[pgpool-general: 1588] (3.1.3 hatsuiboshi) sleep on query cancel

[Pawel Veselov]

Hi.

Is there any reason for pgpool to sleep when processing query cancellation?
Is it possible to unconfigure this sleep (set it to 0)?

I see explicit attempt to sleep on processing cancellation request here
(strace):

# received connection from client, recognized it's cancellation request
24626      0.070666 accept(5, {sa_family=AF_INET, sin_port=htons(64885),
sin_addr=inet_addr("172.18.10.42")}, [16]) = 6
24626      0.000066 read(6, "\0\0\0\20\4\322\26.\0\0o.z\360\243?", 1024) =
16
# connecting to postgres and relaying
24626      0.000063 connect(7, {sa_family=AF_INET, sin_port=htons(5432),
sin_addr=inet_addr("172.18.10.230")}, 16) = 0
24626      0.000060 write(7, "\0\0\0\20\4\322\26.\0\0o.z\360\243?", 16) = 16
# closing connection to postgres
24626      0.000186 shutdown(7, 1 /* send */) = 0
24626      0.000105 close(7)            = 0
# sleeping for 1 sec (!)
24626      0.000061 nanosleep({1, 0}, 0x7fff93d85090) = 0
# closing connection to client
24626      1.000350 shutdown(6, 1 /* send */) = 0
24626      0.000290 close(6)            = 0

It's a HUGE problem for me, as I'm using pgpool with WebLogic server.
WebLogic cancels all cached statements when
- rolling back (an XA?) transaction
- closing the pool

The closure is done on a single thread, so for large pools it takes long
minutes to close, and often a shared lock is held (as there is apparently
no expectation that cancellation would take a long amount of time) Postgres
JDBC driver also doesn't know better and keeps calling cancelQuery() on the
same connection, even if multiple statements are being closed.

Thank you,
  Pawel.
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