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Author: tlrx

server/src/main/java/org/elasticsearch/index/shard/IndexShard.java

@@ -1314,9 +1314,7 @@ public void close(String reason, boolean flushEngine) throws IOException {
     }
 
     public void preRecovery() {
-        if (state != IndexShardState.RECOVERING) {
-            throw new IndexShardNotRecoveringException(shardId, state);
-        }
+        assert state == IndexShardState.RECOVERING : "expected a recovering shard " + shardId + " but got " + state;
         indexEventListener.beforeIndexShardRecovery(this, indexSettings);
     }
 

server/src/main/java/org/elasticsearch/index/translog/Translog.java

@@ -1843,6 +1843,23 @@ static String createEmptyTranslog(Path location, long initialGlobalCheckpoint, S
         return createEmptyTranslog(location, shardId, initialGlobalCheckpoint, primaryTerm, null, channelFactory);
     }
 
+    /**
+     * Creates a new empty translog within the specified {@code location} that contains the given {@code initialGlobalCheckpoint},
+     * {@code primaryTerm} and {@code translogUUID}.
+     *
+     * This method should be used directly under specific circumstances like for shards that will see no indexing. Specifying a non-unique
+     * translog UUID could cause a lot of issues and that's why in all (but one) cases the method
+     * {@link #createEmptyTranslog(Path, long, ShardId, long)} should be used instead.
+     *
+     * @param location                a {@link Path} to the directory that will contains the translog files (translog + translog checkpoint)
+     * @param shardId                 the {@link ShardId}
+     * @param initialGlobalCheckpoint the global checkpoint to initialize the translog with
+     * @param primaryTerm             the shard's primary term to initialize the translog with
+     * @param translogUUID            the unique identifier to initialize the translog with
+     * @param factory                 a {@link ChannelFactory} used to open translog files
+     * @return the translog's unique identifier
+     * @throws IOException if something went wrong during translog creation
+     */
     public static String createEmptyTranslog(final Path location,
                                              final ShardId shardId,
                                              final long initialGlobalCheckpoint,

server/src/main/java/org/elasticsearch/indices/recovery/PeerRecoveryTargetService.java

@@ -171,8 +171,8 @@ private void doRecovery(final long recoveryId) {
             final RecoveryTarget recoveryTarget = recoveryRef.target();
             timer = recoveryTarget.state().getTimer();
             cancellableThreads = recoveryTarget.cancellableThreads();
-            final IndexShard indexShard = recoveryTarget.indexShard();
             try {
+                final IndexShard indexShard = recoveryTarget.indexShard();
                 indexShard.preRecovery();
                 assert recoveryTarget.sourceNode() != null : "can not do a recovery without a source node";
                 logger.trace("{} preparing shard for peer recovery", recoveryTarget.shardId());