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PhutilDaemonOverseer.php
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Fri, Nov 22, 13:34

PhutilDaemonOverseer.php
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<?php
/**
* Oversees a daemon and restarts it if it fails.
*
* @task signals Signal Handling
*/
final class PhutilDaemonOverseer extends Phobject {
private $argv;
private static $instance;
private $config;
private $pools = array();
private $traceMode;
private $traceMemory;
private $daemonize;
private $piddir;
private $log;
private $libraries = array();
private $modules = array();
private $verbose;
private $lastPidfile;
private $startEpoch;
private $autoscale = array();
private $autoscaleConfig = array();
const SIGNAL_NOTIFY = 'signal/notify';
const SIGNAL_RELOAD = 'signal/reload';
const SIGNAL_GRACEFUL = 'signal/graceful';
const SIGNAL_TERMINATE = 'signal/terminate';
private $err = 0;
private $inAbruptShutdown;
private $inGracefulShutdown;
public function __construct(array $argv) {
PhutilServiceProfiler::getInstance()->enableDiscardMode();
$args = new PhutilArgumentParser($argv);
$args->setTagline(pht('daemon overseer'));
$args->setSynopsis(<<<EOHELP
**launch_daemon.php** [__options__] __daemon__
Launch and oversee an instance of __daemon__.
EOHELP
);
$args->parseStandardArguments();
$args->parse(
array(
array(
'name' => 'trace-memory',
'help' => pht('Enable debug memory tracing.'),
),
array(
'name' => 'verbose',
'help' => pht('Enable verbose activity logging.'),
),
array(
'name' => 'label',
'short' => 'l',
'param' => 'label',
'help' => pht(
'Optional process label. Makes "%s" nicer, no behavioral effects.',
'ps'),
),
));
$argv = array();
if ($args->getArg('trace')) {
$this->traceMode = true;
$argv[] = '--trace';
}
if ($args->getArg('trace-memory')) {
$this->traceMode = true;
$this->traceMemory = true;
$argv[] = '--trace-memory';
}
$verbose = $args->getArg('verbose');
if ($verbose) {
$this->verbose = true;
$argv[] = '--verbose';
}
$label = $args->getArg('label');
if ($label) {
$argv[] = '-l';
$argv[] = $label;
}
$this->argv = $argv;
if (function_exists('posix_isatty') && posix_isatty(STDIN)) {
fprintf(STDERR, pht('Reading daemon configuration from stdin...')."\n");
}
$config = @file_get_contents('php://stdin');
$config = id(new PhutilJSONParser())->parse($config);
$this->libraries = idx($config, 'load');
$this->log = idx($config, 'log');
$this->daemonize = idx($config, 'daemonize');
$this->piddir = idx($config, 'piddir');
$this->config = $config;
if (self::$instance) {
throw new Exception(
pht('You may not instantiate more than one Overseer per process.'));
}
self::$instance = $this;
$this->startEpoch = time();
// Check this before we daemonize, since if it's an issue the child will
// exit immediately.
if ($this->piddir) {
$dir = $this->piddir;
try {
Filesystem::assertWritable($dir);
} catch (Exception $ex) {
throw new Exception(
pht(
"Specified daemon PID directory ('%s') does not exist or is ".
"not writable by the daemon user!",
$dir));
}
}
if (!idx($config, 'daemons')) {
throw new PhutilArgumentUsageException(
pht('You must specify at least one daemon to start!'));
}
if ($this->log) {
// NOTE: Now that we're committed to daemonizing, redirect the error
// log if we have a `--log` parameter. Do this at the last moment
// so as many setup issues as possible are surfaced.
