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bb0fd944ae
Improve sample PostgreSQL replication configuration, including links to the PostgreSQL documentation for each configuration item. Also set "max_replication_slots" to the same value as "max_wal_senders" to ensure the sample configuration will work regardless of whether replication slots are in use, though we do still encourage careful reading of the comments in the sample configuration and the documentation in general.
512 lines
21 KiB
Plaintext
512 lines
21 KiB
Plaintext
<chapter id="quickstart" xreflabel="Quick-start guide">
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<title>Quick-start guide</title>
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<indexterm>
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<primary>quickstart</primary>
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</indexterm>
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<para>
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This section gives a quick introduction to &repmgr;, including setting up a
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sample &repmgr; installation and a basic replication cluster.
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</para>
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<para>
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These instructions for demonstration purposes and are not suitable for a production
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install, as issues such as account security considerations, and system administration
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best practices are omitted.
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</para>
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<note>
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<simpara>
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To upgrade an existing &repmgr; 3.x installation, see section
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<xref linkend="upgrading-from-repmgr-3">.
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</simpara>
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</note>
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<sect1 id="quickstart-prerequisites">
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<title>Prerequisites for setting up a basic replication cluster with &repmgr;</title>
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<para>
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The following section will describe how to set up a basic replication cluster
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with a primary and a standby server using the <application>repmgr</application>
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command line tool.
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</para>
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<para>
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We'll assume the primary is called <literal>node1</literal> with IP address
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<literal>192.168.1.11</literal>, and the standby is called <literal>node2</literal>
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with IP address <literal>192.168.1.12</literal>
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</para>
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<para>
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Following software must be installed on both servers:
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<itemizedlist spacing="compact" mark="bullet">
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<listitem>
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<simpara><application>PostgreSQL</application></simpara>
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</listitem>
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<listitem>
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<simpara>
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<application>repmgr</application> (matching the installed
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<application>PostgreSQL</application> major version)
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</simpara>
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</listitem>
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</itemizedlist>
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</para>
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<para>
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At network level, connections between the PostgreSQL port (default: <literal>5432</literal>)
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must be possible in both directions.
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</para>
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<para>
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If you want <application>repmgr</application> to copy configuration files which are
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located outside the PostgreSQL data directory, and/or to test
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<command><link linkend="repmgr-standby-switchover">switchover</link></command>
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functionality, you will also need passwordless SSH connections between both servers, and
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<application>rsync</application> should be installed.
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</para>
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<tip>
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<simpara>
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For testing <application>repmgr</application>, it's possible to use multiple PostgreSQL
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instances running on different ports on the same computer, with
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passwordless SSH access to <filename>localhost</filename> enabled.
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</simpara>
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</tip>
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</sect1>
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<sect1 id="quickstart-postgresql-configuration" xreflabel="PostgreSQL configuration">
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<title>PostgreSQL configuration</title>
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<para>
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On the primary server, a PostgreSQL instance must be initialised and running.
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The following replication settings may need to be adjusted:
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</para>
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<programlisting>
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# Enable replication connections; set this value to at least one more
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# than the number of standbys which will connect to this server
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# (note that repmgr will execute "pg_basebackup" in WAL streaming mode,
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# which requires two free WAL senders).
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#
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# See: https://www.postgresql.org/docs/current/runtime-config-replication.html#GUC-MAX-WAL-SENDERS
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max_wal_senders = 10
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# If using replication slots, set this value to at least one more
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# than the number of standbys which will connect to this server.
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# Note that repmgr will only make use of replication slots if
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# "use_replication_slots" is set to "true" in "repmgr.conf".
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# (If you are not intending to use replication slots, this value
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# can be set to "0").
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#
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# See: https://www.postgresql.org/docs/current/runtime-config-replication.html#GUC-MAX-REPLICATION-SLOTS
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max_replication_slots = 10
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# Ensure WAL files contain enough information to enable read-only queries
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# on the standby.
