[GitHub] [samza] lakshmi-manasa-g commented on a change in pull request #1385: SAMZA-2550: Move side input processing to use RunLoop

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lakshmi-manasa-g commented on a change in pull request #1385:
URL: https://github.com/apache/samza/pull/1385#discussion_r442646491



##########
File path: samza-core/src/main/java/org/apache/samza/storage/SideInputTask.java
##########
@@ -0,0 +1,124 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.samza.storage;
+
+import java.util.Collections;
+import java.util.Set;
+import org.apache.samza.checkpoint.OffsetManager;
+import org.apache.samza.container.RunLoopTask;
+import org.apache.samza.container.TaskInstanceMetrics;
+import org.apache.samza.container.TaskName;
+import org.apache.samza.scheduler.EpochTimeScheduler;
+import org.apache.samza.system.IncomingMessageEnvelope;
+import org.apache.samza.system.SystemStreamPartition;
+import org.apache.samza.task.ReadableCoordinator;
+import org.apache.samza.task.TaskCallback;
+import org.apache.samza.task.TaskCallbackFactory;
+
+
+/**
+ * This class encapsulates the processing logic for side input streams. It is executed by {@link org.apache.samza.container.RunLoop}
+ */
+public class SideInputTask implements RunLoopTask {

Review comment:
       RunLoopTask doc says that if async commit is enabled then process and commit could happen in parallel. Since SideInputTask implements this interface, should we think about adding "synchronized" to SideInputTask.process and SideInputTask.commit methods?
   
   From our offline discussion, I understand that these two methods wont be parallel cause the sideInputRunLoop has asycnCommit = false hard coded and it is always single threaded. 
   
   However, purely from the interface guarantee point of view, shouldnt this impl of RunLoopTask guard against async commits? 

##########
File path: samza-core/src/main/java/org/apache/samza/storage/SideInputTask.java
##########
@@ -0,0 +1,124 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.samza.storage;
+
+import java.util.Collections;
+import java.util.Set;
+import org.apache.samza.checkpoint.OffsetManager;
+import org.apache.samza.container.RunLoopTask;
+import org.apache.samza.container.TaskInstanceMetrics;
+import org.apache.samza.container.TaskName;
+import org.apache.samza.scheduler.EpochTimeScheduler;
+import org.apache.samza.system.IncomingMessageEnvelope;
+import org.apache.samza.system.SystemStreamPartition;
+import org.apache.samza.task.ReadableCoordinator;
+import org.apache.samza.task.TaskCallback;
+import org.apache.samza.task.TaskCallbackFactory;
+
+
+/**
+ * This class encapsulates the processing logic for side input streams. It is executed by {@link org.apache.samza.container.RunLoop}
+ */
+public class SideInputTask implements RunLoopTask {
+  private final TaskName taskName;
+  private final Set<SystemStreamPartition> taskSSPs;
+  private final TaskSideInputHandler taskSideInputHandler;
+  private final TaskInstanceMetrics metrics;
+
+  public SideInputTask(
+      TaskName taskName,
+      Set<SystemStreamPartition> taskSSPs,
+      TaskSideInputHandler taskSideInputHandler,
+      TaskInstanceMetrics metrics) {
+    this.taskName = taskName;
+    this.taskSSPs = taskSSPs;
+    this.taskSideInputHandler = taskSideInputHandler;
+    this.metrics = metrics;
+  }
+
+  @Override
+  public TaskName taskName() {
+    return this.taskName;
+  }
+
+  @Override
+  public void process(IncomingMessageEnvelope envelope, ReadableCoordinator coordinator,
+      TaskCallbackFactory callbackFactory) {
+    TaskCallback callback = callbackFactory.createCallback();
+    this.metrics.processes().inc();

Review comment:
       Since regular task's process and side input task's process are both essentially treated the same (as they both implement RunLoopTask.process) - will this not increase the process_ns metric of the task to include side input processing time? 
   From our offline discussion, I understand that prefixing the source with "side-input" will avoid this issue. 
   Additional doubt: was there a metric for process_ns of side input processing time before your change in this PR? are we changing the metric name as seen by the end user? if so, i think we might have to count it as API change




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