Re: bad wal on replica / incorrect resource manager data checksum in record / zfs
On Wed, Feb 19, 2020 at 4:35 PM Alex Malek wrote: > > Hello Postgres Hackers - > > We are having a reoccurring issue on 2 of our replicas where replication > stops due to this message: > "incorrect resource manager data checksum in record at ..." > This has been occurring on average once every 1 to 2 weeks during large > data imports (100s of GBs being written) > on one of two replicas. > Fixing the issue has been relatively straight forward: shutdown replica, > remove the bad wal file, restart replica and > the good wal file is retrieved from the master. > We are doing streaming replication using replication slots. > However twice now, the master had already removed the WAL file so the file > had to retrieved from the wal archive. > > The WAL log directories on the master and the replicas are on ZFS file > systems. > All servers are running RHEL 7.7 (Maipo) > PostgreSQL 10.11 > ZFS v0.7.13-1 > > The issue seems similar to > https://www.postgresql.org/message-id/CANQ55Tsoa6%3Dvk2YkeVUN7qO-2YdqJf_AMVQxqsVTYJm0qqQQuw%40mail.gmail.com > and to https://github.com/timescale/timescaledb/issues/1443 > > One quirk in our ZFS setup is ZFS is not handling our RAID array, so ZFS > sees our array as a single device. > > > An update in case someone else encounters the same issue. About 5 weeks ago, on the master database server, we turned off ZFS compression for the volume where the WAL log resides. The error has not occurred on any replica since. Best, Alex
Re: bad wal on replica / incorrect resource manager data checksum in record / zfs
On Thu, Apr 2, 2020 at 2:10 PM Andres Freund wrote: > Hi, > > On 2020-02-19 16:35:53 -0500, Alex Malek wrote: > > We are having a reoccurring issue on 2 of our replicas where replication > > stops due to this message: > > "incorrect resource manager data checksum in record at ..." > > Could you show the *exact* log output please? Because this could > temporarily occur without signalling anything bad, if e.g. the > replication connection goes down. > Feb 23 00:02:02 wrds-pgdata10-2-w postgres[68329]: [12491-1] 5e4aac44.10ae9 (@) LOG: incorrect resource manager data checksum in record at 39002/57AC0338 When it occurred replication stopped. The only way to resume replication was to stop server and remove bad WAL file. > > > > Right before the issue started we did some upgrades and altered some > > postgres configs and ZFS settings. > > We have been slowly rolling back changes but so far the the issue > continues. > > > > Some interesting data points while debugging: > > We had lowered the ZFS recordsize from 128K to 32K and for that week the > > issue started happening every other day. > > Using xxd and diff we compared "good" and "bad" wal files and the > > differences were not random bad bytes. > > > > The bad file either had a block of zeros that were not in the good file > at > > that position or other data. Occasionally the bad data has contained > > legible strings not in the good file at that position. At least one of > > those exact strings has existed elsewhere in the files. > > However I am not sure if that is the case for all of them. > > > > This made me think that maybe there was an issue w/ wal file recycling > and > > ZFS under heavy load, so we tried lowering > > min_wal_size in order to "discourage" wal file recycling but my > > understanding is a low value discourages recycling but it will still > > happen (unless setting wal_recycle in psql 12). > > This sounds a lot more like a broken filesystem than anythingon the PG > level. > Probably. In my recent updated comment turning off ZFS compression on master seems to have fixed the issue. However I will note that the WAL file stored on the master was always fine upon inspection. > > > > When using replication slots, what circumstances would cause the master > to > > not save the WAL file? > > What do you mean by "save the WAL file"? > Typically, when using replication slots, when replication stops the master will save the next needed WAL file. However once or twice when this error occurred the master recycled/removed the WAL file needed. I suspect perhaps b/c the replica had started to read the WAL file it sent some signal to the master that the WAL file was already consumed. I am guessing, not knowing exactly what is happening and w/ the caveat that this situation was rare and not the norm. It is also possible caused by a different error. Thanks. Alex
bad wal on replica / incorrect resource manager data checksum in record / zfs
Hello Postgres Hackers - We are having a reoccurring issue on 2 of our replicas where replication stops due to this message: "incorrect resource manager data checksum in record at ..." This has been occurring on average once every 1 to 2 weeks during large data imports (100s of GBs being written) on one of two replicas. Fixing the issue has been relatively straight forward: shutdown replica, remove the bad wal file, restart replica and the good wal file is retrieved from the master. We are doing streaming replication using replication slots. However twice now, the master had already removed the WAL file so the file had to retrieved from the wal archive. The WAL log directories on the master and the replicas are on ZFS file systems. All servers are running RHEL 7.7 (Maipo) PostgreSQL 10.11 ZFS v0.7.13-1 The issue seems similar to https://www.postgresql.org/message-id/CANQ55Tsoa6%3Dvk2YkeVUN7qO-2YdqJf_AMVQxqsVTYJm0qqQQuw%40mail.gmail.com and to