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#
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# PostgreSQL 9.5 and earlier: one of 'hot_standby' or 'logical'
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# PostgreSQL 9.6 and later: one of 'replica' or 'logical'
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# ('hot_standby' will still be accepted as an alias for 'replica')
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#
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# See: https://www.postgresql.org/docs/current/runtime-config-wal.html#GUC-WAL-LEVEL
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wal_level = 'hot_standby'
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# Enable read-only queries on a standby
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# (Note: this will be ignored on a primary but we recommend including
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# it anyway, in case the primary later becomes a standby)
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#
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# See: https://www.postgresql.org/docs/current/runtime-config-replication.html#GUC-HOT-STANDBY
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hot_standby = on
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# Enable WAL file archiving
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#
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# See: https://www.postgresql.org/docs/current/runtime-config-wal.html#GUC-ARCHIVE-MODE
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archive_mode = on
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# Set archive command to a dummy command; this can later be changed without
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# needing to restart the PostgreSQL instance.
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#
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# See: https://www.postgresql.org/docs/current/runtime-config-wal.html#GUC-ARCHIVE-COMMAND
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archive_command = '/bin/true'
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</programlisting>
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<tip>
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<simpara>
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Rather than editing these settings in the default <filename>postgresql.conf</filename>
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file, create a separate file such as <filename>postgresql.replication.conf</filename> and
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include it from the end of the main configuration file with:
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<command>include 'postgresql.replication.conf'</command>.
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</simpara>
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</tip>
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<para>
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Additionally, if you are intending to use <application>pg_rewind</application>,
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and the cluster was not initialised using data checksums, you may want to consider enabling
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<varname>wal_log_hints</varname>; for more details see <xref linkend="repmgr-node-rejoin-pg-rewind">.
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</para>
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<para>
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See also the <link linkend="configuration-postgresql">PostgreSQL configuration</link> section in the
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<link linkend="configuration">repmgr configuration guide</link>.
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</para>
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</sect1>
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<sect1 id="quickstart-repmgr-user-database">
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<title>Create the repmgr user and database</title>
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<para>
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Create a dedicated PostgreSQL superuser account and a database for
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the &repmgr; metadata, e.g.
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</para>
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<programlisting>
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createuser -s repmgr
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createdb repmgr -O repmgr
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</programlisting>
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<para>
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For the examples in this document, the name <literal>repmgr</literal> will be
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used for both user and database, but any names can be used.
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</para>
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<note>
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<para>
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For the sake of simplicity, the <literal>repmgr</literal> user is created
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as a superuser. If desired, it's possible to create the <literal>repmgr</literal>
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user as a normal user. However for certain operations superuser permissions
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are requiredl; in this case the command line option <command>--superuser</command>
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can be provided to specify a superuser.
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</para>
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<para>
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It's also assumed that the <literal>repmgr</literal> user will be used to make the
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replication connection from the standby to the primary; again this can be
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overridden by specifying a separate replication user when registering each node.
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</para>
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</note>
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<tip>
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<para>
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&repmgr; will install the <literal>repmgr</literal> extension, which creates a
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<literal>repmgr</literal> schema containing the &repmgr;'s metadata tables as
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well as other functions and views. We also recommend that you set the
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<literal>repmgr</literal> user's search path to include this schema name, e.g.
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<programlisting>
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ALTER USER repmgr SET search_path TO repmgr, "$user", public;</programlisting>
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</para>
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</tip>
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</sect1>
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<sect1 id="quickstart-authentication">
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<title>Configuring authentication in pg_hba.conf</title>
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<para>
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Ensure the <literal>repmgr</literal> user has appropriate permissions in <filename>pg_hba.conf</filename> and
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can connect in replication mode; <filename>pg_hba.conf</filename> should contain entries
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similar to the following:
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</para>
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<programlisting>
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local replication repmgr trust
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host replication repmgr 127.0.0.1/32 trust
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host replication repmgr 192.168.1.0/24 trust
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local repmgr repmgr trust
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host repmgr repmgr 127.0.0.1/32 trust
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host repmgr repmgr 192.168.1.0/24 trust
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</programlisting>
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<para>
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Note that these are simple settings for testing purposes.
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Adjust according to your network environment and authentication requirements.
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</para>
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</sect1>
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<sect1 id="quickstart-standby-preparation">
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<title>Preparing the standby</title>
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<para>
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On the standby, do <emphasis>not</emphasis> create a PostgreSQL instance (i.e.
