Garbage collects unfinished XA transactions after severe errors
int mysqlnd_ms_xa_gc(mixed connection,
Garbage collects unfinished XA transactions.
The XA protocol is a blocking protocol. There exist cases when servers participating in a global transaction cannot make progress when the transaction coordinator crashes or disconnects. In such a case, the MySQL servers keep waiting for instructions to finish the XA transaction in question. Because transactions occupy resources, transactions should always be terminated properly.
Garbage collection requires configuring a state store to track global transactions. Should a PHP client crash in the middle of a transaction and a new PHP client be started, then the built-in garbage collection can learn about the aborted global transaction and terminate it. If you do not configure a state store, the garbage collection cannot perform any cleanup tasks.
The state store should be crash-safe and be highly available to survive its own crash. Currently, only MySQL is supported as a state store.
Garbage collection can also be performed automatically in the
background. See the plugin configuration directive
garbage_collection for details.
The feature is currently under development. There may be issues and/or feature limitations. Do not use in production environments.
Global transaction identifier (gtrid). If given, the garbage collection considers the transaction only. Otherwise, the state store is scanned for any unfinished transaction.
Whether to ignore the plugin configuration
max_retries setting. If garbage
collection continously fails and the
max_retries limit is reached prior to
finishing the failed global transaction, you can attempt
further runs prior to investigating the cause and solving
the issue manually by issueing appropriate SQL statements
on the participants. Setting the parameter has the same
effect as temporarily setting
TRUE if garbage collection was
successful. Otherwise, returns
|Quickstart XA/Distributed transactions|
|State store configuration|