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Subject: Re: [SR-Users] Strange application hang querying DB
From: Tim Chubb <tim.chubb () voicesimplified ! com>
Date: 2014-06-27 12:03:19
Message-ID: a0ce3fbf20094d46b4db455d832a4082 () DBXPR07MB189 ! eurprd07 ! prod ! outlook ! com
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Just thought I would post a quick update:
After further digging around I stumbled upon what looked to a recursive loop in the \
freetds connection logs. Which led me to some posts on the freetds mailing list to \
do with handling closed connections by SQL Azure. The crux of the problem seems to \
be that the load balancer on SQL Azure will close "idle" connections before the SQL \
Server closes the connection, resulting in the connection being closed without any \
feedback to the odbc driver, which still maintains the connection reference in its \
connection pool, thus Kamailio will attempt to utilise a connection which is in \
effect orphaned. However if you shorten the TCP Keep alive time and interval from \
the default of 2 hours and 75 seconds respectively you can detect the closed \
connection and the ODBC driver handles it properly.
I have currently set my keep alive time to 120 s (2 mins) with a 10 second interval, \
and so far I have maintained 4 hours of continuous service. I will continue to \
monitor the situation, but hopefully this has solved the intermittent issues I was \
experiencing.
Tim.
From: sr-users-bounces@lists.sip-router.org \
[mailto:sr-users-bounces@lists.sip-router.org] On Behalf Of Tim Chubb
Sent: 26 June 2014 10:07
To: miconda@gmail.com; Kamailio (SER) - Users Mailing List
Subject: Re: [SR-Users] Strange application hang querying DB
Hi Daniel
There is no load on the system as I'm developing the implementation at the moment, I \
have a softphone and hardphone registered and that is it. Im using Centos 6.5 32bit \
as the OS and have disabled SElinux whilst developing.
There is no rhyme or reason as far as I can tell, sometime's registration hangs \
(using auth_db against my Asterisk RT tables), sometimes it's the dispatcher, and \
sometimes just calling ‘kamctl dispatcher reload'. One thing I have tried to help \
narrow the search focus down was run this when I experienced loss of connectivity \
‘date && kamctl dispatcher reload && date' which would give the start and end time \
of the query, where I seem to experience a 30min delay between start and finish (I \
have 2 entires in the dispatcher table, so its not a lack of index or anything like \
that).
I have a nasty feeling this may be caused by SQL Azures idle connection handling \
which is quite different to the standard server implementation (which works \
frustratingly fine, i.e. if I work from home the kamailio process handles vpn \
disconnections and resumes operations as soon as I connect).
Im going to try disabling connection pooling in unixodbc, see if that helps, if that \
doesn't help then I fear I am going to have to brush off my c skills and dive into \
the db_unixodbc module and general DB logic to get a better understanding of how \
Kamailio is handling db connections.
Tim.
From: sr-users-bounces@lists.sip-router.org<mailto:sr-users-bounces@lists.sip-router.org> \
[mailto:sr-users-bounces@lists.sip-router.org] On Behalf Of \
Daniel-Constantin Mierla
Sent: 26 June 2014 09:08
To: Kamailio (SER) - Users Mailing List
Subject: Re: [SR-Users] Strange application hang querying DB
Hello,
have you identified the config function that hangs? Is a sqlops function or something \
related to authentication, location, etc?
If not, then you can use benchmark module to measure the duration of execution of \
various parts of config, in this way identifying the function that takes too long.
You should eventually run directly with debug=3 and watch the logs in syslog file.
Once you tell the function taking too long, I will try to dig further to see if I can \
spot any issue.
Some other details would help:
- is the system under load or it happens only for one request and always?
- what is the operating system? I encountered many issues with selinux in the past, \
under high load or too many connections opened
Cheers,
Daniel
On 25/06/14 20:06, Tim Chubb wrote:
Hi,
I'm currently wracking my brains trying to deduce where an application hang can be \
coming from.
