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PhutilDaemonOverseer.php
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Sat, Nov 23, 14:02

PhutilDaemonOverseer.php
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<?php
/*
* Copyright 2012 Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/**
* Oversees a daemon and restarts it if it fails.
*
* @group daemon
*/
final class PhutilDaemonOverseer {
private $captureBufferSize = 65536;
private $deadline;
private $deadlineTimeout = 86400;
private $restartDelay = 60;
private $killDelay = 3;
private $daemon;
private $argv;
private $childPID;
private $signaled;
private static $instance;
private $traceMode;
private $traceMemory;
private $daemonize;
private $phddir;
private $conduit;
private $conduitURI;
public function __construct(array $argv) {
$original_argv = $argv;
$args = new PhutilArgumentParser($argv);
$args->setTagline('daemon overseer');
$args->setSynopsis(<<<EOHELP
**launch_daemon.php** [__options__] __daemon__
Launch and oversee an instance of __daemon__.
EOHELP
);
$args->parsePartial(
array(
array(
'name' => 'trace',
'help' => 'Enable debug tracing.',
),
array(
'name' => 'trace-memory',
'help' => 'Enable debug memory tracing.',
),
array(
'name' => 'log',
'param' => 'file',
'help' => 'Send output to __file__.',
),
array(
'name' => 'daemonize',
'help' => 'Run in the background.',
),
array(
'name' => 'phd',
'param' => 'dir',
'help' => 'Write PID information to __dir__.',
),
array(
'name' => 'conduit-uri',
'param' => 'uri',
'help' => 'Send logs to Conduit on __uri__.'
),
));
$argv = $args->getUnconsumedArgumentVector();
$this->daemon = array_shift($argv);
if (!$this->daemon) {
$args->printHelpAndExit();
}
if ($args->getArg('trace')) {
$this->traceMode = true;
array_unshift($argv, '--trace');
}
if ($args->getArg('trace-memory')) {
$this->traceMode = true;
$this->traceMemory = true;
array_unshift($argv, '--trace-memory');
}
$log = $args->getArg('log');
if ($log) {
ini_set('error_log', $log);
array_unshift($argv, '--log='.$log);
}
$this->daemonize = $args->getArg('daemonize');
$this->phddir = $args->getArg('phd');
$this->conduitURI = $args->getArg('conduit-uri');
$this->argv = $argv;
error_log("Bringing daemon '{$this->daemon}' online...");
if (self::$instance) {
throw new Exception(
"You may not instantiate more than one Overseer per process.");
}
self::$instance = $this;
if ($this->daemonize) {
// We need to get rid of these or the daemon will hang when we TERM it
// waiting for something to read the buffers. TODO: Learn how unix works.
fclose(STDOUT);
fclose(STDERR);
ob_start();
$pid = pcntl_fork();
if ($pid === -1) {
throw new Exception("Unable to fork!");
} else if ($pid) {
exit(0);
}
}
if ($this->phddir) {
$desc = array(
'name' => $this->daemon,
'pid' => getmypid(),
'start' => time(),
);
Filesystem::writeFile(
$this->phddir.'/daemon.'.getmypid(),
json_encode($desc));
}
if ($this->conduitURI) {
$this->conduit = new ConduitClient($this->conduitURI);
$this->daemonLogID = $this->conduit->callMethodSynchronous(
'daemon.launched',
array(
'daemon' => $this->daemon,
'host' => php_uname('n'),
'pid' => getmypid(),
'argv' => json_encode(array_slice($original_argv, 1)),
));
}
declare(ticks = 1);
pcntl_signal(SIGUSR1, array($this, 'didReceiveKeepaliveSignal'));
pcntl_signal(SIGINT, array($this, 'didReceiveTerminalSignal'));
pcntl_signal(SIGTERM, array($this, 'didReceiveTerminalSignal'));
}
public function run() {
if (!$this->traceMode) {
echo "Running daemon '{$this->daemon}' silently. Use '--trace' to ".
