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doc: update "node rejoin" documentation

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In particular, update examples to reflect changed output in repmgr 4.3.
This commit is contained in:
Ian Barwick
2019-01-31 10:49:39 +09:00
parent 9349171b55
commit 19e0b6a1b6
1 changed files with 66 additions and 35 deletions
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101
doc/repmgr-node-rejoin.sgml
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@@ -216,6 +216,10 @@
postgres --single -D /var/lib/pgsql/data/ &lt; /dev/null</programlisting> postgres --single -D /var/lib/pgsql/data/ &lt; /dev/null</programlisting>
</para> </para>
</tip> </tip>
<para>
&repmgr; will attempt to verify whether the node can rejoin as-is, or whether
<command>pg_rewind</command> must be used (see following section).
</para>
</refsect1> </refsect1>
<refsect1 id="repmgr-node-rejoin-pg-rewind" xreflabel="Using pg_rewind"> <refsect1 id="repmgr-node-rejoin-pg-rewind" xreflabel="Using pg_rewind">
@@ -241,65 +245,92 @@
</para> </para>
</note> </note>
<para>
We strongly recommend familiarizing yourself with <command>pg_rewind</command> before attempting
to use it with &repmgr;, as while it is an extremely useful tool, it is <emphasis>not</emphasis>
a &quot;magic bullet&quot;.
</para>
<para>
A typical use-case for <command>pg_rewind</command> is when a scenario like the following
is encountered:
<programlisting>
$ repmgr node rejoin -f /etc/repmgr.conf -d 'host=node3 dbname=repmgr user=repmgr' \
--force-rewind --config-files=postgresql.local.conf,postgresql.conf --verbose --dry-run
INFO: replication connection to the follow target node was successful
INFO: local and follow target system identifiers match
DETAIL: system identifier is 6652184002263212600
ERROR: this node cannot attach to follow target node 3
DETAIL: follow target server's timeline 2 forked off current database system timeline 1 before current recovery point 0/610D710
HINT: use --force-rewind to execute pg_rewind</programlisting>
Here, <literal>node3</literal> was promoted to a primary while the local node was
still attached to the previous primary; this can potentially happen during e.g. a
network split. <command>pg_rewind</command> can re-sync the local node with <literal>node3</literal>,
removing the need for a full reclone.
</para>
<para> <para>
To have <command>repmgr node rejoin</command> use <command>pg_rewind</command>, To have <command>repmgr node rejoin</command> use <command>pg_rewind</command>,
pass the command line option <literal>--force-rewind</literal>, which will tell &repmgr; pass the command line option <literal>--force-rewind</literal>, which will tell &repmgr;
to execute <command>pg_rewind</command> to ensure the node can be rejoined successfully. to execute <command>pg_rewind</command> to ensure the node can be rejoined successfully.
</para> </para>
<para> <important>
Be aware that if <command>pg_rewind</command> is executed and actually performs a <para>
rewind operation, any configuration files in the PostgreSQL data directory will be Be aware that if <command>pg_rewind</command> is executed and actually performs a
overwritten with those from the source server. rewind operation, any configuration files in the PostgreSQL data directory will be
</para> overwritten with those from the source server.
<para> </para>
To prevent this happening, provide a comma-separated list of files to retain <para>
using the <literal>--config-file</literal> command line option; the specified files To prevent this happening, provide a comma-separated list of files to retain
will be archived in a temporary directory (whose parent directory can be specified with using the <literal>--config-file</literal> command line option; the specified files
<literal>--config-archive-dir</literal>) and restored once the rewind operation is will be archived in a temporary directory (whose parent directory can be specified with
complete. <literal>--config-archive-dir</literal>) and restored once the rewind operation is
</para> complete.
</para>
</important>
<para> <para>
Example, first using <literal>--dry-run</literal>, then actually executing the Example, first using <literal>--dry-run</literal>, then actually executing the
<literal>node rejoin command</literal>. <literal>node rejoin command</literal>.
