One more point of clarification: these are concurrent REST API requests. One request is deleting a relationship, another request is querying for a(nother) relationship.
A simple analogy is a user unliking one thing on Facebook then immediately liking something else. I wouldn't expect the database to throw an error in this case, right? Am I wrong in assuming that the requests should be serialized / handled gracefully? If I'm wrong, should I just be optimistically retrying failed requests? Thanks again! Aseem On Mon, Nov 21, 2011 at 12:47 AM, Aseem Kishore <aseem.kish...@gmail.com>wrote: > I'm definitely modifying the graph at the same time; that's why this is > happening. But my assumption was that that shouldn't be breaking Neo4j -- I > thought requests are transactional/serialized. > > I don't have a repro test at the moment, but the behavior is really > simple. Here's an example analogy. We have a subgraph like User A [LIKES] > Object 1 and also [LIKES] Object 2: > > (Object 1) <--LIKES-- (User A) --LIKES--> (Object 2) > > One operation will delete the [LIKE] to Object 1, while another operation > queries whether User A [LIKES] Object 2. The query can be a Cypher query, > e.g.: > > START user=(123), obj=(456) > MATCH (user)-[rel]->(obj) > WHERE rel~TYPE = 'LIKES' > RETURN rel > > But we've also seen this bug where we used a simple traverse (specifying > just max depth 1 and the LIKES relationship type). > > When you say "looks like a normal case", do you mean that the query should > indeed fail like this? I wouldn't expect this -- what can I do to prevent > an error? Should I be retrying? > > Thanks Peter! > > Aseem > > > On Sun, Nov 20, 2011 at 10:08 PM, Peter Neubauer < > peter.neuba...@neotechnology.com> wrote: > >> Aseem, >> What query are you running, and are you modifying your graph on any way at >> the same time? Do you have a small example test reproducing this? Looks >> like a normal case where this relationship is deleted for some reason, no >> failure. Maybe a better Cypher error should point that out... >> >> /peter >> >> Sent from my phone, please excuse typos and autocorrection. >> On Nov 21, 2011 3:22 AM, "Aseem Kishore" <aseem.kish...@gmail.com> wrote: >> >> > Hey guys, >> > >> > If we put our app under a bit of load, creating and removing nodes and >> > relationships concurrently, sometimes we get back a 500 Internal Server >> > Error from the REST API when we do a traverse or Cypher query. Here's an >> > example stack trace: >> > >> > https://gist.github.com/1381423 >> > >> > We're running Neo4j. 1.4 still, but does this stack trace provide any >> > insight/ideas into what might be wrong, what we could do as a >> workaround, >> > etc.? Can I provide any other info that would help? >> > >> > It goes without saying that our assumption is that Neo4j shouldn't be >> > failing/crashing on queries; our expectation was that operations are >> > transactional, etc. >> > >> > Thanks! >> > >> > Aseem >> > _______________________________________________ >> > Neo4j mailing list >> > User@lists.neo4j.org >> > https://lists.neo4j.org/mailman/listinfo/user >> > >> _______________________________________________ >> Neo4j mailing list >> User@lists.neo4j.org >> https://lists.neo4j.org/mailman/listinfo/user >> > > _______________________________________________ Neo4j mailing list User@lists.neo4j.org https://lists.neo4j.org/mailman/listinfo/user
