diff options
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/config.sgml | 68 | ||||
| -rw-r--r-- | doc/src/sgml/high-availability.sgml | 44 | ||||
| -rw-r--r-- | doc/src/sgml/monitoring.sgml | 9 |
3 files changed, 91 insertions, 30 deletions
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index 3b614b6ecdf..1b98c416e06 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -3054,41 +3054,71 @@ include_dir 'conf.d' transactions waiting for commit will be allowed to proceed after these standby servers confirm receipt of their data. The synchronous standbys will be those whose names appear - earlier in this list, and + in this list, and that are both currently connected and streaming data in real-time (as shown by a state of <literal>streaming</literal> in the <link linkend="monitoring-stats-views-table"> <literal>pg_stat_replication</></link> view). - Other standby servers appearing later in this list represent potential - synchronous standbys. If any of the current synchronous - standbys disconnects for whatever reason, - it will be replaced immediately with the next-highest-priority standby. - Specifying more than one standby name can allow very high availability. + Specifying more than one standby names can allow very high availability. </para> <para> This parameter specifies a list of standby servers using either of the following syntaxes: <synopsis> -<replaceable class="parameter">num_sync</replaceable> ( <replaceable class="parameter">standby_name</replaceable> [, ...] ) +[FIRST] <replaceable class="parameter">num_sync</replaceable> ( <replaceable class="parameter">standby_name</replaceable> [, ...] ) +ANY <replaceable class="parameter">num_sync</replaceable> ( <replaceable class="parameter">standby_name</replaceable> [, ...] ) <replaceable class="parameter">standby_name</replaceable> [, ...] </synopsis> where <replaceable class="parameter">num_sync</replaceable> is the number of synchronous standbys that transactions need to wait for replies from, and <replaceable class="parameter">standby_name</replaceable> - is the name of a standby server. For example, a setting of - <literal>3 (s1, s2, s3, s4)</> makes transaction commits wait - until their WAL records are received by three higher-priority standbys - chosen from standby servers <literal>s1</>, <literal>s2</>, - <literal>s3</> and <literal>s4</>. - </para> - <para> - The second syntax was used before <productname>PostgreSQL</> + is the name of a standby server. + <literal>FIRST</> and <literal>ANY</> specify the method to choose + synchronous standbys from the listed servers. + </para> + <para> + The keyword <literal>FIRST</>, coupled with + <replaceable class="parameter">num_sync</replaceable>, specifies a + priority-based synchronous replication and makes transaction commits + wait until their WAL records are replicated to + <replaceable class="parameter">num_sync</replaceable> synchronous + standbys chosen based on their priorities. For example, a setting of + <literal>FIRST 3 (s1, s2, s3, s4)</> will cause each commit to wait for + replies from three higher-priority standbys chosen from standby servers + <literal>s1</>, <literal>s2</>, <literal>s3</> and <literal>s4</>. + The standbys whose names appear earlier in the list are given higher + priority and will be considered as synchronous. Other standby servers + appearing later in this list represent potential synchronous standbys. + If any of the current synchronous standbys disconnects for whatever + reason, it will be replaced immediately with the next-highest-priority + standby. The keyword <literal>FIRST</> is optional. + </para> + <para> + The keyword <literal>ANY</>, coupled with + <replaceable class="parameter">num_sync</replaceable>, specifies a + quorum-based synchronous replication and makes transaction commits + wait until their WAL records are replicated to <emphasis>at least</> + <replaceable class="parameter">num_sync</replaceable> listed standbys. + For example, a setting of <literal>ANY 3 (s1, s2, s3, s4)</> will cause + each commit to proceed as soon as at least any three standbys of + <literal>s1</>, <literal>s2</>, <literal>s3</> and <literal>s4</> + reply. + </para> + <para> + <literal>FIRST</> and <literal>ANY</> are case-insensitive. If these + keywords are used as the name of a standby server, + its <replaceable class="parameter">standby_name</replaceable> must + be double-quoted. + </para> + <para> + The third syntax was used before <productname>PostgreSQL</> version 9.6 and is still supported. It's the same as the first syntax - with <replaceable class="parameter">num_sync</replaceable> equal to 1. - For example, <literal>1 (s1, s2)</> and - <literal>s1, s2</> have the same meaning: either <literal>s1</> - or <literal>s2</> is chosen as a synchronous standby. + with <literal>FIRST</> and + <replaceable class="parameter">num_sync</replaceable> equal to 1. + For example, <literal>FIRST 1 (s1, s2)</> and <literal>s1, s2</> have + the same meaning: either <literal>s1</> or <literal>s2</> is chosen + as a synchronous standby. </para> <para> The name of a standby server for this purpose is the diff --git a/doc/src/sgml/high-availability.sgml b/doc/src/sgml/high-availability.sgml index 6b89507c8c9..a1a9532088a 100644 --- a/doc/src/sgml/high-availability.sgml +++ b/doc/src/sgml/high-availability.sgml @@ -1138,19 +1138,25 @@ primary_slot_name = 'node_a_slot' as synchronous confirm receipt of their data. The number of synchronous standbys that transactions must wait for replies from is specified in <varname>synchronous_standby_names</>. This parameter also specifies - a list of standby names, which determines the priority of each standby - for being chosen as a synchronous standby. The standbys whose names - appear earlier in the list are given higher priority and will be considered - as synchronous. Other standby servers appearing later in this list - represent potential synchronous standbys. If any of the current - synchronous standbys disconnects for whatever reason, it will be replaced - immediately with the next-highest-priority standby. + a list of standby names and the method (<literal>FIRST</> and + <literal>ANY</>) to choose synchronous standbys from the listed ones. </para> <para> - An example of <varname>synchronous_standby_names</> for multiple - synchronous standbys is: + The method <literal>FIRST</> specifies a priority-based synchronous + replication and makes transaction commits wait until their WAL records are + replicated to the requested number of synchronous standbys chosen based on + their priorities. The standbys whose names appear earlier in the list are + given higher priority and will be considered as synchronous. Other standby + servers appearing later in this list represent potential synchronous + standbys. If any of the current synchronous standbys disconnects for + whatever reason, it will be replaced immediately with the + next-highest-priority standby. + </para> + <para> + An example of <varname>synchronous_standby_names</> for + a priority-based multiple synchronous standbys is: <programlisting> -synchronous_standby_names = '2 (s1, s2, s3)' +synchronous_standby_names = 'FIRST 2 (s1, s2, s3)' </programlisting> In this example, if four standby servers <literal>s1</>, <literal>s2</>, <literal>s3</> and <literal>s4</> are running, the two standbys @@ -1162,6 +1168,24 @@ synchronous_standby_names = '2 (s1, s2, s3)' its name is not in the list. </para> <para> + The method <literal>ANY</> specifies a quorum-based synchronous + replication and makes transaction commits wait until their WAL records + are replicated to <emphasis>at least</> the requested number of + synchronous standbys in the list. + </para> + <para> + An example of <varname>synchronous_standby_names</> for + a quorum-based multiple synchronous standbys is: +<programlisting> + synchronous_standby_names = 'ANY 2 (s1, s2, s3)' +</programlisting> + In this example, if four standby servers <literal>s1</>, <literal>s2</>, + <literal>s3</> and <literal>s4</> are running, transaction commits will + wait for replies from at least any two standbys of <literal>s1</>, + <literal>s2</> and <literal>s3</>. <literal>s4</> is an asynchronous + standby since its name is not in the list. + </para> + <para> The synchronous states of standby servers can be viewed using the <structname>pg_stat_replication</structname> view. </para> diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml index 5b58d2e84dc..02bc8feca77 100644 --- a/doc/src/sgml/monitoring.sgml +++ b/doc/src/sgml/monitoring.sgml @@ -1404,7 +1404,8 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i <entry><structfield>sync_priority</></entry> <entry><type>integer</></entry> <entry>Priority of this standby server for being chosen as the - synchronous standby</entry> + synchronous standby in a priority-based synchronous replication. + This has no effect in a quorum-based synchronous replication.</entry> </row> <row> <entry><structfield>sync_state</></entry> @@ -1429,6 +1430,12 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i <literal>sync</>: This standby server is synchronous. </para> </listitem> + <listitem> + <para> + <literal>quorum</>: This standby server is considered as a candidate + for quorum standbys. + </para> + </listitem> </itemizedlist> </entry> </row> |