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postgres/doc/src/sgml/ref/pg_ctl-ref.sgml
Tom Lane b4d8be9f6d Fix postmaster's behavior during smart shutdown. 
Up to now, upon receipt of a SIGTERM ("smart shutdown" command), the
postmaster has immediately killed all "optional" background processes,
and subsequently refused to launch new ones while it's waiting for
foreground client processes to exit.  No doubt this seemed like an OK
policy at some point; but it's a pretty bad one now, because it makes
for a seriously degraded environment for the remaining clients:

* Parallel queries are killed, and new ones fail to launch. (And our
parallel-query infrastructure utterly fails to deal with the case
in a reasonable way --- it just hangs waiting for workers that are
not going to arrive.  There is more work needed in that area IMO.)

* Autovacuum ceases to function.  We can tolerate that for awhile,
but if bulk-update queries continue to run in the surviving client
sessions, there's eventually going to be a mess.  In the worst case
the system could reach a forced shutdown to prevent XID wraparound.

* The bgwriter and walwriter are also stopped immediately, likely
resulting in performance degradation.

Hence, let's rearrange things so that the only immediate change in
behavior is refusing to let in new normal connections.  Once the last
normal connection is gone, shut everything down as though we'd received
a "fast" shutdown.  To implement this, remove the PM_WAIT_BACKUP and
PM_WAIT_READONLY states, instead staying in PM_RUN or PM_HOT_STANDBY
while normal connections remain.  A subsidiary state variable tracks
whether or not we're letting in new connections in those states.

This also allows having just one copy of the logic for killing child
processes in smart and fast shutdown modes.  I moved that logic into
PostmasterStateMachine() by inventing a new state PM_STOP_BACKENDS.

Back-patch to 9.6 where parallel query was added.  In principle
this'd be a good idea in 9.5 as well, but the risk/reward ratio
is not as good there, since lack of autovacuum is not a problem
during typical uses of smart shutdown.

Per report from Bharath Rupireddy.

Patch by me, reviewed by Thomas Munro

Discussion: https://postgr.es/m/CALj2ACXAZ5vKxT9P7P89D87i3MDO9bfS+_bjMHgnWJs8uwUOOw@mail.gmail.com
2020-08-14 13:26:57 -04:00

