From ff203bc4eac57325c094e020a0738a4e1bbcf7c4 Mon Sep 17 00:00:00 2001
From: Daniel Lienert <daniel@lienert.cc>
Date: Fri, 7 Oct 2016 10:30:09 +0200
Subject: [PATCH] FEATURE: Add configuration option to prevent parallel
 scheduler execution

---
 .../Command/TaskCommandController.php         | 26 +++++++++++++++++++
 Configuration/Settings.yaml                   |  6 ++++-
 README.md                                     |  8 ++++++
 3 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/Classes/Ttree/Scheduler/Command/TaskCommandController.php b/Classes/Ttree/Scheduler/Command/TaskCommandController.php
index 3b75ded..c67c97b 100644
--- a/Classes/Ttree/Scheduler/Command/TaskCommandController.php
+++ b/Classes/Ttree/Scheduler/Command/TaskCommandController.php
@@ -16,6 +16,8 @@
 use TYPO3\Flow\Annotations as Flow;
 use TYPO3\Flow\Cli\CommandController;
 use TYPO3\Flow\Object\ObjectManagerInterface;
+use TYPO3\Flow\Utility\Lock\Lock;
+use TYPO3\Flow\Utility\Lock\LockNotAcquiredException;
 
 /**
  * Task Command Controller
@@ -35,6 +37,17 @@ class TaskCommandController extends CommandController
      */
     protected $objectManager;
 
+    /**
+     * @Flow\InjectConfiguration(package="Ttree.Scheduler", path="allowParallelExecution")
+     * @var boolean
+     */
+    protected $allowParallelExecution = true;
+
+    /**
+     * @var Lock
+     */
+    protected $parallelExecutionLock;
+
     /**
      * Run all pending task
      *
@@ -42,10 +55,21 @@ class TaskCommandController extends CommandController
      */
     public function runCommand($dryRun = false)
     {
+
+        if($this->allowParallelExecution !== true) {
+            try {
+                $this->parallelExecutionLock = new Lock('Ttree.Scheduler.ParallelExecutionLock');
+            } catch (LockNotAcquiredException $exception) {
+                $this->tellStatus('The scheduler is already running and parallel execution is disabled.');
+                $this->sendAndExit(0);
+            }
+        }
+
         foreach ($this->taskService->getDueTasks() as $taskDescriptor) {
             /** @var Task $task */
             $task = $taskDescriptor['object'];
             $arguments = [$task->getImplementation(), $taskDescriptor['identifier']];
+
             try {
                 if (!$dryRun) {
                     $task->execute($this->objectManager);
@@ -58,6 +82,8 @@ public function runCommand($dryRun = false)
                 $this->tellStatus('[Error] Task "%s" (%s) throw an exception, check your log', $arguments);
             }
         }
+
+        $this->parallelExecutionLock->release();
     }
 
     /**
diff --git a/Configuration/Settings.yaml b/Configuration/Settings.yaml
index bce00ab..2088d10 100644
--- a/Configuration/Settings.yaml
+++ b/Configuration/Settings.yaml
@@ -3,4 +3,8 @@ TYPO3:
     object:
       excludeClasses:
         'beberlei.assert' : ['.*']
-        'mtdowling.cronexpression' : ['.*']
\ No newline at end of file
+        'mtdowling.cronexpression' : ['.*']
+
+Ttree:
+  Scheduler:
+    allowParallelExecution: true
\ No newline at end of file
diff --git a/README.md b/README.md
index 2e80fe5..71c856c 100644
--- a/README.md
+++ b/README.md
@@ -55,6 +55,14 @@ multiple times, if your arguments are different between each task. You can pass
 
     flow task:register --expression "* */3 * * *" --task "Ttree\Aggregator\Task\AggregatorTask" --arguments '{"node": "af97b530-0c70-7b87-3cf4-f9a611f88c18"}'
 
+Available Configuration Options
+-------------------------------
+
+| Option                 | Default | Description                                                                                                                                   |
+|------------------------|---------|-----------------------------------------------------------------------------------------------------------------------------------------------|
+| allowParallelExecution | true    | If the scheduler command is executed while the scheduler is already running tasks, the second scheduler waits until the first one is finished |
+
+
 Available CLI helpers
 ---------------------