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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24 namespace Wikimedia\Rdbms
;
26 use InvalidArgumentException
;
29 * An interface for generating database load balancers
33 interface ILBFactory
{
34 const SHUTDOWN_NO_CHRONPROT
= 0; // don't save DB positions at all
35 const SHUTDOWN_CHRONPROT_ASYNC
= 1; // save DB positions, but don't wait on remote DCs
36 const SHUTDOWN_CHRONPROT_SYNC
= 2; // save DB positions, waiting on all DCs
39 * Construct a manager of ILoadBalancer objects
41 * Sub-classes will extend the required keys in $conf with additional parameters
43 * @param array $conf Array with keys:
44 * - localDomain: A DatabaseDomain or domain ID string.
45 * - readOnlyReason: Reason the master DB is read-only if so [optional]
46 * - srvCache: BagOStuff object for server cache [optional]
47 * - memStash: BagOStuff object for cross-datacenter memory storage [optional]
48 * - wanCache: WANObjectCache object [optional]
49 * - hostname: The name of the current server [optional]
50 * - cliMode: Whether the execution context is a CLI script. [optional]
51 * - profiler: Class name or instance with profileIn()/profileOut() methods. [optional]
52 * - trxProfiler: TransactionProfiler instance. [optional]
53 * - replLogger: PSR-3 logger instance. [optional]
54 * - connLogger: PSR-3 logger instance. [optional]
55 * - queryLogger: PSR-3 logger instance. [optional]
56 * - perfLogger: PSR-3 logger instance. [optional]
57 * - errorLogger: Callback that takes an Exception and logs it. [optional]
58 * - deprecationLogger: Callback to log a deprecation warning. [optional]
59 * @throws InvalidArgumentException
61 public function __construct( array $conf );
64 * Disables all load balancers. All connections are closed, and any attempt to
65 * open a new connection will result in a DBAccessError.
66 * @see ILoadBalancer::disable()
68 public function destroy();
71 * Get the local (and default) database domain ID of connection handles
74 * @return string Database domain ID; this specifies DB name, schema, and table prefix
77 public function getLocalDomainID();
80 * @param DatabaseDomain|string|bool $domain Database domain
81 * @return string Value of $domain if provided or the local domain otherwise
84 public function resolveDomainID( $domain );
87 * Create a new load balancer object. The resulting object will be untracked,
88 * not chronology-protected, and the caller is responsible for cleaning it up.
90 * This method is for only advanced usage and callers should almost always use
91 * getMainLB() instead. This method can be useful when a table is used as a key/value
92 * store. In that cases, one might want to query it in autocommit mode (DBO_TRX off)
93 * but still use DBO_TRX transaction rounds on other tables.
95 * @param bool|string $domain Domain ID, or false for the current domain
96 * @return ILoadBalancer
98 public function newMainLB( $domain = false );
101 * Get a cached (tracked) load balancer object.
103 * @param bool|string $domain Domain ID, or false for the current domain
104 * @return ILoadBalancer
106 public function getMainLB( $domain = false );
109 * Create a new load balancer for external storage. The resulting object will be
110 * untracked, not chronology-protected, and the caller is responsible for cleaning it up.
112 * This method is for only advanced usage and callers should almost always use
113 * getExternalLB() instead. This method can be useful when a table is used as a
114 * key/value store. In that cases, one might want to query it in autocommit mode
115 * (DBO_TRX off) but still use DBO_TRX transaction rounds on other tables.
117 * @param string $cluster External storage cluster name
118 * @return ILoadBalancer
120 public function newExternalLB( $cluster );
123 * Get a cached (tracked) load balancer for external storage
125 * @param string $cluster External storage cluster name
126 * @return ILoadBalancer
128 public function getExternalLB( $cluster );
131 * Get cached (tracked) load balancers for all main database clusters
133 * @return LoadBalancer[] Map of (cluster name => LoadBalancer)
136 public function getAllMainLBs();
139 * Get cached (tracked) load balancers for all external database clusters
141 * @return LoadBalancer[] Map of (cluster name => LoadBalancer)
144 public function getAllExternalLBs();
147 * Execute a function for each tracked load balancer
148 * The callback is called with the load balancer as the first parameter,
149 * and $params passed as the subsequent parameters.
151 * @param callable $callback
152 * @param array $params
154 public function forEachLB( $callback, array $params = [] );
157 * Prepare all tracked load balancers for shutdown
158 * @param int $mode One of the class SHUTDOWN_* constants
159 * @param callable|null $workCallback Work to mask ChronologyProtector writes
160 * @param int|null &$cpIndex Position key write counter for ChronologyProtector
161 * @param string|null &$cpClientId Client ID hash for ChronologyProtector
163 public function shutdown(
164 $mode = self
::SHUTDOWN_CHRONPROT_SYNC
,
165 callable
$workCallback = null,
171 * Commit all replica DB transactions so as to flush any REPEATABLE-READ or SSI snapshot
173 * @param string $fname Caller name
175 public function flushReplicaSnapshots( $fname = __METHOD__
);
178 * Commit open transactions on all connections. This is useful for two main cases:
179 * - a) To commit changes to the masters.
180 * - b) To release the snapshot on all connections, master and replica DBs.
181 * @param string $fname Caller name
182 * @param array $options Options map:
183 * - maxWriteDuration: abort if more than this much time was spent in write queries
185 public function commitAll( $fname = __METHOD__
, array $options = [] );
188 * Flush any master transaction snapshots and set DBO_TRX (if DBO_DEFAULT is set)
190 * The DBO_TRX setting will be reverted to the default in each of these methods:
191 * - commitMasterChanges()
192 * - rollbackMasterChanges()
195 * This allows for custom transaction rounds from any outer transaction scope.