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<!--
doc/src/sgml/ref/pg_ctl-ref.sgml
PostgreSQL documentation
-->
<refentry id="app-pg-ctl">
<indexterm zone="app-pg-ctl">
<primary>pg_ctl</primary>
</indexterm>
<refmeta>
<refentrytitle><application>pg_ctl</application></refentrytitle>
<manvolnum>1</manvolnum>
<refmiscinfo>Application</refmiscinfo>
</refmeta>
<refnamediv>
<refname>pg_ctl</refname>
<refpurpose>initialize, start, stop, or control a <productname>PostgreSQL</productname> server</refpurpose>
</refnamediv>
<refsynopsisdiv>
<cmdsynopsis>
<command>pg_ctl</command>
<arg choice="plain"><option>init[db]</option></arg>
<arg choice="opt"><option>-s</option></arg>
<arg choice="opt"><option>-D</option> <replaceable>datadir</replaceable></arg>
<arg choice="opt"><option>-o</option> <replaceable>initdb-options</replaceable></arg>
</cmdsynopsis>
<cmdsynopsis>
<command>pg_ctl</command>
<arg choice="plain"><option>start</option></arg>
<arg choice="opt"><option>-w</option></arg>
<arg choice="opt"><option>-t</option> <replaceable>seconds</replaceable></arg>
<arg choice="opt"><option>-s</option></arg>
<arg choice="opt"><option>-D</option> <replaceable>datadir</replaceable></arg>
<arg choice="opt"><option>-l</option> <replaceable>filename</replaceable></arg>
<arg choice="opt"><option>-o</option> <replaceable>options</replaceable></arg>
<arg choice="opt"><option>-p</option> <replaceable>path</replaceable></arg>
<arg choice="opt"><option>-c</option></arg>
</cmdsynopsis>
<cmdsynopsis>
<command>pg_ctl</command>
<arg choice="plain"><option>stop</option></arg>
<arg choice="opt"><option>-W</option></arg>
<arg choice="opt"><option>-t</option> <replaceable>seconds</replaceable></arg>
<arg choice="opt"><option>-s</option></arg>
<arg choice="opt"><option>-D</option> <replaceable>datadir</replaceable></arg>
<arg choice="opt"><option>-m</option>
<group choice="plain">
<arg choice="plain"><option>s[mart]</option></arg>
<arg choice="plain"><option>f[ast]</option></arg>
<arg choice="plain"><option>i[mmediate]</option></arg>
</group>
</arg>
</cmdsynopsis>
<cmdsynopsis>
<command>pg_ctl</command>
<arg choice="plain"><option>restart</option></arg>
<arg choice="opt"><option>-w</option></arg>
<arg choice="opt"><option>-t</option> <replaceable>seconds</replaceable></arg>
<arg choice="opt"><option>-s</option></arg>
<arg choice="opt"><option>-D</option> <replaceable>datadir</replaceable></arg>
<arg choice="opt"><option>-c</option></arg>
<arg choice="opt"><option>-m</option>
<group choice="plain">
<arg choice="plain"><option>s[mart]</option></arg>
<arg choice="plain"><option>f[ast]</option></arg>
<arg choice="plain"><option>i[mmediate]</option></arg>
</group>
</arg>
<arg choice="opt"><option>-o</option> <replaceable>options</replaceable></arg>
</cmdsynopsis>
<cmdsynopsis>
<command>pg_ctl</command>
<arg choice="plain"><option>reload</option></arg>
<arg choice="opt"><option>-s</option></arg>
<arg choice="opt"><option>-D</option> <replaceable>datadir</replaceable></arg>
</cmdsynopsis>
<cmdsynopsis>
<command>pg_ctl</command>
<arg choice="plain"><option>status</option></arg>
<arg choice="opt"><option>-D</option> <replaceable>datadir</replaceable></arg>
</cmdsynopsis>
<cmdsynopsis>
<command>pg_ctl</command>
<arg choice="plain"><option>promote</option></arg>
<arg choice="opt"><option>-s</option></arg>
<arg choice="opt"><option>-D</option> <replaceable>datadir</replaceable></arg>
</cmdsynopsis>
<cmdsynopsis>
<command>pg_ctl</command>
<arg choice="plain"><option>kill</option></arg>
<arg choice="plain"><replaceable>signal_name</replaceable></arg>
<arg choice="plain"><replaceable>process_id</replaceable></arg>
</cmdsynopsis>
<cmdsynopsis>
<command>pg_ctl</command>
<arg choice="plain"><option>register</option></arg>
<arg choice="opt"><option>-N</option> <replaceable>servicename</replaceable></arg>
<arg choice="opt"><option>-U</option> <replaceable>username</replaceable></arg>
<arg choice="opt"><option>-P</option> <replaceable>password</replaceable></arg>
<arg choice="opt"><option>-D</option> <replaceable>datadir</replaceable></arg>
<arg choice="opt"><option>-S</option>
<group choice="plain">
<arg choice="plain"><option>a[uto]</option></arg>
<arg choice="plain"><option>d[emand]</option></arg>
</group>
</arg>
<arg choice="opt"><option>-w</option></arg>
<arg choice="opt"><option>-t</option> <replaceable>seconds</replaceable></arg>
<arg choice="opt"><option>-s</option></arg>
<arg choice="opt"><option>-o</option> <replaceable>options</replaceable></arg>
</cmdsynopsis>
<cmdsynopsis>
<command>pg_ctl</command>
<arg choice="plain"><option>unregister</option></arg>
<arg choice="opt"><option>-N</option> <replaceable>servicename</replaceable></arg>
</cmdsynopsis>
</refsynopsisdiv>
<refsect1 id="app-pg-ctl-description">
<title>Description</title>
<para>
<application>pg_ctl</application> is a utility for initializing a
<productname>PostgreSQL</productname> database cluster, starting,
stopping, or restarting the <productname>PostgreSQL</productname>
database server (<xref linkend="app-postgres">), or displaying the