https://github.com/timescale/timescaledb/issues/1443 One quirk in our ZFS setup is ZFS is not handling our RAID array, so ZFS sees our array as a single device. Right before the issue started we did some upgrades and altered some postgres configs and ZFS settings. We have been slowly rolling back changes but so far the the issue continues. Some interesting data points while debugging: We had lowered the ZFS recordsize from 128K to 32K and for that week the issue started happening every other day. Using xxd and diff we compared "good" and "bad" wal files and the differences were not random bad bytes. The bad file either had a block of zeros that were not in the good file at that position or other data. Occasionally the bad data has contained legible strings not in the good file at that position. At least one of those exact strings has existed elsewhere in the files. However I am not sure if that is the case for all of them. This made me think that maybe there was an issue w/ wal file recycling and ZFS under heavy load, so we tried lowering min_wal_size in order to "discourage" wal file recycling but my understanding is a low value discourages recycling but it will still happen (unless setting wal_recycle in psql 12). There is a third replica where this bug has not (yet?) surfaced. This leads me to guess the bad data does not originate on the master. This replica is older than the other replicas, slower CPUs, less RAM, and the WAL disk array is spinning disks. The OS, version of Postgres, and version of ZFS are the same as the other replicas. This replica is not using a replication slot. This replica does not serve users so load/contention is much lower than the others. The other replicas often have 100% utilization of the disk array that houses the (non-wal) data. Any insight into the source of this bug or how to address it? Since the master has a good copy of the WAL file, can the replica re-request the file from the master? Or from the archive? When using replication slots, what circumstances would cause the master to not save the WAL file? (I can't remember if it always had the next wal file or the one after that) Thanks in advance, Alex Malek
Fwd: bad wal on replica / incorrect resource manager data checksum in record / zfs
On Thu, Feb 20, 2020, 6:16 AM Amit Kapila wrote: > On Thu, Feb 20, 2020 at 3:06 AM Alex Malek wrote: > > > > > > Hello Postgres Hackers - > > > > We are having a reoccurring issue on 2 of our replicas where replication > stops due to this message: > > "incorrect resource manager data checksum in record at ..." > > This has been occurring on average once every 1 to 2 weeks during large > data imports (100s of GBs being written) > > on one of two replicas. > > Fixing the issue has been relatively straight forward: shutdown replica, > remove the bad wal file, restart replica and > > the good wal file is retrieved from the master. > > We are doing streaming replication using replication slots. > > However twice now, the master had already removed the WAL file so the > file had to retrieved from the wal archive. > > > > The WAL log directories on the master and the replicas are on ZFS file > systems. > > All servers are running RHEL 7.7 (Maipo) > > PostgreSQL 10.11 > > ZFS v0.7.13-1 > > > > The issue seems similar to > https://www.postgresql.org/message-id/CANQ55Tsoa6%3Dvk2YkeVUN7qO-2YdqJf_AMVQxqsVTYJm0qqQQuw%40mail.gmail.com > and to https://github.com/timescale/timescaledb/issues/1443 > > > > One quirk in our ZFS setup is ZFS is not handling our RAID array, so ZFS > sees our array as a single device. > > > > Right before the issue started we did some upgrades and altered some > postgres configs and ZFS settings. > > We have been slowly rolling back changes but so far the the issue > continues. > > > > Some interesting data points while debugging: > > We had lowered the ZFS recordsize from 128K to 32K and for that week the > issue started happening every other day. > > Using xxd and diff we compared "good" and "bad" wal files and the > differences were not random bad bytes. > > > > The bad file either had a block of zeros that were not in the good file > at that position or other data. Occasionally the bad data has contained > legible strings not in the good file at that position. At least one of > those exact strings has existed elsewhere in the files. > > However I am not sure if that is the case for all of them. > > > > This made me think that maybe there was an issue w/ wal file recycling > and ZFS under heavy load, so we tried lowering > > min_wal_size in order to "discourage" wal file recycling but my > understanding is a low value discourages recycling but it will still > > happen (unless setting wal_recycle in psql 12). > > > > We do print a message "recycled write-ahead log file .." in DEBUG2 > mode. You either want to run the server with DEBUG2 or maybe change > the code to make it LOG and see if that is printed. If you do that, > you can verify if the corrupted WAL is the same as a recycled one. > Are you suggesting having the master, the replicas or all in debug mode? How much extra logging would this generate? A replica typically consumes over 1 TB of WAL files before a bad wal file is encountered. > > There is a third replica where this bug has not (yet?) surfaced. > > This leads me to guess the bad data does not originate on the master. > > This replica is older than the other replicas, slower CPUs, less RAM, > and the WAL disk array is spinning disks. > > The OS, version of Postgres, and version of ZFS are the same as the > other replicas. > > This replica is not using a replication slot. > > This replica does not serve users so load/contention is much lower than > the others. > > The other replicas often have 100% utilization of the disk array that > houses the (non-wal) data. > > > > Any insight into the source of this bug or how to address it? > > > > Since the master has a good copy of the WAL file, can the replica > re-request the file from the master? Or from the archive? > > > > I think we do check in the archive if we get the error during > streaming, but archive might also have the same data due to which this > problem happens. Have you checked that the archive WAL file, is it > different from the bad WAL? See the Typically the master, the archive and the other replicas all have a good copy of the WAL file. relevant bits of code in > WaitForWALToBecomeAvailable especially the code near below comment: > > "Failure while streaming. Most likely, we got here because streaming > replication was terminated, or promotion was triggered. But we also > get here if we find an invalid record in the WAL streamed from master, > in which case something is seriously wrong. There's little chance that > the problem will jus
Re: bad wal on replica / incorrect resource manager data checksum in record / zfs
On Thu, Feb 20, 2020 at 12:01 PM Alex Malek wrote: > On Thu, Feb 20, 2020, 6:16 AM Amit Kapila wrote: > >> On Thu, Feb 20, 2020 at 3:06 AM Alex Malek wrote: >> > >> > >> > Hello Postgres Hackers - >> > >> > We are having a reoccurring issue on 2 of our replicas where >> replication stops due to this message: >> > "incorrect resource manager data checksum in record at ..." >> > This has been occurring on average once every 1 to 2 weeks during large >> data imports (100s of GBs being written) >> > on one of two replicas. >> > Fixing the issue has been relatively straight forward: shutdown >> replica, remove the bad wal file, restart replica and >> > the good wal file is retrieved from the master. >> > We are doing streaming replication using replication slots. >> > However twice now, the master had already removed the WAL file so the >> file had to retrieved from the wal archive. >> > >> > The WAL log directories on the master and the replicas are on ZFS file >> systems. >> > All servers are running RHEL 7.7 (Maipo) >> > PostgreSQL 10.11 >> > ZFS v0.7.13-1 >> > >> > The issue seems similar to >> https://www.postgresql.org/message-id/CANQ55Tsoa6%3Dvk2YkeVUN7qO-2YdqJf_AMVQxqsVTYJm0qqQQuw%40mail.gmail.com >> and to https://github.com/timescale/timescaledb/issues/1443 >> > >> > One quirk in our ZFS setup is ZFS is not handling our RAID array, so >> ZFS sees our array as a single device. >> > >> > Right before the issue started we did some upgrades and altered some >> postgres configs and ZFS settings. >> > We have been slowly rolling back changes but so far the the issue >> continues. >> > >> > Some interesting data points while debugging: >> > We had lowered the ZFS recordsize from 128K to 32K and for that week >> the issue started happening every other day. >> > Using xxd and diff we compared "good" and "bad" wal files and the >> differences were not random bad bytes. >> > >> > The bad file either had a block of zeros that were not in the good file >> at that position or other data. Occasionally the bad data has contained >> legible strings not in the good file at that position. At least one of >> those exact strings has existed elsewhere in the files. >> > However I am not sure if that is the case for all of them. >> > >> > This made me think that maybe there was an issue w/ wal file recycling >> and ZFS under heavy load, so we tried lowering >> > min_wal_size in order to "discourage" wal file recycling but my >> understanding is a low value discourages recycling but it will still >> > happen (unless setting wal_recycle in psql 12). >> > >> >> We do print a message "recycled write-ahead log file .." in DEBUG2 >> mode. You either want to run the server with DEBUG2 or maybe change >> the code to make it LOG and see if that is printed. If you do that, >> you can verify if the corrupted WAL is the same as a recycled one. >> > > Are you suggesting having the master, the replicas or all in debug mode? > How much extra logging would this generate? > A replica typically consumes over 1 TB of WAL files before a bad wal file > is encountered. > > > >> > There is a third replica where this bug has not (yet?) surfaced. >> > This leads me to guess the bad data does not originate on the master. >> > This replica is older than the other replicas, slower CPUs, less RAM, >> and the WAL disk array is spinning disks. >> > The OS, version of Postgres, and version of ZFS are the same as the >> other replicas. >> > This replica is not using a replication slot. >> > This replica does not serve users so load/contention is much lower than >> the others. >> > The other replicas often have 100% utilization of the disk array that >> houses the (non-wal) data. >> > >> > Any insight into the source of this bug or how to address it? >> > >> > Since the master has a good copy of the WAL file, can the replica >> re-request the file from the master? Or from the archive? >> > >> >> I think we do check in the archive if we get the error during >> streaming, but archive might also have the same data due to which this >> problem happens. Have you checked that the archive WAL file, is it >> different from the bad WAL? See the > > > Typically the master, the archive and the other replicas all have a good > copy of
