3 * Generator and manager of database load balancing objects
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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 $conf $params 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 * - memCache : BagOStuff object for cluster memory cache [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 * @throws InvalidArgumentException
60 public function __construct( array $conf );
63 * Disables all load balancers. All connections are closed, and any attempt to
64 * open a new connection will result in a DBAccessError.
65 * @see ILoadBalancer::disable()
67 public function destroy();
70 * Create a new load balancer object. The resulting object will be untracked,
71 * not chronology-protected, and the caller is responsible for cleaning it up.
73 * This method is for only advanced usage and callers should almost always use
74 * getMainLB() instead. This method can be useful when a table is used as a key/value
75 * store. In that cases, one might want to query it in autocommit mode (DBO_TRX off)
76 * but still use DBO_TRX transaction rounds on other tables.
78 * @param bool|string $domain Domain ID, or false for the current domain
79 * @return ILoadBalancer
81 public function newMainLB( $domain = false );
84 * Get a cached (tracked) load balancer object.
86 * @param bool|string $domain Domain ID, or false for the current domain
87 * @return ILoadBalancer
89 public function getMainLB( $domain = false );
92 * Create a new load balancer for external storage. The resulting object will be
93 * untracked, not chronology-protected, and the caller is responsible for cleaning it up.
95 * This method is for only advanced usage and callers should almost always use
96 * getExternalLB() instead. This method can be useful when a table is used as a
97 * key/value store. In that cases, one might want to query it in autocommit mode
98 * (DBO_TRX off) but still use DBO_TRX transaction rounds on other tables.
100 * @param string $cluster External storage cluster name
101 * @return ILoadBalancer
103 public function newExternalLB( $cluster );
106 * Get a cached (tracked) load balancer for external storage
108 * @param string $cluster External storage cluster name
109 * @return ILoadBalancer
111 public function getExternalLB( $cluster );
114 * Get cached (tracked) load balancers for all main database clusters
116 * @return LoadBalancer[] Map of (cluster name => LoadBalancer)
119 public function getAllMainLBs();
122 * Get cached (tracked) load balancers for all external database clusters
124 * @return LoadBalancer[] Map of (cluster name => LoadBalancer)
127 public function getAllExternalLBs();
130 * Execute a function for each tracked load balancer
131 * The callback is called with the load balancer as the first parameter,
132 * and $params passed as the subsequent parameters.
134 * @param callable $callback
135 * @param array $params
137 public function forEachLB( $callback, array $params = [] );
140 * Prepare all tracked load balancers for shutdown
141 * @param integer $mode One of the class SHUTDOWN_* constants
142 * @param callable|null $workCallback Work to mask ChronologyProtector writes
144 public function shutdown(
145 $mode = self
::SHUTDOWN_CHRONPROT_SYNC
, callable
$workCallback = null
149 * Commit all replica DB transactions so as to flush any REPEATABLE-READ or SSI snapshot
151 * @param string $fname Caller name
153 public function flushReplicaSnapshots( $fname = __METHOD__
);
156 * Commit open transactions on all connections. This is useful for two main cases:
157 * - a) To commit changes to the masters.
158 * - b) To release the snapshot on all connections, master and replica DBs.
159 * @param string $fname Caller name
160 * @param array $options Options map:
161 * - maxWriteDuration: abort if more than this much time was spent in write queries
163 public function commitAll( $fname = __METHOD__
, array $options = [] );
166 * Flush any master transaction snapshots and set DBO_TRX (if DBO_DEFAULT is set)
168 * The DBO_TRX setting will be reverted to the default in each of these methods:
169 * - commitMasterChanges()
170 * - rollbackMasterChanges()
173 * This allows for custom transaction rounds from any outer transaction scope.
