HDFS-4238. Standby namenode should not do purging of shared storage edits. Contributed by Todd Lipcon.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1417652 13f79535-47bb-0310-9956-ffa450edef68

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -292,6 +292,9 @@ Release 2.0.3-alpha - Unreleased
 
     HDFS-4231. BackupNode: Introduce BackupState. (shv)
 
+    HDFS-4238. Standby namenode should not do purging of shared
+    storage edits. (todd)
+
   BREAKDOWN OF HDFS-3077 SUBTASKS
 
     HDFS-3077. Quorum-based protocol for reading and writing edit logs.

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLog.java

@@ -858,6 +858,11 @@ public class FSEditLog implements LogsPurgeable {
     return journalSet;
   }
   
+  @VisibleForTesting
+  synchronized void setJournalSetForTesting(JournalSet js) {
+    this.journalSet = js;
+  }
+  
   /**
    * Used only by tests.
    */
@@ -978,9 +983,18 @@ public class FSEditLog implements LogsPurgeable {
 
   /**
    * Archive any log files that are older than the given txid.
+   * 
+   * If the edit log is not open for write, then this call returns with no
+   * effect.
    */
   @Override
   public synchronized void purgeLogsOlderThan(final long minTxIdToKeep) {
+    // Should not purge logs unless they are open for write.
+    // This prevents the SBN from purging logs on shared storage, for example.
+    if (!isOpenForWrite()) {
+      return;
+    }
+    
     assert curSegmentTxId == HdfsConstants.INVALID_TXID || // on format this is no-op
       minTxIdToKeep <= curSegmentTxId :
       "cannot purge logs older than txid " + minTxIdToKeep +

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/NameNodeAdapter.java

@@ -179,6 +179,13 @@ public class NameNodeAdapter {
     return spy;
   }
   
+  public static JournalSet spyOnJournalSet(NameNode nn) {
+    FSEditLog editLog = nn.getFSImage().getEditLog();
+    JournalSet js = Mockito.spy(editLog.getJournalSet());
+    editLog.setJournalSetForTesting(js);
+    return js;
+  }
+  
   public static String getMkdirOpPath(FSEditLogOp op) {
     if (op.opCode == FSEditLogOpCodes.OP_MKDIR) {
       return ((MkdirOp) op).path;

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/ha/TestStandbyCheckpoints.java

@@ -35,6 +35,7 @@ import org.apache.hadoop.hdfs.MiniDFSNNTopology;
 import org.apache.hadoop.hdfs.server.namenode.FSImage;
 import org.apache.hadoop.hdfs.server.namenode.FSImageTestUtil;
 import org.apache.hadoop.hdfs.server.namenode.FSNamesystem;
+import org.apache.hadoop.hdfs.server.namenode.JournalSet;
 import org.apache.hadoop.hdfs.server.namenode.NNStorage;
 import org.apache.hadoop.hdfs.server.namenode.NameNode;
 import org.apache.hadoop.hdfs.server.namenode.NameNodeAdapter;
@@ -66,6 +67,12 @@ public class TestStandbyCheckpoints {
     conf.setInt(DFSConfigKeys.DFS_NAMENODE_CHECKPOINT_CHECK_PERIOD_KEY, 1);
     conf.setInt(DFSConfigKeys.DFS_NAMENODE_CHECKPOINT_TXNS_KEY, 5);
     conf.setInt(DFSConfigKeys.DFS_HA_TAILEDITS_PERIOD_KEY, 1);
+    
+    // Dial down the retention of extra edits and checkpoints. This is to
+    // help catch regressions of HDFS-4238 (SBN should not purge shared edits)
+    conf.setInt(DFSConfigKeys.DFS_NAMENODE_NUM_CHECKPOINTS_RETAINED_KEY, 1);
+    conf.setInt(DFSConfigKeys.DFS_NAMENODE_NUM_EXTRA_EDITS_RETAINED_KEY, 0);
+    
     conf.setBoolean(DFSConfigKeys.DFS_IMAGE_COMPRESS_KEY, true);
     conf.set(DFSConfigKeys.DFS_IMAGE_COMPRESSION_CODEC_KEY,
         SlowCodec.class.getCanonicalName());
@@ -99,15 +106,20 @@ public class TestStandbyCheckpoints {
 
   @Test
   public void testSBNCheckpoints() throws Exception {
-    doEdits(0, 10);
+    JournalSet standbyJournalSet = NameNodeAdapter.spyOnJournalSet(nn1);
     
+    doEdits(0, 10);
     HATestUtil.waitForStandbyToCatchUp(nn0, nn1);
     // Once the standby catches up, it should notice that it needs to
     // do a checkpoint and save one to its local directories.
-    HATestUtil.waitForCheckpoint(cluster, 1, ImmutableList.of(0, 12));
+    HATestUtil.waitForCheckpoint(cluster, 1, ImmutableList.of(12));
     
     // It should also upload it back to the active.
-    HATestUtil.waitForCheckpoint(cluster, 0, ImmutableList.of(0, 12));
+    HATestUtil.waitForCheckpoint(cluster, 0, ImmutableList.of(12));
+    
+    // The standby should never try to purge edit logs on shared storage.
+    Mockito.verify(standbyJournalSet, Mockito.never()).
+      purgeLogsOlderThan(Mockito.anyLong());
   }
 
   /**
@@ -129,8 +141,8 @@ public class TestStandbyCheckpoints {
     // so the standby will catch up. Then, both will be in standby mode
     // with enough uncheckpointed txns to cause a checkpoint, and they
     // will each try to take a checkpoint and upload to each other.
-    HATestUtil.waitForCheckpoint(cluster, 1, ImmutableList.of(0, 12));
+    HATestUtil.waitForCheckpoint(cluster, 1, ImmutableList.of(12));
-    HATestUtil.waitForCheckpoint(cluster, 0, ImmutableList.of(0, 12));
+    HATestUtil.waitForCheckpoint(cluster, 0, ImmutableList.of(12));
     
     assertEquals(12, nn0.getNamesystem().getFSImage()
         .getMostRecentCheckpointTxId());