I have ported the PostGres schema to be compatible with MS Sql Server and have had no \
issues getting a working dev environment working. However when I try and use SQL \
Azure as the backend db as opposed to SQL Server 2012 (running locally on my dev \
machine) Kamailio will seem to hang after about 10 – 15 mins of flawless operation. \
I have recreated the SQL Azure schema from the working schema running on my dev \
machine and copied all data in a 1:1 manner so I can be certain it's not a data \
quality issue. I am using the same FreeTDS/UnixODBC config that I am using for \
Asterisk realtime (which doesn't exhibit this behaviour). The really strange thing \
is that I can see the queries being sent by Kmailio in the freetds trace log, and the \
response from SQL Azure, however its as if the db response handler is \
deadlocked/hung. The kamailio process continues to work fine, and as long as its not \
required to commiunicate with the DB all appears well i.e. no error messages in the \
log file.
This behaviour only happens when im using SQL Azure as opposed to SQL Server, so \
there must be something causing the issue, that's unique to SQL azure as opposed to \
SQL Server. As far as I can tell this is not something I can create a backtrace for \
as no core dumps are produced, as far as I can tell there is no easy way debug what \
the lock is. If anyone has any suggestions I would be very grateful to hear them.
One thing that occurs to me is that the db_unixodbc module doesn't have half as many \
parameters as its equilent in Asterisk, and that connection pooling may be in use, \
this could be a bit of a show stopper AFAIK you have to disable connection pooling \
with SQL server, certainly any of the guides I have come across configuring Asterisk \
to work with SQL server suggests that.
Tim Chubb
Developer
[VS-logo-email]
The Coach House, Heywood House, Park Lane, Heywood, Westbury, BA13 4NA
Direct: +44 (0)333 0110164
Email: tim.chubb@voicesimplified.com<mailto:tim.chubb@voicesimplified.com>
Web: www.VoiceSimplified.com<http://www.voicesimplified.com/>
Voice Simplified Ltd (registered in England & Wales: 07171825) registered office: \
Curzon House, 2nd Floor, 24 High Street, Banstead, Surrey. SM7 2LJ. The information \
in this email is confidential and may be legally privileged. It is intended solely \
for the addressee. Access to this email by anyone else is unauthorised. If you are \
not the intended recipient, any disclosure, copying, distribution or any action taken \
or omitted to be taken in reliance on it, is prohibited and may be unlawful. If you \
are not the intended recipient, please return the message to the sender and delete it \
from your records.
_______________________________________________
SIP Express Router (SER) and Kamailio (OpenSER) - sr-users mailing list
sr-users@lists.sip-router.org<mailto:sr-users@lists.sip-router.org>
http://lists.sip-router.org/cgi-bin/mailman/listinfo/sr-users
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http://twitter.com/#!/miconda - http://www.linkedin.com/in/miconda
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<p class="MsoNormal"><span style="color:#1F497D">Just thought I would post a quick \
update:<o:p></o:p></span></p> <p class="MsoNormal"><span \
style="color:#1F497D"><o:p> </o:p></span></p> <p class="MsoNormal"><span \
style="color:#1F497D">After further digging around I stumbled upon what looked to a \
recursive loop in the freetds connection logs. Which led me to some posts on \
the freetds mailing list to do with handling closed connections by SQL Azure. \
The crux of the problem seems to be that the load balancer on SQL Azure will close \
"idle" connections before the SQL Server closes the connection, resulting in the \
connection being closed without any feedback to the odbc driver, which still \
maintains the connection reference in its connection pool, thus Kamailio will \
attempt to utilise a connection which is in effect orphaned. However if you \
shorten the TCP Keep alive time and interval from the default of 2 hours and 75 \
seconds respectively you can detect the closed connection and the ODBC driver \
handles it properly.<o:p></o:p></span></p> <p class="MsoNormal"><span \
style="color:#1F497D"><o:p> </o:p></span></p> <p class="MsoNormal"><span \
style="color:#1F497D">I have currently set my keep alive time to 120 s (2 mins) with \
a 10 second interval, and so far I have maintained 4 hours of continuous \
service. I will continue to monitor the situation, but hopefully this has \
