Batch daemon clear config (#596)

* Clear batch config if the serialized data is corrupted.

If you attempt to store a closure into shared memory, it will error out
and leave corrupt data in shared memory. When the daemon tries to read
the corrupt data, it crashes, but currently does not clear the config.
Thus, the batch daemon will continue to crash until the shared memory is
manually cleared.

Instead, if we detect corrupt data, we will clear the corrupt data from
shared memory.

* Clear shared memory when the write fails on serialization as well

* If BatchConfig serialization fails, clear it out.

Don't force the readers to do it, although the also will clear it out
if deserialization fails.

* Return the result of the storage write

Batch/BatchRunner.php

@@ -107,12 +107,12 @@ public function registerJob($identifier, $func, array $options = [])
         $this->config = $this->configStorage->load();
         $this->config->registerJob($identifier, $func, $options);
 
-        $result = $this->configStorage->save($this->config);
-        if ($result === false) {
-            return false;
+        try {
+            $result = $this->configStorage->save($this->config);
+        } finally {
+            $this->configStorage->unlock();
         }
-        $this->configStorage->unlock();
-        return true;
+        return $result;
     }
 
     /**
@@ -182,11 +182,15 @@ public function loadConfig()
         if ($result === false) {
             throw new \RuntimeException('Failed to lock the configStorage');
         }
-        $result = $this->configStorage->load();
-        $this->configStorage->unlock();
-        if ($result === false) {
-            throw new \RuntimeException('Failed to load the BatchConfig');
+        try {
+            $result = $this->configStorage->load();
+        } catch (\RuntimeException $e) {
+            $this->configStorage->clear();
+            throw $e;
+        } finally {
+            $this->configStorage->unlock();
         }
+
         $this->config = $result;
         return true;
     }

Batch/ConfigStorageInterface.php

@@ -55,4 +55,9 @@ public function save(BatchConfig $config);
      * @throws \RuntimeException when failed to load the BatchConfig.
      */
     public function load();
+
+    /**
+     * Clear the BatchConfig from storage.
+     */
+    public function clear();
 }

Batch/InMemoryConfigStorage.php

@@ -136,6 +136,14 @@ public function load()
         return $this->config;
     }
 
+    /**
+     * Clear the BatchConfig from storage.
+     */
+    public function clear()
+    {
+        $this->config = new BatchConfig();
+    }
+
     /**
      * Hold the items in memory and run the job in the same process when it
      * meets the condition.

Batch/SysvConfigStorage.php

@@ -69,7 +69,7 @@ public function unlock()
      *
      * @param BatchConfig $config A BatchConfig to save.
      * @return bool
-     * @throws \RuntimeException when failed to attach to the shared memory.
+     * @throws \RuntimeException when failed to attach to the shared memory or serialization fails
      */
     public function save(BatchConfig $config)
     {
@@ -79,16 +79,24 @@ public function save(BatchConfig $config)
                 'Failed to attach to the shared memory'
             );
         }
-        $result = shm_put_var($shmid, self::VAR_KEY, $config);
-        shm_detach($shmid);
+
+        // If the variable write fails, clear the memory and re-raise the exception
+        try {
+            $result = shm_put_var($shmid, self::VAR_KEY, $config);
+        } catch (\Exception $e) {
+            $this->clear();
+            throw new \RuntimeException($e->getMessage());
+        } finally {
+            shm_detach($shmid);
+        }
         return $result;
     }
 
     /**
      * Load a BatchConfig from the storage.
      *
      * @return BatchConfig
-     * @throws \RuntimeException when failed to attach to the shared memory.
+     * @throws \RuntimeException when failed to attach to the shared memory or deserialization fails
      */
     public function load()
     {
@@ -103,6 +111,22 @@ public function load()
         } else {
             $result = shm_get_var($shmid, self::VAR_KEY);
         }
+        shm_detach($shmid);
+
+        if ($result === false) {
+            throw new \RuntimeException(
+                'Failed to deserialize data from shared memory'
+            );
+        }
         return $result;
     }
+
+    /**
+     * Clear the BatchConfig from storage.
+     */
+    public function clear()
+    {
+        $shmid = shm_attach($this->sysvKey);
+        shm_remove_var($shmid, self::VAR_KEY);
+    }
 }