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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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 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 * Create a new load balancer object. The resulting object will be untracked,
72 * not chronology-protected, and the caller is responsible for cleaning it up.
74 * This method is for only advanced usage and callers should almost always use
75 * getMainLB() instead. This method can be useful when a table is used as a key/value
76 * store. In that cases, one might want to query it in autocommit mode (DBO_TRX off)
77 * but still use DBO_TRX transaction rounds on other tables.
79 * @param bool|string $domain Domain ID, or false for the current domain
80 * @return ILoadBalancer
82 public function newMainLB( $domain = false );
85 * Get a cached (tracked) load balancer object.
87 * @param bool|string $domain Domain ID, or false for the current domain
88 * @return ILoadBalancer
90 public function getMainLB( $domain = false );
93 * Create a new load balancer for external storage. The resulting object will be
94 * untracked, not chronology-protected, and the caller is responsible for cleaning it up.
96 * This method is for only advanced usage and callers should almost always use
97 * getExternalLB() instead. This method can be useful when a table is used as a
98 * key/value store. In that cases, one might want to query it in autocommit mode
99 * (DBO_TRX off) but still use DBO_TRX transaction rounds on other tables.
101 * @param string $cluster External storage cluster name
102 * @return ILoadBalancer
104 public function newExternalLB( $cluster );
107 * Get a cached (tracked) load balancer for external storage
109 * @param string $cluster External storage cluster name
110 * @return ILoadBalancer
112 public function getExternalLB( $cluster );
115 * Get cached (tracked) load balancers for all main database clusters
117 * @return LoadBalancer[] Map of (cluster name => LoadBalancer)
120 public function getAllMainLBs();
123 * Get cached (tracked) load balancers for all external database clusters
125 * @return LoadBalancer[] Map of (cluster name => LoadBalancer)
128 public function getAllExternalLBs();
131 * Execute a function for each tracked load balancer
132 * The callback is called with the load balancer as the first parameter,
133 * and $params passed as the subsequent parameters.
135 * @param callable $callback
136 * @param array $params
138 public function forEachLB( $callback, array $params = [] );
141 * Prepare all tracked load balancers for shutdown
142 * @param int $mode One of the class SHUTDOWN_* constants
143 * @param callable|null $workCallback Work to mask ChronologyProtector writes
144 * @param int|null &$cpIndex Position key write counter for ChronologyProtector
146 public function shutdown(
147 $mode = self
::SHUTDOWN_CHRONPROT_SYNC
, callable
$workCallback = null, &$cpIndex = null
151 * Commit all replica DB transactions so as to flush any REPEATABLE-READ or SSI snapshot
153 * @param string $fname Caller name
155 public function flushReplicaSnapshots( $fname = __METHOD__
);
158 * Commit open transactions on all connections. This is useful for two main cases:
159 * - a) To commit changes to the masters.
160 * - b) To release the snapshot on all connections, master and replica DBs.
161 * @param string $fname Caller name
162 * @param array $options Options map:
163 * - maxWriteDuration: abort if more than this much time was spent in write queries
165 public function commitAll( $fname = __METHOD__
, array $options = [] );
168 * Flush any master transaction snapshots and set DBO_TRX (if DBO_DEFAULT is set)
170 * The DBO_TRX setting will be reverted to the default in each of these methods:
171 * - commitMasterChanges()
172 * - rollbackMasterChanges()
175 * This allows for custom transaction rounds from any outer transaction scope.
177 * @param string $fname
178 * @throws DBTransactionError
180 public function beginMasterChanges( $fname = __METHOD__
);
183 * Commit changes on all master connections
184 * @param string $fname Caller name
185 * @param array $options Options map:
186 * - maxWriteDuration: abort if more than this much time was spent in write queries
187 * @throws DBTransactionError
189 public function commitMasterChanges( $fname = __METHOD__
, array $options = [] );
192 * Rollback changes on all master connections
193 * @param string $fname Caller name
195 public function rollbackMasterChanges( $fname = __METHOD__
);
198 * Check if an explicit transaction round is active
202 public function hasTransactionRound();
205 * Check if transaction rounds can be started, committed, or rolled back right now
207 * This can be used as a recusion guard to avoid exceptions in transaction callbacks
212 public function isReadyForRoundOperations();
215 * Determine if any master connection has pending changes
218 public function hasMasterChanges();
221 * Detemine if any lagged replica DB connection was used
224 public function laggedReplicaUsed();
227 * Determine if any master connection has pending/written changes from this request
228 * @param float $age How many seconds ago is "recent" [defaults to LB lag wait timeout]
231 public function hasOrMadeRecentMasterChanges( $age = null );
234 * Waits for the replica DBs to catch up to the current master position
236 * Use this when updating very large numbers of rows, as in maintenance scripts,
237 * to avoid causing too much lag. Of course, this is a no-op if there are no replica DBs.
