HDDS-638. Enable ratis snapshots for HDDS datanodes. Contributed by Mukul Kumar Singh.

hadoop-hdds/common/src/main/java/org/apache/hadoop/hdds/scm/ScmConfigKeys.java

@@ -104,6 +104,10 @@ public final class ScmConfigKeys {
       DFS_RATIS_LEADER_ELECTION_MINIMUM_TIMEOUT_DURATION_DEFAULT =
       TimeDuration.valueOf(1, TimeUnit.SECONDS);
 
+  public static final String DFS_RATIS_SNAPSHOT_THRESHOLD_KEY =
+      "dfs.ratis.snapshot.threshold";
+  public static final long DFS_RATIS_SNAPSHOT_THRESHOLD_DEFAULT = 10000;
+
   public static final String DFS_RATIS_SERVER_FAILURE_DURATION_KEY =
       "dfs.ratis.server.failure.duration";
   public static final TimeDuration

hadoop-hdds/common/src/main/java/org/apache/hadoop/ozone/OzoneConfigKeys.java

@@ -266,6 +266,10 @@ public final class OzoneConfigKeys {
   public static final TimeDuration
       DFS_RATIS_LEADER_ELECTION_MINIMUM_TIMEOUT_DURATION_DEFAULT =
       ScmConfigKeys.DFS_RATIS_LEADER_ELECTION_MINIMUM_TIMEOUT_DURATION_DEFAULT;
+  public static final String DFS_RATIS_SNAPSHOT_THRESHOLD_KEY =
+      ScmConfigKeys.DFS_RATIS_SNAPSHOT_THRESHOLD_KEY;
+  public static final long DFS_RATIS_SNAPSHOT_THRESHOLD_DEFAULT =
+      ScmConfigKeys.DFS_RATIS_SNAPSHOT_THRESHOLD_DEFAULT;
 
   public static final String DFS_RATIS_SERVER_FAILURE_DURATION_KEY =
       ScmConfigKeys.DFS_RATIS_SERVER_FAILURE_DURATION_KEY;

hadoop-hdds/common/src/main/resources/ozone-default.xml

@@ -118,6 +118,14 @@
       etc. This picks one of those for this cluster.
     </description>
   </property>
+  <property>
+    <name>dfs.ratis.snapshot.threshold</name>
+    <value>10000</value>
+    <tag>OZONE, RATIS</tag>
+    <description>Number of transactions after which a ratis snapshot should be
+      taken.
+    </description>
+  </property>
   <property>
     <name>dfs.container.ratis.num.write.chunk.threads</name>
     <value>60</value>

hadoop-hdds/container-service/src/main/java/org/apache/hadoop/ozone/container/common/transport/server/ratis/ContainerStateMachine.java

@@ -25,6 +25,9 @@ import org.apache.hadoop.ozone.container.common.helpers.BlockData;
 import org.apache.ratis.protocol.RaftGroup;
 import org.apache.ratis.protocol.RaftGroupId;
 import org.apache.ratis.server.RaftServer;
+import org.apache.ratis.server.impl.RaftServerConstants;
+import org.apache.ratis.server.protocol.TermIndex;
+import org.apache.ratis.statemachine.impl.SingleFileSnapshotInfo;
 import org.apache.ratis.thirdparty.com.google.protobuf
     .InvalidProtocolBufferException;
 import org.apache.hadoop.hdds.protocol.datanode.proto.ContainerProtos.Type;
@@ -55,8 +58,10 @@ import org.apache.ratis.statemachine.impl.TransactionContextImpl;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import java.io.File;
 import java.io.IOException;
 import java.util.List;
+import java.util.Map;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ThreadPoolExecutor;
@@ -115,6 +120,7 @@ public class ContainerStateMachine extends BaseStateMachine {
       createContainerFutureMap;
   private ExecutorService[] executors;
   private final int numExecutors;
+  private final Map<Long, Long> containerCommandCompletionMap;
   /**
    * CSM metrics.
    */
@@ -131,6 +137,7 @@ public class ContainerStateMachine extends BaseStateMachine {
     this.createContainerFutureMap = new ConcurrentHashMap<>();
     this.numExecutors = numOfExecutors;
     executors = new ExecutorService[numExecutors];
+    containerCommandCompletionMap = new ConcurrentHashMap<>();
     for (int i = 0; i < numExecutors; i++) {
       executors[i] = Executors.newSingleThreadExecutor();
     }
@@ -151,10 +158,47 @@ public class ContainerStateMachine extends BaseStateMachine {
       throws IOException {
     super.initialize(server, id, raftStorage);
     storage.init(raftStorage);
-    //  TODO handle snapshots
 