solved the intermittent issues I was experiencing.<o:p></o:p></span></p> <p \
class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p> <p \
class="MsoNormal"><span style="color:#1F497D">Tim.<o:p></o:p></span></p> <p \
class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p> <div>
<div style="border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b><span lang="EN-US" \
style="color:windowtext;mso-fareast-language:EN-GB">From:</span></b><span \
lang="EN-US" style="color:windowtext;mso-fareast-language:EN-GB"> \
sr-users-bounces@lists.sip-router.org [mailto:sr-users-bounces@lists.sip-router.org] \
<b>On Behalf Of </b>Tim Chubb<br> <b>Sent:</b> 26 June 2014 10:07<br>
<b>To:</b> miconda@gmail.com; Kamailio (SER) - Users Mailing List<br>
<b>Subject:</b> Re: [SR-Users] Strange application hang querying \
DB<o:p></o:p></span></p> </div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="color:#1F497D">Hi Daniel<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">There is no load on the system as \
I'm developing the implementation at the moment, I have a softphone and hardphone \
registered and that is it.<o:p></o:p></span></p> <p class="MsoNormal"><span \
style="color:#1F497D">Im using Centos 6.5 32bit as the OS and have disabled SElinux \
whilst developing.<o:p></o:p></span></p> <p class="MsoNormal"><span \
style="color:#1F497D"><o:p> </o:p></span></p> <p class="MsoNormal"><span \
style="color:#1F497D">There is no rhyme or reason as far as I can tell, sometime's \
registration hangs (using auth_db against my Asterisk RT tables), sometimes it's the \
dispatcher, and sometimes just calling ‘kamctl dispatcher reload'. One thing \
I have tried to help narrow the search focus down was run this when I experienced \
loss of connectivity<o:p></o:p></span></p> <p class="MsoNormal"><span \
style="color:#1F497D">‘date && kamctl dispatcher reload && date' \
which would give the start and end time of the query, where I seem to experience a \
30min delay between start and finish (I have 2 entires in the dispatcher table, so \
its not a lack of index or anything like that).<o:p></o:p></span></p> <p \
class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p> <p \
class="MsoNormal"><span style="color:#1F497D">I have a nasty feeling this may be \
caused by SQL Azures idle connection handling which is quite different to the \
standard server implementation (which works frustratingly fine, i.e. if I work from \
home the kamailio process handles vpn disconnections and resumes operations as soon \
as I connect).<o:p></o:p></span></p> <p class="MsoNormal"><span \
style="color:#1F497D"><o:p> </o:p></span></p> <p class="MsoNormal"><span \
style="color:#1F497D">Im going to try disabling connection pooling in unixodbc, see \
if that helps, if that doesn't help then I fear I am going to have to brush off my c \
skills and dive into the db_unixodbc module and general DB logic to get a better \
understanding of how Kamailio is handling db connections.<o:p></o:p></span></p> <p \
class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p> <p \
class="MsoNormal"><span style="color:#1F497D">Tim.<o:p></o:p></span></p> <p \
class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p> <div>
<div style="border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b><span lang="EN-US" \
style="color:windowtext;mso-fareast-language:EN-GB">From:</span></b><span \
lang="EN-US" style="color:windowtext;mso-fareast-language:EN-GB"> <a \
href="mailto:sr-users-bounces@lists.sip-router.org">sr-users-bounces@lists.sip-router.org</a> \
[<a href="mailto:sr-users-bounces@lists.sip-router.org">mailto:sr-users-bounces@lists.sip-router.org</a>]
<b>On Behalf Of </b>Daniel-Constantin Mierla<br>
<b>Sent:</b> 26 June 2014 09:08<br>
<b>To:</b> Kamailio (SER) - Users Mailing List<br>
<b>Subject:</b> Re: [SR-Users] Strange application hang querying \
DB<o:p></o:p></span></p> </div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="margin-bottom:12.0pt">Hello,<br>
<br>
have you identified the config function that hangs? Is a sqlops function or something \
related to authentication, location, etc?<br> <br>
If not, then you can use benchmark module to measure the duration of execution of \
various parts of config, in this way identifying the function that takes too \
long.<br> <br>
You should eventually run directly with debug=3 and watch the logs in syslog \
file.<br> <br>
Once you tell the function taking too long, I will try to dig further to see if I can \
spot any issue.<br> <br>
Some other details would help:<br>