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do not execute <application>initdb</application> or any database creation
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scripts provided by packages), but do ensure the destination
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data directory (and any other directories which you want PostgreSQL to use)
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exist and are owned by the <literal>postgres</literal> system user. Permissions
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must be set to <literal>0700</literal> (<literal>drwx------</literal>).
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</para>
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<tip>
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<simpara>
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&repmgr; will place a copy of the primary's database files in this directory.
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It will however refuse to run if a PostgreSQL instance has already been
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created there.
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</simpara>
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</tip>
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<para>
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Check the primary database is reachable from the standby using <application>psql</application>:
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</para>
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<programlisting>
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psql 'host=node1 user=repmgr dbname=repmgr connect_timeout=2'</programlisting>
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<note>
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<para>
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&repmgr; stores connection information as <ulink
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url="https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNSTRING">libpq
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connection strings</ulink> throughout. This documentation refers to them as <literal>conninfo</literal>
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strings; an alternative name is <literal>DSN</literal> (<literal>data source name</literal>).
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We'll use these in place of the <command>-h hostname -d databasename -U username</command> syntax.
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</para>
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</note>
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</sect1>
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<sect1 id="quickstart-repmgr-conf">
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<title>repmgr configuration file</title>
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<para>
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Create a <filename>repmgr.conf</filename> file on the primary server. The file must
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contain at least the following parameters:
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</para>
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<programlisting>
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node_id=1
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node_name=node1
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conninfo='host=node1 user=repmgr dbname=repmgr connect_timeout=2'
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data_directory='/var/lib/postgresql/data'
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</programlisting>
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<para>
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<filename>repmgr.conf</filename> should not be stored inside the PostgreSQL data directory,
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as it could be overwritten when setting up or reinitialising the PostgreSQL
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server. See sections <xref linkend="configuration"> and <xref linkend="configuration-file">
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for further details about <filename>repmgr.conf</filename>.
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</para>
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<note>
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<para>
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&repmgr; only uses <option>pg_bindir</option> when it executes
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PostgreSQL binaries directly.
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</para>
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<para>
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For user-defined scripts such as <option>promote_command</option> and the
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various <option>service_*_command</option>s, you <emphasis>must</emphasis>
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always explicitly provide the full path to the binary or script being
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executed, even if it is &repmgr; itself.
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</para>
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<para>
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This is because these options can contain user-defined scripts in arbitrary
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locations, so prepending <option>pg_bindir</option> may break them.
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</para>
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</note>
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<tip>
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<simpara>
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For Debian-based distributions we recommend explictly setting
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<option>pg_bindir</option> to the directory where <command>pg_ctl</command> and other binaries
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not in the standard path are located. For PostgreSQL 9.6 this would be <filename>/usr/lib/postgresql/9.6/bin/</filename>.
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</simpara>
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</tip>
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<tip>
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<simpara>
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If your distribution places the &repmgr; binaries in a location other than the
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PostgreSQL installation directory, specify this with <option>repmgr_bindir</option>
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to enable &repmgr; to perform operations (e.g.
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<command><link linkend="repmgr-cluster-crosscheck">repmgr cluster crosscheck</link></command>)
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on other nodes.
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</simpara>
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</tip>
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<para>
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See the file
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<ulink url="https://raw.githubusercontent.com/2ndQuadrant/repmgr/master/repmgr.conf.sample">repmgr.conf.sample</>
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for details of all available configuration parameters.
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</para>
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</sect1>
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<sect1 id="quickstart-primary-register">
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<title>Register the primary server</title>
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<para>
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To enable &repmgr; to support a replication cluster, the primary node must
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be registered with &repmgr;. This installs the <literal>repmgr</literal>
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extension and metadata objects, and adds a metadata record for the primary server:
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</para>
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<programlisting>
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$ repmgr -f /etc/repmgr.conf primary register
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INFO: connecting to primary database...
