3 * Generator and manager of database load balancing objects
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25 * An interface for generating database load balancers
29 interface ILBFactory
{
30 const SHUTDOWN_NO_CHRONPROT
= 0; // don't save DB positions at all
31 const SHUTDOWN_CHRONPROT_ASYNC
= 1; // save DB positions, but don't wait on remote DCs
32 const SHUTDOWN_CHRONPROT_SYNC
= 2; // save DB positions, waiting on all DCs
35 * Construct a manager of ILoadBalancer objects
37 * Sub-classes will extend the required keys in $conf with additional parameters
39 * @param $conf $params Array with keys:
40 * - localDomain: A DatabaseDomain or domain ID string.
41 * - readOnlyReason : Reason the master DB is read-only if so [optional]
42 * - srvCache : BagOStuff object for server cache [optional]
43 * - memCache : BagOStuff object for cluster memory cache [optional]
44 * - wanCache : WANObjectCache object [optional]
45 * - hostname : The name of the current server [optional]
46 * - cliMode: Whether the execution context is a CLI script. [optional]
47 * - profiler : Class name or instance with profileIn()/profileOut() methods. [optional]
48 * - trxProfiler: TransactionProfiler instance. [optional]
49 * - replLogger: PSR-3 logger instance. [optional]
50 * - connLogger: PSR-3 logger instance. [optional]
51 * - queryLogger: PSR-3 logger instance. [optional]
52 * - perfLogger: PSR-3 logger instance. [optional]
53 * - errorLogger : Callback that takes an Exception and logs it. [optional]
54 * @throws InvalidArgumentException
56 public function __construct( array $conf );
59 * Disables all load balancers. All connections are closed, and any attempt to
60 * open a new connection will result in a DBAccessError.
61 * @see ILoadBalancer::disable()
63 public function destroy();
66 * Create a new load balancer object. The resulting object will be untracked,
67 * not chronology-protected, and the caller is responsible for cleaning it up.
69 * This method is for only advanced usage and callers should almost always use
70 * getMainLB() instead. This method can be useful when a table is used as a key/value
71 * store. In that cases, one might want to query it in autocommit mode (DBO_TRX off)
72 * but still use DBO_TRX transaction rounds on other tables.
74 * @param bool|string $domain Domain ID, or false for the current domain
75 * @return ILoadBalancer
77 public function newMainLB( $domain = false );
80 * Get a cached (tracked) load balancer object.
82 * @param bool|string $domain Domain ID, or false for the current domain
83 * @return ILoadBalancer
85 public function getMainLB( $domain = false );
88 * Create a new load balancer for external storage. The resulting object will be
89 * untracked, not chronology-protected, and the caller is responsible for cleaning it up.
91 * This method is for only advanced usage and callers should almost always use
92 * getExternalLB() instead. This method can be useful when a table is used as a
93 * key/value store. In that cases, one might want to query it in autocommit mode
94 * (DBO_TRX off) but still use DBO_TRX transaction rounds on other tables.
96 * @param string $cluster External storage cluster name
97 * @return ILoadBalancer
99 public function newExternalLB( $cluster );
102 * Get a cached (tracked) load balancer for external storage
104 * @param string $cluster External storage cluster name
105 * @return ILoadBalancer
107 public function getExternalLB( $cluster );
110 * Execute a function for each tracked load balancer
111 * The callback is called with the load balancer as the first parameter,
112 * and $params passed as the subsequent parameters.
114 * @param callable $callback
115 * @param array $params
117 public function forEachLB( $callback, array $params = [] );
120 * Prepare all tracked load balancers for shutdown
121 * @param integer $mode One of the class SHUTDOWN_* constants
122 * @param callable|null $workCallback Work to mask ChronologyProtector writes
124 public function shutdown(
125 $mode = self
::SHUTDOWN_CHRONPROT_SYNC
, callable
$workCallback = null
129 * Commit all replica DB transactions so as to flush any REPEATABLE-READ or SSI snapshot
131 * @param string $fname Caller name
133 public function flushReplicaSnapshots( $fname = __METHOD__
);
136 * Commit open transactions on all connections. This is useful for two main cases:
137 * - a) To commit changes to the masters.
138 * - b) To release the snapshot on all connections, master and replica DBs.
139 * @param string $fname Caller name
140 * @param array $options Options map:
141 * - maxWriteDuration: abort if more than this much time was spent in write queries
143 public function commitAll( $fname = __METHOD__
, array $options = [] );
146 * Flush any master transaction snapshots and set DBO_TRX (if DBO_DEFAULT is set)
148 * The DBO_TRX setting will be reverted to the default in each of these methods:
149 * - commitMasterChanges()
150 * - rollbackMasterChanges()
153 * This allows for custom transaction rounds from any outer transaction scope.
