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10425d6967
As they are now XML files. In PostgreSQL itself they remain with the .sgml suffix for backwards compatibility, but that's not important for us.
80 lines
4.0 KiB
XML
80 lines
4.0 KiB
XML
<chapter id="promoting-standby" xreflabel="Promoting a standby">
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<title>Promoting a standby server with repmgr</title>
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<indexterm>
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<primary>promoting a standby</primary>
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<seealso>repmgr standby promote</seealso>
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</indexterm>
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<para>
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If a primary server fails or needs to be removed from the replication cluster,
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a new primary server must be designated, to ensure the cluster continues
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to function correctly. This can be done with <xref linkend="repmgr-standby-promote"/>,
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which promotes the standby on the current server to primary.
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</para>
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<para>
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To demonstrate this, set up a replication cluster with a primary and two attached
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standby servers so that the cluster looks like this:
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<programlisting>
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$ repmgr -f /etc/repmgr.conf cluster show
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ID | Name | Role | Status | Upstream | Location | Connection string
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----+-------+---------+-----------+----------+----------+--------------------------------------
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1 | node1 | primary | * running | | default | host=node1 dbname=repmgr user=repmgr
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2 | node2 | standby | running | node1 | default | host=node2 dbname=repmgr user=repmgr
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3 | node3 | standby | running | node1 | default | host=node3 dbname=repmgr user=repmgr</programlisting>
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</para>
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<para>
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Stop the current primary with e.g.:
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<programlisting>
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$ pg_ctl -D /var/lib/postgresql/data -m fast stop</programlisting>
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</para>
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<para>
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At this point the replication cluster will be in a partially disabled state, with
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both standbys accepting read-only connections while attempting to connect to the
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stopped primary. Note that the &repmgr; metadata table will not yet have been updated;
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executing <xref linkend="repmgr-cluster-show"/> will note the discrepancy:
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<programlisting>
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$ repmgr -f /etc/repmgr.conf cluster show
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ID | Name | Role | Status | Upstream | Location | Connection string
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----+-------+---------+---------------+----------+----------+--------------------------------------
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1 | node1 | primary | ? unreachable | | default | host=node1 dbname=repmgr user=repmgr
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2 | node2 | standby | running | node1 | default | host=node2 dbname=repmgr user=repmgr
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3 | node3 | standby | running | node1 | default | host=node3 dbname=repmgr user=repmgr
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WARNING: following issues were detected
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node "node1" (ID: 1) is registered as an active primary but is unreachable</programlisting>
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</para>
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<para>
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Now promote the first standby with:
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<programlisting>
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$ repmgr -f /etc/repmgr.conf standby promote</programlisting>
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</para>
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<para>
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This will produce output similar to the following:
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<programlisting>
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INFO: connecting to standby database
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NOTICE: promoting standby
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DETAIL: promoting server using "pg_ctl -l /var/log/postgresql/startup.log -w -D '/var/lib/postgresql/data' promote"
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server promoting
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INFO: reconnecting to promoted server
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NOTICE: STANDBY PROMOTE successful
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DETAIL: node 2 was successfully promoted to primary</programlisting>
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</para>
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<para>
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Executing <xref linkend="repmgr-cluster-show"/> will show the current state; as there is now an
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active primary, the previous warning will not be displayed:
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<programlisting>
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$ repmgr -f /etc/repmgr.conf cluster show
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ID | Name | Role | Status | Upstream | Location | Connection string
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----+-------+---------+-----------+----------+----------+--------------------------------------
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1 | node1 | primary | - failed | | default | host=node1 dbname=repmgr user=repmgr
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2 | node2 | primary | * running | | default | host=node2 dbname=repmgr user=repmgr
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3 | node3 | standby | running | node1 | default | host=node3 dbname=repmgr user=repmgr</programlisting>
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</para>
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<para>
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However the sole remaining standby (<literal>node3</literal>) is still trying to replicate from the failed
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primary; <xref linkend="repmgr-standby-follow"/> must now be executed to rectify this situation
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(see <xref linkend="follow-new-primary"/> for example).
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</para>
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</chapter>
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