3 * Generator and manager of database load balancing objects
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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 * - maxLag: Try to avoid DB replicas with lag above this many seconds [optional]
52 * - profiler: Class name or instance with profileIn()/profileOut() methods. [optional]
53 * - trxProfiler: TransactionProfiler instance. [optional]
54 * - replLogger: PSR-3 logger instance. [optional]
55 * - connLogger: PSR-3 logger instance. [optional]
56 * - queryLogger: PSR-3 logger instance. [optional]
57 * - perfLogger: PSR-3 logger instance. [optional]
58 * - errorLogger: Callback that takes an Exception and logs it. [optional]
59 * - deprecationLogger: Callback to log a deprecation warning. [optional]
60 * - secret: Secret string to use for HMAC hashing [optional]
61 * @throws InvalidArgumentException
63 public function __construct( array $conf );
66 * Disables all load balancers. All connections are closed, and any attempt to
67 * open a new connection will result in a DBAccessError.
68 * @see ILoadBalancer::disable()
70 public function destroy();
73 * Get the local (and default) database domain ID of connection handles
76 * @return string Database domain ID; this specifies DB name, schema, and table prefix
79 public function getLocalDomainID();
82 * @param DatabaseDomain|string|bool $domain Database domain
83 * @return string Value of $domain if provided or the local domain otherwise
86 public function resolveDomainID( $domain );
89 * Close all connection and redefine the local domain for testing or schema creation
91 * @param DatabaseDomain|string $domain
94 public function redefineLocalDomain( $domain );
97 * Create a new load balancer object. The resulting object will be untracked,
98 * not chronology-protected, and the caller is responsible for cleaning it up.
100 * This method is for only advanced usage and callers should almost always use
101 * getMainLB() instead. This method can be useful when a table is used as a key/value
102 * store. In that cases, one might want to query it in autocommit mode (DBO_TRX off)
103 * but still use DBO_TRX transaction rounds on other tables.
105 * @param bool|string $domain Domain ID, or false for the current domain
106 * @return ILoadBalancer
108 public function newMainLB( $domain = false );
111 * Get a cached (tracked) load balancer object.
113 * @param bool|string $domain Domain ID, or false for the current domain
114 * @return ILoadBalancer
116 public function getMainLB( $domain = false );
119 * Create a new load balancer for external storage. The resulting object will be
120 * untracked, not chronology-protected, and the caller is responsible for cleaning it up.
122 * This method is for only advanced usage and callers should almost always use
123 * getExternalLB() instead. This method can be useful when a table is used as a
124 * key/value store. In that cases, one might want to query it in autocommit mode
125 * (DBO_TRX off) but still use DBO_TRX transaction rounds on other tables.
127 * @param string $cluster External storage cluster name
128 * @return ILoadBalancer
130 public function newExternalLB( $cluster );
133 * Get a cached (tracked) load balancer for external storage
135 * @param string $cluster External storage cluster name
136 * @return ILoadBalancer
138 public function getExternalLB( $cluster );
141 * Get cached (tracked) load balancers for all main database clusters
143 * @return LoadBalancer[] Map of (cluster name => LoadBalancer)
146 public function getAllMainLBs();
149 * Get cached (tracked) load balancers for all external database clusters
151 * @return LoadBalancer[] Map of (cluster name => LoadBalancer)
154 public function getAllExternalLBs();
157 * Execute a function for each tracked load balancer
158 * The callback is called with the load balancer as the first parameter,
159 * and $params passed as the subsequent parameters.
161 * @param callable $callback
162 * @param array $params
164 public function forEachLB( $callback, array $params = [] );
167 * Prepare all tracked load balancers for shutdown
168 * @param int $mode One of the class SHUTDOWN_* constants
169 * @param callable|null $workCallback Work to mask ChronologyProtector writes
170 * @param int|null &$cpIndex Position key write counter for ChronologyProtector
171 * @param string|null &$cpClientId Client ID hash for ChronologyProtector
173 public function shutdown(
174 $mode = self
::SHUTDOWN_CHRONPROT_SYNC
,
175 callable
$workCallback = null,
181 * Commit all replica DB transactions so as to flush any REPEATABLE-READ or SSI snapshot
183 * @param string $fname Caller name
185 public function flushReplicaSnapshots( $fname = __METHOD__
);
188 * Commit open transactions on all connections. This is useful for two main cases:
189 * - a) To commit changes to the masters.
190 * - b) To release the snapshot on all connections, master and replica DBs.
191 * @param string $fname Caller name
192 * @param array $options Options map:
193 * - maxWriteDuration: abort if more than this much time was spent in write queries
195 public function commitAll( $fname = __METHOD__
, array $options = [] );
198 * Flush any master transaction snapshots and set DBO_TRX (if DBO_DEFAULT is set)
200 * The DBO_TRX setting will be reverted to the default in each of these methods:
201 * - commitMasterChanges()
202 * - rollbackMasterChanges()
205 * This allows for custom transaction rounds from any outer transaction scope.