-    // TODO: Add a flag that tells you that initialize has been called.
+    loadSnapshot(storage.getLatestSnapshot());
-    // Check with Ratis if this feature is done in Ratis.
+  }
+
+  private long loadSnapshot(SingleFileSnapshotInfo snapshot) {
+    if (snapshot == null) {
+      TermIndex empty = TermIndex.newTermIndex(0, 0);
+      LOG.info("The snapshot info is null." +
+          "Setting the last applied index to:" + empty);
+      setLastAppliedTermIndex(empty);
+      return RaftServerConstants.INVALID_LOG_INDEX;
+    }
+
+    final TermIndex last =
+        SimpleStateMachineStorage.getTermIndexFromSnapshotFile(
+            snapshot.getFile().getPath().toFile());
+    LOG.info("Setting the last applied index to " + last);
+    setLastAppliedTermIndex(last);
+    return last.getIndex();
+  }
+
+  @Override
+  public long takeSnapshot() throws IOException {
+    TermIndex ti = getLastAppliedTermIndex();
+    LOG.info("Taking snapshot at termIndex:" + ti);
+    if (ti != null) {
+      final File snapshotFile =
+          storage.getSnapshotFile(ti.getTerm(), ti.getIndex());
+      LOG.info("Taking a snapshot to file {}", snapshotFile);
+      try {
+        //TODO: For now, just create the file to save the term index,
+        //persist open container info to snapshot later.
+        snapshotFile.createNewFile();
+      } catch(IOException ioe) {
+        LOG.warn("Failed to write snapshot file \"" + snapshotFile
+            + "\", last applied index=" + ti);
+        throw ioe;
+      }
+      return ti.getIndex();
+    }
+    return -1;
   }
 
   @Override
@@ -353,10 +397,9 @@ public class ContainerStateMachine extends BaseStateMachine {
   public CompletableFuture<Void> flushStateMachineData(long index) {
     List<CompletableFuture<Message>> futureList =
         writeChunkFutureMap.entrySet().stream().filter(x -> x.getKey() <= index)
-            .map(x -> x.getValue()).collect(Collectors.toList());
+            .map(Map.Entry::getValue).collect(Collectors.toList());
-    CompletableFuture<Void> combinedFuture = CompletableFuture.allOf(
+    return CompletableFuture.allOf(
         futureList.toArray(new CompletableFuture[futureList.size()]));
-    return combinedFuture;
   }
   /*
    * This api is used by the leader while appending logs to the follower
@@ -394,11 +437,28 @@ public class ContainerStateMachine extends BaseStateMachine {
     }
   }
 
+  private void updateLastApplied() {
+    Long appliedTerm = null;
+    long appliedIndex = -1;
+    for(long i = getLastAppliedTermIndex().getIndex() + 1;; i++) {
+      final Long removed = containerCommandCompletionMap.remove(i);
+      if (removed == null) {
+        break;
+      }
+      appliedTerm = removed;
+      appliedIndex = i;
+    }
+    if (appliedTerm != null) {
+      updateLastAppliedTermIndex(appliedIndex, appliedTerm);
+    }
+  }
+
   /*
    * ApplyTransaction calls in Ratis are sequential.
    */
   @Override
   public CompletableFuture<Message> applyTransaction(TransactionContext trx) {
+    long index = trx.getLogEntry().getIndex();
     try {
       metrics.incNumApplyTransactionsOps();
       ContainerCommandRequestProto requestProto =
@@ -418,7 +478,7 @@ public class ContainerStateMachine extends BaseStateMachine {
               blockDataProto.getBlockID());
           return completeExceptionally(ioe);
         }
-        blockData.setBlockCommitSequenceId(trx.getLogEntry().getIndex());
+        blockData.setBlockCommitSequenceId(index);
         final ContainerProtos.PutBlockRequestProto putBlockRequestProto =
             ContainerProtos.PutBlockRequestProto
                 .newBuilder(requestProto.getPutBlock())
@@ -440,6 +500,14 @@ public class ContainerStateMachine extends BaseStateMachine {
         future.thenApply(
             r -> createContainerFutureMap.remove(containerID).complete(null));
       }
+
+      future.thenAccept(m -> {
+        final Long previous =
+            containerCommandCompletionMap
+                .put(index, trx.getLogEntry().getTerm());
+        Preconditions.checkState(previous == null);
+        updateLastApplied();
+      });
       return future;
     } catch (IOException e) {
       metrics.incNumApplyTransactionsFails();
@@ -466,7 +534,8 @@ public class ContainerStateMachine extends BaseStateMachine {
 
