On Tue, Mar 6, 2018 at 10:58 PM, Raghavendra Gowdappa <rgowd...@redhat.com> wrote:
> > > On Tue, Mar 6, 2018 at 10:22 PM, Paul Anderson <p...@umich.edu> wrote: > >> Raghavendra, >> >> I've commited my tests case to https://github.com/powool/gluster.git - >> it's grungy, and a work in progress, but I am happy to take change >> suggestions, especially if it will save folks significant time. >> >> For the rest, I'll reply inline below... >> >> On Mon, Mar 5, 2018 at 10:39 PM, Raghavendra Gowdappa >> <rgowd...@redhat.com> wrote: >> > +Csaba. >> > >> > On Tue, Mar 6, 2018 at 2:52 AM, Paul Anderson <p...@umich.edu> wrote: >> >> >> >> Raghavendra, >> >> >> >> Thanks very much for your reply. >> >> >> >> I fixed our data corruption problem by disabling the volume >> >> performance.write-behind flag as you suggested, and simultaneously >> >> disabling caching in my client side mount command. >> > >> > >> > Good to know it worked. Can you give us the output of >> > # gluster volume info >> >> [root@node-1 /]# gluster volume info >> >> Volume Name: dockerstore >> Type: Replicate >> Volume ID: fb08b9f4-0784-4534-9ed3-e01ff71a0144 >> Status: Started >> Snapshot Count: 0 >> Number of Bricks: 1 x 3 = 3 >> Transport-type: tcp >> Bricks: >> Brick1: 172.18.0.4:/data/glusterfs/store/dockerstore >> Brick2: 172.18.0.3:/data/glusterfs/store/dockerstore >> Brick3: 172.18.0.2:/data/glusterfs/store/dockerstore >> Options Reconfigured: >> performance.client-io-threads: off >> nfs.disable: on >> transport.address-family: inet >> locks.mandatory-locking: optimal >> performance.flush-behind: off >> performance.write-behind: off >> >> > >> > We would like to debug the problem in write-behind. Some questions: >> > >> > 1. What version of Glusterfs are you using? >> >> On the server nodes: >> >> [root@node-1 /]# gluster --version >> glusterfs 3.13.2 >> Repository revision: git://git.gluster.org/glusterfs.git >> >> On the docker container sqlite test node: >> >> root@b4055d8547d2:/# glusterfs --version >> glusterfs 3.8.8 built on Jan 11 2017 14:07:11 >> > > I guess this is where client is mounted. If I am correct on where > glusterfs client is mounted, client is running quite a old version. There > have been significant number of fixes between 3.8.8 and current master. > ... significant number of fixes to write-behind... I would suggest to try out 3.13.2 patched with [1]. If you get a chance to > try this out, please report back how did the tests go. > I would suggest to try out 3.13.2 patched with [1] and run tests with write-behind turned on. > [1] https://review.gluster.org/19673 > > >> I recognize that version skew could be an issue. >> >> > 2. Were you able to figure out whether its stale data or metadata that >> is >> > causing the issue? >> >> I lean towards stale data based on the only real observation I have: >> >> While debugging, I put log messages in as to when the flock() is >> acquired, and when it is released. There is no instance where two >> different processes ever hold the same flock()'d file. From what I >> have read, the locks are considered metadata, and they appear to me to >> be working, so that's why I'm inclined to think stale data is the >> issue. >> >> > >> > There have been patches merged in write-behind in recent past and one >> in the >> > works which address metadata consistency. Would like to understand >> whether >> > you've run into any of the already identified issues. >> >> Agreed! >> >> Thanks, >> >> Paul >> >> > >> > regards, >> > Raghavendra >> >> >> >> >> >> In very modest testing, the flock() case appears to me to work well - >> >> before it would corrupt the db within a few transactions. >> >> >> >> Testing using built in sqlite3 locks is better (fcntl range locks), >> >> but has some behavioral issues (probably just requires query retry >> >> when the file is locked). I'll research this more, although the test >> >> case is not critical to our use case. >> >> >> >> There are no signs of O_DIRECT use in the sqlite3 code that I can see. >> >> >> >> I intend to set up tests that run much longer than a few minutes, to >> >> see if there are any longer term issues. Also, I want to experiment >> >> with data durability by killing various gluster server nodes during >> >> the tests. >> >> >> >> If anyone would like our test scripts, I can either tar them up and >> >> email them or put them in github - either is fine with me. (they rely >> >> on current builds of docker and docker-compose) >> >> >> >> Thanks again!! >> >> >> >> Paul >> >> >> >> On Mon, Mar 5, 2018 at 11:26 AM, Raghavendra Gowdappa >> >> <rgowd...