"produce debugging output.\n";
}
$root = phutil_get_library_root('phutil');
$root = dirname($root);
$exec_dir = $root.'/scripts/daemon/exec/';
// NOTE: PHP implements proc_open() by running 'sh -c'. On most systems this
// is bash, but on Ubuntu it's dash. When you proc_open() using bash, you
// get one new process (the command you ran). When you proc_open() using
// dash, you get two new processes: the command you ran and a parent
// "dash -c" (or "sh -c") process. This means that the child process's PID
// is actually the 'dash' PID, not the command's PID. To avoid this, use
// 'exec' to replace the shell process with the real process; without this,
// the child will call posix_getppid(), be given the pid of the 'sh -c'
// process, and send it SIGUSR1 to keepalive which will terminate it
// immediately. We also won't be able to do process group management because
// the shell process won't properly posix_setsid() so the pgid of the child
// won't be meaningful.
$exec_daemon = './exec_daemon.php';
$argv = $this->argv;
array_unshift($argv, 'exec', $exec_daemon, $this->daemon);
foreach ($argv as $k => $arg) {
$argv[$k] = escapeshellarg($arg);
}
$command = implode(' ', $argv);
while (true) {
$this->logMessage('INIT', 'Starting process.');
$future = new ExecFuture($command);
$future->setCWD($exec_dir);
$future->setStdoutSizeLimit($this->captureBufferSize);
$future->setStderrSizeLimit($this->captureBufferSize);
$this->deadline = time() + $this->deadlineTimeout;
$future->isReady();
$this->childPID = $future->getPID();
do {
do {
if ($this->traceMemory) {
$memuse = number_format(memory_get_usage() / 1024, 1);
$this->logMessage('RAMS', 'Overseer Memory Usage: '.$memuse.' KB');
}
// We need a shortish timeout here so we can run the tick handler
// frequently in order to process signals.
$result = $future->resolve(1);
if ($this->traceMode || $this->conduit) {
list($stdout, $stderr) = $future->read();
$stdout = trim($stdout);
$stderr = trim($stderr);
if (strlen($stdout)) {
$this->logMessage('STDO', $stdout, $stdout);
}
if (strlen($stderr)) {
$this->logMessage('STDE', $stderr, $stderr);
}
$future->discardBuffers();
}
if ($result !== null) {
list($err) = $result;
if ($err) {
$this->logMessage(
'FAIL',
'Process exited with error '.$err.'.',
$err);
} else {
$this->logMessage('DONE', 'Process exited successfully.');
}
break 2;
}
} while (time() < $this->deadline);
$this->logMessage('HANG', 'Hang detected. Restarting process.');
$this->annihilateProcessGroup();
} while (false);
$this->logMessage('WAIT', 'Waiting to restart process.');
sleep($this->restartDelay);
}
}
public function didReceiveKeepaliveSignal($signo) {
$this->deadline = time() + $this->deadlineTimeout;
}
public function didReceiveTerminalSignal($signo) {
if ($this->signaled) {
exit(128 + $signo);
}
echo "\n>>> Shutting down...\n";
fflush(STDOUT);
fflush(STDERR);
fclose(STDOUT);
fclose(STDERR);
$this->signaled = true;
$this->annihilateProcessGroup();
exit(128 + $signo);
}
private function logMessage($type, $message, $remote = null) {
if ($this->traceMode) {
echo date('Y-m-d g:i:s A').' ['.$type.'] '.$message."\n";
}
if ($this->conduit) {
// TODO: This is kind of sketchy to do without any timeouts since a
// conduit server hang could throw a wrench into things.
try {
$this->conduit->callMethodSynchronous(
'daemon.log',
array(
'daemonLogID' => $this->daemonLogID,
'type' => $type,
'message' => $remote,
));
} catch (Exception $ex) {
// TOOD: Send this somewhere useful instead of eating it.
}
}
}
private function annihilateProcessGroup() {
$pid = $this->childPID;
$pgid = posix_getpgid($pid);
if ($pid && $pgid) {
// NOTE: On Ubuntu, 'kill' does not recognize the use of "--" to
// explicitly delineate PID/PGIDs from signals. We don't actually need it,
// so use the implicit "kill -TERM -pgid" form instead of the explicit
// "kill -TERM -- -pgid" form.
exec("kill -TERM -{$pgid}");
sleep($this->killDelay);
// On OSX, we'll get a permission error on stderr if the SIGTERM was
// successful in ending the life of the process group, presumably because
// all that's left is the daemon itself as a zombie waiting for us to
// reap it. However, we still need to issue this command for process
// groups that resist SIGTERM. Rather than trying to figure out if the
// process group is still around or not, just SIGKILL unconditionally and
// ignore any error which may be raised.
exec("kill -KILL -{$pgid} 2>/dev/null");
$this->childPID = null;
}
}
}

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