3 * Generator and manager of database load balancing objects
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6 * it under the terms of the GNU General Public License as published by
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.
15 * You should have received a copy of the GNU General Public License along
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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;
41 /** @var string Default main LB cluster name (do not change this) */
42 const CLUSTER_MAIN_DEFAULT
= 'DEFAULT';
45 * Construct a manager of ILoadBalancer objects
47 * Sub-classes will extend the required keys in $conf with additional parameters
49 * @param array $conf Array with keys:
50 * - localDomain: A DatabaseDomain or domain ID string.
51 * - readOnlyReason: Reason the master DB is read-only if so [optional]
52 * - srvCache: BagOStuff object for server cache [optional]
53 * - memStash: BagOStuff object for cross-datacenter memory storage [optional]
54 * - wanCache: WANObjectCache object [optional]
55 * - hostname: The name of the current server [optional]
56 * - cliMode: Whether the execution context is a CLI script. [optional]
57 * - maxLag: Try to avoid DB replicas with lag above this many seconds [optional]
58 * - profiler: Class name or instance with profileIn()/profileOut() methods. [optional]
59 * - trxProfiler: TransactionProfiler instance. [optional]
60 * - replLogger: PSR-3 logger instance. [optional]
61 * - connLogger: PSR-3 logger instance. [optional]
62 * - queryLogger: PSR-3 logger instance. [optional]
63 * - perfLogger: PSR-3 logger instance. [optional]
64 * - errorLogger: Callback that takes an Exception and logs it. [optional]
65 * - deprecationLogger: Callback to log a deprecation warning. [optional]
66 * - secret: Secret string to use for HMAC hashing [optional]
67 * @throws InvalidArgumentException
69 public function __construct( array $conf );
72 * Disables all load balancers. All connections are closed, and any attempt to
73 * open a new connection will result in a DBAccessError.
74 * @see ILoadBalancer::disable()
76 public function destroy();
79 * Get the local (and default) database domain ID of connection handles
82 * @return string Database domain ID; this specifies DB name, schema, and table prefix
85 public function getLocalDomainID();
88 * @param DatabaseDomain|string|bool $domain Database domain
89 * @return string Value of $domain if provided or the local domain otherwise
92 public function resolveDomainID( $domain );
95 * Close all connection and redefine the local domain for testing or schema creation
97 * @param DatabaseDomain|string $domain
100 public function redefineLocalDomain( $domain );
103 * Create a new load balancer object. The resulting object will be untracked,
104 * not chronology-protected, and the caller is responsible for cleaning it up.
106 * This method is for only advanced usage and callers should almost always use
107 * getMainLB() instead. This method can be useful when a table is used as a key/value
108 * store. In that cases, one might want to query it in autocommit mode (DBO_TRX off)
109 * but still use DBO_TRX transaction rounds on other tables.
111 * @param bool|string $domain Domain ID, or false for the current domain
112 * @return ILoadBalancer
114 public function newMainLB( $domain = false );
117 * Get a cached (tracked) load balancer object.
119 * @param bool|string $domain Domain ID, or false for the current domain
120 * @return ILoadBalancer
122 public function getMainLB( $domain = false );
125 * Create a new load balancer for external storage. The resulting object will be
126 * untracked, not chronology-protected, and the caller is responsible for cleaning it up.
128 * This method is for only advanced usage and callers should almost always use
129 * getExternalLB() instead. This method can be useful when a table is used as a
130 * key/value store. In that cases, one might want to query it in autocommit mode
131 * (DBO_TRX off) but still use DBO_TRX transaction rounds on other tables.
