Hi Guys, I'm very very happy, reasons of my failures are identified. issue is in: --- src/srvnet.c (wersja 177) +++ src/srvnet.c (kopia robocza) @@ -99,7 +99,7 @@ rs_log_info("listening on %s", sa_buf ? sa_buf : "UNKNOWN"); free(sa_buf);
- if (listen(fd, 10)) { + if (listen(fd, 256)) { rs_log_error("listen failed: %s", strerror(errno)); close(fd); return EXIT_BIND_FAILED; Index: src/io.c queue for new connetcion was minited to 10, that's why in case that cluster is overloaded, many connection are reseted. aim is to even wait 5 min for cluster availability, then compile localy. @Jarek, thanks for support! let's discuss if we should fix it or not. regards Lukasz Łukasz Tasz 2014-10-24 10:27 GMT+02:00 Łukasz Tasz <luk...@tasz.eu>: > Hi Martin > > What I have noticed. > Client tries to connect distccd 3 times with 500ms delays in between. > Linux kernel by default accept 128 connection. > If client creates connection, even if no executors are avaliable, > connection is accepted and queued by kernel running distccd. > This leads to situation that client thinks that distccd is reserved, > but in fact connection still waits to be accepted by distccd server. > I suspect that then client starts communication too fast, distcc wont > receive DIST token, and both sides waits, communication is broken, and > then timeouts are applied for client default is applied, for server > there is no defaults. > > fail scenarion is: > one distccd, and two distcc users, both of them will try to compile > with DISTCC_HOSTS=distccd/1,cpp,lzo, both users have lot of big > objects, cluster is overloaded with ratio 2. > This still should be OK, that third, and forth user will join cluster. > > Easy reproducer is to set one distcc, and set distcc_hosts=distccd/20, > this is broken configuration, but simulates overload by 20 - 20 > developers uses cluster in a same time. > Please remember that those are exceptional situation, but developer > can start compilation with -j 1000 from his laptop, and cluster will > timeout, then receiving 1000 jobs on a laptop will end with memmory > killer :D > Those are exceptional situation, and somehow cluster should handle that. > > In the attachement, next to some pump changes, you can find change > which is moving making connection to very beginning, when distcc is > picking host, also remote connection is made. if this will fail, discc > follow default behaviour, goes sleep for one sec, and will pick host > again. But this requires additional administration change on distccd > machine: > iptables -I INPUT -p tcp --dport 3632 -m connlimit --connlimit-above > <NUMBER OF DISTCCD> --connlimit-mask 0 -j REJECT --reject-with > tcp-reset > which accept only number of connection which equals to number of executors. > > So far so good! > remark, patch is done on top of arankine_distcc_issue16-r335, since > his pump changes are making pump mode working on my environment. > But distccd allocation I tested also on latest official distcc release. > > let me know what you think! > > with best regards > Lukasz > > > > Łukasz Tasz > > > 2014-10-24 2:42 GMT+02:00 Martin Pool <m...@sourcefrog.net>: >> It seems like if there's nowhere to execute the job, we want the client >> program to just pause, before using too many resources, until it gets >> unqueued by a server ready to do the job. (Or, by a local slot being >> available.) >> >> >> On Thu Oct 16 2014 at 2:43:35 AM Łukasz Tasz <luk...@tasz.eu> wrote: >>> >>> Hi Martin, >>> >>> Lets assume that you can trigger more compilation tasks executors then you >>> have. >>> In this scenario you are facing situation that cluster is saturated. >>> When such a compilation will be triggered by two developers, or two CI >>> (e.g jenkins) jobs, then cluster is saturated twice... >>> >>> Default behaviour is to lock locally slot, and try to connect three >>> times, if not, fallback, if fallback is disabled CI got failed build >>> (fallback is not the case, since local machine cannot handle -j >>> $(distcc -j)). >>> >>> consider scenario, I have 1000 objects, 500 executors, >>> - clean build on one machine takes >>> 1000 * 20 sec (one obj) = 20000 / 16 processors = 1000 sec, >>> - on cluster (1000/500) * 20 sec = 40 sec >>> >>> Saturating cluster was impossible without pump mode, but now with pump >>> mode after "warm up" effect, pump can dispatch many tasks, and I faced >>> situation that saturated cluster destroys almost every compilation. >>> >>> My expectation is that cluster wont reject my connect, or reject will >>> be handled, either by client, either by server. >>> >>> by server: >>> - accept every connetion, >>> - fork child if not accepted by child, >>> - in case of pump prepare local dir structure, receive headers >>> - --critical section starts here-- multi value semaphore with value >>> maxchild >>> - execute job >>> - release semaphore >>> >>> >>> Also what you suggested may be even better solution, since client will >>> pick first avaliable executor instead of entering queue, so distcc >>> could make connection already in function dcc_lock_one() >>> >>> I already tried to set DISTCC_DIR on a common nfs share, but in case >>> you are triggering so many jobs, this started to be bottle neck... I >>> won't tell about locking on nfs, and also scenario that somebody will >>> make a lock on nfs and machine will got crash - will not work by >>> design :) >>> >>> I know that scenario is not happening very often, and it has more or >>> less picks characteristic, but we should be happy that distcc cluster >>> is saturated and this case should be handled. >>> >>> hope it's more clear now! >>> br >>> LT >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> Łukasz Tasz >>> >>> >>> 2014-10-16 1:39 GMT+02:00 Martin Pool <m...@sourcefrog.net>: >>> > Can you try to explain more clearly what difference in queueing behavior >>> > you >>> > expect from this change? >>> > >>> > I think probably the main change that's needed is for the client to ask >>> > all >>> > masters if they have space, to avoid needing to effectively poll by >>> > retrying, or getting stuck waiting for a particular server. >>> > >>> > On Wed, Oct 15, 2014 at 12:53 PM, Łukasz Tasz <luk...@tasz.eu> wrote: >>> >> >>> >> Hi Guys, >>> >> >>> >> please correct me if I'm wrong, >>> >> - currently distcc tries to connect server 3 times, with small delay, >>> >> - server forks x childs and all of them are trying to accept incoming >>> >> connection. >>> >> If server runs out of childs (all of them are busy), client will >>> >> fallback, and within next 60 sec will not try this machine. >>> >> >>> >> What do you think about redesigning distcc in a way that master server >>> >> will always accept inconing connection, fork a child, but in a same >>> >> time only x of them will be able to enter compilation >>> >> task(dcc_spawn_child)? (mayby preforking still could be used?) >>> >> >>> >> This may create kind of queue, client always can decide by his own, if >>> >> can wait some time, or maximum is DISTCC_IO_TIMEOUT, but still it's >>> >> faster to wait, since probably on a cluster side it's just a pick of >>> >> saturation then making falback to local machine. >>> >> >>> >> currently I'm facing situation that many jobs are making fallback, and >>> >> localmachine is being killed by make's -j calculated for distccd... >>> >> >>> >> other trick maybe to pick different machine, if current is busy, but >>> >> this may be much more complex in my opinion. >>> >> >>> >> what do you think? >>> >> regards >>> >> Łukasz Tasz >>> >> __ >>> >> distcc mailing list http://distcc.samba.org/ >>> >> To unsubscribe or change options: >>> >> https://lists.samba.org/mailman/listinfo/distcc >>> > >>> > >>> > >>> > >>> > -- >>> > Martin __ distcc mailing list http://distcc.samba.org/ To unsubscribe or change options: https://lists.samba.org/mailman/listinfo/distcc