status of a running server. Although the server can be started
manually, <application>pg_ctl</application> encapsulates tasks such
as redirecting log output and properly detaching from the terminal
and process group. It also provides convenient options for
controlled shutdown.
</para>
<para>
The <option>init</option> or <option>initdb</option> mode creates a new
<productname>PostgreSQL</productname> database cluster. A database
cluster is a collection of databases that are managed by a single
server instance. This mode invokes the <command>initdb</command>
command. See <xref linkend="app-initdb"> for details.
</para>
<para>
In <option>start</option> mode, a new server is launched. The
server is started in the background, and its standard input is attached
to <filename>/dev/null</filename> (or <literal>nul</> on Windows).
On Unix-like systems, by default, the server's standard output and
standard error are sent to <application>pg_ctl</application>'s
standard output (not standard error). The standard output of
<application>pg_ctl</application> should then be redirected to a
file or piped to another process such as a log rotating program
like <application>rotatelogs</>; otherwise <command>postgres</command>
will write its output to the controlling terminal (from the
background) and will not leave the shell's process group. On
Windows, by default the server's standard output and standard error
are sent to the terminal. These default behaviors can be changed
by using <option>-l</option> to append the server's output to a log file.
Use of either <option>-l</option> or output redirection is recommended.
</para>
<para>
In <option>stop</option> mode, the server that is running in
the specified data directory is shut down. Three different
shutdown methods can be selected with the <option>-m</option>
option. <quote>Smart</quote> mode disallows new connections, then waits
for all existing clients to disconnect and any online backup to finish.
If the server is in hot standby, recovery and streaming replication
will be terminated once all clients have disconnected.
<quote>Fast</quote> mode (the default) does not wait for clients to disconnect and
will terminate an online backup in progress. All active transactions are
rolled back and clients are forcibly disconnected, then the
server is shut down. <quote>Immediate</quote> mode will abort
all server processes immediately, without a clean shutdown.
This will lead to a crash-recovery run on the next restart.
</para>
<para>
<option>restart</option> mode effectively executes a stop followed
by a start. This allows changing the <command>postgres</command>
command-line options. <option>restart</option> might fail if
relative paths specified were specified on the command-line during
server start.
</para>
<para>
<option>reload</option> mode simply sends the
<command>postgres</command> process a <systemitem>SIGHUP</>
signal, causing it to reread its configuration files
(<filename>postgresql.conf</filename>,
<filename>pg_hba.conf</filename>, etc.). This allows changing of
configuration-file options that do not require a complete restart
to take effect.
</para>
<para>
<option>status</option> mode checks whether a server is running in
the specified data directory. If it is, the <acronym>PID</acronym>
and the command line options that were used to invoke it are
displayed. If the server is not running, the process returns an
exit status of 3. If an accessible data directory is not specified,
the process returns an exit status of 4.
</para>
<para>
In <option>promote</option> mode, the standby server that is
running in the specified data directory is commanded to exit
recovery and begin read-write operations.
</para>
<para>
<option>kill</option> mode allows you to send a signal to a specified
process. This is particularly valuable for <productname>Microsoft Windows</>
which does not have a <application>kill</> command. Use
<literal>--help</> to see a list of supported signal names.
</para>
<para>
<option>register</option> mode allows you to register a system service
on <productname>Microsoft Windows</>. The <option>-S</option> option
allows selection of service start type, either <quote>auto</quote> (start
service automatically on system startup) or <quote>demand</quote> (start
service on demand).
</para>
<para>
<option>unregister</option> mode allows you to unregister a system service
on <productname>Microsoft Windows</>. This undoes the effects of the
<option>register</option> command.
</para>
</refsect1>
<refsect1 id="app-pg-ctl-options">
<title>Options</title>
<variablelist>
<varlistentry>
<term><option>-c</option></term>
<term><option>--core-file</option></term>
<listitem>
<para>
Attempt to allow server crashes to produce core files, on platforms
where this is possible, by lifting any soft resource limit placed on
core files.
This is useful in debugging or diagnosing problems by allowing a
stack trace to be obtained from a failed server process.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-D <replaceable class="parameter">datadir</replaceable></option></term>
