[GitHub] [ozone] siddhantsangwan commented on a diff in pull request #3307: HDDS-6551. Introduce StatefulService in scm

[GitBox <gi...@apache.org>]

siddhantsangwan commented on code in PR #3307:
URL: https://github.com/apache/ozone/pull/3307#discussion_r862642011


##########
hadoop-hdds/server-scm/src/main/java/org/apache/hadoop/hdds/scm/ha/StatefulServiceStateManagerImpl.java:
##########
@@ -0,0 +1,126 @@
+/*
+ * 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
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * 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.hadoop.hdds.scm.ha;
+
+import com.google.protobuf.ByteString;
+import org.apache.hadoop.hdds.protocol.proto.SCMRatisProtocol.RequestType;
+import org.apache.hadoop.hdds.scm.metadata.DBTransactionBuffer;
+import org.apache.hadoop.hdds.utils.db.Table;
+
+import java.io.IOException;
+import java.lang.reflect.Proxy;
+
+/**
+ * This class implements methods to save and read configurations of a
+ * stateful service from DB.
+ */
+public final class StatefulServiceStateManagerImpl
+    implements StatefulServiceStateManager {
+
+  // this table maps the service name to the configuration (ByteString)
+  private Table<String, ByteString> statefulServiceConfig;
+  private final DBTransactionBuffer transactionBuffer;
+
+  private StatefulServiceStateManagerImpl(
+      Table<String, ByteString> statefulServiceConfig,
+      DBTransactionBuffer scmDBTransactionBuffer) {
+    this.statefulServiceConfig = statefulServiceConfig;
+    this.transactionBuffer = scmDBTransactionBuffer;
+  }
+
+  /**
+   * {@inheritDoc}
+   */
+  @Override
+  public void saveConfiguration(String serviceName, ByteString bytes)
+      throws IOException {
+    // do we need a write lock here?
+    // do we need the buffer here or should we directly put the key-value?
+    /*
+    Alternative: statefulServiceConfig.put(serviceName, bytes);
+     */
+    transactionBuffer.addToBuffer(statefulServiceConfig, serviceName, bytes);
+    if (transactionBuffer instanceof SCMHADBTransactionBuffer) {
+      SCMHADBTransactionBuffer buffer =
+              (SCMHADBTransactionBuffer) transactionBuffer;
+      buffer.flush();
+    }
+  }
+
+  /**
+   * {@inheritDoc}
+   */
+  @Override
+  public ByteString readConfiguration(String serviceName) throws IOException {
+    // do we need a read lock here?
+    return statefulServiceConfig.get(serviceName);
+  }
+
+  /**
+   * {@inheritDoc}
+   */
+  @Override
+  public void reinitialize(Table<String, ByteString> configs) {
+    this.statefulServiceConfig = configs;
+  }
+
+  public static Builder newBuilder() {
+    return new Builder();
+  }
+
+  /**
+   * Builder for StatefulServiceStateManager.
+   */
+  public static class Builder {
+    private Table<String, ByteString> statefulServiceConfig;
+    private DBTransactionBuffer transactionBuffer;
+    private SCMRatisServer scmRatisServer;
+
+    public Builder setStatefulServiceConfig(
+        final Table<String, ByteString> statefulServiceConfig) {
+      this.statefulServiceConfig = statefulServiceConfig;
+      return this;
+    }
+
+    public Builder setSCMDBTransactionBuffer(
+        final DBTransactionBuffer dbTransactionBuffer) {
+      this.transactionBuffer = dbTransactionBuffer;
+      return this;
+    }
+
+    public Builder setRatisServer(final SCMRatisServer ratisServer) {
+      scmRatisServer = ratisServer;
+      return this;
+    }
+
+    public StatefulServiceStateManager build() {

Review Comment:
   Can we exclude the not null check for `scmRatisServer`? `SCMHAInvocationHandler` takes care of the null case by calling the `invokeLocal` method.



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