175 * @param string $fname
176 * @throws DBTransactionError
178 public function beginMasterChanges( $fname = __METHOD__
);
181 * Commit changes on all master connections
182 * @param string $fname Caller name
183 * @param array $options Options map:
184 * - maxWriteDuration: abort if more than this much time was spent in write queries
185 * @throws DBTransactionError
187 public function commitMasterChanges( $fname = __METHOD__
, array $options = [] );
190 * Rollback changes on all master connections
191 * @param string $fname Caller name
193 public function rollbackMasterChanges( $fname = __METHOD__
);
196 * Determine if any master connection has pending changes
199 public function hasMasterChanges();
202 * Detemine if any lagged replica DB connection was used
205 public function laggedReplicaUsed();
208 * Determine if any master connection has pending/written changes from this request
209 * @param float $age How many seconds ago is "recent" [defaults to LB lag wait timeout]
212 public function hasOrMadeRecentMasterChanges( $age = null );
215 * Waits for the replica DBs to catch up to the current master position
217 * Use this when updating very large numbers of rows, as in maintenance scripts,
218 * to avoid causing too much lag. Of course, this is a no-op if there are no replica DBs.
220 * By default this waits on all DB clusters actually used in this request.
221 * This makes sense when lag being waiting on is caused by the code that does this check.
222 * In that case, setting "ifWritesSince" can avoid the overhead of waiting for clusters
223 * that were not changed since the last wait check. To forcefully wait on a specific cluster
224 * for a given domain, use the 'domain' parameter. To forcefully wait on an "external" cluster,
225 * use the "cluster" parameter.
227 * Never call this function after a large DB write that is *still* in a transaction.
228 * It only makes sense to call this after the possible lag inducing changes were committed.
230 * @param array $opts Optional fields that include:
231 * - domain : wait on the load balancer DBs that handles the given domain ID
232 * - cluster : wait on the given external load balancer DBs
233 * - timeout : Max wait time. Default: ~60 seconds
234 * - ifWritesSince: Only wait if writes were done since this UNIX timestamp
235 * @throws DBReplicationWaitError If a timeout or error occured waiting on a DB cluster
237 public function waitForReplication( array $opts = [] );
240 * Add a callback to be run in every call to waitForReplication() before waiting
242 * Callbacks must clear any transactions that they start
244 * @param string $name Callback name
245 * @param callable|null $callback Use null to unset a callback
247 public function setWaitForReplicationListener( $name, callable
$callback = null );
250 * Get a token asserting that no transaction writes are active
252 * @param string $fname Caller name (e.g. __METHOD__)
253 * @return mixed A value to pass to commitAndWaitForReplication()
255 public function getEmptyTransactionTicket( $fname );
258 * Convenience method for safely running commitMasterChanges()/waitForReplication()
260 * This will commit and wait unless $ticket indicates it is unsafe to do so
262 * @param string $fname Caller name (e.g. __METHOD__)
263 * @param mixed $ticket Result of getEmptyTransactionTicket()
264 * @param array $opts Options to waitForReplication()
265 * @throws DBReplicationWaitError
267 public function commitAndWaitForReplication( $fname, $ticket, array $opts = [] );
270 * @param string $dbName DB master name (e.g. "db1052")
271 * @return float|bool UNIX timestamp when client last touched the DB or false if not recent
273 public function getChronologyProtectorTouched( $dbName );
276 * Disable the ChronologyProtector for all load balancers
278 * This can be called at the start of special API entry points
280 public function disableChronologyProtection();
283 * Set a new table prefix for the existing local domain ID for testing
285 * @param string $prefix
287 public function setDomainPrefix( $prefix );
290 * Close all open database connections on all open load balancers.
292 public function closeAll();
295 * @param string $agent Agent name for query profiling
297 public function setAgentName( $agent );
300 * Append ?cpPosTime parameter to a URL for ChronologyProtector purposes if needed
302 * Note that unlike cookies, this works accross domains
305 * @param float $time UNIX timestamp just before shutdown() was called
308 public function appendPreShutdownTimeAsQuery( $url, $time );
311 * @param array $info Map of fields, including:
312 * - IPAddress : IP address
313 * - UserAgent : User-Agent HTTP header
314 * - ChronologyProtection : cookie/header value specifying ChronologyProtector usage
316 public function setRequestInfo( array $info );