197 * @param string $fname
198 * @throws DBTransactionError
200 public function beginMasterChanges( $fname = __METHOD__
);
203 * Commit changes on all master connections
204 * @param string $fname Caller name
205 * @param array $options Options map:
206 * - maxWriteDuration: abort if more than this much time was spent in write queries
207 * @throws DBTransactionError
209 public function commitMasterChanges( $fname = __METHOD__
, array $options = [] );
212 * Rollback changes on all master connections
213 * @param string $fname Caller name
215 public function rollbackMasterChanges( $fname = __METHOD__
);
218 * Check if an explicit transaction round is active
222 public function hasTransactionRound();
225 * Check if transaction rounds can be started, committed, or rolled back right now
227 * This can be used as a recusion guard to avoid exceptions in transaction callbacks
232 public function isReadyForRoundOperations();
235 * Determine if any master connection has pending changes
238 public function hasMasterChanges();
241 * Detemine if any lagged replica DB connection was used
244 public function laggedReplicaUsed();
247 * Determine if any master connection has pending/written changes from this request
248 * @param float|null $age How many seconds ago is "recent" [defaults to LB lag wait timeout]
251 public function hasOrMadeRecentMasterChanges( $age = null );
254 * Waits for the replica DBs to catch up to the current master position
256 * Use this when updating very large numbers of rows, as in maintenance scripts,
257 * to avoid causing too much lag. Of course, this is a no-op if there are no replica DBs.
259 * By default this waits on all DB clusters actually used in this request.
260 * This makes sense when lag being waiting on is caused by the code that does this check.
261 * In that case, setting "ifWritesSince" can avoid the overhead of waiting for clusters
262 * that were not changed since the last wait check. To forcefully wait on a specific cluster
263 * for a given domain, use the 'domain' parameter. To forcefully wait on an "external" cluster,
264 * use the "cluster" parameter.
266 * Never call this function after a large DB write that is *still* in a transaction.
267 * It only makes sense to call this after the possible lag inducing changes were committed.
269 * @param array $opts Optional fields that include:
270 * - domain : wait on the load balancer DBs that handles the given domain ID
271 * - cluster : wait on the given external load balancer DBs
272 * - timeout : Max wait time. Default: ~60 seconds
273 * - ifWritesSince: Only wait if writes were done since this UNIX timestamp
274 * @throws DBReplicationWaitError If a timeout or error occurred waiting on a DB cluster
276 public function waitForReplication( array $opts = [] );
279 * Add a callback to be run in every call to waitForReplication() before waiting
281 * Callbacks must clear any transactions that they start
283 * @param string $name Callback name
284 * @param callable|null $callback Use null to unset a callback
286 public function setWaitForReplicationListener( $name, callable
$callback = null );
289 * Get a token asserting that no transaction writes are active
291 * @param string $fname Caller name (e.g. __METHOD__)
292 * @return mixed A value to pass to commitAndWaitForReplication()
294 public function getEmptyTransactionTicket( $fname );
297 * Convenience method for safely running commitMasterChanges()/waitForReplication()
299 * This will commit and wait unless $ticket indicates it is unsafe to do so
301 * @param string $fname Caller name (e.g. __METHOD__)
302 * @param mixed $ticket Result of getEmptyTransactionTicket()
303 * @param array $opts Options to waitForReplication()
304 * @throws DBReplicationWaitError
306 public function commitAndWaitForReplication( $fname, $ticket, array $opts = [] );
309 * @param string $dbName DB master name (e.g. "db1052")
310 * @return float|bool UNIX timestamp when client last touched the DB or false if not recent
312 public function getChronologyProtectorTouched( $dbName );
315 * Disable the ChronologyProtector for all load balancers
317 * This can be called at the start of special API entry points
319 public function disableChronologyProtection();
322 * Set a new table prefix for the existing local domain ID for testing
324 * @param string $prefix
326 public function setDomainPrefix( $prefix );
329 * Close all open database connections on all open load balancers.
331 public function closeAll();
334 * @param string $agent Agent name for query profiling
336 public function setAgentName( $agent );
339 * Append ?cpPosIndex parameter to a URL for ChronologyProtector purposes if needed
341 * Note that unlike cookies, this works accross domains
344 * @param int $index Write counter index
347 public function appendShutdownCPIndexAsQuery( $url, $index );
350 * @param array $info Map of fields, including:
351 * - IPAddress : IP address
352 * - UserAgent : User-Agent HTTP header
353 * - ChronologyProtection : cookie/header value specifying ChronologyProtector usage
354 * - ChronologyPositionIndex: timestamp used to get up-to-date DB positions for the agent
356 public function setRequestInfo( array $info );
359 * Make certain table names use their own database, schema, and table prefix
360 * when passed into SQL queries pre-escaped and without a qualified database name
362 * For example, "user" can be converted to "myschema.mydbname.user" for convenience.
363 * Appearances like `user`, somedb.user, somedb.someschema.user will used literally.
365 * Calling this twice will completely clear any old table aliases. Also, note that
366 * callers are responsible for making sure the schemas and databases actually exist.
368 * @param array[] $aliases Map of (table => (dbname, schema, prefix) map)
371 public function setTableAliases( array $aliases );
374 * Convert certain index names to alternative names before querying the DB
376 * Note that this applies to indexes regardless of the table they belong to.
378 * This can be employed when an index was renamed X => Y in code, but the new Y-named
379 * indexes were not yet built on all DBs. After all the Y-named ones are added by the DBA,
380 * the aliases can be removed, and then the old X-named indexes dropped.
382 * @param string[] $aliases
386 public function setIndexAliases( array $aliases );