   @Override
   public void close() throws IOException {
-    for (int i = 0; i < numExecutors; i++){
+    takeSnapshot();
+    for (int i = 0; i < numExecutors; i++) {
       executors[i].shutdown();
     }
   }

hadoop-hdds/container-service/src/main/java/org/apache/hadoop/ozone/container/common/transport/server/ratis/XceiverServerRatis.java

@@ -130,6 +130,10 @@ public final class XceiverServerRatis implements XceiverServerSpi {
         .build();
   }
 
+  @VisibleForTesting
+  public ContainerStateMachine getStateMachine() {
+    return stateMachine;
+  }
 
   private RaftProperties newRaftProperties(Configuration conf) {
     final RaftProperties properties = new RaftProperties();
@@ -254,6 +258,15 @@ public final class XceiverServerRatis implements XceiverServerSpi {
     } else if (rpc == SupportedRpcType.NETTY) {
       NettyConfigKeys.Server.setPort(properties, port);
     }
+
+    long snapshotThreshold =
+        conf.getLong(OzoneConfigKeys.DFS_RATIS_SNAPSHOT_THRESHOLD_KEY,
+            OzoneConfigKeys.DFS_RATIS_SNAPSHOT_THRESHOLD_DEFAULT);
+    RaftServerConfigKeys.Snapshot.
+      setAutoTriggerEnabled(properties, true);
+    RaftServerConfigKeys.Snapshot.
+      setAutoTriggerThreshold(properties, snapshotThreshold);
+
     return properties;
   }
 
@@ -298,7 +311,6 @@ public final class XceiverServerRatis implements XceiverServerSpi {
   public void stop() {
     try {
       chunkExecutor.shutdown();
-      stateMachine.close();
       server.close();
     } catch (IOException e) {
       throw new RuntimeException(e);

hadoop-hdds/container-service/src/main/java/org/apache/hadoop/ozone/container/ozoneimpl/OzoneContainer.java

@@ -230,6 +230,11 @@ public class OzoneContainer {
     return this.hddsDispatcher;
   }
 
+  @VisibleForTesting
+  public XceiverServerSpi getServer(ReplicationType replicationType) {
+    return servers.get(replicationType);
+  }
+
   public VolumeSet getVolumeSet() {
     return volumeSet;
   }

hadoop-ozone/tools/src/test/java/org/apache/hadoop/ozone/freon/TestFreonWithDatanodeRestart.java

