Async connection blocks when server unavailable

Hi,

not sure if this is psycopg2's fault but my script blocks when connecting to unavailable server (or when i drop outgoing connections to port 5432 for testing puposes).

Here's gdb stack trace:

#0  0x00007ffff6eda308 in poll () from /lib64/libc.so.6
#1  0x00007fffedad101f in pqSocketPoll (conn=0x7c43d0, forRead=1, forWrite=1, end_time=-1) at fe-misc.c:1088
#2  pqSocketCheck (conn=0x7c43d0, forRead=1, forWrite=1, end_time=-1) at fe-misc.c:1030
#3  0x00007fffedad10a0 in pqWaitTimed (forRead=<value optimized out>, forWrite=<value optimized out>, conn=0x7c43d0, finish_time=<value optimized out>) at fe-misc.c:962
#4  0x00007fffedad1510 in pqSendSome (conn=0x7c43d0, len=8) at fe-misc.c:896
#5  0x00007fffedac9f86 in pqPacketSend (conn=0x7c43d0, pack_type=<value optimized out>, buf=0x7fffffffb3a4, buf_len=4) at fe-connect.c:3324
#6  0x00007fffedacbce3 in PQconnectPoll (conn=0x7c43d0) at fe-connect.c:1976
#7  0x00007fffedcfa569 in conn_poll_connecting (self=0x7c32d0) at psycopg/connection_int.c:648
#8  conn_poll (self=0x7c32d0) at psycopg/connection_int.c:877
#9  0x00007fffedcfb6ad in psycoconn_poll (self=<value optimized out>) at psycopg/connection_type.c:850

A checked psycopg2 and libpq source and it looks like the problem is that psycopg2's conn_poll calls _conn_poll_connecting before setting async flag on connection so libpq's pqSendSome thinks connection is in blocking mode.

https://github.com/postgres/postgres/blob/master/src/interfaces/lib...

psycopg2: 2.5.2
postgresql-libs: 9.3.2

Thanks for response.
Adam