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PhabricatorCaches.php
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Tue, Apr 15, 11:57

PhabricatorCaches.php
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<?php
/**
* @task setup Setup Cache
*/
final class PhabricatorCaches {
/* -( Setup Cache )-------------------------------------------------------- */
/**
* Highly specialized cache for performing setup checks. We use this cache
* to determine if we need to run expensive setup checks (e.g., verifying
* submodule versions, PATH, the presence of binaries, etc.) when the page
* loads. Without it, we would need to run these checks every time.
*
* Normally, this cache is just APC. In the absence of APC, this cache
* degrades into a slow, quirky on-disk cache.
*
* NOTE: Do not use this cache for anything else! It is not a general-purpose
* cache!
*
* @return PhutilKeyValueCacheStack Most qualified available cache stack.
* @task setup
*/
public static function getSetupCache() {
static $cache;
if (!$cache) {
$caches = self::buildSetupCaches();
$caches = self::addProfilerToCaches($caches);
$cache = id(new PhutilKeyValueCacheStack())
->setCaches($caches);
}
return $cache;
}
/**
* @task setup
*/
private static function buildSetupCaches() {
// In most cases, we should have APC. This is an ideal cache for our
// purposes -- it's fast and empties on server restart.
$apc = new PhutilKeyValueCacheAPC();
if ($apc->isAvailable()) {
return array($apc);
}
// If we don't have APC, build a poor approximation on disk. This is still
// much better than nothing; some setup steps are quite slow.
$disk_path = self::getSetupCacheDiskCachePath();
if ($disk_path) {
$disk = new PhutilKeyValueCacheOnDisk();
$disk->setCacheFile($disk_path);
if ($disk->isAvailable()) {
return array($disk);
}
}
return array();
}
/**
* @task setup
*/
private static function getSetupCacheDiskCachePath() {
// The difficulty here is in choosing a path which will change on server
// restart (we MUST have this property), but as rarely as possible
// otherwise (we desire this property to give the cache the best hit rate
// we can).
// In some setups, the parent PID is more stable and longer-lived that the
// PID (e.g., under apache, our PID will be a worker while the ppid will
// be the main httpd process). If we're confident we're running under such
// a setup, we can try to use the PPID as the basis for our cache instead
// of our own PID.
$use_ppid = false;
switch (php_sapi_name()) {
case 'cli-server':
// This is the PHP5.4+ built-in webserver. We should use the pid
// (the server), not the ppid (probably a shell or something).
$use_ppid = false;
break;
case 'fpm-fcgi':
// We should be safe to use PPID here.
$use_ppid = true;
break;
case 'apache2handler':
// We're definitely safe to use the PPID.
$use_ppid = true;
break;
}
$pid_basis = getmypid();
if ($use_ppid) {
if (function_exists('posix_getppid')) {
$parent_pid = posix_getppid();
// On most systems, normal processes can never have PIDs lower than 100,
// so something likely went wrong if we we get one of these.
if ($parent_pid > 100) {
$pid_basis = $parent_pid;
}
}
}
// If possible, we also want to know when the process launched, so we can
// drop the cache if a process restarts but gets the same PID an earlier
// process had. "/proc" is not available everywhere (e.g., not on OSX), but
// check if we have it.
$epoch_basis = null;
$stat = @stat("/proc/{$pid_basis}");
if ($stat !== false) {
$epoch_basis = $stat['ctime'];
}
$tmp_dir = sys_get_temp_dir();
$tmp_path = $tmp_dir.DIRECTORY_SEPARATOR.'phabricator-setup';
if (!file_exists($tmp_path)) {
@mkdir($tmp_path);
}
$is_ok = self::testTemporaryDirectory($tmp_path);
if (!$is_ok) {
$tmp_path = $tmp_dir;
$is_ok = self::testTemporaryDirectory($tmp_path);
if (!$is_ok) {
// We can't find anywhere to write the cache, so just bail.
return null;
}
}
$tmp_name = 'setup-'.$pid_basis;
if ($epoch_basis) {
$tmp_name .= '.'.$epoch_basis;
}
$tmp_name .= '.cache';
return $tmp_path.DIRECTORY_SEPARATOR.$tmp_name;
}
/**
* @task setup
*/
private static function testTemporaryDirectory($dir) {
if (!@file_exists($dir)) {
return false;
}
if (!@is_dir($dir)) {
return false;
}
if (!@is_writable($dir)) {
return false;
}
return true;
}
private static function addProfilerToCaches(array $caches) {
foreach ($caches as $key => $cache) {
$pcache = new PhutilKeyValueCacheProfiler($cache);
$pcache->setProfiler(PhutilServiceProfiler::getInstance());
$caches[$key] = $pcache;
}
return $caches;
}
}

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