Thread: Slave promotion problem...
Last week we had some problems on the master server which caused a failover on the slave (the master was completely unresponsive due to reasons still unknown). The slave received the promote signal (pg_ctl promote) and logged that in the logs: 2015-08-28 23:05:10 UTC [6]: [50-1] user=,db= LOG: received promote request 2015-08-28 23:05:10 UTC [467]: [2-1] user=,db= FATAL: terminating walreceiver process due to administrator command 5 hours later the slave still didn't promote. Meanwhile we fixed the master and restarted it. The slave was restarted and it behaved just like the promote signal didn't arrive, connecting to the master as a regular slave. Because of maintenance we had to issue a failover a few days after, and this time the failover was successful: 2015-08-30 19:40:08 UTC [312]: [2-1] user=,db= LOG: replication terminated by primary server 2015-08-30 19:40:08 UTC [312]: [3-1] user=,db= DETAIL: End of WAL reached on timeline 3 at 1AC/4D000090. 2015-08-30 19:40:08 UTC [312]: [4-1] user=,db= FATAL: could not send end-of-streaming message to primary: no COPY in progress 2015-08-30 19:40:08 UTC [6]: [34-1] user=,db= LOG: invalid record length at 1AC/4D000090 2015-08-30 19:40:10 UTC [6]: [35-1] user=,db= LOG: received promote request 2015-08-30 19:40:13 UTC [6]: [36-1] user=,db= LOG: redo done at 1AC/4D000028 2015-08-30 19:40:13 UTC [6]: [37-1] user=,db= LOG: last completed transaction was at log time 2015-08-30 19:40:07.18114+00 2015-08-30 19:40:14 UTC [6]: [38-1] user=,db= LOG: selected new timeline ID: 4 2015-08-30 19:40:14 UTC [6]: [39-1] user=,db= LOG: restored log file "00000003.history" from archive 2015-08-30 19:40:14 UTC [6]: [40-1] user=,db= LOG: archive recovery complete 2015-08-30 19:40:14 UTC [6]: [41-1] user=,db= LOG: MultiXact member wraparound protections are now enabled 2015-08-30 19:40:14 UTC [29303]: [1-1] user=,db= LOG: autovacuum launcher started 2015-08-30 19:40:14 UTC [1]: [4-1] user=,db= LOG: database system is ready to accept connections I am unsure if this promotion failure is a bug/glitch, but the promote procedure is automated and tested a couple of hundred times so I am certain we initiated the promote correctly. Looking in the internet I haven't found anything similar. Does anybody know any reason why the slave didn't promote after receiving the promote signal? Looking at the data it seems like the slave aborted the promote process. Both instances are 9.4.4 connected with streaming replication. Regards, Mladen Marinović
El 31/08/15 a las 03:29, marin@kset.org escribió: > Last week we had some problems on the master server which caused a > failover on the slave (the master was completely unresponsive due to > reasons still unknown). The slave received the promote signal (pg_ctl > promote) and logged that in the logs: > 2015-08-28 23:05:10 UTC [6]: [50-1] user=,db= LOG: received promote > request > 2015-08-28 23:05:10 UTC [467]: [2-1] user=,db= FATAL: terminating > walreceiver process due to administrator command > > 5 hours later the slave still didn't promote. Meanwhile we fixed the > master and restarted it. The slave was restarted and it behaved just > like the promote signal didn't arrive, connecting to the master as a > regular slave. Aren't there any further logs after the walreceiver termination? Up to here everything looks fine, but we have no idea on what was logged afterwards. > I am unsure if this promotion failure is a bug/glitch, but the promote > procedure is automated and tested a couple of hundred times so I am > certain we initiated the promote correctly. Are you using homemade scripts? Maybe you need to test them more thoroughly, with different environment parameters. Regards, -- Martín Marqués http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services
