3 * Generator and manager of database load balancing objects
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7 * the Free Software Foundation; either version 2 of the License, or
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11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
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17 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
18 * http://www.gnu.org/copyleft/gpl.html
24 namespace Wikimedia\Rdbms
;
26 use InvalidArgumentException
;
29 * An interface for generating database load balancers
33 interface ILBFactory
{
34 /** @var int Don't save DB positions at all */
35 const SHUTDOWN_NO_CHRONPROT
= 0; // don't save DB positions at all
36 /** @var int Save DB positions, but don't wait on remote DCs */
37 const SHUTDOWN_CHRONPROT_ASYNC
= 1;
38 /** @var int Save DB positions, waiting on all DCs */
39 const SHUTDOWN_CHRONPROT_SYNC
= 2;
42 * Construct a manager of ILoadBalancer objects
44 * Sub-classes will extend the required keys in $conf with additional parameters
46 * @param array $conf Array with keys:
47 * - localDomain: A DatabaseDomain or domain ID string.
48 * - readOnlyReason: Reason the master DB is read-only if so [optional]
49 * - srvCache: BagOStuff object for server cache [optional]
50 * - memStash: BagOStuff object for cross-datacenter memory storage [optional]
51 * - wanCache: WANObjectCache object [optional]
52 * - hostname: The name of the current server [optional]
53 * - cliMode: Whether the execution context is a CLI script. [optional]
54 * - maxLag: Try to avoid DB replicas with lag above this many seconds [optional]
55 * - profiler: Class name or instance with profileIn()/profileOut() methods. [optional]
56 * - trxProfiler: TransactionProfiler instance. [optional]
57 * - replLogger: PSR-3 logger instance. [optional]
58 * - connLogger: PSR-3 logger instance. [optional]
59 * - queryLogger: PSR-3 logger instance. [optional]
60 * - perfLogger: PSR-3 logger instance. [optional]
61 * - errorLogger: Callback that takes an Exception and logs it. [optional]
62 * - deprecationLogger: Callback to log a deprecation warning. [optional]
63 * - secret: Secret string to use for HMAC hashing [optional]
64 * @throws InvalidArgumentException
66 public function __construct( array $conf );
69 * Disables all load balancers. All connections are closed, and any attempt to
70 * open a new connection will result in a DBAccessError.
71 * @see ILoadBalancer::disable()
73 public function destroy();
76 * Get the local (and default) database domain ID of connection handles
79 * @return string Database domain ID; this specifies DB name, schema, and table prefix
82 public function getLocalDomainID();
85 * @param DatabaseDomain|string|bool $domain Database domain
86 * @return string Value of $domain if provided or the local domain otherwise
89 public function resolveDomainID( $domain );
92 * Close all connection and redefine the local domain for testing or schema creation
94 * @param DatabaseDomain|string $domain
97 public function redefineLocalDomain( $domain );
100 * Create a new load balancer object. The resulting object will be untracked,
101 * not chronology-protected, and the caller is responsible for cleaning it up.
103 * This method is for only advanced usage and callers should almost always use
104 * getMainLB() instead. This method can be useful when a table is used as a key/value
105 * store. In that cases, one might want to query it in autocommit mode (DBO_TRX off)
106 * but still use DBO_TRX transaction rounds on other tables.
108 * @param bool|string $domain Domain ID, or false for the current domain
109 * @return ILoadBalancer
111 public function newMainLB( $domain = false );
114 * Get a cached (tracked) load balancer object.
116 * @param bool|string $domain Domain ID, or false for the current domain
117 * @return ILoadBalancer
119 public function getMainLB( $domain = false );
122 * Create a new load balancer for external storage. The resulting object will be
123 * untracked, not chronology-protected, and the caller is responsible for cleaning it up.
125 * This method is for only advanced usage and callers should almost always use
126 * getExternalLB() instead. This method can be useful when a table is used as a
127 * key/value store. In that cases, one might want to query it in autocommit mode
128 * (DBO_TRX off) but still use DBO_TRX transaction rounds on other tables.
