<p dir="ltr"><br>
On 1 Nov 2014 15:08, "Łukasz Tasz" <<a href="mailto:lukasz@tasz.eu">lukasz@tasz.eu</a>> wrote:<br>
><br>
> Sure, I just made quick fix to test my test case, and immediately share it with you.</p>
<p dir="ltr">Sure, understood -- that's great, thanks.</p>
<p dir="ltr">> I will try to send more polite fix:)<br>
> Regards<br>
> lt<br>
><br>
> 1 lis 2014 09:06 "Fergus Henderson" <<a href="mailto:fergus@google.com">fergus@google.com</a>> napisał(a):<br>
><br>
>> Well, perhaps it would be a good idea to add a distccd flag or environment variable to control the queue length rather than hard-coding 10 or 256?<br>
>><br>
>> On 31 Oct 2014 11:37, "Łukasz Tasz" <<a href="mailto:lukasz@tasz.eu">lukasz@tasz.eu</a>> wrote:<br>
>>><br>
>>> Hi Guys,<br>
>>><br>
>>> I'm very very happy, reasons of my failures are identified.<br>
>>> issue is in:<br>
>>> --- src/srvnet.c (wersja 177)<br>
>>> +++ src/srvnet.c (kopia robocza)<br>
>>> @@ -99,7 +99,7 @@<br>
>>> rs_log_info("listening on %s", sa_buf ? sa_buf : "UNKNOWN");<br>
>>> free(sa_buf);<br>
>>><br>
>>> - if (listen(fd, 10)) {<br>
>>> + if (listen(fd, 256)) {<br>
>>> rs_log_error("listen failed: %s", strerror(errno));<br>
>>> close(fd);<br>
>>> return EXIT_BIND_FAILED;<br>
>>> Index: src/io.c<br>
>>><br>
>>> queue for new connetcion was minited to 10, that's why in case that<br>
>>> cluster is overloaded, many connection are reseted.<br>
>>> aim is to even wait 5 min for cluster availability, then compile localy.<br>
>>><br>
>>> @Jarek, thanks for support!<br>
>>><br>
>>> let's discuss if we should fix it or not.<br>
>>><br>
>>> regards<br>
>>> Lukasz<br>
>>><br>
>>><br>
>>> Łukasz Tasz<br>
>>><br>
>>><br>
>>> 2014-10-24 10:27 GMT+02:00 Łukasz Tasz <<a href="mailto:lukasz@tasz.eu">lukasz@tasz.eu</a>>:<br>
>>> > Hi Martin<br>
>>> ><br>
>>> > What I have noticed.<br>
>>> > Client tries to connect distccd 3 times with 500ms delays in between.<br>
>>> > Linux kernel by default accept 128 connection.<br>
>>> > If client creates connection, even if no executors are avaliable,<br>
>>> > connection is accepted and queued by kernel running distccd.<br>
>>> > This leads to situation that client thinks that distccd is reserved,<br>
>>> > but in fact connection still waits to be accepted by distccd server.<br>
>>> > I suspect that then client starts communication too fast, distcc wont<br>
>>> > receive DIST token, and both sides waits, communication is broken, and<br>
>>> > then timeouts are applied for client default is applied, for server<br>
>>> > there is no defaults.<br>
>>> ><br>
>>> > fail scenarion is:<br>
>>> > one distccd, and two distcc users, both of them will try to compile<br>
>>> > with DISTCC_HOSTS=distccd/1,cpp,lzo, both users have lot of big<br>
>>> > objects, cluster is overloaded with ratio 2.<br>
>>> > This still should be OK, that third, and forth user will join cluster.<br>
>>> ><br>
>>> > Easy reproducer is to set one distcc, and set distcc_hosts=distccd/20,<br>
>>> > this is broken configuration, but simulates overload by 20 - 20<br>
>>> > developers uses cluster in a same time.<br>
>>> > Please remember that those are exceptional situation, but developer<br>
>>> > can start compilation with -j 1000 from his laptop, and cluster will<br>
>>> > timeout, then receiving 1000 jobs on a laptop will end with memmory<br>
>>> > killer :D<br>
>>> > Those are exceptional situation, and somehow cluster should handle that.<br>
>>> ><br>
>>> > In the attachement, next to some pump changes, you can find change<br>