ini_set('error_log', $this->log);
}
if ($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(pht('Unable to fork!'));
} else if ($pid) {
exit(0);
}
$sid = posix_setsid();
if ($sid <= 0) {
throw new Exception(pht('Failed to create new process session!'));
}
}
$this->logMessage(
'OVER',
pht(
'Started new daemon overseer (with PID "%s").',
getmypid()));
$this->modules = PhutilDaemonOverseerModule::getAllModules();
$this->installSignalHandlers();
}
public function addLibrary($library) {
$this->libraries[] = $library;
return $this;
}
public function run() {
$this->createDaemonPools();
while (true) {
if ($this->shouldReloadDaemons()) {
$this->didReceiveSignal(SIGHUP);
}
$futures = array();
$running_pools = false;
foreach ($this->getDaemonPools() as $pool) {
$pool->updatePool();
if (!$this->shouldShutdown()) {
if ($pool->isHibernating()) {
if ($this->shouldWakePool($pool)) {
$pool->wakeFromHibernation();
}
}
}
foreach ($pool->getFutures() as $future) {
$futures[] = $future;
}
if ($pool->getDaemons()) {
$running_pools = true;
}
}
$this->updatePidfile();
$this->updateMemory();
$this->waitForDaemonFutures($futures);
if (!$futures && !$running_pools) {
if ($this->shouldShutdown()) {
break;
}
}
}
exit($this->err);
}
private function waitForDaemonFutures(array $futures) {
assert_instances_of($futures, 'ExecFuture');
if ($futures) {
// TODO: This only wakes if any daemons actually exit. It would be a bit
// cleaner to wait on any I/O with Channels.
$iter = id(new FutureIterator($futures))
->setUpdateInterval(1);
foreach ($iter as $future) {
break;
}
} else {
if (!$this->shouldShutdown()) {
sleep(1);
}
}
}
private function createDaemonPools() {
$configs = $this->config['daemons'];
$forced_options = array(
'load' => $this->libraries,
'log' => $this->log,
);
foreach ($configs as $config) {
$config = $forced_options + $config;
$pool = PhutilDaemonPool::newFromConfig($config)
->setOverseer($this)
->setCommandLineArguments($this->argv);
$this->pools[] = $pool;
}
}
private function getDaemonPools() {
return $this->pools;
}
/**
* Identify running daemons by examining the process table. This isn't
* completely reliable, but can be used as a fallback if the pid files fail
* or we end up with stray daemons by other means.
*
* Example output (array keys are process IDs):
*
* array(
* 12345 => array(
* 'type' => 'overseer',
* 'command' => 'php launch_daemon.php --daemonize ...',
* 'pid' => 12345,
* ),
* 12346 => array(
* 'type' => 'daemon',
* 'command' => 'php exec_daemon.php ...',
* 'pid' => 12346,
* ),
* );
*
* @return dict Map of PIDs to process information, identifying running
* daemon processes.
*/
public static function findRunningDaemons() {
$results = array();
list($err, $processes) = exec_manual('ps -o pid,command -a -x -w -w -w');
if ($err) {
return $results;
}
$processes = array_filter(explode("\n", trim($processes)));
foreach ($processes as $process) {
list($pid, $command) = preg_split('/\s+/', trim($process), 2);
$pattern = '/((launch|exec)_daemon.php|phd-daemon)/';
$matches = null;
if (!preg_match($pattern, $command, $matches)) {
continue;
}
switch ($matches[1]) {
case 'exec_daemon.php':
$type = 'daemon';
break;
case 'launch_daemon.php':
case 'phd-daemon':
default:
$type = 'overseer';
break;
}
$results[(int)$pid] = array(
'type' => $type,
'command' => $command,
'pid' => (int)$pid,
);
}
return $results;
}
private function updatePidfile() {
if (!$this->piddir) {
return;
}
$pidfile = $this->toDictionary();
if ($pidfile !== $this->lastPidfile) {
$this->lastPidfile = $pidfile;
$pidfile_path = $this->piddir.'/daemon.'.getmypid();
try {
Filesystem::writeFile(
$pidfile_path,
phutil_json_encode($pidfile));
} catch (Exception $ex) {
// This write can fail if the disk is full. We already tested the
// directory for writability on startup, so just ignore this and
// move on rather than crashing. If the disk is full this error may
// not make it to a log file, but at least we tried.
