I have read that paper. I see. Even with current design, this PG lock is there, so multiple client writes to the same PG in parallel will not work, right? If I only allow one client write to OSDs in parallel, will that be a problem? On Fri, Jul 22, 2016 at 11:36 AM, Samuel Just <sjust@xxxxxxxxxx> wrote: > There is a per-pg log of recent operations (see PGLog.h/cc). It has > an order. If you allow multiple clients to submit operations to > replicas in parallel, different replicas may have different log > orderings (worse, in the general case, you have no guarantee that > every log entry -- and the write which it represents -- actually makes > it to every replica). That would pretty much completely break the > peering process. You might want to read the rados paper > (http://ceph.com/papers/weil-rados-pdsw07.pdf). > -Sam > > On Fri, Jul 22, 2016 at 8:30 AM, Sugang Li <sugangli@xxxxxxxxxxxxxxxxxx> wrote: >> I am confused. Could you describe a little bit more about that? >> >> Sugang >> >> On Fri, Jul 22, 2016 at 11:27 AM, Samuel Just <sjust@xxxxxxxxxx> wrote: >>> Not if you want the PG log to have consistent ordering. >>> -Sam >>> >>> On Fri, Jul 22, 2016 at 7:00 AM, Sugang Li <sugangli@xxxxxxxxxxxxxxxxxx> wrote: >>>> Actually write lock the object only. Is that gonna work? >>>> >>>> Sugang >>>> >>>> On Thu, Jul 21, 2016 at 5:59 PM, Samuel Just <sjust@xxxxxxxxxx> wrote: >>>>> Write lock on the whole pg? How do parallel clients work? >>>>> -Sam >>>>> >>>>> On Thu, Jul 21, 2016 at 12:36 PM, Sugang Li <sugangli@xxxxxxxxxxxxxxxxxx> wrote: >>>>>> The error above occurs when I am sending MOSOp to the replicas, and I >>>>>> have to fix that first. >>>>>> >>>>>> For the consistency, we are still using the Primary OSD as a control >>>>>> center. That is, the client always goes to Primary OSD to ask for a >>>>>> write lock, then write the replica. >>>>>> >>>>>> Sugang >>>>>> >>>>>> On Thu, Jul 21, 2016 at 3:28 PM, Samuel Just <sjust@xxxxxxxxxx> wrote: >>>>>>> Well, they are actually different types with different encodings and >>>>>>> different contents. The client doesn't really have the information >>>>>>> needed to build a MSG_OSD_REPOP. Your best bet will be to send an >>>>>>> MOSDOp to the replicas and hack up a write path that makes that work. >>>>>>> >>>>>>> How do you plan to address the consistency problems? >>>>>>> -Sam >>>>>>> >>>>>>> On Thu, Jul 21, 2016 at 11:11 AM, Sugang Li <sugangli@xxxxxxxxxxxxxxxxxx> wrote: >>>>>>>> So, to start with, I think one naive way is to make the replica think >>>>>>>> it receives an op from the primary OSD, which actually comes from the >>>>>>>> client. And the branching point looks like started from >>>>>>>> OSD::dispatch_op_fast, where handle_op or handle_replica_op is called >>>>>>>> based on the type of the request. So my question is, at the client >>>>>>>> side, is there a way that I could set the corresponding variables >>>>>>>> referred by "op->get_req()->get_type()" to MSG_OSD_SUBOP or >>>>>>>> MSG_OSD_REPOP? >>>>>>>> >>>>>>>> Sugang >>>>>>>> >>>>>>>> On Thu, Jul 21, 2016 at 12:03 PM, Samuel Just <sjust@xxxxxxxxxx> wrote: >>>>>>>>> Parallel read will be a *lot* easier since read-from-replica already >>>>>>>>> works. Write to replica, however, is tough. The write path uses a >>>>>>>>> lot of structures which are only populated on the primary. You're >>>>>>>>> going to have to hack up most of the write path to bypass the existing >>>>>>>>> replication machinery. Beyond that, maintaining consistency will >>>>>>>>> obviously be a challenge. >>>>>>>>> -Sam >>>>>>>>> >>>>>>>>> On Thu, Jul 21, 2016 at 8:49 AM, Sugang Li <sugangli@xxxxxxxxxxxxxxxxxx> wrote: >>>>>>>>>> My goal is to achieve parallel write/read from the client instead of >>>>>>>>>> the primary OSD. >>>>>>>>>> >>>>>>>>>> Sugang >>>>>>>>>> >>>>>>>>>> On Thu, Jul 21, 2016 at 11:47 AM, Samuel Just <sjust@xxxxxxxxxx> wrote: >>>>>>>>>>> I may be misunderstanding your goal. What are you trying to achieve? >>>>>>>>>>> -Sam >>>>>>>>>>> >>>>>>>>>>> On Thu, Jul 21, 2016 at 8:43 AM, Samuel Just <sjust@xxxxxxxxxx> wrote: >>>>>>>>>>>> Well, that assert is asserting that the object is in the pool that the >>>>>>>>>>>> pg operating on it belongs to. Something very wrong must have >>>>>>>>>>>> happened for it to be not true. Also, replicas have basically none of >>>>>>>>>>>> the code required to handle a write, so I'm kind of surprised it got >>>>>>>>>>>> that far. I suggest that you read the debug logging and read the OSD >>>>>>>>>>>> op handling path. >>>>>>>>>>>> -Sam >>>>>>>>>>>> >>>>>>>>>>>> On Thu, Jul 21, 2016 at 8:34 AM, Sugang Li <sugangli@xxxxxxxxxxxxxxxxxx> wrote: >>>>>>>>>>>>> Yes, I understand that. I was introduced to Ceph only 1 month ago, but >>>>>>>>>>>>> I have the basic idea of Ceph communication pattern now. I have not >>>>>>>>>>>>> make any changes to OSD yet. So I was wondering what is purpose of >>>>>>>>>>>>> this "assert(oid.pool == static_cast<int64_t>(info.pgid.pool()))", and >>>>>>>>>>>>> to change the code in OSD, what are the main aspects I should pay >>>>>>>>>>>>> attention to? >>>>>>>>>>>>> Since this is only a research project, the implementation does not >>>>>>>>>>>>> have to be very sophisticated. >>>>>>>>>>>>> >>>>>>>>>>>>> I know my question is kinda too broad, any hints or suggestions will >>>>>>>>>>>>> be highly appreciated. >>>>>>>>>>>>> >>>>>>>>>>>>> Thanks, >>>>>>>>>>>>> >>>>>>>>>>>>> Sugang >>>>>>>>>>>>> >>>>>>>>>>>>> On Thu, Jul 21, 2016 at 11:22 AM, Samuel Just <sjust@xxxxxxxxxx> wrote: >>>>>>>>>>>>>> Oh, that's a much more complicated change. You are going to need to >>>>>>>>>>>>>> make extensive changes to the OSD to make that work. >>>>>>>>>>>>>> -Sam >>>>>>>>>>>>>> >>>>>>>>>>>>>> On Thu, Jul 21, 2016 at 8:21 AM, Sugang Li <sugangli@xxxxxxxxxxxxxxxxxx> wrote: >>>>>>>>>>>>>>> Hi Sam, >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> Thanks for the quick reply. The main modification I made is to call >>>>>>>>>>>>>>> calc_target within