[GitHub] sijie commented on a change in pull request #205: Issue 208: Improve ledger fence logic

[gi...@git.apache.org]

sijie commented on a change in pull request #205: Issue 208: Improve ledger fence logic
URL: https://github.com/apache/bookkeeper/pull/205#discussion_r124834567
 
 

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 File path: bookkeeper-server/src/main/java/org/apache/bookkeeper/bookie/LedgerDescriptorImpl.java
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 @@ -81,6 +85,52 @@ ByteBuf getExplicitLac() {
         return ledgerStorage.getExplicitLac(ledgerId);
     }
 
+    synchronized SettableFuture<Boolean> fenceAndLogInJournal(Journal journal) throws IOException {
+        boolean success = this.setFenced();
+        if(success) {
+            // fenced for first time, we should add the key to journal ensure we can rebuild.
+            return logFenceEntryInJournal(journal);
+        } else {
+            // If we reach here, it means this ledger has been fenced before.
+            // However, fencing might still be in progress.
+            if(logFenceResult == null || fenceEntryPersisted.get()){
+                // Either ledger's fenced state is recovered from Journal
+                // Or Log fence entry in Journal succeed
+                SettableFuture<Boolean> result = SettableFuture.create();
+                result.set(true);
+                return result;
+            } else if (logFenceResult.isDone()) {
+                // We failed to log fence entry in Journal, try again.
+                return logFenceEntryInJournal(journal);
+            }
+            // Fencing is in progress
+            return logFenceResult;
+        }
+    }
+
+    /**
+     * Log the fence ledger entry in Journal so that we can rebuild the state.
+     * @param journal log the fence entry in the Journal
+     * @return A future which will be satisfied when add entry to journal complete
+     */
+    private SettableFuture<Boolean> logFenceEntryInJournal(Journal journal) {
+        SettableFuture<Boolean> result;
+        synchronized (this) {
+            result = logFenceResult = SettableFuture.create();
 
 Review comment:
   Because the fence is failed , line 102 is the else branch of line 96..
 
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