Re: Customize Cassandra to execute a query multiple times
Why not simply have a microservice that does this for you? It may expose an API that allows to either store queries and/or conditions that trigger the queries (maybe time elapsed, an alert generated, whatever...) and it would then connect to Cassandra and execute the stored query(ies). Given that there is no client waiting for a response, then latency is not even a (major) issue, so the extra network hop is probably of little consequence. Why would you want this to be an integral part of Cassandra? (like Jeff I also am struggling to come up with a concrete use case where this would be desirable) -- *Marco Massenzio* http://codetrips.com On Wed, Jul 26, 2017 at 11:06 PM, Ke Wang <klwan...@gmail.com> wrote: > Hi Jeff, > > Thanks for the prompt reply. > > I'm sorry I wasn't clear about my use case. Let's say I just want the > server to execute writes that are not directly generated from clients. It > can be previously stored queries (the case in my last email), or it can be > arbitrarily made-up write requests by the server itself. > > Can you describe a little bit more on how to implement serializing the > mutation into the table? > > Best, > Ke > > 2017-07-26 22:57 GMT-07:00 Jeff Jirsa <jji...@apache.org>: > > > > > > > On 2017-07-26 22:19 (-0700), Ke Wang <klwan...@gmail.com> wrote: > > > Hello all, > > > > > > Is there a way to customize Cassandra to execute a query multiple > times? > > > > > > > There's always a way... > > > > > My use case is the following. When the Cassandra server receives > queries > > > from remote clients, besides executing those queries, the server also > > > stores the queries. In the future, the server can re-execute stored > > queries > > > under certain circumstances. > > > > > > > Seems like an unusual request. Where are you storing the queries? Are > > these reads or writes? For writes you could just serialize the resulting > > partitionupdate/mutation into a table a la pre-3.0 hints, and then > re-play > > as needed (though tbh I don't really get the use case)? > > > > > > > > - > > To unsubscribe, e-mail: dev-unsubscr...@cassandra.apache.org > > For additional commands, e-mail: dev-h...@cassandra.apache.org > > > > >
Re: Customize Cassandra to execute a query multiple times
Hi Jeff, Thanks for the prompt reply. I'm sorry I wasn't clear about my use case. Let's say I just want the server to execute writes that are not directly generated from clients. It can be previously stored queries (the case in my last email), or it can be arbitrarily made-up write requests by the server itself. Can you describe a little bit more on how to implement serializing the mutation into the table? Best, Ke 2017-07-26 22:57 GMT-07:00 Jeff Jirsa <jji...@apache.org>: > > > On 2017-07-26 22:19 (-0700), Ke Wang <klwan...@gmail.com> wrote: > > Hello all, > > > > Is there a way to customize Cassandra to execute a query multiple times? > > > > There's always a way... > > > My use case is the following. When the Cassandra server receives queries > > from remote clients, besides executing those queries, the server also > > stores the queries. In the future, the server can re-execute stored > queries > > under certain circumstances. > > > > Seems like an unusual request. Where are you storing the queries? Are > these reads or writes? For writes you could just serialize the resulting > partitionupdate/mutation into a table a la pre-3.0 hints, and then re-play > as needed (though tbh I don't really get the use case)? > > > > - > To unsubscribe, e-mail: dev-unsubscr...@cassandra.apache.org > For additional commands, e-mail: dev-h...@cassandra.apache.org > >
Re: Customize Cassandra to execute a query multiple times
On 2017-07-26 22:19 (-0700), Ke Wang <klwan...@gmail.com> wrote: > Hello all, > > Is there a way to customize Cassandra to execute a query multiple times? > There's always a way... > My use case is the following. When the Cassandra server receives queries > from remote clients, besides executing those queries, the server also > stores the queries. In the future, the server can re-execute stored queries > under certain circumstances. > Seems like an unusual request. Where are you storing the queries? Are these reads or writes? For writes you could just serialize the resulting partitionupdate/mutation into a table a la pre-3.0 hints, and then re-play as needed (though tbh I don't really get the use case)? - To unsubscribe, e-mail: dev-unsubscr...@cassandra.apache.org For additional commands, e-mail: dev-h...@cassandra.apache.org
Customize Cassandra to execute a query multiple times
Hello all, Is there a way to customize Cassandra to execute a query multiple times? My use case is the following. When the Cassandra server receives queries from remote clients, besides executing those queries, the server also stores the queries. In the future, the server can re-execute stored queries under certain circumstances. Currently, when I re-execute a query, I create an internal QueryState object using: qstate = QueryState forInternalCalls(), and then calls the request.execute(qstate, queryStartNanoTime); However, the execution seems to have no effect on the database. There is also no exception message. Does anyone have a clue on this? Great thanks! Best, Ke
