[GitHub] [samza] mynameborat commented on a change in pull request #938: SAMZA-1531: Support run.id in standalone for batch processing.

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mynameborat commented on a change in pull request #938: SAMZA-1531: Support run.id in standalone for batch processing.
URL: https://github.com/apache/samza/pull/938#discussion_r281265458
 
 

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 File path: samza-core/src/main/java/org/apache/samza/coordinator/RunIdGenerator.java
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+/*
+ * 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.coordinator;
+
+import com.google.common.base.Preconditions;
+import java.io.UnsupportedEncodingException;
+import java.util.UUID;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+import org.apache.samza.SamzaException;
+import org.apache.samza.metadatastore.MetadataStore;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+
+/**
+ * Generates RunId for Standalone use case
+ * If there is only one processor in the quorum (registered with ClusterMembership) then create new runid and add to store
+ * Else read runid from the store
+ *
+ * Steps to generate:
+ * 1. acquire lock
+ * 2. add self to quorum (register itself with ClusterMembership)
+ * 3. get number of processors in quorum
+ * 4. if qurorum size is 1 (only self) then create new runid and write to store
+ * 5. if quorum size if greater than 1 then read runid from store
+ * 6. unlock
+ */
+public class RunIdGenerator {
+  private static final Logger LOG = LoggerFactory.getLogger(RunIdGenerator.class);
+
+  private final CoordinationUtils coordinationUtils;
+  private final MetadataStore metadataStore;
+  private ClusterMembership clusterMembership = null;
 
 Review comment:
   Why can't we make it final and have it initialized through the coordination utils in the constructor? I'd prefer to enforce pre conditions in the constructor if it isn't too expensive to construct ClusterMemberShip.

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