>>> > which is moving making connection to very beginning, when distcc is<br>
>>> > picking host, also remote connection is made. if this will fail, discc<br>
>>> > follow default behaviour, goes sleep for one sec, and will pick host<br>
>>> > again. But this requires additional administration change on distccd<br>
>>> > machine:<br>
>>> > iptables -I INPUT -p tcp --dport 3632 -m connlimit --connlimit-above<br>
>>> > <NUMBER OF DISTCCD> --connlimit-mask 0 -j REJECT --reject-with<br>
>>> > tcp-reset<br>
>>> > which accept only number of connection which equals to number of executors.<br>
>>> ><br>
>>> > So far so good!<br>
>>> > remark, patch is done on top of arankine_distcc_issue16-r335, since<br>
>>> > his pump changes are making pump mode working on my environment.<br>
>>> > But distccd allocation I tested also on latest official distcc release.<br>
>>> ><br>
>>> > let me know what you think!<br>
>>> ><br>
>>> > with best regards<br>
>>> > Lukasz<br>
>>> ><br>
>>> ><br>
>>> ><br>
>>> > Łukasz Tasz<br>
>>> ><br>
>>> ><br>
>>> > 2014-10-24 2:42 GMT+02:00 Martin Pool <<a href="mailto:mbp@sourcefrog.net">mbp@sourcefrog.net</a>>:<br>
>>> >> It seems like if there's nowhere to execute the job, we want the client<br>
>>> >> program to just pause, before using too many resources, until it gets<br>
>>> >> unqueued by a server ready to do the job. (Or, by a local slot being<br>
>>> >> available.)<br>
>>> >><br>
>>> >><br>
>>> >> On Thu Oct 16 2014 at 2:43:35 AM Łukasz Tasz <<a href="mailto:lukasz@tasz.eu">lukasz@tasz.eu</a>> wrote:<br>
>>> >>><br>
>>> >>> Hi Martin,<br>
>>> >>><br>
>>> >>> Lets assume that you can trigger more compilation tasks executors then you<br>
>>> >>> have.<br>
>>> >>> In this scenario you are facing situation that cluster is saturated.<br>
>>> >>> When such a compilation will be triggered by two developers, or two CI<br>
>>> >>> (e.g jenkins) jobs, then cluster is saturated twice...<br>
>>> >>><br>
>>> >>> Default behaviour is to lock locally slot, and try to connect three<br>
>>> >>> times, if not, fallback, if fallback is disabled CI got failed build<br>
>>> >>> (fallback is not the case, since local machine cannot handle -j<br>
>>> >>> $(distcc -j)).<br>
>>> >>><br>
>>> >>> consider scenario, I have 1000 objects, 500 executors,<br>
>>> >>> - clean build on one machine takes<br>
>>> >>> 1000 * 20 sec (one obj) = 20000 / 16 processors = 1000 sec,<br>
>>> >>> - on cluster (1000/500) * 20 sec = 40 sec<br>
>>> >>><br>
>>> >>> Saturating cluster was impossible without pump mode, but now with pump<br>
>>> >>> mode after "warm up" effect, pump can dispatch many tasks, and I faced<br>
>>> >>> situation that saturated cluster destroys almost every compilation.<br>
>>> >>><br>
>>> >>> My expectation is that cluster wont reject my connect, or reject will<br>
>>> >>> be handled, either by client, either by server.<br>
>>> >>><br>
>>> >>> by server:<br>
>>> >>> - accept every connetion,<br>
>>> >>> - fork child if not accepted by child,<br>
>>> >>> - in case of pump prepare local dir structure, receive headers<br>
>>> >>> - --critical section starts here-- multi value semaphore with value<br>
>>> >>> maxchild<br>
>>> >>> - execute job<br>
>>> >>> - release semaphore<br>
>>> >>><br>
>>> >>><br>
>>> >>> Also what you suggested may be even better solution, since client will<br>
>>> >>> pick first avaliable executor instead of entering queue, so distcc<br>
>>> >>> could make connection already in function dcc_lock_one()<br>