239 * By default this waits on all DB clusters actually used in this request.
240 * This makes sense when lag being waiting on is caused by the code that does this check.
241 * In that case, setting "ifWritesSince" can avoid the overhead of waiting for clusters
242 * that were not changed since the last wait check. To forcefully wait on a specific cluster
243 * for a given domain, use the 'domain' parameter. To forcefully wait on an "external" cluster,
244 * use the "cluster" parameter.
246 * Never call this function after a large DB write that is *still* in a transaction.
247 * It only makes sense to call this after the possible lag inducing changes were committed.
249 * @param array $opts Optional fields that include:
250 * - domain : wait on the load balancer DBs that handles the given domain ID
251 * - cluster : wait on the given external load balancer DBs
252 * - timeout : Max wait time. Default: ~60 seconds
253 * - ifWritesSince: Only wait if writes were done since this UNIX timestamp
254 * @throws DBReplicationWaitError If a timeout or error occurred waiting on a DB cluster
256 public function waitForReplication( array $opts = [] );
259 * Add a callback to be run in every call to waitForReplication() before waiting
261 * Callbacks must clear any transactions that they start
263 * @param string $name Callback name
264 * @param callable|null $callback Use null to unset a callback
266 public function setWaitForReplicationListener( $name, callable
$callback = null );
269 * Get a token asserting that no transaction writes are active
271 * @param string $fname Caller name (e.g. __METHOD__)
272 * @return mixed A value to pass to commitAndWaitForReplication()
274 public function getEmptyTransactionTicket( $fname );
277 * Convenience method for safely running commitMasterChanges()/waitForReplication()
279 * This will commit and wait unless $ticket indicates it is unsafe to do so
281 * @param string $fname Caller name (e.g. __METHOD__)
282 * @param mixed $ticket Result of getEmptyTransactionTicket()
283 * @param array $opts Options to waitForReplication()
284 * @throws DBReplicationWaitError
286 public function commitAndWaitForReplication( $fname, $ticket, array $opts = [] );
289 * @param string $dbName DB master name (e.g. "db1052")
290 * @return float|bool UNIX timestamp when client last touched the DB or false if not recent
292 public function getChronologyProtectorTouched( $dbName );
295 * Disable the ChronologyProtector for all load balancers
297 * This can be called at the start of special API entry points
299 public function disableChronologyProtection();
302 * Set a new table prefix for the existing local domain ID for testing
304 * @param string $prefix
306 public function setDomainPrefix( $prefix );
309 * Close all open database connections on all open load balancers.
311 public function closeAll();
314 * @param string $agent Agent name for query profiling
316 public function setAgentName( $agent );
319 * Append ?cpPosIndex parameter to a URL for ChronologyProtector purposes if needed
321 * Note that unlike cookies, this works accross domains
324 * @param int $index Write counter index
327 public function appendShutdownCPIndexAsQuery( $url, $index );
330 * @param array $info Map of fields, including:
331 * - IPAddress : IP address
332 * - UserAgent : User-Agent HTTP header
333 * - ChronologyProtection : cookie/header value specifying ChronologyProtector usage
334 * - ChronologyPositionIndex: timestamp used to get up-to-date DB positions for the agent
336 public function setRequestInfo( array $info );
339 * Make certain table names use their own database, schema, and table prefix
340 * when passed into SQL queries pre-escaped and without a qualified database name
342 * For example, "user" can be converted to "myschema.mydbname.user" for convenience.
343 * Appearances like `user`, somedb.user, somedb.someschema.user will used literally.
345 * Calling this twice will completely clear any old table aliases. Also, note that
346 * callers are responsible for making sure the schemas and databases actually exist.
348 * @param array[] $aliases Map of (table => (dbname, schema, prefix) map)
351 public function setTableAliases( array $aliases );
354 * Convert certain index names to alternative names before querying the DB
356 * Note that this applies to indexes regardless of the table they belong to.
358 * This can be employed when an index was renamed X => Y in code, but the new Y-named
359 * indexes were not yet built on all DBs. After all the Y-named ones are added by the DBA,
360 * the aliases can be removed, and then the old X-named indexes dropped.
362 * @param string[] $aliases
366 public function setIndexAliases( array $aliases );