$this->logMessage(
'PIDF',
pht(
'Unable to update PID file: %s.',
$ex->getMessage()));
}
}
}
public function toDictionary() {
$daemons = array();
foreach ($this->getDaemonPools() as $pool) {
foreach ($pool->getDaemons() as $daemon) {
if (!$daemon->isRunning()) {
continue;
}
$daemons[] = $daemon->toDictionary();
}
}
return array(
'pid' => getmypid(),
'start' => $this->startEpoch,
'config' => $this->config,
'daemons' => $daemons,
);
}
private function updateMemory() {
if (!$this->traceMemory) {
return;
}
$this->logMessage(
'RAMS',
pht(
'Overseer Memory Usage: %s KB',
new PhutilNumber(memory_get_usage() / 1024, 1)));
}
public function logMessage($type, $message, $context = null) {
$always_log = false;
switch ($type) {
case 'OVER':
case 'SGNL':
case 'PIDF':
$always_log = true;
break;
}
if ($always_log || $this->traceMode || $this->verbose) {
error_log(date('Y-m-d g:i:s A').' ['.$type.'] '.$message);
}
}
/* -( Signal Handling )---------------------------------------------------- */
/**
* @task signals
*/
private function installSignalHandlers() {
$signals = array(
SIGUSR2,
SIGHUP,
SIGINT,
SIGTERM,
);
foreach ($signals as $signal) {
pcntl_signal($signal, array($this, 'didReceiveSignal'));
}
}
/**
* @task signals
*/
public function didReceiveSignal($signo) {
$this->logMessage(
'SGNL',
pht(
'Overseer ("%d") received signal %d ("%s").',
getmypid(),
$signo,
phutil_get_signal_name($signo)));
switch ($signo) {
case SIGUSR2:
$signal_type = self::SIGNAL_NOTIFY;
break;
case SIGHUP:
$signal_type = self::SIGNAL_RELOAD;
break;
case SIGINT:
// If we receive SIGINT more than once, interpret it like SIGTERM.
if ($this->inGracefulShutdown) {
return $this->didReceiveSignal(SIGTERM);
}
$this->inGracefulShutdown = true;
$signal_type = self::SIGNAL_GRACEFUL;
break;
case SIGTERM:
// If we receive SIGTERM more than once, terminate abruptly.
$this->err = 128 + $signo;
if ($this->inAbruptShutdown) {
exit($this->err);
}
$this->inAbruptShutdown = true;
$signal_type = self::SIGNAL_TERMINATE;
break;
default:
throw new Exception(
pht(
'Signal handler called with unknown signal type ("%d")!',
$signo));
}
foreach ($this->getDaemonPools() as $pool) {
$pool->didReceiveSignal($signal_type, $signo);
}
}
/* -( Daemon Modules )----------------------------------------------------- */
private function getModules() {
return $this->modules;
}
private function shouldReloadDaemons() {
$modules = $this->getModules();
$should_reload = false;
foreach ($modules as $module) {
try {
// NOTE: Even if one module tells us to reload, we call the method on
// each module anyway to make calls a little more predictable.
if ($module->shouldReloadDaemons()) {
$this->logMessage(
'RELO',
pht(
'Reloading daemons (triggered by overseer module "%s").',
get_class($module)));
$should_reload = true;
}
} catch (Exception $ex) {
phlog($ex);
}
}
return $should_reload;
}
private function shouldWakePool(PhutilDaemonPool $pool) {
$modules = $this->getModules();
$should_wake = false;
foreach ($modules as $module) {
try {
if ($module->shouldWakePool($pool)) {
$this->logMessage(
'WAKE',
pht(
'Waking pool "%s" (triggered by overseer module "%s").',
$pool->getPoolLabel(),
get_class($module)));
$should_wake = true;
}
} catch (Exception $ex) {
phlog($ex);
}
}
return $should_wake;
}
private function shouldShutdown() {
return $this->inGracefulShutdown || $this->inAbruptShutdown;
}
}

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