Azure: Pyodbc Connection Got stuck

[piyushiitg]

The issue is: In Azure environment it is observed that sometimes pyodbc library gets hunged while login happens.
This was evaluated using following script.
import pyodbc
import time
import os

conn_str="DRIVER={FreeTDS};SERVER=10.47.0.4;PORT=1433;UID=sa;PWD=info@123;TDS_VERSION=7.2;timeout=0;Trusted_Connection=no;UseNTLMv2=yes;"
{code}
while(True):
try:
conn = pyodbc.connect(conn_str)
print conn
print os.getpid()
conn.close()
except Exception, e:
print e
{code}

GDB Trace
{code}
(gdb) bt
#0 0x00007fc906d170d8 in poll () from /lib64/libc.so.6
#1 0x00007fc8fd58bdd7 in tds_select (tds=0x1bb13c0, tds_sel=, timeout_seconds=0) at net.c:376
#2 0x00007fc8fd58caa0 in tds_goodread (tds=0x1bb13c0, buf=0x7fffd68821e0 "", buflen=8, unfinished=0 '\000') at net.c:449
#3 0x00007fc8fd58cfcd in tds_read_packet (tds=0x1bb13c0) at net.c:530
#4 0x00007fc8fd579148 in tds_get_byte (tds=0x1bb13c0) at read.c:73
#5 0x00007fc8fd5768b8 in tds_process_login_tokens (tds=0x1bb13c0) at token.c:336
#6 0x00007fc8fd5786ad in tds_connect (tds=0x1bb13c0, connection=0x1bb18c0, p_oserr=0x7fffd68826ac) at login.c:467
#7 0x00007fc8fd578f06 in tds_connect_and_login (tds=, connection=) at login.c:508
#8 0x00007fc8fd55ec16 in odbc_connect (dbc=0x1bb0fd0, connection=0x1bb18c0) at odbc.c:393
#9 0x00007fc8fd560653 in _SQLDriverConnect (hdbc=0x1bb0fd0, hwnd=0x0, szConnStrIn=, cbConnStrIn=,

szConnStrOut=0x0, cbConnStrOutMax=0, pcbConnStrOut=0x0, fDriverCompletion=0) at odbc.c:619

#10 0x00007fc900950b4a in SQLDriverConnectW () from /usr/lib64/libodbc.so.2
#11 0x00007fc900b9a6ca in Connect (pConnectString=0x7fc907c64810, hdbc=0x1b503c0, fAnsi=false, timeout=)

at /root/workspace/pyodbc-3.0.7/build/bdist.linux-x86_64/rpm/BUILD/pyodbc-3.0.7/src/connection.cpp:85

#12 0x00007fc900b9a7ed in Connection_New (pConnectString=0x7fc907c64810, fAutoCommit=false, fAnsi=false, fUnicodeResults=,

timeout=0, fReadOnly=false) at /root/workspace/pyodbc-3.0.7/build/bdist.linux-x86_64/rpm/BUILD/pyodbc-3.0.7/src/connection.cpp:166

#13 0x00007fc900b981da in mod_connect (self=, args=, kwargs=)

at /root/workspace/pyodbc-3.0.7/build/bdist.linux-x86_64/rpm/BUILD/pyodbc-3.0.7/src/pyodbcmodule.cpp:371

#14 0x00007fc9079499d4 in PyEval_EvalFrameEx () from /usr/lib64/libpython2.6.so.1.0
#15 0x00007fc90794b647 in PyEval_EvalCodeEx () from /usr/lib64/libpython2.6.so.1.0
#16 0x00007fc90794b722 in PyEval_EvalCode () from /usr/lib64/libpython2.6.so.1.0
#17 0x00007fc907965b9c in ?? () from /usr/lib64/libpython2.6.so.1.0
#18 0x00007fc907965c70 in PyRun_FileExFlags () from /usr/lib64/libpython2.6.so.1.0
#19 0x00007fc90796715c in PyRun_SimpleFileExFlags () from /usr/lib64/libpython2.6.so.1.0
#20 0x00007fc907973892 in Py_Main () from /usr/lib64/libpython2.6.so.1.0
#21 0x00007fc906c56d5d in __libc_start_main () from /lib64/libc.so.6
#22 0x0000000000400649 in _start ()

{code}

[mkleehammer]

OK, I can't explain the actual pause, which is between FreeTDS and SQL Server, but I can say that I forgot to document the connection functions timeout parameter. It is a number of seconds (an integer), that will set SQL_ATTR_LOGIN_TIMEOUT. This will at least cause an error and you can retry the connection. (I've pushed updated docs now.)

The actual pause will need to be passed on to FreeTDS, though.