133 * @param string $cluster External storage cluster name
134 * @return ILoadBalancer
136 public function newExternalLB( $cluster );
139 * Get a cached (tracked) load balancer for external storage
141 * @param string $cluster External storage cluster name
142 * @return ILoadBalancer
144 public function getExternalLB( $cluster );
147 * Get cached (tracked) load balancers for all main database clusters
149 * The default cluster name is ILoadBalancer::CLUSTER_MAIN_DEFAULT
151 * @return ILoadBalancer[] Map of (cluster name => ILoadBalancer)
154 public function getAllMainLBs();
157 * Get cached (tracked) load balancers for all external database clusters
159 * @return ILoadBalancer[] Map of (cluster name => ILoadBalancer)
162 public function getAllExternalLBs();
165 * Execute a function for each currently tracked (instantiated) load balancer
167 * The callback is called with the load balancer as the first parameter,
168 * and $params passed as the subsequent parameters.
170 * @param callable $callback
171 * @param array $params
173 public function forEachLB( $callback, array $params = [] );
176 * Prepare all currently tracked (instantiated) load balancers for shutdown
178 * @param int $mode One of the class SHUTDOWN_* constants
179 * @param callable|null $workCallback Work to mask ChronologyProtector writes
180 * @param int|null &$cpIndex Position key write counter for ChronologyProtector
181 * @param string|null &$cpClientId Client ID hash for ChronologyProtector
183 public function shutdown(
184 $mode = self
::SHUTDOWN_CHRONPROT_SYNC
,
185 callable
$workCallback = null,
191 * Commit all replica DB transactions so as to flush any REPEATABLE-READ or SSI snapshot
193 * This is useful for getting rid of stale data from an implicit transaction round
195 * @param string $fname Caller name
197 public function flushReplicaSnapshots( $fname = __METHOD__
);
200 * Commit open transactions on all connections. This is useful for two main cases:
201 * - a) To commit changes to the masters.
202 * - b) To release the snapshot on all connections, master and replica DBs.
203 * @param string $fname Caller name
204 * @param array $options Options map:
205 * - maxWriteDuration: abort if more than this much time was spent in write queries
207 public function commitAll( $fname = __METHOD__
, array $options = [] );
210 * Flush any master transaction snapshots and set DBO_TRX (if DBO_DEFAULT is set)
212 * The DBO_TRX setting will be reverted to the default in each of these methods:
213 * - commitMasterChanges()
214 * - rollbackMasterChanges()
217 * This allows for custom transaction rounds from any outer transaction scope.
219 * @param string $fname
220 * @throws DBTransactionError
222 public function beginMasterChanges( $fname = __METHOD__
);
225 * Commit changes and clear view snapshots on all master connections
226 * @param string $fname Caller name
227 * @param array $options Options map:
228 * - maxWriteDuration: abort if more than this much time was spent in write queries
229 * @throws DBTransactionError
231 public function commitMasterChanges( $fname = __METHOD__
, array $options = [] );
234 * Rollback changes on all master connections
235 * @param string $fname Caller name
237 public function rollbackMasterChanges( $fname = __METHOD__
);
240 * Check if an explicit transaction round is active
244 public function hasTransactionRound();
247 * Check if transaction rounds can be started, committed, or rolled back right now
249 * This can be used as a recusion guard to avoid exceptions in transaction callbacks
254 public function isReadyForRoundOperations();
257 * Determine if any master connection has pending changes
260 public function hasMasterChanges();
263 * Detemine if any lagged replica DB connection was used
266 public function laggedReplicaUsed();
269 * Determine if any master connection has pending/written changes from this request
270 * @param float|null $age How many seconds ago is "recent" [defaults to LB lag wait timeout]
273 public function hasOrMadeRecentMasterChanges( $age = null );
276 * Waits for the replica DBs to catch up to the current master position
278 * Use this when updating very large numbers of rows, as in maintenance scripts,
279 * to avoid causing too much lag. Of course, this is a no-op if there are no replica DBs.
281 * By default this waits on all DB clusters actually used in this request.
282 * This makes sense when lag being waiting on is caused by the code that does this check.
283 * In that case, setting "ifWritesSince" can avoid the overhead of waiting for clusters
284 * that were not changed since the last wait check. To forcefully wait on a specific cluster
285 * for a given domain, use the 'domain' parameter. To forcefully wait on an "external" cluster,
286 * use the "cluster" parameter.
