Re: [HACKERS] The behavior of CheckRequiredParameterValues()
On Wed, Mar 5, 2014 at 5:13 PM, Amit Langote wrote: > On Wed, Mar 5, 2014 at 12:07 PM, Amit Langote wrote: >> On Wed, Mar 5, 2014 at 2:09 AM, Sawada Masahiko >> wrote: >> >>> >>> xlog.c:6177 >>> if (ControlFile->wal_level < WAL_LEVEL_HOT_STANDBY) >>> ereport(ERROR, >>> (errmsg("hot standby is not possible because wal_level was not >>> >>> So we have to start and stop standby server with changed >>> wal_level(i.g., hot_standby) if we want to enable hot standby. >>> In this case, I think that the standby server didn't need to confirm >>> wal_level value of ControlFile. >>> I think that it should confirm value which is written in postgreql.conf. >>> >> >> I think checking it from the control file on a standby in recovery >> means that we should confirm if the *wal_level with which the WAL was >> generated* is sufficient to now become a hot standby after recovery >> finishes. >> > > Sorry, should have said: > *become a hot standby after recovery reaches a consistent state > Thank you for explain! I understood it! Regards, --- Sawada Masahiko -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] The behavior of CheckRequiredParameterValues()
On Wed, Mar 5, 2014 at 12:07 PM, Amit Langote wrote: > On Wed, Mar 5, 2014 at 2:09 AM, Sawada Masahiko wrote: > >> >> xlog.c:6177 >> if (ControlFile->wal_level < WAL_LEVEL_HOT_STANDBY) >> ereport(ERROR, >> (errmsg("hot standby is not possible because wal_level was not >> >> So we have to start and stop standby server with changed >> wal_level(i.g., hot_standby) if we want to enable hot standby. >> In this case, I think that the standby server didn't need to confirm >> wal_level value of ControlFile. >> I think that it should confirm value which is written in postgreql.conf. >> > > I think checking it from the control file on a standby in recovery > means that we should confirm if the *wal_level with which the WAL was > generated* is sufficient to now become a hot standby after recovery > finishes. > Sorry, should have said: *become a hot standby after recovery reaches a consistent state -- Amit -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] The behavior of CheckRequiredParameterValues()
On Wed, Mar 5, 2014 at 2:09 AM, Sawada Masahiko wrote: > > xlog.c:6177 > if (ControlFile->wal_level < WAL_LEVEL_HOT_STANDBY) > ereport(ERROR, > (errmsg("hot standby is not possible because wal_level was not > > So we have to start and stop standby server with changed > wal_level(i.g., hot_standby) if we want to enable hot standby. > In this case, I think that the standby server didn't need to confirm > wal_level value of ControlFile. > I think that it should confirm value which is written in postgreql.conf. > I think checking it from the control file on a standby in recovery means that we should confirm if the *wal_level with which the WAL was generated* is sufficient to now become a hot standby after recovery finishes. -- Amit -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] The behavior of CheckRequiredParameterValues()
On Wed, Mar 5, 2014 at 4:09 AM, Sawada Masahiko wrote: > Hi all, > > I had doubts regarding behavior of CheckRequiredParameterValues() function. > > I could not start standby server which is created by pg_basebackup > with following scenario. > 1. Start the master server with 'wal_level = archve' , 'hot_standby = > on' and other settings of replication. > 2. Create the standby server from the master server by using pg_basebackup. > 3. Change the wal_level value of both master and standby server to > 'hot_standby'. > 4. Restarting the master server. > 5. Starting the standby server. > > In #5, I got following error even if I set wal_level to 'hot_standby'. > > FATAL: hot standby is not possible because wal_level was not set to > "hot_standby" or higher on the master server > > I tried to investigate this behaviour. > Currently CheckRequiredParameterValues() function uses wal_level value > which is got from ControlFile when comparing between wal_level and > WAL_LEVEL_HOT_STANDBY as following code. > > xlog.c:6177 > if (ControlFile->wal_level < WAL_LEVEL_HOT_STANDBY) > ereport(ERROR, > (errmsg("hot standby is not possible because wal_level was not > > So we have to start and stop standby server with changed > wal_level(i.g., hot_standby) if we want to enable hot standby. > In this case, I think that the standby server didn't need to confirm > wal_level value of ControlFile. > I think that it should confirm value which is written in postgreql.conf. > The snapshot of running transaction information is written to WAL only when the wal_level is set to 'hot_standby'. This information is required on the standby side to recreate the running transactions. Regards, Hari Babu Fujitsu Australia