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Document the 'wal_cleanup_delay' option #3350

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merged 4 commits into from
Feb 27, 2023
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Document the 'wal_cleanup_delay' option #3350

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Document the 'wal_cleanup_delay' option
andreyaksenov Feb 20, 2023
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'wal_cleanup_delay' - cosmetics
andreyaksenov Feb 20, 2023
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'wal_cleanup_delay' - update per review
andreyaksenov Feb 27, 2023
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'wal_cleanup_delay' - update per review
andreyaksenov Feb 27, 2023
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24 changes: 24 additions & 0 deletions doc/reference/configuration/cfg_binary_logging_snapshots.rst
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Expand Up @@ -4,6 +4,7 @@
* :ref:`wal_mode <cfg_binary_logging_snapshots-wal_mode>`
* :ref:`wal_dir_rescan_delay <cfg_binary_logging_snapshots-wal_dir_rescan_delay>`
* :ref:`wal_queue_max_size <cfg_binary_logging_snapshots-wal_queue_max_size>`
* :ref:`wal_cleanup_delay <cfg_binary_logging_snapshots-wal_cleanup_delay>`

.. _cfg_binary_logging_snapshots-force_recovery:

Expand Down Expand Up @@ -111,3 +112,26 @@
| Default: 16777216 bytes
| Environment variable: TT_WAL_QUEUE_MAX_SIZE
| Dynamic: **yes**

.. _cfg_binary_logging_snapshots-wal_cleanup_delay:

.. confval:: wal_cleanup_delay

Since version :doc:`2.8.1 </release/2.8.1>`.
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@sergepetrenko sergepetrenko Feb 27, 2023 •
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The option already appeared in 2.6.3 (2.6.2-148-gd129729d9) and 2.7.2 (2.7.1-152-ge8c094644) (we had rolling releases back then, so 2.8.1 was released together with 2.7.2. and 2.6.3). This was considered a bugfix, so it was cherry-picked from 2.8.1 to the older versions.

The delay (in seconds) used to prevent the :ref:`Tarantool garbage collector <cfg_checkpoint_daemon-garbage-collector>`
from immediate removing :ref:`write-ahead log<internals-wal>` files after a node restart.
This delay helps :ref:`replicas <replication-roles>` sync with a master faster after its restart and
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I wouldn't say it helps to sync faster: it eliminates the risk that master deletes WALs needed for replicas after a restart. It fixes a possible erroneous situation rather than improves anything.

Although, yes, this means replicas do not risk downloading the data all over again, and thus can sync faster.

eliminates the need to download all the data again.

Once all the nodes in the replica set are up and running,
automatic cleanup is started again even if ``wal_cleanup_delay`` has not expired.

.. NOTE::

The ``wal_cleanup_delay`` option is not in effect if a node is running as an
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If I get it right , this wording will be more precise:

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The ``wal_cleanup_delay`` option is not in effect if a node is running as an
The ``wal_cleanup_delay`` option has no effect on nodes running as

I mean, it still has effect on other nodes in the replica set except anonymous replicas, right?

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Thanks, sounds better.

:ref:`anonymous replica<cfg_replication-replication_anon>`.

| Type: number
| Default: 14400 seconds
| Environment variable: TT_WAL_CLEANUP_DELAY
| Dynamic: **yes**