From 790baed7551ba005732d530b1a6ccaad253ebb4c Mon Sep 17 00:00:00 2001
From: Lee Hinman <lee@writequit.org>
Date: Thu, 28 May 2015 10:00:36 -0600
Subject: [PATCH] Fall back to reading SegmentInfos from Store if reading from
 commit fails

In the event that reading from the latest commit fails, we should fall
back to reading from the `Store` using the traditional
`Directory.listAll()`

Related to #11361
---
 .../java/org/elasticsearch/index/engine/Engine.java    | 10 +++++++++-
 .../org/elasticsearch/index/engine/InternalEngine.java |  2 +-
 .../org/elasticsearch/index/engine/ShadowEngine.java   |  4 ++--
 3 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/src/main/java/org/elasticsearch/index/engine/Engine.java b/src/main/java/org/elasticsearch/index/engine/Engine.java
index e2811bb0698..41adf2b3b45 100644
--- a/src/main/java/org/elasticsearch/index/engine/Engine.java
+++ b/src/main/java/org/elasticsearch/index/engine/Engine.java
@@ -319,11 +319,19 @@ public abstract class Engine implements Closeable {
     /**
      * Read the last segments info from the commit pointed to by the searcher manager
      */
-    protected static SegmentInfos readLastCommittedSegmentInfos(SearcherManager sm) throws IOException {
+    protected static SegmentInfos readLastCommittedSegmentInfos(final SearcherManager sm, final Store store) throws IOException {
         IndexSearcher searcher = sm.acquire();
         try {
             IndexCommit latestCommit = ((DirectoryReader) searcher.getIndexReader()).getIndexCommit();
             return Lucene.readSegmentInfos(latestCommit);
+        } catch (IOException e) {
+            // Fall back to reading from the store if reading from the commit fails
+            try {
+                return store. readLastCommittedSegmentsInfo();
+            } catch (IOException e2) {
+                e2.addSuppressed(e);
+                throw e2;
+            }
         } finally {
             sm.release(searcher);
         }
diff --git a/src/main/java/org/elasticsearch/index/engine/InternalEngine.java b/src/main/java/org/elasticsearch/index/engine/InternalEngine.java
index 393dff33907..42bab8ca7fe 100644
--- a/src/main/java/org/elasticsearch/index/engine/InternalEngine.java
+++ b/src/main/java/org/elasticsearch/index/engine/InternalEngine.java
@@ -275,7 +275,7 @@ public class InternalEngine extends Engine {
             try {
                 final DirectoryReader directoryReader = ElasticsearchDirectoryReader.wrap(DirectoryReader.open(indexWriter, true), shardId);
                 searcherManager = new SearcherManager(directoryReader, searcherFactory);
-                lastCommittedSegmentInfos = readLastCommittedSegmentInfos(searcherManager);
+                lastCommittedSegmentInfos = readLastCommittedSegmentInfos(searcherManager, store);
                 success = true;
                 return searcherManager;
             } catch (IOException e) {
diff --git a/src/main/java/org/elasticsearch/index/engine/ShadowEngine.java b/src/main/java/org/elasticsearch/index/engine/ShadowEngine.java
index 301f6176a00..95b3810d330 100644
--- a/src/main/java/org/elasticsearch/index/engine/ShadowEngine.java
+++ b/src/main/java/org/elasticsearch/index/engine/ShadowEngine.java
@@ -79,7 +79,7 @@ public class ShadowEngine extends Engine {
                 if (Lucene.waitForIndex(store.directory(), nonexistentRetryTime)) {
                     reader = ElasticsearchDirectoryReader.wrap(DirectoryReader.open(store.directory()), shardId);
                     this.searcherManager = new SearcherManager(reader, searcherFactory);
-                    this.lastCommittedSegmentInfos = readLastCommittedSegmentInfos(searcherManager);
+                    this.lastCommittedSegmentInfos = readLastCommittedSegmentInfos(searcherManager, store);
                     success = true;
                 } else {
                     throw new IndexShardException(shardId, "failed to open a shadow engine after" +
@@ -148,7 +148,7 @@ public class ShadowEngine extends Engine {
         store.incRef();
         try (ReleasableLock lock = readLock.acquire()) {
             // reread the last committed segment infos
-            lastCommittedSegmentInfos = readLastCommittedSegmentInfos(searcherManager);
+            lastCommittedSegmentInfos = readLastCommittedSegmentInfos(searcherManager, store);
         } catch (Throwable e) {
             if (isClosed.get() == false) {
                 logger.warn("failed to read latest segment infos on flush", e);