2011/11/21 Aseem Kishore <aseem.kish...@gmail.com> > 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? > > That isn't possible through pure REST a.t.m.
A retry would do the trick but feels like jut a workaround, really. It would be nice with a way to control isolation using an http header or similar. And no, you shouldn't need to worry about these things. > 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 > -- Mattias Persson, [matt...@neotechnology.com] Hacker, Neo Technology www.neotechnology.com _______________________________________________ Neo4j mailing list User@lists.neo4j.org https://lists.neo4j.org/mailman/listinfo/user
