storage
 502 }  // namespace mozilla
 503
 504 /**
 505  * Casting Connection to nsISupports is ambiguous.
 506  * This method handles that.
 507  */
 508 inline nsISupports* ToSupports(mozilla::storage::Connection* p) {
 509   return NS_ISUPPORTS_CAST(mozIStorageAsyncConnection*, p);
 510 }
 511
 512 #endif  // mozilla_storage_Connection_h