@redhat.com> wrote: >> >> > >> >> > >> >> > On Mon, Mar 5, 2018 at 8:21 PM, Paul Anderson <p...@umich.edu> wrote: >> >> >> >> >> >> Hi, >> >> >> >> >> >> tl;dr summary of below: flock() works, but what does it take to make >> >> >> sync()/fsync() work in a 3 node GFS cluster? >> >> >> >> >> >> I am under the impression that POSIX flock, POSIX >> >> >> fcntl(F_SETLK/F_GETLK,...), and POSIX read/write/sync/fsync are all >> >> >> supported in cluster operations, such that in theory, SQLite3 should >> >> >> be able to atomically lock the file (or a subset of page), modify >> >> >> pages, flush the pages to gluster, then release the lock, and thus >> >> >> satisfy the ACID property that SQLite3 appears to try to accomplish >> on >> >> >> a local filesystem. >> >> >> >> >> >> In a test we wrote that fires off 10 simple concurrernt SQL insert, >> >> >> read, update loops, we discovered that we at least need to use >> flock() >> >> >> around the SQLite3 db connection open/update/close to protect it. >> >> >> >> >> >> However, that is not enough - although from testing, it looks like >> >> >> flock() works as advertised across gluster mounted files, sync/fsync >> >> >> don't appear to, so we end up getting corruption in the SQLite3 file >> >> >> (pragma integrity_check generally will show a bunch of problems >> after >> >> >> a short test). >> >> >> >> >> >> Is what we're trying to do achievable? We're testing using the >> docker >> >> >> container gluster/gluster-centos as the three servers, with a php >> test >> >> >> inside of php-cli using filesystem mounts. If we mount the gluster >> FS >> >> >> via sapk/plugin-gluster into the php-cli containers using docker, we >> >> >> seem to have better success sometimes, but I haven't figured out >> why, >> >> >> yet. >> >> >> >> >> >> I did see that I needed to set the server volume parameter >> >> >> 'performance.flush-behind off', otherwise it seems that flushes >> won't >> >> >> block as would be needed by SQLite3. >> >> > >> >> > >> >> > If you are relying on fsync this shouldn't matter as fsync makes sure >> >> > data >> >> > is synced to disk. >> >> > >> >> >> >> >> >> Does anyone have any suggestions? Any words of widsom would be much >> >> >> appreciated. >> >> > >> >> > >> >> > Can you experiment with turning on/off various performance xlators? >> >> > Based on >> >> > earlier issues, its likely that there is stale metadata which might >> be >> >> > causing the issue (not necessarily improper fsync behavior). I would >> >> > suggest >> >> > turning off all performance xlators. You can refer [1] for a related >> >> > discussion. In theory the only perf xlator relevant for fsync is >> >> > write-behind and I am not aware of any issues where fsync is not >> >> > working. >> >> > Does glusterfs log file has any messages complaining about writes or >> >> > fsync >> >> > failing? Does your application use O_DIRECT? If yes, please note that >> >> > you >> >> > need to turn the option performance.strict-o-direct on for >> write-behind >> >> > to >> >> > honour O_DIRECT >> >> > >> >> > Also, is it possible to identify nature of corruption - Data or >> >> > metadata? >> >> > More detailed explanation will help to RCA the issue. >> >> > >> >> > Also, is your application running on a single mount or from multiple >> >> > mounts? >> >> > Can you collect strace of your application (strace -ff -T -p <pid> -o >> >> > <file>)? If possible can you also collect fuse-dump using option >> >> > --dump-fuse >> >> > while mounting glusterfs? >> >> > >> >> > [1] >> >> > >> >> > http://lists.gluster.org/pipermail/gluster-users/2018-Februa >> ry/033503.html >> >> > >> >> >> >> >> >> Thanks, >> >> >> >> >> >> Paul >> >> >> _______________________________________________ >> >> >> Gluster-users mailing list >> >> >> Gluster-users@gluster.org >> >> >> http://lists.gluster.org/mailman/listinfo/gluster-users >> >> > >> >> > >> > >> > >> > >
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