Horton

Re: Minimal logical decoding on standbys

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: tushar <tushar.ahuja@enterprisedb.com>
Cc: Petr Jelinek <petr.jelinek@2ndquadrant.com>, Robert Haas <robertmhaas@gmail.com>, Craig Ringer <craig@2ndquadrant.com>, Petr Jelinek <petr@2ndquadrant.com>, pgsql-hackers@postgresql.org
Date: 2019-04-10T16:09:25Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Reduce the log level in 035_standby_logical_decoding.pl.

  2. 035_standby_logical_decoding: Add missing waits for replication

  3. For cascading replication, wake physical and logical walsenders separately

  4. Handle logical slot conflicts on standby

  5. Support invalidating replication slots due to horizon and wal_level

  6. Prevent use of invalidated logical slot in CreateDecodingContext()

  7. Replace replication slot's invalidated_at LSN with an enum

  8. Pass down table relation into more index relation functions

  9. Assert only valid flag bits are passed to visibilitymap_set()

  10. Remove unused _bt_delitems_delete() argument.

  11. Add xl_btree_delete optimization.

Hi,

On 2019-04-10 12:11:21 +0530, tushar wrote:
> 
> On 03/13/2019 08:40 PM, tushar wrote:
> > Hi ,
> > 
> > I am getting a server crash on standby while executing
> > pg_logical_slot_get_changes function   , please refer this scenario
> > 
> > Master cluster( ./initdb -D master)
> > set wal_level='hot_standby in master/postgresql.conf file
> > start the server , connect to  psql terminal and create a physical
> > replication slot ( SELECT * from
> > pg_create_physical_replication_slot('p1');)
> > 
> > perform pg_basebackup using --slot 'p1'  (./pg_basebackup -D slave/ -R
> > --slot p1 -v))
> > set wal_level='logical' , hot_standby_feedback=on,
> > primary_slot_name='p1' in slave/postgresql.conf file
> > start the server , connect to psql terminal and create a logical
> > replication slot (  SELECT * from
> > pg_create_logical_replication_slot('t','test_decoding');)
> > 
> > run pgbench ( ./pgbench -i -s 10 postgres) on master and select
> > pg_logical_slot_get_changes on Slave database
> > 
> > postgres=# select * from pg_logical_slot_get_changes('t',null,null);
> > 2019-03-13 20:34:50.274 IST [26817] LOG:  starting logical decoding for
> > slot "t"
> > 2019-03-13 20:34:50.274 IST [26817] DETAIL:  Streaming transactions
> > committing after 0/6C000060, reading WAL from 0/6C000028.
> > 2019-03-13 20:34:50.274 IST [26817] STATEMENT:  select * from
> > pg_logical_slot_get_changes('t',null,null);
> > 2019-03-13 20:34:50.275 IST [26817] LOG:  logical decoding found
> > consistent point at 0/6C000028
> > 2019-03-13 20:34:50.275 IST [26817] DETAIL:  There are no running
> > transactions.
> > 2019-03-13 20:34:50.275 IST [26817] STATEMENT:  select * from
> > pg_logical_slot_get_changes('t',null,null);
> > TRAP: FailedAssertion("!(data == tupledata + tuplelen)", File:
> > "decode.c", Line: 977)
> > server closed the connection unexpectedly
> >     This probably means the server terminated abnormally
> >     before or while processing the request.
> > The connection to the server was lost. Attempting reset: 2019-03-13
> > 20:34:50.276 IST [26809] LOG:  server process (PID 26817) was terminated
> > by signal 6: Aborted
> > 
> Andres - Do you think - this is an issue which needs to  be fixed ?

Yes, it definitely needs to be fixed. I just haven't had sufficient time
to look into it. Have you reproduced this with Amit's latest version?

Amit, have you spent any time looking into it? I know that you're not
that deeply steeped into the internals of logical decoding, but perhaps
there's something obvious going on.

Greetings,

Andres Freund