Re: [HACKERS] logical decoding of two-phase transactions

On Mon, Mar 8, 2021 at 11:30 AM Ajin Cherian <itsajin(at)gmail(dot)com> wrote:
>
> On Fri, Mar 5, 2021 at 9:25 PM vignesh C <vignesh21(at)gmail(dot)com> wrote:
>
>
> Created new patch v53:

Thanks for the updated patch.
I had noticed one issue, publisher does not get stopped normally in
the following case:
# Publisher steps
psql -d postgres -c "CREATE TABLE do_write(id serial primary key);"
psql -d postgres -c "INSERT INTO do_write VALUES(generate_series(1,10));"
psql -d postgres -c "CREATE PUBLICATION mypub FOR TABLE do_write;"

# Subscriber steps
psql -d postgres -p 9999 -c "CREATE TABLE do_write(id serial primary key);"
psql -d postgres -p 9999 -c "INSERT INTO do_write VALUES(1);" # to
cause a PK violation
psql -d postgres -p 9999 -c "CREATE SUBSCRIPTION mysub CONNECTION
'host=localhost port=5432 dbname=postgres' PUBLICATION mypub WITH
(two_phase = true);"

# prepare & commit prepared at publisher
psql -d postgres -c \
"begin; insert into do_write values (100); prepare transaction 'test1';"
psql -d postgres -c "commit prepared 'test1';"

Stop publisher:
./pg_ctl -D publisher stop
waiting for server to shut
down...............................................................
failed
pg_ctl: server does not shut down

This is because the following process does not exit:
postgres: walsender vignesh 127.0.0.1(41550) START_REPLICATION

It continuously loops at the below:
#0 0x00007f1c520d3bca in __libc_pread64 (fd=6, buf=0x555b1b3f7870,
count=8192, offset=0) at ../sysdeps/unix/sysv/linux/pread64.c:29
#1 0x0000555b1a8f6d20 in WALRead (state=0x555b1b3f1ce0,
buf=0x555b1b3f7870 "\n\321\002", startptr=16777216, count=8192, tli=1,
errinfo=0x7ffe693b78c0) at xlogreader.c:1116
#2 0x0000555b1ac8ce10 in logical_read_xlog_page
(state=0x555b1b3f1ce0, targetPagePtr=16777216, reqLen=8192,
targetRecPtr=23049936, cur_page=0x555b1b3f7870 "\n\321\002")
at walsender.c:837
#3 0x0000555b1a8f6040 in ReadPageInternal (state=0x555b1b3f1ce0,
pageptr=23044096, reqLen=5864) at xlogreader.c:608
#4 0x0000555b1a8f5849 in XLogReadRecord (state=0x555b1b3f1ce0,
errormsg=0x7ffe693b79c0) at xlogreader.c:329
#5 0x0000555b1ac8ff4a in XLogSendLogical () at walsender.c:2846
#6 0x0000555b1ac8f1e5 in WalSndLoop (send_data=0x555b1ac8ff0e
<XLogSendLogical>) at walsender.c:2289
#7 0x0000555b1ac8db2a in StartLogicalReplication (cmd=0x555b1b3b78b8)
at walsender.c:1206
#8 0x0000555b1ac8e4dd in exec_replication_command (
cmd_string=0x555b1b331670 "START_REPLICATION SLOT \"mysub\"
LOGICAL 0/0 (proto_version '2', two_phase 'on', publication_names
'\"mypub\"')") at walsender.c:1646
#9 0x0000555b1ad04460 in PostgresMain (argc=1, argv=0x7ffe693b7cc0,
dbname=0x555b1b35cc58 "postgres", username=0x555b1b35cc38 "vignesh")
at postgres.c:4323

I felt the publisher should get stopped in this case.
Thoughts?

Regards,
Vignesh