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NOTICE: attempting to install extension "repmgr"
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NOTICE: "repmgr" extension successfully installed
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NOTICE: primary node record (id: 1) registered</programlisting>
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<para>
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Verify status of the cluster like this:
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</para>
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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 | Connection string
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----+-------+---------+-----------+----------+--------------------------------------------------------
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1 | node1 | primary | * running | | host=node1 dbname=repmgr user=repmgr connect_timeout=2
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</programlisting>
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<para>
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The record in the <literal>repmgr</literal> metadata table will look like this:
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</para>
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<programlisting>
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repmgr=# SELECT * FROM repmgr.nodes;
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-[ RECORD 1 ]----+-------------------------------------------------------
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node_id | 1
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upstream_node_id |
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active | t
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node_name | node1
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type | primary
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location | default
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priority | 100
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conninfo | host=node1 dbname=repmgr user=repmgr connect_timeout=2
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repluser | repmgr
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slot_name |
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config_file | /etc/repmgr.conf</programlisting>
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<para>
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Each server in the replication cluster will have its own record. If <application>repmgrd</application>
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is in use, the fields <literal>upstream_node_id</literal>, <literal>active</literal> and
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<literal>type</literal> will be updated when the node's status or role changes.
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</para>
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</sect1>
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<sect1 id="quickstart-standby-clone">
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<title>Clone the standby server</title>
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<para>
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Create a <filename>repmgr.conf</filename> file on the standby server. It must contain at
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least the same parameters as the primary's <filename>repmgr.conf</filename>, but with
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the mandatory values <literal>node</literal>, <literal>node_name</literal>, <literal>conninfo</literal>
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(and possibly <literal>data_directory</literal>) adjusted accordingly, e.g.:
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</para>
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<programlisting>
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node_id=2
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node_name=node2
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conninfo='host=node2 user=repmgr dbname=repmgr connect_timeout=2'
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data_directory='/var/lib/postgresql/data'</programlisting>
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<para>
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Use the <command>--dry-run</command> option to check the standby can be cloned:
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</para>
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<programlisting>
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$ repmgr -h node1 -U repmgr -d repmgr -f /etc/repmgr.conf standby clone --dry-run
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NOTICE: using provided configuration file "/etc/repmgr.conf"
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NOTICE: destination directory "/var/lib/postgresql/data" provided
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INFO: connecting to source node
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NOTICE: checking for available walsenders on source node (2 required)
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INFO: sufficient walsenders available on source node (2 required)
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NOTICE: standby will attach to upstream node 1
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HINT: consider using the -c/--fast-checkpoint option
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INFO: all prerequisites for "standby clone" are met</programlisting>
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<para>
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If no problems are reported, the standby can then be cloned with:
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</para>
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<programlisting>
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$ repmgr -h node1 -U repmgr -d repmgr -f /etc/repmgr.conf standby clone
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NOTICE: using configuration file "/etc/repmgr.conf"
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NOTICE: destination directory "/var/lib/postgresql/data" provided
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INFO: connecting to source node
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NOTICE: checking for available walsenders on source node (2 required)
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INFO: sufficient walsenders available on source node (2 required)
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INFO: creating directory "/var/lib/postgresql/data"...
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NOTICE: starting backup (using pg_basebackup)...
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HINT: this may take some time; consider using the -c/--fast-checkpoint option
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INFO: executing:
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pg_basebackup -l "repmgr base backup" -D /var/lib/postgresql/data -h node1 -U repmgr -X stream
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NOTICE: standby clone (using pg_basebackup) complete
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NOTICE: you can now start your PostgreSQL server
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HINT: for example: pg_ctl -D /var/lib/postgresql/data start
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</programlisting>
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<para>
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This has cloned the PostgreSQL data directory files from the primary <literal>node1</literal>
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using PostgreSQL's <command>pg_basebackup</command> utility. A <filename>recovery.conf</filename>
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file containing the correct parameters to start streaming from this primary server will be created
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automatically.
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</para>
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<note>
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<simpara>
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By default, any configuration files in the primary's data directory will be
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copied to the standby. Typically these will be <filename>postgresql.conf</filename>,
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<filename>postgresql.auto.conf</filename>, <filename>pg_hba.conf</filename> and
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<filename>pg_ident.conf</filename>. These may require modification before the standby
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is started.
