# When running snapshot, BufferedChecksumIndexInput cannot seek backwards

**URL:** <https://discuss.elastic.co/t/when-running-snapshot-bufferedchecksumindexinput-cannot-seek-backwards/66800>\
**Category:** Elasticsearch\
**Created:** [November 22, 2016, 12:16am UTC](https://discuss.elastic.co/t/when-running-snapshot-bufferedchecksumindexinput-cannot-seek-backwards/66800 "2016-11-22T00:16:36Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![garbagefire](https://avatars.discourse-cdn.com/v4/letter/g/46a35a/32.png) [@garbagefire](https://discuss.elastic.co/u/garbagefire)\
**Post date:** [November 22, 2016, 12:16am UTC](https://discuss.elastic.co/t/when-running-snapshot-bufferedchecksumindexinput-cannot-seek-backwards/66800/1 "2016-11-22T00:16:36Z")

</div>

Hello,

We are running Elasticsearch 2.3.5.

About a month ago and a half ago, we optimized all of our indexes. E.g.:

POST /w-indexname-2016.07.21\_v1.4/\_optimize?max\_num\_segments=1

Since then, when we run our daily snapshop, we get this log entry for many of our indexes and shards:

```auto
[w-indexname-2016.07.21_v1.4][[w-indexname-2016.07.21_v1.4][2]] IndexShardSnapshotFailedException[class org.apache.lucene.store.BufferedChecksumIndexInput cannot seek backwards (pos=-16 getFilePointer()=0)]; nested: IllegalStateException[class org.apache.lucene.store.BufferedChecksumIndexInput cannot seek backwards (pos=-16 getFilePointer()=0)];
	at org.elasticsearch.index.snapshots.blobstore.BlobStoreIndexShardRepository.snapshot(BlobStoreIndexShardRepository.java:201)
	at org.elasticsearch.snapshots.SnapshotShardsService.snapshot(SnapshotShardsService.java:340)
	at org.elasticsearch.snapshots.SnapshotShardsService.access$200(SnapshotShardsService.java:76)
	at org.elasticsearch.snapshots.SnapshotShardsService$1.doRun(SnapshotShardsService.java:296)
	at org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:37)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.IllegalStateException: class org.apache.lucene.store.BufferedChecksumIndexInput cannot seek backwards (pos=-16 getFilePointer()=0)
	at org.apache.lucene.store.ChecksumIndexInput.seek(ChecksumIndexInput.java:50)
	at org.apache.lucene.codecs.CodecUtil.checksumEntireFile(CodecUtil.java:450)
	at org.elasticsearch.repositories.blobstore.ChecksumBlobStoreFormat.readBlob(ChecksumBlobStoreFormat.java:97)
	at org.elasticsearch.index.snapshots.blobstore.BlobStoreIndexShardRepository$Context.buildBlobStoreIndexShardSnapshots(BlobStoreIndexShardRepository.java:481)
	at org.elasticsearch.index.snapshots.blobstore.BlobStoreIndexShardRepository$SnapshotContext.snapshot(BlobStoreIndexShardRepository.java:537)
	at org.elasticsearch.index.snapshots.blobstore.BlobStoreIndexShardRepository.snapshot(BlobStoreIndexShardRepository.java:191)
	... 7 more

```

Any thoughts?

---

<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [December 20, 2016, 12:16am UTC](https://discuss.elastic.co/t/when-running-snapshot-bufferedchecksumindexinput-cannot-seek-backwards/66800/2 "2016-12-20T00:16:40Z")

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