From 32b981044f8c35ba2d1ece13cb0ec3aa941aef48 Mon Sep 17 00:00:00 2001
From: Michael McCandless <mikemccand@apache.org>
Date: Fri, 3 Aug 2007 18:41:22 +0000
Subject: [PATCH] LUCENE-948: handle stale dir listing caches on NFS (so
 quickly switching writers between machines works)

git-svn-id: https://svn.apache.org/repos/asf/lucene/java/trunk@562546 13f79535-47bb-0310-9956-ffa450edef68
---
 CHANGES.txt                                   |  5 +++
 .../apache/lucene/index/IndexFileDeleter.java | 32 +++++++++++++++----
 .../org/apache/lucene/index/IndexWriter.java  |  4 +++
 3 files changed, 35 insertions(+), 6 deletions(-)

diff --git a/CHANGES.txt b/CHANGES.txt
index d8e4ab77fe6..2c24dfdfb78 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -61,6 +61,11 @@ Bug fixes
  9. LUCENE-832: ParallelReader fixed to not throw NPE if isCurrent(),
     isOptimized() or getVersion() is called. (Michael Busch)
       
+10. LUCENE-948: Fix FNFE exception caused by stale NFS client
+    directory listing caches when writers on different machines are
+    sharing an index over NFS and using a custom deletion policy (Mike
+    McCandless)
+
 New features
 
  1. LUCENE-906: Elision filter for French.
diff --git a/src/java/org/apache/lucene/index/IndexFileDeleter.java b/src/java/org/apache/lucene/index/IndexFileDeleter.java
index 2675517dc05..fd39c8d98c3 100644
--- a/src/java/org/apache/lucene/index/IndexFileDeleter.java
+++ b/src/java/org/apache/lucene/index/IndexFileDeleter.java
@@ -23,6 +23,7 @@ import org.apache.lucene.index.SegmentInfo;
 import org.apache.lucene.store.Directory;
 
 import java.io.IOException;
+import java.io.FileNotFoundException;
 import java.io.PrintStream;
 import java.util.Map;
 import java.util.HashMap;
@@ -123,6 +124,9 @@ final class IndexFileDeleter {
     this.docWriter = docWriter;
     this.infoStream = infoStream;
 
+    if (infoStream != null)
+      message("init: current segments file is \"" + segmentInfos.getCurrentSegmentFileName() + "\"");
+
     this.policy = policy;
     this.directory = directory;
 
@@ -156,13 +160,29 @@ final class IndexFileDeleter {
               message("init: load commit \"" + fileName + "\"");
             }
             SegmentInfos sis = new SegmentInfos();
-            sis.read(directory, fileName);
-            CommitPoint commitPoint = new CommitPoint(sis);
-            if (sis.getGeneration() == segmentInfos.getGeneration()) {
-              currentCommitPoint = commitPoint;
+            try {
+              sis.read(directory, fileName);
+            } catch (FileNotFoundException e) {
+              // LUCENE-948: on NFS (and maybe others), if
+              // you have writers switching back and forth
+              // between machines, it's very likely that the
+              // dir listing will be stale and will claim a
+              // file segments_X exists when in fact it
+              // doesn't.  So, we catch this and handle it
+              // as if the file does not exist
+              if (infoStream != null) {
+                message("init: hit FileNotFoundException when loading commit \"" + fileName + "\"; skipping this commit point");
+              }
+              sis = null;
+            }
+            if (sis != null) {
+              CommitPoint commitPoint = new CommitPoint(sis);
+              if (sis.getGeneration() == segmentInfos.getGeneration()) {
+                currentCommitPoint = commitPoint;
+              }
+              commits.add(commitPoint);
+              incRef(sis, true);
             }
-            commits.add(commitPoint);
-            incRef(sis, true);
           }
         }
       }
diff --git a/src/java/org/apache/lucene/index/IndexWriter.java b/src/java/org/apache/lucene/index/IndexWriter.java
index 02826ada590..7cb68faf7e3 100644
--- a/src/java/org/apache/lucene/index/IndexWriter.java
+++ b/src/java/org/apache/lucene/index/IndexWriter.java
@@ -928,6 +928,8 @@ public class IndexWriter {
 
       if (commitPending) {
         segmentInfos.write(directory);         // now commit changes
+        if (infoStream != null)
+          infoStream.println("close: wrote segments file \"" + segmentInfos.getCurrentSegmentFileName() + "\"");
         deleter.checkpoint(segmentInfos, true);
         commitPending = false;
         rollbackSegmentInfos = null;
@@ -1478,6 +1480,8 @@ public class IndexWriter {
   private void checkpoint() throws IOException {
     if (autoCommit) {
       segmentInfos.write(directory);
+      if (infoStream != null)
+        infoStream.println("checkpoint: wrote segments file \"" + segmentInfos.getCurrentSegmentFileName() + "\"");
     } else {
       commitPending = true;
     }