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PhabricatorWorker.php
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Tue, Nov 5, 10:32

PhabricatorWorker.php
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<?php
/**
* @task config Configuring Retries and Failures
*/
abstract class PhabricatorWorker {
private $data;
private static $runAllTasksInProcess = false;
private $queuedTasks = array();
// NOTE: Lower priority numbers execute first. The priority numbers have to
// have the same ordering that IDs do (lowest first) so MySQL can use a
// multipart key across both of them efficiently.
const PRIORITY_ALERTS = 1000;
const PRIORITY_DEFAULT = 2000;
const PRIORITY_BULK = 3000;
const PRIORITY_IMPORT = 4000;
/* -( Configuring Retries and Failures )----------------------------------- */
/**
* Return the number of seconds this worker needs hold a lease on the task for
* while it performs work. For most tasks you can leave this at `null`, which
* will give you a default lease (currently 2 hours).
*
* For tasks which may take a very long time to complete, you should return
* an upper bound on the amount of time the task may require.
*
* @return int|null Number of seconds this task needs to remain leased for,
* or null for a default lease.
*
* @task config
*/
public function getRequiredLeaseTime() {
return null;
}
/**
* Return the maximum number of times this task may be retried before it is
* considered permanently failed. By default, tasks retry indefinitely. You
* can throw a @{class:PhabricatorWorkerPermanentFailureException} to cause an
* immediate permanent failure.
*
* @return int|null Number of times the task will retry before permanent
* failure. Return `null` to retry indefinitely.
*
* @task config
*/
public function getMaximumRetryCount() {
return null;
}
/**
* Return the number of seconds a task should wait after a failure before
* retrying. For most tasks you can leave this at `null`, which will give you
* a short default retry period (currently 60 seconds).
*
* @param PhabricatorWorkerTask The task itself. This object is probably
* useful mostly to examine the failure count
* if you want to implement staggered retries,
* or to examine the execution exception if
* you want to react to different failures in
* different ways.
* @return int|null Number of seconds to wait between retries,
* or null for a default retry period
* (currently 60 seconds).
*
* @task config
*/
public function getWaitBeforeRetry(PhabricatorWorkerTask $task) {
return null;
}
abstract protected function doWork();
final public function __construct($data) {
$this->data = $data;
}
final protected function getTaskData() {
return $this->data;
}
final public function executeTask() {
$this->doWork();
}
final public static function scheduleTask(
$task_class,
$data,
$priority = null) {
if ($priority === null) {
$priority = self::PRIORITY_DEFAULT;
}
$task = id(new PhabricatorWorkerActiveTask())
->setTaskClass($task_class)
->setData($data)
->setPriority($priority);
if (self::$runAllTasksInProcess) {
// Do the work in-process.
$worker = newv($task_class, array($data));
while (true) {
try {
$worker->doWork();
foreach ($worker->getQueuedTasks() as $queued_task) {
list($queued_class, $queued_data, $queued_priority) = $queued_task;
self::scheduleTask($queued_class, $queued_data, $queued_priority);
}
break;
} catch (PhabricatorWorkerYieldException $ex) {
phlog(
pht(
'In-process task "%s" yielded for %s seconds, sleeping...',
$task_class,
$ex->getDuration()));
sleep($ex->getDuration());
}
}
// Now, save a task row and immediately archive it so we can return an
// object with a valid ID.
$task->openTransaction();
$task->save();
$archived = $task->archiveTask(
PhabricatorWorkerArchiveTask::RESULT_SUCCESS,
0);
$task->saveTransaction();
return $archived;
} else {
$task->save();
return $task;
}
}
/**
* Wait for tasks to complete. If tasks are not leased by other workers, they
* will be executed in this process while waiting.
*
* @param list<int> List of queued task IDs to wait for.
* @return void
*/
final public static function waitForTasks(array $task_ids) {
if (!$task_ids) {
return;
}
$task_table = new PhabricatorWorkerActiveTask();
$waiting = array_fuse($task_ids);
while ($waiting) {
$conn_w = $task_table->establishConnection('w');
// Check if any of the tasks we're waiting on are still queued. If they
// are not, we're done waiting.
$row = queryfx_one(
$conn_w,
'SELECT COUNT(*) N FROM %T WHERE id IN (%Ld)',
$task_table->getTableName(),
$waiting);
if (!$row['N']) {
// Nothing is queued anymore. Stop waiting.
break;
}
$tasks = id(new PhabricatorWorkerLeaseQuery())
->withIDs($waiting)
->setLimit(1)
->execute();
if (!$tasks) {
// We were not successful in leasing anything. Sleep for a bit and
// see if we have better luck later.
sleep(1);
continue;
}
$task = head($tasks)->executeTask();
$ex = $task->getExecutionException();
if ($ex) {
throw $ex;
}
}
$tasks = id(new PhabricatorWorkerArchiveTaskQuery())
->withIDs($task_ids);
foreach ($tasks as $task) {
if ($task->getResult() != PhabricatorWorkerArchiveTask::RESULT_SUCCESS) {
throw new Exception(pht('Task %d failed!', $task->getID()));
}
}
}
public function renderForDisplay(PhabricatorUser $viewer) {
$data = PhutilReadableSerializer::printableValue($this->data);
return phutil_tag('pre', array(), $data);
}
/**
* Set this flag to execute scheduled tasks synchronously, in the same
* process. This is useful for debugging, and otherwise dramatically worse
* in every way imaginable.
*/
public static function setRunAllTasksInProcess($all) {
self::$runAllTasksInProcess = $all;
}
final protected function log($pattern /* , ... */) {
$console = PhutilConsole::getConsole();
$argv = func_get_args();
call_user_func_array(array($console, 'writeLog'), $argv);
return $this;
}
/**
* Queue a task to be executed after this one succeeds.
*
* The followup task will be queued only if this task completes cleanly.
*
* @param string Task class to queue.
* @param array Data for the followup task.
* @param int|null Priority for the followup task.
* @return this
*/
final protected function queueTask($class, array $data, $priority = null) {
$this->queuedTasks[] = array($class, $data, $priority);
return $this;
}
/**
* Get tasks queued as followups by @{method:queueTask}.
*
* @return list<tuple<string, wild, int|null>> Queued task specifications.
*/
final public function getQueuedTasks() {
return $this->queuedTasks;
}
}

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