On 2015-08-31 14:38, Martín Marqués wrote: > El 31/08/15 a las 03:29, marin@kset.org escribió: >> Last week we had some problems on the master server which caused a >> failover on the slave (the master was completely unresponsive due to >> reasons still unknown). The slave received the promote signal (pg_ctl >> promote) and logged that in the logs: >> 2015-08-28 23:05:10 UTC [6]: [50-1] user=,db= LOG: received promote >> request >> 2015-08-28 23:05:10 UTC [467]: [2-1] user=,db= FATAL: terminating >> walreceiver process due to administrator command >> >> 5 hours later the slave still didn't promote. Meanwhile we fixed the >> master and restarted it. The slave was restarted and it behaved just >> like the promote signal didn't arrive, connecting to the master as a >> regular slave. > > Aren't there any further logs after the walreceiver termination? > Up to here everything looks fine, but we have no idea on what was > logged > afterwards. There are logs (quite a few, cca. 5 hours of it), every second something like this: 2015-08-28 23:05:12 UTC [79867]: [1-1] user=[unknown],db=[unknown] LOG: connection received: host=[local] 2015-08-28 23:05:12 UTC [79867]: [2-1] user=postgres,db=postgres LOG: connection authorized: user=postgres database=postgres This logs the connection of the process that probes the server is alive. I was expecting to see something like: redo done at xxxxx last completed transaction was at log time xxxxxxx But those lines didn't appear after 5 hours. As I understand, these are written before the server uses the restore_command to get WAL and history files from the archive. > >> I am unsure if this promotion failure is a bug/glitch, but the promote >> procedure is automated and tested a couple of hundred times so I am >> certain we initiated the promote correctly. > > Are you using homemade scripts? Maybe you need to test them more > thoroughly, with different environment parameters. We use a custom script for the restore_command, but is seems that it was not invoked. Regards, Mladen Marinović
On 2015-08-31 16:05, marin@kset.org wrote: > On 2015-08-31 14:38, Martín Marqués wrote: >> El 31/08/15 a las 03:29, marin@kset.org escribió: >>> Last week we had some problems on the master server which caused a >>> failover on the slave (the master was completely unresponsive due to >>> reasons still unknown). The slave received the promote signal (pg_ctl >>> promote) and logged that in the logs: >>> 2015-08-28 23:05:10 UTC [6]: [50-1] user=,db= LOG: received promote >>> request >>> 2015-08-28 23:05:10 UTC [467]: [2-1] user=,db= FATAL: terminating >>> walreceiver process due to administrator command >>> >>> 5 hours later the slave still didn't promote. Meanwhile we fixed the >>> master and restarted it. The slave was restarted and it behaved just >>> like the promote signal didn't arrive, connecting to the master as a >>> regular slave. >> >> Aren't there any further logs after the walreceiver termination? >> Up to here everything looks fine, but we have no idea on what was >> logged >> afterwards. > There are logs (quite a few, cca. 5 hours of it), every second > something like this: > 2015-08-28 23:05:12 UTC [79867]: [1-1] user=[unknown],db=[unknown] > LOG: connection received: host=[local] > 2015-08-28 23:05:12 UTC [79867]: [2-1] user=postgres,db=postgres LOG: > connection authorized: user=postgres database=postgres > This logs the connection of the process that probes the server is > alive. > > I was expecting to see something like: > redo done at xxxxx > last completed transaction was at log time xxxxxxx > > But those lines didn't appear after 5 hours. As I understand, these > are written before the server uses the restore_command to get WAL and > history files from the archive. After careful testing of two scenarios: 1. Master is alive (or at least the slave thinks so), slave is signaled to promote 2. Master is dead, slave is signaled to promote. We have come to a conclusion that in the scenario 1. the slave requires an additional WAL file from the archive before the "redo done at xxxxxx" message. Knowing that we established that the problem was in the restore_command script (wrapper around several rsync commands) which hanged indefinitely. >> >>> I am unsure if this promotion failure is a bug/glitch, but the >>> promote >>> procedure is automated and tested a couple of hundred times so I am >>> certain we initiated the promote correctly. >> >> Are you using homemade scripts? Maybe you need to test them more >> thoroughly, with different environment parameters. > > We use a custom script for the restore_command, but is seems that it > was not invoked. > > Regards, > Mladen Marinović