· neo4j

neo4j: Setting query timeout

Updated December 2015

When I initially wrote this post in 2013 this was an experimental feature that worked using the Neo4j 1.9 series but no longer does in more recent Neo4j versions (2.2, 2.3). The terminating a running transaction page in the docs describes the supported way of terminating queries.

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When I was first learning cypher, neo4j's query language, I frequently wrote queries which traversed the whole graph multiple times and 'hung' for hours as they were evaluated.

At the time I terminated them by restarting the server but I recently learned from an old post on the mailing list and from my colleague Stefan Armbruster that you can set a query timeout to avoid this problem.

To do this you need to set the following properties:

conf/neo4j-server.properties

~~~text # timeout in milliseconds org.neo4j.server.webserver.limit.executiontime=1000 ~~~

conf/neo4j.properties

~~~text execution_guard_enabled=true ~~~

Now if I run a query which takes longer than 1 second to evaluate it will terminate early with the following exception:


$ start n = node(*) return n;
==> GuardTimeoutException: timeout occured (overtime=1718)

If you want a stricter maximum execution time on a per query basis you can do so by passing the 'max-execution-time' header on the request. e.g.


$ curl -H "Content-Type:application/json" -H "max-execution-time: 500" -X POST -d '{"query" : "start n = node(*) return n"}' http://localhost:7474/db/data/cypher
{
  "message" : "timeout occured (overtime=1)",
  "exception" : "BadInputException",
  "fullname" : "org.neo4j.server.rest.repr.BadInputException",
  "stacktrace" : [ "org.neo4j.server.rest.repr.RepresentationExceptionHandlingIterable.exceptionOnNext(RepresentationExceptionHandlingIterable.java:39)", "org.neo4j.helpers.collection.ExceptionHandlingIterable$1.next(ExceptionHandlingIterable.java:55)", "org.neo4j.helpers.collection.IteratorWrapper.next(IteratorWrapper.java:47)", "org.neo4j.server.rest.repr.ListRepresentation.serialize(ListRepresentation.java:58)", "org.neo4j.server.rest.repr.Serializer.serialize(Serializer.java:75)", "org.neo4j.server.rest.repr.MappingSerializer.putList(MappingSerializer.java:61)", "org.neo4j.server.rest.repr.CypherResultRepresentation.serialize(CypherResultRepresentation.java:83)", "org.neo4j.server.rest.repr.MappingRepresentation.serialize(MappingRepresentation.java:41)", "org.neo4j.server.rest.repr.OutputFormat.assemble(OutputFormat.java:215)", "org.neo4j.server.rest.repr.OutputFormat.formatRepresentation(OutputFormat.java:147)", "org.neo4j.server.rest.repr.OutputFormat.response(OutputFormat.java:130)", "org.neo4j.server.rest.repr.OutputFormat.ok(OutputFormat.java:67)", "org.neo4j.server.rest.web.CypherService.cypher(CypherService.java:101)", "java.lang.reflect.Method.invoke(Method.java:601)", "org.neo4j.server.rest.transactional.TransactionalRequestDispatcher.dispatch(TransactionalRequestDispatcher.java:132)", "org.neo4j.server.rest.security.SecurityFilter.doFilter(SecurityFilter.java:112)", "org.neo4j.server.guard.GuardingRequestFilter.doFilter(GuardingRequestFilter.java:68)", "java.lang.Thread.run(Thread.java:722)" ],
  "cause" : {
    "message" : "timeout occured (overtime=1)",
    "exception" : "GuardTimeoutException",
    "stacktrace" : [ "org.neo4j.kernel.guard.Guard$Timeout.check(Guard.java:132)", "org.neo4j.kernel.guard.Guard.check(Guard.java:43)", "org.neo4j.kernel.InternalAbstractGraphDatabase$4.getNodeByIdOrNull(InternalAbstractGraphDatabase.java:692)", "org.neo4j.kernel.impl.core.NodeManager$3.fetchNextOrNull(NodeManager.java:339)", "org.neo4j.kernel.impl.core.NodeManager$3.fetchNextOrNull(NodeManager.java:326)", "org.neo4j.helpers.collection.PrefetchingIterator.hasNext(PrefetchingIterator.java:55)", "scala.collection.convert.Wrappers$JIteratorWrapper.hasNext(Wrappers.scala:41)", "scala.collection.Iterator$$anon$11.hasNext(Iterator.scala:327)", "scala.collection.Iterator$$anon$13.hasNext(Iterator.scala:371)", "org.neo4j.cypher.internal.ClosingIterator$$anonfun$next$1.apply(ClosingIterator.scala:48)", "org.neo4j.cypher.internal.ClosingIterator$$anonfun$next$1.apply(ClosingIterator.scala:45)", "org.neo4j.cypher.internal.ClosingIterator.failIfThrows(ClosingIterator.scala:91)", "org.neo4j.cypher.internal.ClosingIterator.next(ClosingIterator.scala:45)", "org.neo4j.cypher.PipeExecutionResult.next(PipeExecutionResult.scala:168)", "org.neo4j.cypher.PipeExecutionResult.next(PipeExecutionResult.scala:34)", "scala.collection.Iterator$$anon$11.next(Iterator.scala:328)", "scala.collection.convert.Wrappers$IteratorWrapper.next(Wrappers.scala:30)", "org.neo4j.cypher.PipeExecutionResult$$anon$1.next(PipeExecutionResult.scala:76)", "org.neo4j.helpers.collection.ExceptionHandlingIterable$1.next(ExceptionHandlingIterable.java:53)", "org.neo4j.helpers.collection.IteratorWrapper.next(IteratorWrapper.java:47)", "org.neo4j.server.rest.repr.ListRepresentation.serialize(ListRepresentation.java:58)", "org.neo4j.server.rest.repr.Serializer.serialize(Serializer.java:75)", "org.neo4j.server.rest.repr.MappingSerializer.putList(MappingSerializer.java:61)", "org.neo4j.server.rest.repr.CypherResultRepresentation.serialize(CypherResultRepresentation.java:83)", "org.neo4j.server.rest.repr.MappingRepresentation.serialize(MappingRepresentation.java:41)", "org.neo4j.server.rest.repr.OutputFormat.assemble(OutputFormat.java:215)", "org.neo4j.server.rest.repr.OutputFormat.formatRepresentation(OutputFormat.java:147)", "org.neo4j.server.rest.repr.OutputFormat.response(OutputFormat.java:130)", "org.neo4j.server.rest.repr.OutputFormat.ok(OutputFormat.java:67)", "org.neo4j.server.rest.web.CypherService.cypher(CypherService.java:101)", "java.lang.reflect.Method.invoke(Method.java:601)", "org.neo4j.server.rest.transactional.TransactionalRequestDispatcher.dispatch(TransactionalRequestDispatcher.java:132)", "org.neo4j.server.rest.security.SecurityFilter.doFilter(SecurityFilter.java:112)", "org.neo4j.server.guard.GuardingRequestFilter.doFilter(GuardingRequestFilter.java:68)", "java.lang.Thread.run(Thread.java:722)" ],
    "fullname" : "org.neo4j.kernel.guard.GuardTimeoutException"
  }
}

At some stage hopefully we'll have the ability to terminate individual queries from the server but for now this is a decent workaround.

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