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Merge pull request #5239 from poettering/notify-access-all 

man: document that sd_notify() is racy in some cases
This commit is contained in:
Evgeny Vereshchagin 2017-02-06 23:59:33 +03:00 committed by GitHub
parent 6a1da642b3 aa20394579
commit 1fb8579749
4 changed files with 51 additions and 23 deletions
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5
TODO
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@ -24,6 +24,11 @@ Janitorial Clean-ups:
Features:
* maybe add call sd_journal_set_block_timeout() or so to set SO_SNDTIMEO for
the sd-journal logging socket, and, if the timeout is set to 0, sets
O_NONBLOCK on it. That way people can control if and when to block for
logging.
* journald: when we recv a log datagram via the native or syslog transports,
search for the PID in the active stream connections, and let's make sure to
always process the datagrams before the streams. Then, cache client metadata

9
man/sd_notify.xml
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@ -268,6 +268,15 @@
<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

20
man/systemd-notify.xml
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@ -72,10 +72,24 @@
<para>The command line may carry a list of environment variables
to send as part of the status update.</para>
<para>Note that systemd will refuse reception of status updates
from this command unless <varname>NotifyAccess=all</varname> is
set for the service unit this command is called from.</para>
<para>Note that systemd will refuse reception of status updates from this command unless
<varname>NotifyAccess=</varname> is set for the service unit this command is called from.</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><command>systemd-notify</command> will first attempt to invoke <function>sd_notify()</function> pretending to
have the PID of the invoking process. This will only succeed when invoked with sufficient privileges. On failure,
it will then fall back to invoking it under its own PID. This behaviour is useful in order that when the tool is
invoked from a shell script the shell process — and not the <command>systemd-notify</command> process — appears as
sender of the message, which in turn is helpful if the shell process is the main process of a service, due to the
limitations of <varname>NotifyAccess=</varname><option>all</option> described above.</para>
</refsect1>
<refsect1>

40
man/systemd.service.xml
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@ -792,26 +792,26 @@
<varlistentry>
<term><varname>NotifyAccess=</varname></term>
<listitem><para>Controls access to the service status
notification socket, as accessible via the
<citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>
call. Takes one of <option>none</option> (the default),
<option>main</option>, <option>exec</option> or
<option>all</option>. If <option>none</option>, no daemon status
updates are accepted from the service processes, all status
update messages are ignored. If <option>main</option>, only
service updates sent from the main process of the service are
accepted. If <option>exec</option>, only service updates sent
from any of the control processes originating from one of the
<varname>Exec*=</varname> commands are accepted. If
<option>all</option>, all services updates from all members of
the service's control group are accepted. This option should
be set to open access to the notification socket when using
<varname>Type=notify</varname> or
<varname>WatchdogSec=</varname> (see above). If those options
are used but <varname>NotifyAccess=</varname> is not
configured, it will be implicitly set to
<option>main</option>.</para></listitem>
<listitem><para>Controls access to the service status notification socket, as accessible via the
<citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry> call. Takes one
of <option>none</option> (the default), <option>main</option>, <option>exec</option> or
<option>all</option>. If <option>none</option>, no daemon status updates are accepted from the service
processes, all status update messages are ignored. If <option>main</option>, only service updates sent from the
main process of the service are accepted. If <option>exec</option>, only service updates sent from any of the
main or control processes originating from one of the <varname>Exec*=</varname> commands are accepted. If
<option>all</option>, all services updates from all members of the service's control group are accepted. This
option should be set to open access to the notification socket when using <varname>Type=notify</varname> or
<varname>WatchdogSec=</varname> (see above). If those options are used but <varname>NotifyAccess=</varname> is
not configured, it will be implicitly set to <option>main</option>.</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 <option>main</option> or
<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></listitem>
</varlistentry>
<varlistentry>