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Transaction Log
===============
The Drizzle Transaction Log contains a sequence of
`Google Protocol Buffer <http://code.google.com/p/protobuf/>`_
messages that describe the transactions which have been run.
Loading
-------
This plugin is loaded by default, but it may need to be configured. See
the plugin's :ref:`transaction_log_configuration` and
:ref:`transaction_log_variables`.
To stop the plugin from loading by default, start :program:`drizzled`
with::
--plugin-remove=transaction_log
.. seealso:: :doc:`/options` for more information about adding and removing plugins.
.. _transaction_log_configuration:
Configuration
-------------
These command line options configure the plugin when :program:`drizzled`
is started. See :doc:`/configuration` for more information about specifying
command line options.
.. program:: drizzled
.. option:: --transaction-log.enable
:Default: false
:Variable: :ref:`transaction_log_enable <transaction_log_enable>`
Enable transaction log.
.. option:: --transaction-log.enable-checksum
:Default: false
:Variable: :ref:`transaction_log_enable_checksum <transaction_log_enable_checksum>`
Enable CRC32 Checksumming of each written transaction log entry
.. option:: --transaction-log.file ARG
:Default: :file:`transaction.log`
:Variable: :ref:`transaction_log_file <transaction_log_file>`
Path to the file to use for transaction log.
.. option:: --transaction-log.flush-frequency=arg
:Default: ``0``
:Variable: :ref:`transaction_log_flush_frequency <transaction_log_flush_frequency>`
* 0 : rely on operating system to sync log file (default)
* 1 : sync file at each transaction write
* 2 : sync log file once per second
.. option:: --transaction-log.num-write-buffers ARG
:Default: 8
:Variable: :ref:`transaction_log_num_write_buffers <transaction_log_num_write_buffers>`
Number of slots for in-memory write buffers.
.. option:: --transaction-log.truncate-debug
:Default: false
:Variable: :ref:`transaction_log_truncate_debug <transaction_log_truncate_debug>`
DEBUGGING - Truncate transaction log.
.. option:: --transaction-log.use-replicator ARG
:Default: ``default_replicator``
:Variable: :ref:`transaction_log_use_replicator <transaction_log_use_replicator>`
Name of the replicator plugin to use.
.. _transaction_log_variables:
Variables
---------
These variables show the running configuration of the plugin.
See `variables` for more information about querying and setting variables.
.. _transaction_log_enable:
* ``transaction_log_enable``
:Scope: Global
:Dynamic: No
:Option: :option:`--transaction-log.enable`
If the transaction log is enabled or not.
.. _transaction_log_enable_checksum:
* ``transaction_log_enable_checksum``
:Scope: Global
:Dynamic: No
:Option: :option:`--transaction-log.enable-checksum`
Enable CRC32 Checksumming of each written transaction log entry
.. _transaction_log_file:
* ``transaction_log_file``
:Scope: Global
:Dynamic: No
:Option: :option:`--transaction-log.file`
Path to the file to use for transaction log
.. _transaction_log_flush_frequency:
* ``transaction_log_flush_frequency``
:Scope: Global
:Dynamic: No
:Option: :option:`--transaction-log.flush-frequency`
Flush frequency.
.. _transaction_log_num_write_buffers:
* ``transaction_log_num_write_buffers``
:Scope: Global
:Dynamic: No
:Option: :option:`--transaction-log.num-write-buffers`
Number of slots for in-memory write buffers (default=8).
.. _transaction_log_truncate_debug:
* ``transaction_log_truncate_debug``
:Scope: Global
:Dynamic: No
:Option: :option:`--transaction-log.truncate-debug`
DEBUGGING - Truncate transaction log
.. _transaction_log_use_replicator:
* ``transaction_log_use_replicator``
:Scope: Global
:Dynamic: No
:Option: :option:`--transaction-log.use-replicator`
Name of the replicator plugin to use (default='default_replicator')
Transaction Log Messages
------------------------
Replication events are recorded using messages in the `Google Protocol Buffer
<http://code.google.com/p/protobuf/>`_ (GPB) format. See the :doc:`Replication
documentation </replication>` for more information.
Transaction Log Format
----------------------
Currently, the transaction log file uses a simple, single-file, append-only
format. The format of each entry in the transaction log file is::
4-bytes 4-bytes
+--------------+--------------+----------------------+
| Entry Type | Length | Serialized Message |
+--------------+--------------+----------------------+
The fields in the entry are:
* **Entry Type** - Type of message this entry contains. Currently,
this is always a Transaction GPB message.
* **Length** - The length, in bytes, of the serialized message.
* **Serialized Message** - The actual message data.
.. _transaction_log_examples:
Examples
--------
Sorry, there are no examples for this plugin.
.. _transaction_log_authors:
Authors
-------
Jay Pipes
.. _transaction_log_version:
Version
-------
This documentation applies to **transaction_log 0.1.1**.
To see which version of the plugin a Drizzle server is running, execute:
.. code-block:: mysql
SELECT MODULE_VERSION FROM DATA_DICTIONARY.MODULES WHERE MODULE_NAME='transaction_log'
Changelog
---------
v0.1.1
^^^^^^
* First release.
|