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diff --git a/lib/kernel/doc/src/heart.xml b/lib/kernel/doc/src/heart.xml new file mode 100644 index 0000000000..0df699572d --- /dev/null +++ b/lib/kernel/doc/src/heart.xml @@ -0,0 +1,116 @@ +<?xml version="1.0" encoding="latin1" ?> +<!DOCTYPE erlref SYSTEM "erlref.dtd"> + +<erlref> + <header> + <copyright> + <year>1996</year><year>2009</year> + <holder>Ericsson AB. All Rights Reserved.</holder> + </copyright> + <legalnotice> + The contents of this file are subject to the Erlang Public License, + Version 1.1, (the "License"); you may not use this file except in + compliance with the License. You should have received a copy of the + Erlang Public License along with this software. If not, it can be + retrieved online at http://www.erlang.org/. + + Software distributed under the License is distributed on an "AS IS" + basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See + the License for the specific language governing rights and limitations + under the License. + + </legalnotice> + + <title>heart</title> + <prepared>Magnus Fröberg</prepared> + <docno></docno> + <date>1998-01-28</date> + <rev>A</rev> + </header> + <module>heart</module> + <modulesummary>Heartbeat Monitoring of an Erlang Runtime System</modulesummary> + <description> + <p>This modules contains the interface to the <c>heart</c> process. + <c>heart</c> sends periodic heartbeats to an external port + program, which is also named <c>heart</c>. The purpose of + the heart port program is to check that the Erlang runtime system + it is supervising is still running. If the port program has not + received any heartbeats within <c>HEART_BEAT_TIMEOUT</c> seconds + (default is 60 seconds), the system can be rebooted. Also, if + the system is equipped with a hardware watchdog timer and is + running Solaris, the watchdog can be used to supervise the entire + system.</p> + <p>An Erlang runtime system to be monitored by a heart program, + should be started with the command line flag <c>-heart</c> (see + also <seealso marker="erts:erl">erl(1)</seealso>. The <c>heart</c> + process is then started automatically:</p> + <pre> +% <input>erl -heart ...</input></pre> + <p>If the system should be rebooted because of missing heart-beats, + or a terminated Erlang runtime system, the environment variable + <c>HEART_COMMAND</c> has to be set before the system is started. + If this variable is not set, a warning text will be printed but + the system will not reboot. However, if the hardware watchdog is + used, it will trigger a reboot <c>HEART_BEAT_BOOT_DELAY</c> + seconds later nevertheless (default is 60).</p> + <p>To reboot on the WINDOWS platform <c>HEART_COMMAND</c> can be + set to <c>heart -shutdown</c> (included in the Erlang delivery) + or of course to any other suitable program which can activate a + reboot.</p> + <p>The hardware watchdog will not be started under Solaris if + the environment variable <c>HW_WD_DISABLE</c> is set.</p> + <p>The <c>HEART_BEAT_TIMEOUT</c> and <c>HEART_BEAT_BOOT_DELAY</c> + environment variables can be used to configure the heart timeouts, + they can be set in the operating system shell before Erlang is + started or be specified at the command line:</p> + <pre> +% <input>erl -heart -env HEART_BEAT_TIMEOUT 30 ...</input></pre> + <p>The value (in seconds) must be in the range 10 < X <= 65535.</p> + <p>It should be noted that if the system clock is adjusted with + more than <c>HEART_BEAT_TIMEOUT</c> seconds, <c>heart</c> will + timeout and try to reboot the system. This can happen, for + example, if the system clock is adjusted automatically by use of + NTP (Network Time Protocol).</p> + <p>In the following descriptions, all function fails with reason + <c>badarg</c> if <c>heart</c> is not started.</p> + </description> + <funcs> + <func> + <name>set_cmd(Cmd) -> ok | {error, {bad_cmd, Cmd}}</name> + <fsummary>Set a temporary reboot command</fsummary> + <type> + <v>Cmd = string()</v> + </type> + <desc> + <p>Sets a temporary reboot command. This command is used if + a <c>HEART_COMMAND</c> other than the one specified with + the environment variable should be used in order to reboot + the system. The new Erlang runtime system will (if it + misbehaves) use the environment variable + <c>HEART_COMMAND</c> to reboot.</p> + <p>Limitations: The length of the <c>Cmd</c> command string + must be less than 2047 characters.</p> + </desc> + </func> + <func> + <name>clear_cmd() -> ok</name> + <fsummary>Clear the temporary boot command</fsummary> + <desc> + <p>Clears the temporary boot command. If the system terminates, + the normal <c>HEART_COMMAND</c> is used to reboot.</p> + </desc> + </func> + <func> + <name>get_cmd() -> {ok, Cmd}</name> + <fsummary>Get the temporary reboot command</fsummary> + <type> + <v>Cmd = string()</v> + </type> + <desc> + <p>Get the temporary reboot command. If the command is cleared, + the empty string will be returned.</p> + </desc> + </func> + </funcs> +</erlref> + |