unblock function in pg messes up with unicorn

* unblock function in pg messes up with unicorn
@ 2013-12-06 12:29 Sam Saffron
  2013-12-06 18:48 ` Eric Wong
  0 siblings, 1 reply; 3+ messages in thread
From: Sam Saffron @ 2013-12-06 12:29 UTC (permalink / raw)
  To: mongrel-unicorn

require 'pg'

conn = PG.connect(dbname: 'meta')

trap 'USR1' do
  puts "YAY"
end

Thread.new do
  sleep 0.1
  Process.kill("USR1", Process.pid)
end

sleep 1

puts "HERE"

Thread.new do
  sleep 0.1
  Process.kill("USR1", Process.pid)
end

conn.exec("select pg_sleep(10)")

sam@ubuntu:~/Source$ ruby test2.rb
YAY
HERE
YAY
test2.rb:27:in `exec': ERROR:  canceling statement due to user request
(PG::QueryCanceled)
from test2.rb:27:in `<main>'

this is the ubf defined inside pg.

 void ubf_cancel_running_command(void *c)
 {
   /*
       has no idea why it was interrupted, should it stop the query due to USR1
   */
   PGconn *conn = (PGconn*) c;
   PQrequestCancel(conn);
 }

This leaves a bunch of questions:

1. Is this a pg bug? How could they even implement a ubf in such a way
that it does not stop queries when signals are sent? The main issue is
that without this Thread.kill will have to wait for queries to finish.

2. Is this a ruby bug? should there be a more sophisticated protocol
here? Should trap handlers inform the runtime that a ubf is not
needed?

something else ?

Similar issue exists in mysql afaik.
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