librados::IoCtxImpl::aio_operate before op_submit, >>>>>>>>>>>>>>> so that I can get all replicated OSDs' id, and send a write op to each >>>>>>>>>>>>>>> of them. I can also attach the modified code if necessary. >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> I just reproduced this error with the conf you provided, please see below: >>>>>>>>>>>>>>> osd/ReplicatedPG.cc: In function 'int >>>>>>>>>>>>>>> ReplicatedPG::find_object_context(const hobject_t&, ObjectContextRef*, >>>>>>>>>>>>>>> bool, bool, hobject_t*)' thread 7fd6aba59700 time 2016-07-21 >>>>>>>>>>>>>>> 15:09:26.431436 >>>>>>>>>>>>>>> osd/ReplicatedPG.cc: 9042: FAILED assert(oid.pool == >>>>>>>>>>>>>>> static_cast<int64_t>(info.pgid.pool())) >>>>>>>>>>>>>>> ceph version 10.2.0-2562-g0793a28 (0793a2844baa38f6bcc5c1724a1ceb9f8f1bbd9c) >>>>>>>>>>>>>>> 1: (ceph::__ceph_assert_fail(char const*, char const*, int, char >>>>>>>>>>>>>>> const*)+0x8b) [0x7fd6c5733e8b] >>>>>>>>>>>>>>> 2: (ReplicatedPG::find_object_context(hobject_t const&, >>>>>>>>>>>>>>> std::shared_ptr<ObjectContext>*, bool, bool, hobject_t*)+0x1e54) >>>>>>>>>>>>>>> [0x7fd6c51ef7c4] >>>>>>>>>>>>>>> 3: (ReplicatedPG::do_op(std::shared_ptr<OpRequest>&)+0x186e) [0x7fd6c521fe9e] >>>>>>>>>>>>>>> 4: (ReplicatedPG::do_request(std::shared_ptr<OpRequest>&, >>>>>>>>>>>>>>> ThreadPool::TPHandle&)+0x73c) [0x7fd6c51dca3c] >>>>>>>>>>>>>>> 5: (OSD::dequeue_op(boost::intrusive_ptr<PG>, >>>>>>>>>>>>>>> std::shared_ptr<OpRequest>, ThreadPool::TPHandle&)+0x3f5) >>>>>>>>>>>>>>> [0x7fd6c5094d65] >>>>>>>>>>>>>>> 6: (PGQueueable::RunVis::operator()(std::shared_ptr<OpRequest> >>>>>>>>>>>>>>> const&)+0x5d) [0x7fd6c5094f8d] >>>>>>>>>>>>>>> 7: (OSD::ShardedOpWQ::_process(unsigned int, >>>>>>>>>>>>>>> ceph::heartbeat_handle_d*)+0x86c) [0x7fd6c50b603c] >>>>>>>>>>>>>>> 8: (ShardedThreadPool::shardedthreadpool_worker(unsigned int)+0x947) >>>>>>>>>>>>>>> [0x7fd6c5724117] >>>>>>>>>>>>>>> 9: (ShardedThreadPool::WorkThreadSharded::entry()+0x10) [0x7fd6c5726270] >>>>>>>>>>>>>>> 10: (()+0x8184) [0x7fd6c3b98184] >>>>>>>>>>>>>>> 11: (clone()+0x6d) [0x7fd6c1aa937d] >>>>>>>>>>>>>>> NOTE: a copy of the executable, or `objdump -rdS <executable>` is >>>>>>>>>>>>>>> needed to interpret this. >>>>>>>>>>>>>>> 2016-07-21 15:09:26.454854 7fd6aba59700 -1 osd/ReplicatedPG.cc: In >>>>>>>>>>>>>>> function 'int ReplicatedPG::find_object_context(const hobject_t&, >>>>>>>>>>>>>>> ObjectContextRef*, bool, bool, hobject_t*)' thread 7fd6aba59700 time >>>>>>>>>>>>>>> 2016-07-21 15:09:26.431436 >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> This error occurs three times since I wrote to three OSDs. >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> Thanks, >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> Sugang >>>>>>>>>>>>>>> >>>>>>>>>>>>>>> On Thu, Jul 21, 2016 at 10:54 AM, Samuel Just <sjust@xxxxxxxxxx> wrote: >>>>>>>>>>>>>>>> Hmm. Can you provide more information about the poison op? If you >>>>>>>>>>>>>>>> can reproduce with >>>>>>>>>>>>>>>> debug osd = 20 >>>>>>>>>>>>>>>> debug filestore = 20 >>>>>>>>>>>>>>>> debug ms = 1 >>>>>>>>>>>>>>>> it should be easier to work out what is going on. >>>>>>>>>>>>>>>> -Sam >>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>> On Thu, Jul 21, 2016 at 7:13 AM, Sugang Li <sugangli@xxxxxxxxxxxxxxxxxx> wrote: >>>>>>>>>>>>>>>>> Hi all, >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> I am working on a research project which requires multiple write >>>>>>>>>>>>>>>>> operations for the same object at the same time from the client. At >>>>>>>>>>>>>>>>> the OSD side, I got this error: >>>>>>>>>>>>>>>>> osd/ReplicatedPG.cc: In function 'int >>>>>>>>>>>>>>>>> ReplicatedPG::find_object_context(const hobject_t&, ObjectContextRef*, >>>>>>>>>>>>>>>>> bool, bool, hobject_t*)' thread 7f0586193700 time 2016-07-21 >>>>>>>>>>>>>>>>> 14:02:04.218448 >>>>>>>>>>>>>>>>> osd/ReplicatedPG.cc: 9041: FAILED assert(oid.pool == >>>>>>>>>>>>>>>>> static_cast<int64_t>(info.pgid.pool())) >>>>>>>>>>>>>>>>> ceph version 10.2.0-2562-g0793a28 (0793a2844baa38f6bcc5c1724a1ceb9f8f1bbd9c) >>>>>>>>>>>>>>>>> 1: (ceph::__ceph_assert_fail(char const*, char const*, int, char >>>>>>>>>>>>>>>>> const*)+0x8b) [0x7f059fe6dd7b] >>>>>>>>>>>>>>>>> 2: (ReplicatedPG::find_object_context(hobject_t const&, >>>>>>>>>>>>>>>>> std::shared_ptr<ObjectContext>*, bool, bool, hobject_t*)+0x1dbb) >>>>>>>>>>>>>>>>> [0x7f059f9296fb] >>>>>>>>>>>>>>>>> 3: (ReplicatedPG::do_op(std::shared_ptr<OpRequest>&)+0x186e) [0x7f059f959d7e] >>>>>>>>>>>>>>>>> 4: (ReplicatedPG::do_request(std::shared_ptr<OpRequest>&, >>>>>>>>>>>>>>>>> ThreadPool::TPHandle&)+0x73c) [0x7f059f916a0c] >>>>>>>>>>>>>>>>> 5: (OSD::dequeue_op(boost::intrusive_ptr<PG>, >>>>>>>>>>>>>>>>> std::shared_ptr<OpRequest>, ThreadPool::TPHandle&)+0x3f5) >>>>>>>>>>>>>>>>> [0x7f059f7ced65] >>>>>>>>>>>>>>>>> 6: (PGQueueable::RunVis::operator()(std::shared_ptr<OpRequest> >>>>>>>>>>>>>>>>> const&)+0x5d) [0x7f059f7cef8d] >>>>>>>>>>>>>>>>> 7: (OSD::ShardedOpWQ::_process(unsigned int, >>>>>>>>>>>>>>>>> ceph::heartbeat_handle_d*)+0x86c) [0x7f059f7f003c] >>>>>>>>>>>>>>>>> 8: (ShardedThreadPool::shardedthreadpool_worker(unsigned int)+0x947) >>>>>>>>>>>>>>>>> [0x7f059fe5e007] >>>>>>>>>>>>>>>>> 9: (ShardedThreadPool::WorkThreadSharded::entry()+0x10) [0x7f059fe60160] >>>>>>>>>>>>>>>>> 10: (()+0x8184) [0x7f059e2d2184] >>>>>>>>>>>>>>>>> 11: (clone()+0x6d) [0x7f059c1e337d] >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> And at the client side, I got segmentation fault. >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> I am wondering what will be the possible reason that cause the assert fail? >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> Thanks, >>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>> Sugang >>>>>>>>>>>>>>>>> -- >>>>>>>>>>>>>>>>> To unsubscribe from this list: send the line "unsubscribe ceph-devel" in >>>>>>>>>>>>>>>>> the body of a message to majordomo@xxxxxxxxxxxxxxx >>>>>>>>>>>>>>>>> More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