>>> >>><br>
>>> >>> I already tried to set DISTCC_DIR on a common nfs share, but in case<br>
>>> >>> you are triggering so many jobs, this started to be bottle neck... I<br>
>>> >>> won't tell about locking on nfs, and also scenario that somebody will<br>
>>> >>> make a lock on nfs and machine will got crash - will not work by<br>
>>> >>> design :)<br>
>>> >>><br>
>>> >>> I know that scenario is not happening very often, and it has more or<br>
>>> >>> less picks characteristic, but we should be happy that distcc cluster<br>
>>> >>> is saturated and this case should be handled.<br>
>>> >>><br>
>>> >>> hope it's more clear now!<br>
>>> >>> br<br>
>>> >>> LT<br>
>>> >>><br>
>>> >>><br>
>>> >>><br>
>>> >>><br>
>>> >>><br>
>>> >>><br>
>>> >>><br>
>>> >>><br>
>>> >>><br>
>>> >>> Łukasz Tasz<br>
>>> >>><br>
>>> >>><br>
>>> >>> 2014-10-16 1:39 GMT+02:00 Martin Pool <<a href="mailto:mbp@sourcefrog.net">mbp@sourcefrog.net</a>>:<br>
>>> >>> > Can you try to explain more clearly what difference in queueing behavior<br>
>>> >>> > you<br>
>>> >>> > expect from this change?<br>
>>> >>> ><br>
>>> >>> > I think probably the main change that's needed is for the client to ask<br>
>>> >>> > all<br>
>>> >>> > masters if they have space, to avoid needing to effectively poll by<br>
>>> >>> > retrying, or getting stuck waiting for a particular server.<br>
>>> >>> ><br>
>>> >>> > On Wed, Oct 15, 2014 at 12:53 PM, Łukasz Tasz <<a href="mailto:lukasz@tasz.eu">lukasz@tasz.eu</a>> wrote:<br>
>>> >>> >><br>
>>> >>> >> Hi Guys,<br>
>>> >>> >><br>
>>> >>> >> please correct me if I'm wrong,<br>
>>> >>> >> - currently distcc tries to connect server 3 times, with small delay,<br>
>>> >>> >> - server forks x childs and all of them are trying to accept incoming<br>
>>> >>> >> connection.<br>
>>> >>> >> If server runs out of childs (all of them are busy), client will<br>
>>> >>> >> fallback, and within next 60 sec will not try this machine.<br>
>>> >>> >><br>
>>> >>> >> What do you think about redesigning distcc in a way that master server<br>
>>> >>> >> will always accept inconing connection, fork a child, but in a same<br>
>>> >>> >> time only x of them will be able to enter compilation<br>
>>> >>> >> task(dcc_spawn_child)? (mayby preforking still could be used?)<br>
>>> >>> >><br>
>>> >>> >> This may create kind of queue, client always can decide by his own, if<br>
>>> >>> >> can wait some time, or maximum is DISTCC_IO_TIMEOUT, but still it's<br>
>>> >>> >> faster to wait, since probably on a cluster side it's just a pick of<br>
>>> >>> >> saturation then making falback to local machine.<br>
>>> >>> >><br>
>>> >>> >> currently I'm facing situation that many jobs are making fallback, and<br>
>>> >>> >> localmachine is being killed by make's -j calculated for distccd...<br>
>>> >>> >><br>
>>> >>> >> other trick maybe to pick different machine, if current is busy, but<br>
>>> >>> >> this may be much more complex in my opinion.<br>
>>> >>> >><br>
>>> >>> >> what do you think?<br>
>>> >>> >> regards<br>
>>> >>> >> Łukasz Tasz<br>
>>> >>> >> __<br>
>>> >>> >> distcc mailing list <a href="http://distcc.samba.org/">http://distcc.samba.org/</a><br>
>>> >>> >> To unsubscribe or change options:<br>
>>> >>> >> <a href="https://lists.samba.org/mailman/listinfo/distcc">https://lists.samba.org/mailman/listinfo/distcc</a><br>
>>> >>> ><br>
>>> >>> ><br>
>>> >>> ><br>
>>> >>> ><br>
>>> >>> > --<br>
>>> >>> > Martin<br>
>>> __<br>
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