<term><option>--pgdata <replaceable class="parameter">datadir</replaceable></option></term>
<listitem>
<para>
Specifies the file system location of the database configuration files. If
this is omitted, the environment variable
<envar>PGDATA</envar> is used.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-l <replaceable class="parameter">filename</replaceable></option></term>
<term><option>--log <replaceable class="parameter">filename</replaceable></option></term>
<listitem>
<para>
Append the server log output to
<replaceable>filename</replaceable>. If the file does not
exist, it is created. The <systemitem>umask</> is set to 077,
so access to the log file is disallowed to other users by default.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-m <replaceable class="parameter">mode</replaceable></option></term>
<term><option>--mode <replaceable class="parameter">mode</replaceable></option></term>
<listitem>
<para>
Specifies the shutdown mode. <replaceable>mode</replaceable>
can be <literal>smart</literal>, <literal>fast</literal>, or
<literal>immediate</literal>, or the first letter of one of
these three. If this is omitted, <literal>fast</literal> is used.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-o <replaceable class="parameter">options</replaceable></option></term>
<listitem>
<para>
Specifies options to be passed directly to the
<command>postgres</command> command; multiple
option invocations are appended.
</para>
<para>
The options should usually be surrounded by single or double
quotes to ensure that they are passed through as a group.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-o <replaceable class="parameter">initdb-options</replaceable></option></term>
<listitem>
<para>
Specifies options to be passed directly to the
<command>initdb</command> command.
</para>
<para>
The options should usually be surrounded by single or double
quotes to ensure that they are passed through as a group.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-p <replaceable class="parameter">path</replaceable></option></term>
<listitem>
<para>
Specifies the location of the <filename>postgres</filename>
executable. By default the <filename>postgres</filename> executable is taken from the same
directory as <command>pg_ctl</command>, or failing that, the hard-wired
installation directory. It is not necessary to use this
option unless you are doing something unusual and get errors
that the <filename>postgres</filename> executable was not found.
</para>
<para>
In <literal>init</literal> mode, this option analogously
specifies the location of the <filename>initdb</filename>
executable.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-s</option></term>
<term><option>--silent</option></term>
<listitem>
<para>
Print only errors, no informational messages.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-t</option></term>
<term><option>--timeout</option></term>
<listitem>
<para>
The maximum number of seconds to wait when waiting for startup or
shutdown to complete. Defaults to the value of the
<envar>PGCTLTIMEOUT</> environment variable or, if not set, to 60
seconds.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-V</></term>
<term><option>--version</></term>
<listitem>
<para>
Print the <application>pg_ctl</application> version and exit.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-w</option></term>
<listitem>
<para>
Wait for the startup or shutdown to complete.
Waiting is the default option for shutdowns, but not startups.
When waiting for startup, <command>pg_ctl</command> repeatedly
attempts to connect to the server.
When waiting for shutdown, <command>pg_ctl</command> waits for
the server to remove its <acronym>PID</acronym> file.
This option allows the entry of an <acronym>SSL</> passphrase on startup.
<command>pg_ctl</command> returns an exit code based on the
success of the startup or shutdown.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-W</option></term>
<listitem>
<para>
Do not wait for startup or shutdown to complete. This is the
default for start and restart modes.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-?</></term>
<term><option>--help</></term>
<listitem>
<para>
Show help about <application>pg_ctl</application> command line
arguments, and exit.
</para>
</listitem>
</varlistentry>
</variablelist>
<refsect2 id="app-pg-ctl-windows-options">
<title>Options for Windows</title>
<variablelist>
<varlistentry>
<term><option>-e <replaceable class="parameter">source</replaceable></option></term>
<listitem>
<para>
Name of the event source for <application>pg_ctl</application> to use
for logging to the event log when running as a Windows service. The
default is <literal>PostgreSQL</literal>. Note that this only controls
the logging from <application>pg_ctl</application> itself; once
started, the server will use the event source specified
by <xref linkend="guc-event-source">. Should the server fail during
early startup, it might also log using the default event