207 * @param string $fname
208 * @throws DBTransactionError
210 public function beginMasterChanges( $fname = __METHOD__
);
213 * Commit changes and clear view snapshots on all master connections
214 * @param string $fname Caller name
215 * @param array $options Options map:
216 * - maxWriteDuration: abort if more than this much time was spent in write queries
217 * @throws DBTransactionError
219 public function commitMasterChanges( $fname = __METHOD__
, array $options = [] );
222 * Rollback changes on all master connections
223 * @param string $fname Caller name
225 public function rollbackMasterChanges( $fname = __METHOD__
);
228 * Check if an explicit transaction round is active
232 public function hasTransactionRound();
235 * Check if transaction rounds can be started, committed, or rolled back right now
237 * This can be used as a recusion guard to avoid exceptions in transaction callbacks
242 public function isReadyForRoundOperations();
245 * Determine if any master connection has pending changes
248 public function hasMasterChanges();
251 * Detemine if any lagged replica DB connection was used
254 public function laggedReplicaUsed();
257 * Determine if any master connection has pending/written changes from this request
258 * @param float|null $age How many seconds ago is "recent" [defaults to LB lag wait timeout]
261 public function hasOrMadeRecentMasterChanges( $age = null );
264 * Waits for the replica DBs to catch up to the current master position
266 * Use this when updating very large numbers of rows, as in maintenance scripts,
267 * to avoid causing too much lag. Of course, this is a no-op if there are no replica DBs.
269 * By default this waits on all DB clusters actually used in this request.
270 * This makes sense when lag being waiting on is caused by the code that does this check.
271 * In that case, setting "ifWritesSince" can avoid the overhead of waiting for clusters
272 * that were not changed since the last wait check. To forcefully wait on a specific cluster
273 * for a given domain, use the 'domain' parameter. To forcefully wait on an "external" cluster,
274 * use the "cluster" parameter.
276 * Never call this function after a large DB write that is *still* in a transaction.
277 * It only makes sense to call this after the possible lag inducing changes were committed.
279 * @param array $opts Optional fields that include:
280 * - domain : wait on the load balancer DBs that handles the given domain ID
281 * - cluster : wait on the given external load balancer DBs
282 * - timeout : Max wait time. Default: 60 seconds for CLI, 1 second for web.
283 * - ifWritesSince: Only wait if writes were done since this UNIX timestamp
284 * @return bool True on success, false if a timeout or error occurred while waiting
286 public function waitForReplication( array $opts = [] );
289 * Add a callback to be run in every call to waitForReplication() before waiting
291 * Callbacks must clear any transactions that they start
293 * @param string $name Callback name
294 * @param callable|null $callback Use null to unset a callback
296 public function setWaitForReplicationListener( $name, callable
$callback = null );
299 * Get a token asserting that no transaction writes are active
301 * @param string $fname Caller name (e.g. __METHOD__)
302 * @return mixed A value to pass to commitAndWaitForReplication()
304 public function getEmptyTransactionTicket( $fname );
307 * Convenience method for safely running commitMasterChanges()/waitForReplication()
309 * This will commit and wait unless $ticket indicates it is unsafe to do so
311 * @param string $fname Caller name (e.g. __METHOD__)
312 * @param mixed $ticket Result of getEmptyTransactionTicket()
313 * @param array $opts Options to waitForReplication()
314 * @return bool True if the wait was successful, false on timeout
316 public function commitAndWaitForReplication( $fname, $ticket, array $opts = [] );
319 * @param string $dbName DB master name (e.g. "db1052")
320 * @return float|bool UNIX timestamp when client last touched the DB or false if not recent
322 public function getChronologyProtectorTouched( $dbName );
325 * Disable the ChronologyProtector for all load balancers
327 * This can be called at the start of special API entry points
329 public function disableChronologyProtection();
332 * Set a new table prefix for the existing local domain ID for testing
334 * @param string $prefix
337 public function setLocalDomainPrefix( $prefix );
340 * Close all open database connections on all open load balancers.
342 public function closeAll();
345 * @param string $agent Agent name for query profiling
347 public function setAgentName( $agent );
350 * Append ?cpPosIndex parameter to a URL for ChronologyProtector purposes if needed
352 * Note that unlike cookies, this works across domains
355 * @param int $index Write counter index
358 public function appendShutdownCPIndexAsQuery( $url, $index );
361 * Get the client ID of the ChronologyProtector instance
363 * @return string Client ID
366 public function getChronologyProtectorClientId();
369 * @param array $info Map of fields, including:
370 * - IPAddress : IP address
371 * - UserAgent : User-Agent HTTP header
372 * - ChronologyProtection : cookie/header value specifying ChronologyProtector usage
373 * - ChronologyPositionIndex: timestamp used to get up-to-date DB positions for the agent
375 public function setRequestInfo( array $info );
378 * Make certain table names use their own database, schema, and table prefix
379 * when passed into SQL queries pre-escaped and without a qualified database name
381 * For example, "user" can be converted to "myschema.mydbname.user" for convenience.
382 * Appearances like `user`, somedb.user, somedb.someschema.user will used literally.
384 * Calling this twice will completely clear any old table aliases. Also, note that
385 * callers are responsible for making sure the schemas and databases actually exist.
387 * @param array[] $aliases Map of (table => (dbname, schema, prefix) map)
390 public function setTableAliases( array $aliases );
393 * Convert certain index names to alternative names before querying the DB
395 * Note that this applies to indexes regardless of the table they belong to.
397 * This can be employed when an index was renamed X => Y in code, but the new Y-named
398 * indexes were not yet built on all DBs. After all the Y-named ones are added by the DBA,
399 * the aliases can be removed, and then the old X-named indexes dropped.
401 * @param string[] $aliases
404 public function setIndexAliases( array $aliases );