At Line 238 of OLD code's causes Out-Of-Index error. Because RemoteExecutor's Thread pool size is 5, so this method could be called from multiple threads. And it could remove items from bulkRevsToPull concurrently. To avoid this problem, entire while loop is surrounded by synchronization block.

Author: Hideki Itakura

src/main/java/com/couchbase/lite/replicator/PullerInternal.java

@@ -221,37 +221,35 @@ public void pullRemoteRevisions() {
         //find the work to be done in a synchronized block
         List<RevisionInternal> workToStartNow = new ArrayList<RevisionInternal>();
         List<RevisionInternal> bulkWorkToStartNow = new ArrayList<RevisionInternal>();
-        while (httpConnectionCount + workToStartNow.size() < MAX_OPEN_HTTP_CONNECTIONS) {
-            int nBulk = (bulkRevsToPull.size() < MAX_REVS_TO_GET_IN_BULK) ? bulkRevsToPull.size() : MAX_REVS_TO_GET_IN_BULK;
 
-            if (nBulk == 1) {
-                // Rather than pulling a single revision in 'bulk', just pull it normally:
-                queueRemoteRevision(bulkRevsToPull.remove(0));
-                nBulk = 0;
-            }
+        synchronized (bulkRevsToPull) {
+            while (httpConnectionCount + workToStartNow.size() < MAX_OPEN_HTTP_CONNECTIONS) {
+                int nBulk = (bulkRevsToPull.size() < MAX_REVS_TO_GET_IN_BULK) ? bulkRevsToPull.size() : MAX_REVS_TO_GET_IN_BULK;
+
+                if (nBulk == 1) {
+                    // Rather than pulling a single revision in 'bulk', just pull it normally:
+                    queueRemoteRevision(bulkRevsToPull.remove(0));
+                    nBulk = 0;
+                }
 
-            if (nBulk > 0) {
-                // Prefer to pull bulk revisions:
-                // Note: ArrayList.addAll(Collection) iterates parameter collection
-                //       https://github.com/couchbase/couchbase-lite-java-core/issues/361
-                synchronized (bulkRevsToPull) {
+                if (nBulk > 0) {
                     bulkWorkToStartNow.addAll(bulkRevsToPull.subList(0, nBulk));
                     bulkRevsToPull.subList(0, nBulk).clear();
-                }
-            } else {
-                // Prefer to pull an existing revision over a deleted one:
-                if (revsToPull.size() == 0 && deletedRevsToPull.size() == 0) {
-                    break;  // both queues are empty
-                } else if (revsToPull.size() > 0) {
-                    workToStartNow.add(revsToPull.remove(0));
-                } else if (deletedRevsToPull.size() > 0) {
-                    workToStartNow.add(deletedRevsToPull.remove(0));
+                } else {
+                    // Prefer to pull an existing revision over a deleted one:
+                    if (revsToPull.size() == 0 && deletedRevsToPull.size() == 0) {
+                        break;  // both queues are empty
+                    } else if (revsToPull.size() > 0) {
+                        workToStartNow.add(revsToPull.remove(0));
+                    } else if (deletedRevsToPull.size() > 0) {
+                        workToStartNow.add(deletedRevsToPull.remove(0));
+                    }
                 }
             }
         }
 
         //actually run it outside the synchronized block
-        if(bulkWorkToStartNow.size() > 0) {
+        if (bulkWorkToStartNow.size() > 0) {
             pullBulkRevisions(bulkWorkToStartNow);
         }