-<?xml version='1.0'?> <!--*-nxml-*-->
+<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<funcdef>int <function>sd_notifyf</function></funcdef>
<paramdef>int <parameter>unset_environment</parameter></paramdef>
<paramdef>const char *<parameter>format</parameter></paramdef>
- <paramdef>...</paramdef>
+ <paramdef>…</paramdef>
</funcprototype>
<funcprototype>
<paramdef>pid_t <parameter>pid</parameter></paramdef>
<paramdef>int <parameter>unset_environment</parameter></paramdef>
<paramdef>const char *<parameter>format</parameter></paramdef>
- <paramdef>...</paramdef>
+ <paramdef>…</paramdef>
</funcprototype>
<funcprototype>
<para><function>sd_notify()</function> may be called by a service
to notify the service manager about state changes. It can be used
to send arbitrary information, encoded in an
- environment-block-like string. Most importantly it can be used for
+ environment-block-like string. Most importantly, it can be used for
start-up completion notification.</para>
<para>If the <parameter>unset_environment</parameter> parameter is
</varlistentry>
<varlistentry>
- <term>STATUS=...</term>
+ <term>STATUS=…</term>
<listitem><para>Passes a single-line UTF-8 status string back
to the service manager that describes the service state. This
is free-form and can be used for various purposes: general
state feedback, fsck-like programs could pass completion
- percentages and failing programs could pass a human readable
+ percentages and failing programs could pass a human-readable
error message. Example: <literal>STATUS=Completed 66% of file
- system check...</literal></para></listitem>
+ system check…</literal></para></listitem>
</varlistentry>
<varlistentry>
- <term>ERRNO=...</term>
+ <term>ERRNO=…</term>
<listitem><para>If a service fails, the errno-style error
code, formatted as string. Example: <literal>ERRNO=2</literal>
</varlistentry>
<varlistentry>
- <term>BUSERROR=...</term>
+ <term>BUSERROR=…</term>
<listitem><para>If a service fails, the D-Bus error-style
error code. Example:
</varlistentry>
<varlistentry>
- <term>MAINPID=...</term>
+ <term>MAINPID=…</term>
<listitem><para>The main process ID (PID) of the service, in
case the service manager did not fork off the process itself.
watchdog timestamp. This is the keep-alive ping that services
need to issue in regular intervals if
<varname>WatchdogSec=</varname> is enabled for it. See
- <citerefentry><refentrytitle>elogind.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
for information how to enable this functionality and
<citerefentry><refentrytitle>sd_watchdog_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>
for the details of how the service can check whether the
<varlistentry>
<term>FDSTORE=1</term>
- <listitem><para>Stores additional file descriptors in the
- service manager. File descriptors sent this way will be
- maintained per-service by the service manager and be passed
- again using the usual file descriptor passing logic on the
- next invocation of the service (see
- <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>).
- This is useful for implementing service restart schemes where
- services serialize their state to <filename>/run</filename>,
- push their file descriptors to the system manager, and are
- then restarted, retrieving their state again via socket
- passing and <filename>/run</filename>. Note that the service
- manager will accept messages for a service only if
- <varname>FileDescriptorStoreMax=</varname> is set to non-zero
- for it (defaults to zero). See
- <citerefentry><refentrytitle>elogind.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
- for details. Multiple arrays of file descriptors may be sent
- in separate messages, in which case the arrays are combined.
- Note that the service manager removes duplicate file
- descriptors before passing them to the service. Use
- <function>sd_pid_notify_with_fds()</function> to send messages
- with <literal>FDSTORE=1</literal>, see
- below.</para></listitem>
+ <listitem><para>Stores additional file descriptors in the service manager. File descriptors sent this way will
+ be maintained per-service by the service manager and will later be handed back using the usual file descriptor
+ passing logic at the next invocation of the service, see
+ <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>. This is
+ useful for implementing services that can restart after an explicit request or a crash without losing
+ state. Any open sockets and other file descriptors which should not be closed during the restart may be stored
+ this way. Application state can either be serialized to a file in <filename>/run</filename>, or better, stored
+ in a <citerefentry><refentrytitle>memfd_create</refentrytitle><manvolnum>2</manvolnum></citerefentry> memory
+ file descriptor. Note that the service manager will accept messages for a service only if its
+ <varname>FileDescriptorStoreMax=</varname> setting is non-zero (defaults to zero, see
+ <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>). If file
+ descriptors sent are pollable (see
+ <citerefentry><refentrytitle>epoll_ctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>), then any
+ <constant>EPOLLHUP</constant> or <constant>EPOLLERR</constant> event seen on them will result in their
+ automatic removal from the store. Multiple arrays of file descriptors may be sent in separate messages, in
+ which case the arrays are combined. Note that the service manager removes duplicate (pointing to the same
+ object) file descriptors before passing them to the service. Use <function>sd_pid_notify_with_fds()</function>
+ to send messages with <literal>FDSTORE=1</literal>, see below.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>FDNAME=…</term>
+
+ <listitem><para>When used in combination with
+ <varname>FDSTORE=1</varname>, specifies a name for the
+ submitted file descriptors. This name is passed to the service
+ during activation, and may be queried using
+ <citerefentry><refentrytitle>sd_listen_fds_with_names</refentrytitle><manvolnum>3</manvolnum></citerefentry>. File
+ descriptors submitted without this field set, will implicitly
+ get the name <literal>stored</literal> assigned. Note that, if
+ multiple file descriptors are submitted at once, the specified
+ name will be assigned to all of them. In order to assign
+ different names to submitted file descriptors, submit them in
+ separate invocations of
+ <function>sd_pid_notify_with_fds()</function>. The name may
+ consist of any ASCII character, but must not contain control
+ characters or <literal>:</literal>. It may not be longer than
+ 255 characters. If a submitted name does not follow these
+ restrictions, it is ignored.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>WATCHDOG_USEC=…</term>
+
+ <listitem><para>Reset <varname>watchdog_usec</varname> value during runtime.
