Database hot standby #4436
Database hot standby #4436
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| This mode can be used to provide failover without :ref:`replication <replication>`. | ||
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| Suppose there are two cluster applications. | ||
| Each cluster has one instance with the same configuration: |
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I can't guess from this example the correct way to use this mode in multi-instance apps. Set it for all instances of two identical apps? Or maybe select a subset of instances to run in standby?
Not sure though if the deeper explanation is needed in the reference. Perhaps somewhere in a task-oriented page in the admin's guide (out of this PR's scope).
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I can't guess from this example the correct way to use this mode in multi-instance apps.
The correct way is using two cluster applications with each cluster having one instance. And the GitHub examples at the end should help a reader. I agree that we can document this feature better. But, honestly, I don't think it is a very popular use case for Tarantool (maybe, I'm wrong).
Set it for all instances of two identical apps? Or maybe select a subset of instances to run in standby?
This sounds like a feature request for a new configuration approach. For example, we can allow a user to add two instances, set replication.failover to smth like hot_standby, and provide the same path to WALs/snapshots for both instances. But still not sure that this scenario might be popular. cc @Totktonada
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| * If :ref:`wal.mode <configuration_reference_wal_mode>` is set to ``none``. | ||
| * If :ref:`wal.dir_rescan_delay <configuration_reference_wal_dir_rescan_delay>` is set to a large value on macOS or FreeBSD. On these platforms, the hot standby mode is designed so that the loop repeats every ``wal.dir_rescan_delay`` seconds. | ||
| * If spaces are created with :ref:`engine <space_opts_engine>` set to ``vinyl``. |
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The old wording was clearer:
for spaces created with engine = ‘vinyl’
Now it's ambiguous:
- if there are vinyl spaces?
- if all spaces are vinyl?
- has no effect only on vinyl spaces?
Fixes #3858.
Staging: https://docs.d.tarantool.io/en/doc/database-hot-standby/reference/configuration/configuration_reference/#configuration-reference-database-hot-standby