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Code review for recent patch to terminate online backup during shutdown:

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do CancelBackup at a sane place, fix some oversights in the state transitions,
allow only superusers to connect while we are waiting for backup mode to end.
This commit is contained in:
Tom Lane
2008-04-26 22:47:40 +00:00
parent b6e2fab978
commit ea0382e370
4 changed files with 58 additions and 38 deletions
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25
doc/src/sgml/runtime.sgml
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@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.415 2008/04/23 13:44:58 mha Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.416 2008/04/26 22:47:40 tgl Exp $ -->
<chapter Id="runtime">
<title>Operating System Environment</title>
@ -1306,12 +1306,15 @@ sysctl -w vm.overcommit_memory=2
<term><systemitem>SIGTERM</systemitem><indexterm><primary>SIGTERM</></></term>
<listitem>
<para>
This is the <firstterm>Smart Shutdown</firstterm> mode.
After receiving <systemitem>SIGTERM</systemitem>, the server
waits until online backup mode is no longer active. It then
disallows new connections, but lets existing sessions end their
work normally. It shuts down only after all of the sessions
terminate normally. This is the <firstterm>Smart
Shutdown</firstterm>.
work normally. It shuts down only after all of the sessions terminate.
If the server is in online backup mode, it additionally waits
until online backup mode is no longer active. While backup mode is
active, new connections will still be allowed, but only to superusers
(this exception allows a superuser to connect to terminate
online backup mode).
</para>
</listitem>
</varlistentry>
@ -1320,13 +1323,13 @@ sysctl -w vm.overcommit_memory=2
<term><systemitem>SIGINT</systemitem><indexterm><primary>SIGINT</></></term>
<listitem>
<para>
This is the <firstterm>Fast Shutdown</firstterm> mode.
The server disallows new connections and sends all existing
server processes <systemitem>SIGTERM</systemitem>, which will cause them
to abort their current transactions and exit promptly. It then
waits for the server processes to exit and finally shuts down.
If the server is in online backup mode, backup mode will be
terminated, rendering the backup useless. This is the
<firstterm>Fast Shutdown</firstterm>.
terminated, rendering the backup useless.
</para>
</listitem>
</varlistentry>
@ -1335,8 +1338,8 @@ sysctl -w vm.overcommit_memory=2
<term><systemitem>SIGQUIT</systemitem><indexterm><primary>SIGQUIT</></></term>
<listitem>
<para>
This is the <firstterm>Immediate Shutdown</firstterm>, which
will cause the master <command>postgres</command> process to send a
This is the <firstterm>Immediate Shutdown</firstterm> mode.
The master <command>postgres</command> process will send a
<systemitem>SIGQUIT</systemitem> to all child processes and exit
immediately, without properly shutting itself down. The child processes
likewise exit immediately upon receiving
@ -1377,8 +1380,8 @@ $ <userinput>kill -INT `head -1 /usr/local/pgsql/data/postmaster.pid`</userinput
</important>
<para>
To terminate a session while allowing other sessions to continue, use
<function>pg_terminate_backend()</> (<xref
To terminate an individual session while allowing other sessions to
continue, use <function>pg_terminate_backend()</> (see <xref
linkend="functions-admin-signal-table">) or send a
<systemitem>SIGTERM</> signal to the child process associated with
the session.