Add a "schedule task" trigger action

Summary: Ref T6881. Add a standard "just queue a task" trigger action; I expect almost all application code to use this.

Test Plan: Will test in Instances.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T6881

Differential Revision: https://secure.phabricator.com/D11429

src/__phutil_library_map__.php

@@ -2362,6 +2362,7 @@ phutil_register_library_map(array(
     'PhabricatorSSHWorkflow' => 'infrastructure/ssh/PhabricatorSSHWorkflow.php',
     'PhabricatorSavedQuery' => 'applications/search/storage/PhabricatorSavedQuery.php',
     'PhabricatorSavedQueryQuery' => 'applications/search/query/PhabricatorSavedQueryQuery.php',
+    'PhabricatorScheduleTaskTriggerAction' => 'infrastructure/daemon/workers/action/PhabricatorScheduleTaskTriggerAction.php',
     'PhabricatorScopedEnv' => 'infrastructure/env/PhabricatorScopedEnv.php',
     'PhabricatorSearchAbstractDocument' => 'applications/search/index/PhabricatorSearchAbstractDocument.php',
     'PhabricatorSearchApplication' => 'applications/search/application/PhabricatorSearchApplication.php',
@@ -5643,6 +5644,7 @@ phutil_register_library_map(array(
       'PhabricatorPolicyInterface',
     ),
     'PhabricatorSavedQueryQuery' => 'PhabricatorCursorPagedPolicyAwareQuery',
+    'PhabricatorScheduleTaskTriggerAction' => 'PhabricatorTriggerAction',
     'PhabricatorSearchApplication' => 'PhabricatorApplication',
     'PhabricatorSearchApplicationSearchEngine' => 'PhabricatorApplicationSearchEngine',
     'PhabricatorSearchAttachController' => 'PhabricatorSearchBaseController',

src/infrastructure/daemon/workers/action/PhabricatorScheduleTaskTriggerAction.php

@@ -0,0 +1,45 @@
+<?php
+
+/**
+ * Trigger action which queues a task.
+ *
+ * Most triggers should take this action: triggers need to execute as quickly
+ * as possible, and should generally queue tasks instead of doing any real
+ * work.
+ *
+ * In some cases, triggers could execute more quickly by examining the
+ * scheduled action time and comparing it to the current time, then exiting
+ * early if the trigger is executing too far away from real time (for example,
+ * it might not make sense to send a meeting reminder after a meeting already
+ * happened).
+ *
+ * However, in most cases the task needs to have this logic anyway (because
+ * there may be another arbitrarily long delay between when this code executes
+ * and when the task executes), and the cost of queueing a task is very small,
+ * and situations where triggers are executing far away from real time should
+ * be rare (major downtime or serious problems with the pipeline).
+ *
+ * The properties of this action map to the parameters of
+ * @{method:PhabricatorWorker::scheduleTask}.
+ */
+final class PhabricatorScheduleTaskTriggerAction
+   extends PhabricatorTriggerAction {
+
+  public function validateProperties(array $properties) {
+    PhutilTypeSpec::checkMap(
+      $properties,
+      array(
+        'class' => 'string',
+        'data' => 'map<string, wild>',
+        'options' => 'map<string, wild>',
+      ));
+  }
+
+  public function execute($last_epoch, $this_epoch) {
+    PhabricatorWorker::scheduleTask(
+      $this->getProperty('class'),
+      $this->getProperty('data'),
+      $this->getProperty('options'));
+  }
+
+}

src/infrastructure/daemon/workers/action/PhabricatorTriggerAction.php

@@ -2,6 +2,10 @@
 
 /**
  * A trigger action reacts to a scheduled event.
+ *
+ * Almost all events should use a @{class:PhabricatorScheduleTaskTriggerAction}.
+ * Avoid introducing new actions without strong justification. See that class
+ * for discussion of concerns.
  */
 abstract class PhabricatorTriggerAction extends Phobject {
 
@@ -41,6 +45,9 @@ abstract class PhabricatorTriggerAction extends Phobject {
    * performing processing directly, triggers can execute more involved actions
    * without blocking other triggers.
    *
+   * Almost all events should use @{class:PhabricatorScheduleTaskTriggerAction}
+   * to do this, ensuring that they execute quickly.
+   *
    * An action may trigger a long time after it is scheduled. For example,
    * a meeting reminder may be scheduled at 9:45 AM, but the action may not
    * execute until later (for example, because the server was down for