[GitHub] [hadoop-ozone] sodonnel commented on a change in pull request #86: HDDS-2329 Destroy pipelines on any decommission or maintenance nodes

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sodonnel commented on a change in pull request #86: HDDS-2329 Destroy pipelines on any decommission or maintenance nodes
URL: https://github.com/apache/hadoop-ozone/pull/86#discussion_r343633609
 
 

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 File path: hadoop-hdds/server-scm/src/main/java/org/apache/hadoop/hdds/scm/node/DatanodeAdminMonitor.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
+ * <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.node;
+
+import com.google.common.annotations.VisibleForTesting;
+import org.apache.hadoop.hdds.conf.OzoneConfiguration;
+import org.apache.hadoop.hdds.protocol.DatanodeDetails;
+import org.apache.hadoop.hdds.scm.events.SCMEvents;
+import org.apache.hadoop.hdds.scm.pipeline.PipelineID;
+import org.apache.hadoop.hdds.scm.pipeline.PipelineManager;
+import org.apache.hadoop.hdds.server.events.EventPublisher;
+import org.apache.hadoop.ozone.common.statemachine.InvalidStateTransitionException;
+import org.apache.hadoop.ozone.common.statemachine.StateMachine;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.Queue;
+import java.util.ArrayDeque;
+import java.util.HashSet;
+import java.util.Set;
+
+/**
+ * Monitor thread which watches for nodes to be decommissioned, recommissioned
+ * or placed into maintenance. Newly added nodes are queued in pendingNodes
+ * and recommissoned nodes are queued in cancelled nodes. On each monitor
+ * 'tick', the cancelled nodes are processed and removed from the monitor.
+ * Then any pending nodes are added to the trackedNodes set, where they stay
+ * until decommission or maintenance has ended.
+ *
+ * Once an node is placed into tracked nodes, it goes through a workflow where
+ * the following happens:
+ *
+ * 1. First an event is fired to close any pipelines on the node, which will
+ *    also close any contaners.
+ * 2. Next the containers on the node are obtained and checked to see if new
+ *    replicas are needed. If so, the new replicas are scheduled.
+ * 3. After scheduling replication, the node remains pending until replication
+ *    has completed.
+ * 4. At this stage the node will complete decommission or enter maintenance.
+ * 5. Maintenance nodes will remain tracked by this monitor until maintenance
+ *    is manually ended, or the maintenance window expires.
+ */
+public class DatanodeAdminMonitor implements DatanodeAdminMonitorInterface {
+
+  private OzoneConfiguration conf;
+  private EventPublisher eventQueue;
+  private NodeManager nodeManager;
+  private PipelineManager pipelineManager;
+  private Queue<DatanodeAdminNodeDetails> pendingNodes = new ArrayDeque();
+  private Queue<DatanodeAdminNodeDetails> cancelledNodes = new ArrayDeque();
+  private Set<DatanodeAdminNodeDetails> trackedNodes = new HashSet<>();
+  private StateMachine<States, Transitions> workflowSM;
+
+  /**
+   * States that a node must pass through when being decommissioned or placed
+   * into maintenance.
+   */
+  public enum States {
+    CLOSE_PIPELINES, GET_CONTAINERS, REPLICATE_CONTAINERS,
 
 Review comment:
   I added sequenceNumber to indicate the ordering. ASCII diagram is a good idea, but I will leave it out until we are sure there are no more states or this flow may change before decommission is finished.

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