HDFS-3884. Journal format() should reset cached values. Contributed by Todd Lipcon.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/HDFS-3077@1380979 13f79535-47bb-0310-9956-ffa450edef68

hadoop-hdfs-project/hadoop-hdfs/CHANGES.HDFS-3077.txt

@@ -40,3 +40,5 @@ HDFS-3877. QJM: Provide defaults for dfs.journalnode.*address (eli)
 HDFS-3863. Track last "committed" txid in QJM (todd)
 
 HDFS-3869. Expose non-file journal manager details in web UI (todd)
+
+HDFS-3884. Journal format() should reset cached values (todd)

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/qjournal/server/Journal.java

@@ -105,6 +105,19 @@ class Journal implements Closeable {
   Journal(File logDir, StorageErrorReporter errorReporter) throws IOException {
     storage = new JNStorage(logDir, errorReporter);
 
+    refreshCachedData();
+    
+    this.fjm = storage.getJournalManager();
+  }
+
+  /**
+   * Reload any data that may have been cached. This is necessary
+   * when we first load the Journal, but also after any formatting
+   * operation, since the cached data is no longer relevant.
+   */
+  private synchronized void refreshCachedData() {
+    IOUtils.closeStream(committedTxnId);
+    
     File currentDir = storage.getSingularStorageDir().getCurrentDir();
     this.lastPromisedEpoch = new PersistentLongFile(
         new File(currentDir, LAST_PROMISED_FILENAME), 0);
@@ -113,8 +126,6 @@ class Journal implements Closeable {
     this.committedTxnId = new BestEffortLongFile(
         new File(currentDir, COMMITTED_TXID_FILENAME),
         HdfsConstants.INVALID_TXID);
-    
-    this.fjm = storage.getJournalManager();
   }
   
   /**
@@ -156,6 +167,7 @@ class Journal implements Closeable {
     LOG.info("Formatting " + this + " with namespace info: " +
         nsInfo);
     storage.format(nsInfo);
+    refreshCachedData();
   }
 
   /**
@@ -180,6 +192,11 @@ class Journal implements Closeable {
     checkFormatted();
     return lastPromisedEpoch.get();
   }
+
+  synchronized public long getLastWriterEpoch() throws IOException {
+    checkFormatted();
+    return lastWriterEpoch.get();
+  }
   
   synchronized long getCommittedTxnIdForTests() throws IOException {
     return committedTxnId.get();

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/qjournal/server/TestJournal.java

@@ -148,6 +148,19 @@ public class TestJournal {
     assertEquals(1, newEpoch.getLastSegmentTxId());
   }
   
+  @Test
+  public void testFormatResetsCachedValues() throws Exception {
+    journal.newEpoch(FAKE_NSINFO, 12345L);
+    journal.startLogSegment(new RequestInfo(JID, 12345L, 1L, 0L), 1L);
+
+    assertEquals(12345L, journal.getLastPromisedEpoch());
+    assertEquals(12345L, journal.getLastWriterEpoch());
+
+    journal.format(FAKE_NSINFO_2);
+    assertEquals(0, journal.getLastPromisedEpoch());
+    assertEquals(0, journal.getLastWriterEpoch());
+  }
+  
   /**
    * Test that, if the writer crashes at the very beginning of a segment,
    * before any transactions are written, that the next newEpoch() call