155 * @param string $fname
156 * @throws DBTransactionError
158 public function beginMasterChanges( $fname = __METHOD__
);
161 * Commit changes on all master connections
162 * @param string $fname Caller name
163 * @param array $options Options map:
164 * - maxWriteDuration: abort if more than this much time was spent in write queries
167 public function commitMasterChanges( $fname = __METHOD__
, array $options = [] );
170 * Rollback changes on all master connections
171 * @param string $fname Caller name
173 public function rollbackMasterChanges( $fname = __METHOD__
);
176 * Determine if any master connection has pending changes
179 public function hasMasterChanges();
182 * Detemine if any lagged replica DB connection was used
185 public function laggedReplicaUsed();
188 * Determine if any master connection has pending/written changes from this request
189 * @param float $age How many seconds ago is "recent" [defaults to LB lag wait timeout]
192 public function hasOrMadeRecentMasterChanges( $age = null );
195 * Waits for the replica DBs to catch up to the current master position
197 * Use this when updating very large numbers of rows, as in maintenance scripts,
198 * to avoid causing too much lag. Of course, this is a no-op if there are no replica DBs.
200 * By default this waits on all DB clusters actually used in this request.
201 * This makes sense when lag being waiting on is caused by the code that does this check.
202 * In that case, setting "ifWritesSince" can avoid the overhead of waiting for clusters
203 * that were not changed since the last wait check. To forcefully wait on a specific cluster
204 * for a given domain, use the 'domain' parameter. To forcefully wait on an "external" cluster,
205 * use the "cluster" parameter.
207 * Never call this function after a large DB write that is *still* in a transaction.
208 * It only makes sense to call this after the possible lag inducing changes were committed.
210 * @param array $opts Optional fields that include:
211 * - domain : wait on the load balancer DBs that handles the given domain ID
212 * - cluster : wait on the given external load balancer DBs
213 * - timeout : Max wait time. Default: ~60 seconds
214 * - ifWritesSince: Only wait if writes were done since this UNIX timestamp
215 * @throws DBReplicationWaitError If a timeout or error occured waiting on a DB cluster
217 public function waitForReplication( array $opts = [] );
220 * Add a callback to be run in every call to waitForReplication() before waiting
222 * Callbacks must clear any transactions that they start
224 * @param string $name Callback name
225 * @param callable|null $callback Use null to unset a callback
227 public function setWaitForReplicationListener( $name, callable
$callback = null );
230 * Get a token asserting that no transaction writes are active
232 * @param string $fname Caller name (e.g. __METHOD__)
233 * @return mixed A value to pass to commitAndWaitForReplication()
235 public function getEmptyTransactionTicket( $fname );
238 * Convenience method for safely running commitMasterChanges()/waitForReplication()
240 * This will commit and wait unless $ticket indicates it is unsafe to do so
242 * @param string $fname Caller name (e.g. __METHOD__)
243 * @param mixed $ticket Result of getEmptyTransactionTicket()
244 * @param array $opts Options to waitForReplication()
245 * @throws DBReplicationWaitError
247 public function commitAndWaitForReplication( $fname, $ticket, array $opts = [] );
250 * @param string $dbName DB master name (e.g. "db1052")
251 * @return float|bool UNIX timestamp when client last touched the DB or false if not recent
253 public function getChronologyProtectorTouched( $dbName );
256 * Disable the ChronologyProtector for all load balancers
258 * This can be called at the start of special API entry points
260 public function disableChronologyProtection();
263 * Set a new table prefix for the existing local domain ID for testing
265 * @param string $prefix
267 public function setDomainPrefix( $prefix );
270 * Close all open database connections on all open load balancers.
272 public function closeAll();
275 * @param string $agent Agent name for query profiling
277 public function setAgentName( $agent );
280 * Append ?cpPosTime parameter to a URL for ChronologyProtector purposes if needed
282 * Note that unlike cookies, this works accross domains
285 * @param float $time UNIX timestamp just before shutdown() was called
288 public function appendPreShutdownTimeAsQuery( $url, $time );
291 * @param array $info Map of fields, including:
292 * - IPAddress : IP address
293 * - UserAgent : User-Agent HTTP header
294 * - ChronologyProtection : cookie/header value specifying ChronologyProtector usage
296 public function setRequestInfo( array $info );