@@ -0,0 +1,122 @@
+/**
+ * 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.ozone.freon;
+
+import org.apache.hadoop.hdds.client.ReplicationFactor;
+import org.apache.hadoop.hdds.client.ReplicationType;
+import org.apache.hadoop.hdds.conf.OzoneConfiguration;
+import org.apache.hadoop.hdds.protocol.proto.HddsProtos;
+import org.apache.hadoop.ozone.MiniOzoneCluster;
+import org.apache.hadoop.ozone.container.common.transport.server.XceiverServerSpi;
+import org.apache.hadoop.ozone.container.common.transport.server.ratis.ContainerStateMachine;
+import org.apache.hadoop.ozone.container.common.transport.server.ratis.XceiverServerRatis;
+import org.apache.ratis.server.protocol.TermIndex;
+import org.apache.ratis.statemachine.impl.SimpleStateMachineStorage;
+import org.apache.ratis.statemachine.impl.SingleFileSnapshotInfo;
+import org.junit.AfterClass;
+import org.junit.Assert;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.util.concurrent.TimeUnit;
+
+import static org.apache.hadoop.hdds.scm.ScmConfigKeys.OZONE_SCM_STALENODE_INTERVAL;
+
+/**
+ * Tests Freon with Datanode restarts.
+ */
+public class TestFreonWithDatanodeRestart {
+
+  private static MiniOzoneCluster cluster;
+  private static OzoneConfiguration conf;
+
+  /**
+   * Create a MiniDFSCluster for testing.
+   * <p>
+   * Ozone is made active by setting OZONE_ENABLED = true
+   *
+   */
+  @BeforeClass
+  public static void init() throws Exception {
+    conf = new OzoneConfiguration();
+    conf.setTimeDuration(OZONE_SCM_STALENODE_INTERVAL, 5, TimeUnit.SECONDS);
+    cluster = MiniOzoneCluster.newBuilder(conf)
+      .setHbProcessorInterval(1000)
+      .setHbInterval(1000)
+      .setNumDatanodes(3)
+      .build();
+    cluster.waitForClusterToBeReady();
+  }
+
+  /**
+   * Shutdown MiniDFSCluster.
+   */
+  @AfterClass
+  public static void shutdown() {
+    if (cluster != null) {
+      cluster.shutdown();
+    }
+  }
+
+  @Test
+  public void testRestart() throws Exception {
+    RandomKeyGenerator randomKeyGenerator =
+        new RandomKeyGenerator((OzoneConfiguration) cluster.getConf());
+    randomKeyGenerator.setNumOfVolumes(1);
+    randomKeyGenerator.setNumOfBuckets(1);
+    randomKeyGenerator.setNumOfKeys(1);
+    randomKeyGenerator.setType(ReplicationType.RATIS);
+    randomKeyGenerator.setFactor(ReplicationFactor.THREE);
+    randomKeyGenerator.setKeySize(20971520);
+    randomKeyGenerator.setValidateWrites(true);
+    randomKeyGenerator.call();
+    Assert.assertEquals(1, randomKeyGenerator.getNumberOfVolumesCreated());
+    Assert.assertEquals(1, randomKeyGenerator.getNumberOfBucketsCreated());
+    Assert.assertEquals(1, randomKeyGenerator.getNumberOfKeysAdded());
+    Assert.assertEquals(0, randomKeyGenerator.getUnsuccessfulValidationCount());
+
+    ContainerStateMachine sm = getStateMachine();
+    TermIndex termIndexBeforeRestart = sm.getLastAppliedTermIndex();
+    cluster.restartHddsDatanode(0);
+    sm = getStateMachine();
+    SimpleStateMachineStorage storage =
+        (SimpleStateMachineStorage)sm.getStateMachineStorage();
+    SingleFileSnapshotInfo snapshotInfo = storage.getLatestSnapshot();
+    TermIndex termInSnapshot = snapshotInfo.getTermIndex();
+    String expectedSnapFile =
+        storage.getSnapshotFile(termIndexBeforeRestart.getTerm(),
+            termIndexBeforeRestart.getIndex()).getAbsolutePath();
+    Assert.assertEquals(snapshotInfo.getFile().getPath().toString(),
+        expectedSnapFile);
+    Assert.assertEquals(termInSnapshot, termIndexBeforeRestart);
+
+    // After restart the term index might have progressed to apply pending
+    // transactions.
+    TermIndex termIndexAfterRestart = sm.getLastAppliedTermIndex();
+    Assert.assertTrue(termIndexAfterRestart.getIndex() >=
+        termIndexBeforeRestart.getIndex());
+  }
+
+  private ContainerStateMachine getStateMachine() {
+    XceiverServerSpi server =
+        cluster.getHddsDatanodes().get(0).getDatanodeStateMachine().
+            getContainer().getServer(HddsProtos.ReplicationType.RATIS);
+    return ((XceiverServerRatis)server).getStateMachine();
+  }
+}