+ Notice that this is not available when using <function>sd_event_set_watchdog()</function>
+ or <function>sd_watchdog_enabled()</function>.
+ Example : <literal>WATCHDOG_USEC=20000000</literal></para></listitem>
</varlistentry>
</variablelist>
<para>Note that elogind will accept status data sent from a
service only if the <varname>NotifyAccess=</varname> option is
correctly set in the service definition file. See
- <citerefentry><refentrytitle>elogind.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
for details.</para>
+ <para>Note that <function>sd_notify()</function> notifications may be attributed to units correctly only if either
+ the sending process is still around at the time PID 1 processes the message, or if the sending process is
+ explicitly runtime-tracked by the service manager. The latter is the case if the service manager originally forked
+ off the process, i.e. on all processes that match <varname>NotifyAccess=</varname><option>main</option> or
+ <varname>NotifyAccess=</varname><option>exec</option>. Conversely, if an auxiliary process of the unit sends an
+ <function>sd_notify()</function> message and immediately exits, the service manager might not be able to properly
+ attribute the message to the unit, and thus will ignore it, even if
+ <varname>NotifyAccess=</varname><option>all</option> is set for it.</para>
+
<para><function>sd_notifyf()</function> is similar to
<function>sd_notify()</function> but takes a
<function>printf()</function>-like format string plus
use as originating PID for the message as first argument. This is
useful to send notification messages on behalf of other processes,
provided the appropriate privileges are available. If the PID
- argument is specified as 0 the process ID of the calling process
+ argument is specified as 0, the process ID of the calling process
is used, in which case the calls are fully equivalent to
<function>sd_notify()</function> and
<function>sd_notifyf()</function>.</para>
<refsect1>
<title>Return Value</title>
- <para>On failure, these calls return a negative errno-style error
- code. If <varname>$NOTIFY_SOCKET</varname> was not set and hence
- no status data could be sent, 0 is returned. If the status was
- sent, these functions return with a positive return value. In
- order to support both, init systems that implement this scheme and
- those which do not, it is generally recommended to ignore the
- return value of this call.</para>
+ <para>On failure, these calls return a negative errno-style error code. If <varname>$NOTIFY_SOCKET</varname> was
+ not set and hence no status message could be sent, 0 is returned. If the status was sent, these functions return a
+ positive value. In order to support both service managers that implement this scheme and those which do not, it is
+ generally recommended to ignore the return value of this call. Note that the return value simply indicates whether
+ the notification message was enqueued properly, it does not reflect whether the message could be processed
+ successfully. Specifically, no error is returned when a file descriptor is attempted to be stored using
+ <varname>FDSTORE=1</varname> but the service is not actually configured to permit storing of file descriptors (see
+ above).</para>
</refsect1>
<refsect1>
<xi:include href="libelogind-pkgconfig.xml" xpointer="pkgconfig-text"/>
- <para>Internally, these functions send a single datagram with the
+ <para>These functions send a single datagram with the
state string as payload to the <constant>AF_UNIX</constant> socket
referenced in the <varname>$NOTIFY_SOCKET</varname> environment
variable. If the first character of
initialization:</para>
<programlisting>sd_notifyf(0, "READY=1\n"
- "STATUS=Processing requests...\n"
+ "STATUS=Processing requests…\n"
"MAINPID=%lu",
(unsigned long) getpid());</programlisting>
</example>
<para>To store an open file descriptor in the service manager,
in order to continue operation after a service restart without
- losing state use <literal>FDSTORE=1</literal>:</para>
+ losing state, use <literal>FDSTORE=1</literal>:</para>
- <programlisting>sd_pid_notify_with_fds(0, 0, "FDSTORE=1", &fd, 1);</programlisting>
+ <programlisting>sd_pid_notify_with_fds(0, 0, "FDSTORE=1\nFDNAME=foobar", &fd, 1);</programlisting>
</example>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
- <citerefentry><refentrytitle>elogind</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_listen_fds_with_names</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_watchdog_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>elogind.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd_watchdog_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>
</para>
</refsect1>
~ianmdlvl / elogind.git / blobdiff