From 1daa0e2658f73c418f838fe1d85d5511e11b68c5 Mon Sep 17 00:00:00 2001
From: Andrei Dulceanu <adulceanu@apache.org>
Date: Tue, 11 Aug 2020 10:02:52 +0000
Subject: [PATCH] OAK-9170 - Make loading segment disk cache fail safe in case
 when write operation is interrupted by failure Contribution by Miroslav
 Smiljanic

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/oak/trunk@1880765 13f79535-47bb-0310-9956-ffa450edef68
---
 .../persistentcache/PersistentDiskCache.java  | 21 ++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/oak-segment-remote/src/main/java/org/apache/jackrabbit/oak/segment/remote/persistentcache/PersistentDiskCache.java b/oak-segment-remote/src/main/java/org/apache/jackrabbit/oak/segment/remote/persistentcache/PersistentDiskCache.java
index 81c3ed54727..b109588cdd6 100644
--- a/oak-segment-remote/src/main/java/org/apache/jackrabbit/oak/segment/remote/persistentcache/PersistentDiskCache.java
+++ b/oak-segment-remote/src/main/java/org/apache/jackrabbit/oak/segment/remote/persistentcache/PersistentDiskCache.java
@@ -33,8 +33,10 @@
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.nio.channels.FileChannel;
+import java.nio.file.AtomicMoveNotSupportedException;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.nio.file.StandardCopyOption;
 import java.nio.file.attribute.BasicFileAttributes;
 import java.nio.file.attribute.FileTime;
 import java.util.Comparator;
@@ -131,15 +133,28 @@ public boolean containsSegment(long msb, long lsb) {
     public void writeSegment(long msb, long lsb, Buffer buffer) {
         String segmentId = new UUID(msb, lsb).toString();
         File segmentFile = new File(directory, segmentId);
+        File tempSegmentFile = new File(directory, segmentId + System.nanoTime() + ".part");
+
         Buffer bufferCopy = buffer.duplicate();
 
         Runnable task = () -> {
             if (lockSegmentWrite(segmentId)) {
-                try (FileChannel channel = new FileOutputStream(segmentFile).getChannel()) {
+                try (FileChannel channel = new FileOutputStream(tempSegmentFile).getChannel()) {
                     int fileSize = bufferCopy.write(channel);
+                    try {
+                        Files.move(tempSegmentFile.toPath(), segmentFile.toPath(), StandardCopyOption.ATOMIC_MOVE);
+                    } catch (AtomicMoveNotSupportedException e) {
+                        Files.move(tempSegmentFile.toPath(), segmentFile.toPath());
+                    }
                     cacheSize.addAndGet(fileSize);
-                } catch (Throwable t) {
-                    logger.error("Error writing segment {} to cache: {}", segmentId, t);
+                } catch (Exception e) {
+                    logger.error("Error writing segment {} to cache: {}", segmentId, e);
+                    try {
+                        Files.deleteIfExists(segmentFile.toPath());
+                        Files.deleteIfExists(tempSegmentFile.toPath());
+                    } catch (IOException i) {
+                        logger.error("Error while deleting corrupted segment file {}", segmentId, i);
+                    }
                 } finally {
                     unlockSegmentWrite(segmentId);
                 }