Upon restarting an elasticsearch server, I received a "failed to recover commit_point" message from Elasticsearch. The cause was a null pointer being passed into a concurrent hashmap. The null comes from PercolatorExecutor.parseQuery, which seems to always parse a query or raise an exception. If there is no "query" token, however, the parseQuery method appears to return null.

I patched code in PercolatorService.QueryiesLoaderCollector.collect to check the return value of parseQuery for null before inserting it into the map, and that seemed to fix it. Here's the pull request:

#2547

I'm not familiar enough with ES to know if that's actually the fix. Maybe parseQuery should raise an exception, or maybe the _percolator index needs better sanitization. But in 19.8, at least, it seems possible to get the _percolator index into a state that makes the data unrecoverable without edits to the ES source.

org.elasticsearch.index.gateway.IndexShardGatewayRecoveryException: [_percolator][0] failed to recover commit_point [commit-19]/[45]
at org.elasticsearch.index.gateway.blobstore.BlobStoreIndexShardGateway.recover(BlobStoreIndexShardGateway.java:424)
at org.elasticsearch.index.gateway.IndexShardGatewayService$1.run(IndexShardGatewayService.java:177)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)
Caused by: java.lang.NullPointerException
at java.util.concurrent.ConcurrentHashMap.put(ConcurrentHashMap.java:881)
at java.util.concurrent.ConcurrentHashMap.putAll(ConcurrentHashMap.java:909)
at org.elasticsearch.index.percolator.PercolatorExecutor.addQueries(PercolatorExecutor.java:259)
at org.elasticsearch.index.percolator.PercolatorService.loadQueries(PercolatorService.java:128)
at org.elasticsearch.index.percolator.PercolatorService.access$700(PercolatorService.java:52)
at org.elasticsearch.index.percolator.PercolatorService$ShardLifecycleListener.afterIndexShardStarted(PercolatorService.java:220)
at org.elasticsearch.indices.InternalIndicesLifecycle.afterIndexShardStarted(InternalIndicesLifecycle.java:86)
at org.elasticsearch.index.shard.service.InternalIndexShard.start(InternalIndexShard.java:277)
at org.elasticsearch.index.gateway.blobstore.BlobStoreIndexShardGateway.recoverTranslog(BlobStoreIndexShardGateway.java:435)
at org.elasticsearch.index.gateway.blobstore.BlobStoreIndexShardGateway.recover(BlobStoreIndexShardGateway.java:421)