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Disable WAL streaming on standby node via new boolean tag "nostream" (#2842)

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Add support for ``nostream`` tag. If set to ``true`` the node will not use replication protocol to stream WAL. It will rely instead on archive recovery (if ``restore_command`` is configured) and ``pg_wal``/``pg_xlog`` polling. It also disables copying and synchronization of permanent logical replication slots on the node itself and all its cascading replicas. Setting this tag on primary node has no effect.
This commit is contained in:
Grigory Smolkin
2024-03-20 10:10:53 +01:00
committed by GitHub
parent 014777b20a
commit b09af642e6
14 changed files with 119 additions and 11 deletions
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docs/dynamic_configuration.rst
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@@ -108,3 +108,7 @@ Note: if cluster topology is static (fixed number of nodes that never change the
.. warning::
Permanent replication slots are synchronized only from the ``primary``/``standby_leader`` to replica nodes. That means, applications are supposed to be using them only from the leader node. Using them on replica nodes will cause indefinite growth of ``pg_wal`` on all other nodes in the cluster.
An exception to that rule are permanent physical slots that match the Patroni member names, if you happen to configure any. Those will be synchronized among all nodes as they are used for replication among them.
.. warning::
Setting ``nostream`` tag on standby disables copying and synchronization of permanent logical replication slots on the node itself and all its cascading replicas if any.
docs/replication_modes.rst
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@@ -53,7 +53,7 @@ are available. As a downside, the primary is not be available for writes
blocking all client write requests until at least one synchronous replica comes
up.
You can ensure that a standby never becomes the synchronous standby by setting ``nosync`` tag to true. This is recommended to set for standbys that are behind slow network connections and would cause performance degradation when becoming a synchronous standby.
You can ensure that a standby never becomes the synchronous standby by setting ``nosync`` tag to true. This is recommended to set for standbys that are behind slow network connections and would cause performance degradation when becoming a synchronous standby. Setting tag ``nostream`` to true will also have the same effect.
Synchronous mode can be switched on and off via Patroni REST interface. See :ref:`dynamic configuration <dynamic_configuration>` for instructions.
docs/yaml_configuration.rst
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@@ -399,6 +399,7 @@ Tags
- **nosync**: ``true`` or ``false``. If set to ``true`` the node will never be selected as a synchronous replica.
- **nofailover**: ``true`` or ``false``, controls whether this node is allowed to participate in the leader race and become a leader. Defaults to ``false``, meaning this node _can_ participate in leader races.
- **failover_priority**: integer, controls the priority that this node should have during failover. Nodes with higher priority will be preferred over lower priority nodes if they received/replayed the same amount of WAL. However, nodes with higher values of receive/replay LSN are preferred regardless of their priority. If the ``failover_priority`` is 0 or negative - such node is not allowed to participate in the leader race and to become a leader (similar to ``nofailover: true``).
- **nostream**: ``true`` or ``false``. If set to ``true`` the node will not use replication protocol to stream WAL. It will rely instead on archive recovery (if ``restore_command`` is configured) and ``pg_wal``/``pg_xlog`` polling. It also disables copying and synchronization of permanent logical replication slots on the node itself and all its cascading replicas. Setting this tag on primary node has no effect.
.. warning::
Provide only one of ``nofailover`` or ``failover_priority``. Providing ``nofailover: true`` is the same as ``failover_priority: 0``, and providing ``nofailover: false`` will give the node priority 1.