130 * @param string $cluster External storage cluster name
131 * @return ILoadBalancer
133 public function newExternalLB( $cluster );
136 * Get a cached (tracked) load balancer for external storage
138 * @param string $cluster External storage cluster name
139 * @return ILoadBalancer
141 public function getExternalLB( $cluster );
144 * Get cached (tracked) load balancers for all main database clusters
146 * The default cluster name is ILoadBalancer::CLUSTER_MAIN_DEFAULT
148 * @return ILoadBalancer[] Map of (cluster name => ILoadBalancer)
151 public function getAllMainLBs();
154 * Get cached (tracked) load balancers for all external database clusters
156 * @return ILoadBalancer[] Map of (cluster name => ILoadBalancer)
159 public function getAllExternalLBs();
162 * Execute a function for each currently tracked (instantiated) load balancer
164 * The callback is called with the load balancer as the first parameter,
165 * and $params passed as the subsequent parameters.
167 * @param callable $callback
168 * @param array $params
170 public function forEachLB( $callback, array $params = [] );
173 * Prepare all currently tracked (instantiated) load balancers for shutdown
175 * @param int $mode One of the class SHUTDOWN_* constants
176 * @param callable|null $workCallback Work to mask ChronologyProtector writes
177 * @param int|null &$cpIndex Position key write counter for ChronologyProtector
178 * @param string|null &$cpClientId Client ID hash for ChronologyProtector
180 public function shutdown(
181 $mode = self
::SHUTDOWN_CHRONPROT_SYNC
,
182 callable
$workCallback = null,
188 * Commit all replica DB transactions so as to flush any REPEATABLE-READ or SSI snapshot
190 * This is useful for getting rid of stale data from an implicit transaction round
192 * @param string $fname Caller name
194 public function flushReplicaSnapshots( $fname = __METHOD__
);
197 * Commit open transactions on all connections. This is useful for two main cases:
198 * - a) To commit changes to the masters.
199 * - b) To release the snapshot on all connections, master and replica DBs.
200 * @param string $fname Caller name
201 * @param array $options Options map:
202 * - maxWriteDuration: abort if more than this much time was spent in write queries
204 public function commitAll( $fname = __METHOD__
, array $options = [] );
207 * Flush any master transaction snapshots and set DBO_TRX (if DBO_DEFAULT is set)
209 * The DBO_TRX setting will be reverted to the default in each of these methods:
210 * - commitMasterChanges()
211 * - rollbackMasterChanges()
214 * This allows for custom transaction rounds from any outer transaction scope.
216 * @param string $fname
217 * @throws DBTransactionError
219 public function beginMasterChanges( $fname = __METHOD__
);
222 * Commit changes and clear view snapshots on all master connections
223 * @param string $fname Caller name
224 * @param array $options Options map:
225 * - maxWriteDuration: abort if more than this much time was spent in write queries
226 * @throws DBTransactionError
228 public function commitMasterChanges( $fname = __METHOD__
, array $options = [] );
231 * Rollback changes on all master connections
232 * @param string $fname Caller name
234 public function rollbackMasterChanges( $fname = __METHOD__
);
237 * Check if an explicit transaction round is active
241 public function hasTransactionRound();
244 * Check if transaction rounds can be started, committed, or rolled back right now
246 * This can be used as a recusion guard to avoid exceptions in transaction callbacks
251 public function isReadyForRoundOperations();
254 * Determine if any master connection has pending changes
257 public function hasMasterChanges();
260 * Detemine if any lagged replica DB connection was used
263 public function laggedReplicaUsed();
266 * Determine if any master connection has pending/written changes from this request
267 * @param float|null $age How many seconds ago is "recent" [defaults to LB lag wait timeout]
270 public function hasOrMadeRecentMasterChanges( $age = null );
273 * Waits for the replica DBs to catch up to the current master position
275 * Use this when updating very large numbers of rows, as in maintenance scripts,
276 * to avoid causing too much lag. Of course, this is a no-op if there are no replica DBs.
278 * By default this waits on all DB clusters actually used in this request.
279 * This makes sense when lag being waiting on is caused by the code that does this check.