<programlisting> <programlisting>
$ repmgr node rejoin -f /etc/repmgr.conf -d 'host=node1 dbname=repmgr user=repmgr' \ $ repmgr node rejoin -f /etc/repmgr.conf -d 'host=node3 dbname=repmgr user=repmgr' \
--force-rewind --config-files=postgresql.local.conf,postgresql.conf --verbose --dry-run --config-files=postgresql.local.conf,postgresql.conf --verbose --force-rewind --dry-run
NOTICE: using provided configuration file "/etc/repmgr.conf" INFO: replication connection to the follow target node was successful
INFO: local and follow target system identifiers match
DETAIL: system identifier is 6652460429293670710
NOTICE: pg_rewind execution required for this node to attach to follow target node 3
DETAIL: follow target server's timeline 2 forked off current database system timeline 1 before current recovery point 0/610D710
INFO: prerequisites for using pg_rewind are met INFO: prerequisites for using pg_rewind are met
INFO: file "postgresql.local.conf" would be copied to "/tmp/repmgr-config-archive-node1/postgresql.local.conf" INFO: file "postgresql.local.conf" would be copied to "/tmp/repmgr-config-archive-node2/postgresql.local.conf"
INFO: file "postgresql.conf" would be copied to "/tmp/repmgr-config-archive-node1/postgresql.local.conf" INFO: file "postgresql.replication-setup.conf" would be copied to "/tmp/repmgr-config-archive-node2/postgresql.replication-setup.conf"
INFO: 2 files would have been copied to "/tmp/repmgr-config-archive-node1"
INFO: directory "/tmp/repmgr-config-archive-node1" deleted
INFO: pg_rewind would now be executed INFO: pg_rewind would now be executed
DETAIL: pg_rewind command is: DETAIL: pg_rewind command is:
pg_rewind -D '/var/lib/postgresql/data' --source-server='host=node1 dbname=repmgr user=repmgr'</programlisting> pg_rewind -D '/var/lib/postgresql/data' --source-server='host=node3 dbname=repmgr user=repmgr'
INFO: prerequisites for executing NODE REJOIN are met</programlisting>
<note> <note>
<para> <para>
If <option>--force-rewind</option> is used with the <option>--dry-run</option> option, If <option>--force-rewind</option> is used with the <option>--dry-run</option> option,
this checks the prerequisites for using <application>pg_rewind</application>, but cannot this checks the prerequisites for using <application>pg_rewind</application>, but is
predict the outcome of actually executing <application>pg_rewind</application>. not an absolute guarantee that actually executing <application>pg_rewind</application>
will succeed.
</para> </para>
</note> </note>
<programlisting> <programlisting>
$ repmgr node rejoin -f /etc/repmgr.conf -d 'host=node1 dbname=repmgr user=repmgr' \ $ repmgr node rejoin -f /etc/repmgr.conf -d 'host=node3 dbname=repmgr user=repmgr' \
--force-rewind --config-files=postgresql.local.conf,postgresql.conf --verbose --config-files=postgresql.local.conf,postgresql.conf --verbose --force-rewind
NOTICE: using provided configuration file "/etc/repmgr.conf" NOTICE: pg_rewind execution required for this node to attach to follow target node 3
INFO: prerequisites for using pg_rewind are met DETAIL: follow target server's timeline 2 forked off current database system timeline 1 before current recovery point 0/610D710
INFO: 2 files copied to "/tmp/repmgr-config-archive-node1"
NOTICE: executing pg_rewind NOTICE: executing pg_rewind
NOTICE: 2 files copied to /var/lib/pgsql/data DETAIL: pg_rewind command is "pg_rewind -D '/var/lib/postgresql/data' --source-server='host=node3 dbname=repmgr user=repmgr'"
INFO: directory "/tmp/repmgr-config-archive-node1" deleted NOTICE: 2 files copied to /var/lib/postgresql/data
INFO: deleting "recovery.done" NOTICE: setting node 2's upstream to node 3
INFO: setting node 1's primary to node 2 NOTICE: starting server using "pg_ctl -l /var/log/postgres/startup.log -w -D '/var/lib/pgsql/data' start"
NOTICE: starting server using "pg_ctl-l /var/log/postgres/startup.log -w -D '/var/lib/pgsql/data' start"
waiting for server to start.... done
server started
NOTICE: NODE REJOIN successful NOTICE: NODE REJOIN successful
DETAIL: node 1 is now attached to node 2</programlisting> DETAIL: node 2 is now attached to node 3</programlisting>
</para> </para>
</refsect1> </refsect1>