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</simpara>
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</note>
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<para>
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Make any adjustments to the standby's PostgreSQL configuration files now,
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then start the server.
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</para>
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<para>
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For more details on <command>repmgr standby clone</command>, see the
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<link linkend="repmgr-standby-clone">command reference</link>.
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A more detailed overview of cloning options is available in the
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<link linkend="cloning-standbys">administration manual</link>.
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</para>
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</sect1>
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<sect1 id="quickstart-verify-replication">
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<title>Verify replication is functioning</title>
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<para>
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Connect to the primary server and execute:
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<programlisting>
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repmgr=# SELECT * FROM pg_stat_replication;
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-[ RECORD 1 ]----+------------------------------
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pid | 19111
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usesysid | 16384
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usename | repmgr
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application_name | node2
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client_addr | 192.168.1.12
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client_hostname |
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client_port | 50378
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backend_start | 2017-08-28 15:14:19.851581+09
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backend_xmin |
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state | streaming
|
|
sent_location | 0/7000318
|
|
write_location | 0/7000318
|
|
flush_location | 0/7000318
|
|
replay_location | 0/7000318
|
|
sync_priority | 0
|
|
sync_state | async</programlisting>
|
|
This shows that the previously cloned standby (<literal>node2</literal> shown in the field
|
|
<literal>application_name</literal>) has connected to the primary from IP address
|
|
<literal>192.168.1.12</literal>.
|
|
</para>
|
|
<para>
|
|
From PostgreSQL 9.6 you can also use the view
|
|
<ulink url="https://www.postgresql.org/docs/current/monitoring-stats.html#PG-STAT-WAL-RECEIVER-VIEW">
|
|
<literal>pg_stat_wal_receiver</literal></ulink> to check the replication status from the standby.
|
|
|
|
<programlisting>
|
|
repmgr=# SELECT * FROM pg_stat_wal_receiver;
|
|
Expanded display is on.
|
|
-[ RECORD 1 ]---------+--------------------------------------------------------------------------------
|
|
pid | 18236
|
|
status | streaming
|
|
receive_start_lsn | 0/3000000
|
|
receive_start_tli | 1
|
|
received_lsn | 0/7000538
|
|
received_tli | 1
|
|
last_msg_send_time | 2017-08-28 15:21:26.465728+09
|
|
last_msg_receipt_time | 2017-08-28 15:21:26.465774+09
|
|
latest_end_lsn | 0/7000538
|
|
latest_end_time | 2017-08-28 15:20:56.418735+09
|
|
slot_name |
|
|
conninfo | user=repmgr dbname=replication host=node1 application_name=node2
|
|
</programlisting>
|
|
Note that the <varname>conninfo</varname> value is that generated in <filename>recovery.conf</filename>
|
|
and will differ slightly from the primary's <varname>conninfo</varname> as set in <filename>repmgr.conf</filename> -
|
|
among others it will contain the connecting node's name as <varname>application_name</varname>.
|
|
</para>
|
|
</sect1>
|
|
|
|
<sect1 id="quickstart-register-standby">
|
|
<title>Register the standby</title>
|
|
<para>
|
|
Register the standby server with:
|
|
<programlisting>
|
|
$ repmgr -f /etc/repmgr.conf standby register
|
|
NOTICE: standby node "node2" (ID: 2) successfully registered</programlisting>
|
|
</para>
|
|
<para>
|
|
Check the node is registered by executing <command>repmgr cluster show</command> on the standby:
|
|
<programlisting>
|
|
$ repmgr -f /etc/repmgr.conf cluster show
|
|
ID | Name | Role | Status | Upstream | Location | Connection string
|
|
----+-------+---------+-----------+----------+----------+--------------------------------------
|
|
1 | node1 | primary | * running | | default | host=node1 dbname=repmgr user=repmgr
|
|
2 | node2 | standby | running | node1 | default | host=node2 dbname=repmgr user=repmgr</programlisting>
|
|
</para>
|
|
<para>
|
|
Both nodes are now registered with &repmgr; and the records have been copied to the standby server.
|
|
</para>
|
|
</sect1>
|
|
|
|
</chapter>
|