280 * In that case, setting "ifWritesSince" can avoid the overhead of waiting for clusters
281 * that were not changed since the last wait check. To forcefully wait on a specific cluster
282 * for a given domain, use the 'domain' parameter. To forcefully wait on an "external" cluster,
283 * use the "cluster" parameter.
285 * Never call this function after a large DB write that is *still* in a transaction.
286 * It only makes sense to call this after the possible lag inducing changes were committed.
288 * @param array $opts Optional fields that include:
289 * - domain : wait on the load balancer DBs that handles the given domain ID
290 * - cluster : wait on the given external load balancer DBs
291 * - timeout : Max wait time. Default: 60 seconds for CLI, 1 second for web.
292 * - ifWritesSince: Only wait if writes were done since this UNIX timestamp
293 * @return bool True on success, false if a timeout or error occurred while waiting
295 public function waitForReplication( array $opts = [] );
298 * Add a callback to be run in every call to waitForReplication() before waiting
300 * Callbacks must clear any transactions that they start
302 * @param string $name Callback name
303 * @param callable|null $callback Use null to unset a callback
305 public function setWaitForReplicationListener( $name, callable
$callback = null );
308 * Get a token asserting that no transaction writes are active
310 * @param string $fname Caller name (e.g. __METHOD__)
311 * @return mixed A value to pass to commitAndWaitForReplication()
313 public function getEmptyTransactionTicket( $fname );
316 * Convenience method for safely running commitMasterChanges()/waitForReplication()
318 * This will commit and wait unless $ticket indicates it is unsafe to do so
320 * @param string $fname Caller name (e.g. __METHOD__)
321 * @param mixed $ticket Result of getEmptyTransactionTicket()
322 * @param array $opts Options to waitForReplication()
323 * @return bool True if the wait was successful, false on timeout
325 public function commitAndWaitForReplication( $fname, $ticket, array $opts = [] );
328 * @param string $dbName DB master name (e.g. "db1052")
329 * @return float|bool UNIX timestamp when client last touched the DB or false if not recent
331 public function getChronologyProtectorTouched( $dbName );
334 * Disable the ChronologyProtector for all load balancers
336 * This can be called at the start of special API entry points
338 public function disableChronologyProtection();
341 * Set a new table prefix for the existing local domain ID for testing
343 * @param string $prefix
346 public function setLocalDomainPrefix( $prefix );
349 * Close all open database connections on all open load balancers.
351 public function closeAll();
354 * @param string $agent Agent name for query profiling
356 public function setAgentName( $agent );
359 * Append ?cpPosIndex parameter to a URL for ChronologyProtector purposes if needed
361 * Note that unlike cookies, this works across domains
364 * @param int $index Write counter index
367 public function appendShutdownCPIndexAsQuery( $url, $index );
370 * Get the client ID of the ChronologyProtector instance
372 * @return string Client ID
375 public function getChronologyProtectorClientId();
378 * @param array $info Map of fields, including:
379 * - IPAddress : IP address
380 * - UserAgent : User-Agent HTTP header
381 * - ChronologyProtection : cookie/header value specifying ChronologyProtector usage
382 * - ChronologyPositionIndex: timestamp used to get up-to-date DB positions for the agent
384 public function setRequestInfo( array $info );
387 * Make certain table names use their own database, schema, and table prefix
388 * when passed into SQL queries pre-escaped and without a qualified database name
390 * For example, "user" can be converted to "myschema.mydbname.user" for convenience.
391 * Appearances like `user`, somedb.user, somedb.someschema.user will used literally.
393 * Calling this twice will completely clear any old table aliases. Also, note that
394 * callers are responsible for making sure the schemas and databases actually exist.
396 * @param array[] $aliases Map of (table => (dbname, schema, prefix) map)
399 public function setTableAliases( array $aliases );
402 * Convert certain index names to alternative names before querying the DB
404 * Note that this applies to indexes regardless of the table they belong to.
406 * This can be employed when an index was renamed X => Y in code, but the new Y-named
407 * indexes were not yet built on all DBs. After all the Y-named ones are added by the DBA,
408 * the aliases can be removed, and then the old X-named indexes dropped.
410 * @param string[] $aliases
413 public function setIndexAliases( array $aliases );