288 * Never call this function after a large DB write that is *still* in a transaction.
289 * It only makes sense to call this after the possible lag inducing changes were committed.
291 * @param array $opts Optional fields that include:
292 * - domain : wait on the load balancer DBs that handles the given domain ID
293 * - cluster : wait on the given external load balancer DBs
294 * - timeout : Max wait time. Default: 60 seconds for CLI, 1 second for web.
295 * - ifWritesSince: Only wait if writes were done since this UNIX timestamp
296 * @return bool True on success, false if a timeout or error occurred while waiting
298 public function waitForReplication( array $opts = [] );
301 * Add a callback to be run in every call to waitForReplication() before waiting
303 * Callbacks must clear any transactions that they start
305 * @param string $name Callback name
306 * @param callable|null $callback Use null to unset a callback
308 public function setWaitForReplicationListener( $name, callable
$callback = null );
311 * Get a token asserting that no transaction writes are active
313 * @param string $fname Caller name (e.g. __METHOD__)
314 * @return mixed A value to pass to commitAndWaitForReplication()
316 public function getEmptyTransactionTicket( $fname );
319 * Convenience method for safely running commitMasterChanges()/waitForReplication()
321 * This will commit and wait unless $ticket indicates it is unsafe to do so
323 * @param string $fname Caller name (e.g. __METHOD__)
324 * @param mixed $ticket Result of getEmptyTransactionTicket()
325 * @param array $opts Options to waitForReplication()
326 * @return bool True if the wait was successful, false on timeout
328 public function commitAndWaitForReplication( $fname, $ticket, array $opts = [] );
331 * @param string $dbName DB master name (e.g. "db1052")
332 * @return float|bool UNIX timestamp when client last touched the DB or false if not recent
334 public function getChronologyProtectorTouched( $dbName );
337 * Disable the ChronologyProtector for all load balancers
339 * This can be called at the start of special API entry points
341 public function disableChronologyProtection();
344 * Set a new table prefix for the existing local domain ID for testing
346 * @param string $prefix
349 public function setLocalDomainPrefix( $prefix );
352 * Close all open database connections on all open load balancers.
354 public function closeAll();
357 * @param string $agent Agent name for query profiling
359 public function setAgentName( $agent );
362 * Append ?cpPosIndex parameter to a URL for ChronologyProtector purposes if needed
364 * Note that unlike cookies, this works across domains
367 * @param int $index Write counter index
370 public function appendShutdownCPIndexAsQuery( $url, $index );
373 * Get the client ID of the ChronologyProtector instance
375 * @return string Client ID
378 public function getChronologyProtectorClientId();
381 * @param array $info Map of fields, including:
382 * - IPAddress : IP address
383 * - UserAgent : User-Agent HTTP header
384 * - ChronologyProtection : cookie/header value specifying ChronologyProtector usage
385 * - ChronologyPositionIndex: timestamp used to get up-to-date DB positions for the agent
387 public function setRequestInfo( array $info );
390 * Make certain table names use their own database, schema, and table prefix
391 * when passed into SQL queries pre-escaped and without a qualified database name
393 * For example, "user" can be converted to "myschema.mydbname.user" for convenience.
394 * Appearances like `user`, somedb.user, somedb.someschema.user will used literally.
396 * Calling this twice will completely clear any old table aliases. Also, note that
397 * callers are responsible for making sure the schemas and databases actually exist.
399 * @param array[] $aliases Map of (table => (dbname, schema, prefix) map)
402 public function setTableAliases( array $aliases );
405 * Convert certain index names to alternative names before querying the DB
407 * Note that this applies to indexes regardless of the table they belong to.
409 * This can be employed when an index was renamed X => Y in code, but the new Y-named
410 * indexes were not yet built on all DBs. After all the Y-named ones are added by the DBA,
411 * the aliases can be removed, and then the old X-named indexes dropped.
413 * @param string[] $aliases
416 public function setIndexAliases( array $aliases );