source <literal>PostgreSQL</literal>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-N <replaceable class="parameter">servicename</replaceable></option></term>
<listitem>
<para>
Name of the system service to register. The name will be used
as both the service name and the display name.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-P <replaceable class="parameter">password</replaceable></option></term>
<listitem>
<para>
Password for the user to start the service.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-S <replaceable class="parameter">start-type</replaceable></option></term>
<listitem>
<para>
Start type of the system service to register. start-type can
be <literal>auto</literal>, or <literal>demand</literal>, or
the first letter of one of these two. If this is omitted,
<literal>auto</literal> is used.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-U <replaceable class="parameter">username</replaceable></option></term>
<listitem>
<para>
User name for the user to start the service. For domain users, use the
format <literal>DOMAIN\username</literal>.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect2>
</refsect1>
<refsect1>
<title>Environment</title>
<variablelist>
<varlistentry>
<term><envar>PGCTLTIMEOUT</envar></term>
<listitem>
<para>
Default limit on the number of seconds to wait when waiting for startup
or shutdown to complete. If not set, the default is 60 seconds.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><envar>PGDATA</envar></term>
<listitem>
<para>
Default data directory location.
</para>
</listitem>
</varlistentry>
</variablelist>
<para>
<command>pg_ctl</command>, like most other <productname>PostgreSQL</>
utilities,
also uses the environment variables supported by <application>libpq</>
(see <xref linkend="libpq-envars">).
For additional server variables, see <xref linkend="app-postgres">.
</para>
</refsect1>
<refsect1>
<title>Files</title>
<variablelist>
<varlistentry>
<term><filename>postmaster.pid</filename></term>
<listitem>
<para>
The existence of this file in the data directory is used to help
<application>pg_ctl</application> determine if the server is
currently running.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>postmaster.opts</filename></term>
<listitem>
<para>If this file exists in the data directory,
<application>pg_ctl</application> (in <option>restart</option> mode)
will pass the contents of the file as options to
<application>postgres</application>, unless overridden
by the <option>-o</option> option. The contents of this file
are also displayed in <option>status</option> mode.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 id="R1-APP-PGCTL-2">
<title>Examples</title>
<refsect2 id="R2-APP-PGCTL-3">
<title>Starting the Server</title>
<para>
To start the server:
<screen>
<prompt>$</prompt> <userinput>pg_ctl start</userinput>
</screen>
</para>
<para>
To start the server, waiting until the server is
accepting connections:
<screen>
<prompt>$</prompt> <userinput>pg_ctl -w start</userinput>
</screen>
</para>
<para>
To start the server using port 5433, and
running without <function>fsync</function>, use:
<screen>
<prompt>$</prompt> <userinput>pg_ctl -o "-F -p 5433" start</userinput>
</screen></para>
</refsect2>
<refsect2 id="R2-APP-PGCTL-4">
<title>Stopping the Server</title>
<para>
To stop the server, use:
<screen>
<prompt>$</prompt> <userinput>pg_ctl stop</userinput>
</screen>
The <option>-m</option> option allows control over
<emphasis>how</emphasis> the server shuts down:
<screen>
<prompt>$</prompt> <userinput>pg_ctl stop -m fast</userinput>
</screen></para>
</refsect2>
<refsect2 id="R2-APP-PGCTL-5">
<title>Restarting the Server</title>
<para>
Restarting the server is almost equivalent to stopping the
server and starting it again,
except that <command>pg_ctl</command> saves and reuses the command line options that
were passed to the previously running instance. To restart
the server in the simplest form, use:
<screen>
<prompt>$</prompt> <userinput>pg_ctl restart</userinput>
</screen>
</para>
<para>
To restart the server,
waiting for it to shut down and restart:
<screen>
<prompt>$</prompt> <userinput>pg_ctl -w restart</userinput>
</screen>
</para>
<para>
To restart using port 5433, disabling <function>fsync</> upon restart:
<screen>
<prompt>$</prompt> <userinput>pg_ctl -o "-F -p 5433" restart</userinput>
</screen></para>
</refsect2>
<refsect2 id="R2-APP-PGCTL-6">
<title>Showing the Server Status</title>
<para>
Here is sample status output from
<application>pg_ctl</application>:
<screen>
<prompt>$</prompt> <userinput>pg_ctl status</userinput>
<computeroutput>
pg_ctl: server is running (PID: 13718)
/usr/local/pgsql/bin/postgres "-D" "/usr/local/pgsql/data" "-p" "5433" "-B" "128"
</computeroutput>
</screen>
This is the command line that would be invoked in restart mode.
</para>
</refsect2>
</refsect1>
<refsect1>
<title>See Also</title>
<simplelist type="inline">
<member><xref linkend="app-initdb"></member>
<member><xref linkend="app-postgres"></member>
</simplelist>
</refsect1>
</refentry>
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