HDFS-4739. NN can miscalculate the number of extra edit log segments to retain. Contributed by Aaron T. Myers.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1471773 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -118,11 +118,17 @@ public class NNStorageRetentionManager {
             .result();
       }
     });
+
+    // Remove from consideration any edit logs that are in fact required.
+    while (editLogs.size() > 0 &&
+        editLogs.get(editLogs.size() - 1).getFirstTxId() >= minimumRequiredTxId) {
+      editLogs.remove(editLogs.size() - 1);
+    }
     
     // Next, adjust the number of transactions to retain if doing so would mean
     // keeping too many segments around.
     while (editLogs.size() > maxExtraEditsSegmentsToRetain) {
-      purgeLogsFrom = editLogs.get(0).getFirstTxId();
+      purgeLogsFrom = editLogs.get(0).getLastTxId() + 1;
       editLogs.remove(0);
     }
     

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

@@ -217,11 +217,12 @@ public class TestNNStorageRetentionManager {
     tc.addLog("/foo2/current/" + getFinalizedEditsFileName(176, 200), true);
     tc.addLog("/foo2/current/" + getFinalizedEditsFileName(201, 225), true);
     tc.addLog("/foo2/current/" + getFinalizedEditsFileName(226, 240), true);
-    // Only retain 2 extra segments. The 301-400 segment is considered required,
-    // not extra.
+    // Only retain 2 extra segments. The 301-350 and 351-400 segments are
+    // considered required, not extra.
     tc.addLog("/foo2/current/" + getFinalizedEditsFileName(241, 275), false);
     tc.addLog("/foo2/current/" + getFinalizedEditsFileName(276, 300), false);
-    tc.addLog("/foo2/current/" + getFinalizedEditsFileName(301, 400), false);
+    tc.addLog("/foo2/current/" + getFinalizedEditsFileName(301, 350), false);
+    tc.addLog("/foo2/current/" + getFinalizedEditsFileName(351, 400), false);
     tc.addLog("/foo2/current/" + getInProgressEditsFileName(401), false);
     runTest(tc);
   }