From 43fec17ac0e7860ab9babec1e150069bcdb3874e Mon Sep 17 00:00:00 2001
From: Shay Banon <kimchy@gmail.com>
Date: Thu, 9 Jan 2014 22:57:23 +0100
Subject: [PATCH] Multi data path config can cause a shard to be perceived as
 corrupted Multi data path config support writes a file to a data location
 based on the available size (by default). There is a Lucene file called
 segments.gen that has the same name, and only in that case, we need to make
 sure we alway write it to the same data location, otherwise, the index will
 have multiple segments.gen files, and the shard can seem to be corrupted.

The message if this case happens is that segments_xxx file was not found, in which case, a find for segments.gen can yield multiple files. Deleting the segments.gen files will cause the shard to recover properly (as its an extra protection layer to resolve the segments header by Lucene)

Make sure the segments.gen file is writtne to the same directory every time
fixes #4674
---
 src/main/java/org/elasticsearch/index/store/Store.java | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/main/java/org/elasticsearch/index/store/Store.java b/src/main/java/org/elasticsearch/index/store/Store.java
index 4a5eaed3cc629..a5e7ed04259fc 100644
--- a/src/main/java/org/elasticsearch/index/store/Store.java
+++ b/src/main/java/org/elasticsearch/index/store/Store.java
@@ -22,6 +22,7 @@
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.Maps;
+import org.apache.lucene.index.IndexFileNames;
 import org.apache.lucene.store.*;
 import org.apache.lucene.util.IOUtils;
 import org.elasticsearch.common.Nullable;
@@ -426,7 +427,9 @@ public IndexOutput createOutput(String name, IOContext context) throws IOExcepti
         public IndexOutput createOutput(String name, IOContext context, boolean raw) throws IOException {
             ensureOpen();
             Directory directory;
-            if (isChecksum(name)) {
+            // we want to write the segments gen file to the same directory *all* the time
+            // to make sure we don't create multiple copies of it
+            if (isChecksum(name) || IndexFileNames.SEGMENTS_GEN.equals(name)) {
                 directory = distributor.primary();
             } else {
                 directory = distributor.any();
@@ -441,7 +444,7 @@ public IndexOutput createOutput(String name, IOContext context, boolean raw) thr
                     boolean computeChecksum = !raw;
                     if (computeChecksum) {
                         // don't compute checksum for segment based files
-                        if ("segments.gen".equals(name) || name.startsWith("segments")) {
+                        if (IndexFileNames.SEGMENTS_GEN.equals(name) || name.startsWith(IndexFileNames.SEGMENTS)) {
                             computeChecksum = false;
                         }
                     }
@@ -562,7 +565,7 @@ public void sync(Collection<String> names) throws IOException {
             }
             for (String name : names) {
                 // write the checksums file when we sync on the segments file (committed)
-                if (!name.equals("segments.gen") && name.startsWith("segments")) {
+                if (!name.equals(IndexFileNames.SEGMENTS_GEN) && name.startsWith(IndexFileNames.SEGMENTS)) {
                     writeChecksums();
                     break;
                 }