- is the system under load or it happens only for one request and always?<br>
- what is the operating system? I encountered many issues with selinux in the past, \
under high load or too many connections opened<br> <br>
Cheers,<br>
Daniel<span style="font-size:12.0pt;mso-fareast-language:EN-GB"><o:p></o:p></span></p>
<div>
<p class="MsoNormal">On 25/06/14 20:06, Tim Chubb wrote:<o:p></o:p></p>
</div>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal">Hi,<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">I'm currently wracking my brains trying to deduce where an \
application hang can be coming from.<o:p></o:p></p> <p \
class="MsoNormal"> <o:p></o:p></p> <p class="MsoNormal">I have ported the \
PostGres schema to be compatible with MS Sql Server and have had no issues getting a \
working dev environment working. However when I try and use SQL Azure as the \
backend db as opposed to SQL Server 2012 (running locally on my dev machine) \
Kamailio will seem to hang after about 10 – 15 mins of flawless operation. I \
have recreated the SQL Azure schema from the working schema running on my dev machine \
and copied all data in a 1:1 manner so I can be certain it's not a data quality \
issue. I am using the same FreeTDS/UnixODBC config that I am using for Asterisk \
realtime (which doesn't exhibit this behaviour). The really strange thing is \
that I can see the queries being sent by Kmailio in the freetds trace log, and the \
response from SQL Azure, however its as if the db response handler is \
deadlocked/hung. The kamailio process continues to work fine, and as long as \
its not required to commiunicate with the DB all appears well i.e. no error messages \
in the log file.<o:p></o:p></p> <p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">This behaviour only happens when im using SQL Azure as opposed \
to SQL Server, so there must be something causing the issue, that's unique to SQL \
azure as opposed to SQL Server. As far as I can tell this is not something I \
can create a backtrace for as no core dumps are produced, as far as I can tell there \
is no easy way debug what the lock is. If anyone has any suggestions I would be \
very grateful to hear them.<o:p></o:p></p> <p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">One thing that occurs to me is that the db_unixodbc module \
doesn't have half as many parameters as its equilent in Asterisk, and that connection \
pooling may be in use, this could be a bit of a show stopper AFAIK you have to \
disable connection pooling with SQL server, certainly any of the guides I have come \
across configuring Asterisk to work with SQL server suggests that.<o:p></o:p></p> <p \
class="MsoNormal"> <o:p></o:p></p> <p class="MsoNormal"><b><span \
style="font-size:10.5pt;font-family:"Candara","sans-serif";color:#44546A;mso-fareast-language:EN-GB">Tim \
Chubb</span></b><o:p></o:p></p> <p class="MsoNormal"><span \
style="font-size:10.5pt;font-family:"Candara","sans-serif";color:#44546A;mso-fareast-language:EN-GB">Developer</span><o:p></o:p></p>
<p class="MsoNormal"><span \
style="mso-fareast-language:EN-GB"> </span><o:p></o:p></p> <p \
class="MsoNormal"><span \
style="font-family:"Candara","sans-serif";color:#404040;mso-fareast-language:EN-GB"><img \
border="0" width="208" height="42" id="Picture_x0020_1" \
src="cid:image001.png@01CF9207.98CE3170" alt="VS-logo-email"></span><o:p></o:p></p> \
<p class="MsoNormal"><span \
style="mso-fareast-language:EN-GB"> </span><o:p></o:p></p> <p \
class="MsoNormal"><span \
style="font-size:10.5pt;font-family:"Candara","sans-serif";color:#44546A;mso-fareast-language:EN-GB">The \
Coach House, Heywood House, Park Lane, Heywood, Westbury, BA13 \
4NA</span><o:p></o:p></p> <p class="MsoNormal"><span \
style="font-size:10.5pt;font-family:"Candara","sans-serif";color:# \
44546A;mso-fareast-language:EN-GB">
</span><o:p></o:p></p>
<p class="MsoNormal"><span \
style="font-size:10.5pt;font-family:"Candara","sans-serif";color:#44546A;mso-fareast-language:EN-GB">Direct: \
+44 (0)333 0110164</span><o:p></o:p></p> <p class="MsoNormal"><span \
style="font-size:10.5pt;font-family:"Candara","sans-serif";color:#44546A;mso-fareast-language:EN-GB">Email:
<a href="mailto:tim.chubb@voicesimplified.com">tim.chubb@voicesimplified.com</a></span><o:p></o:p></p>
<p class="MsoNormal"><span \
style="font-size:10.5pt;font-family:"Candara","sans-serif";color:#44546A;mso-fareast-language:EN-GB">Web:
<a href="http://www.voicesimplified.com/">www.VoiceSimplified.com</a></span><o:p></o:p></p>
<p class="MsoNormal" style="text-autospace:none"><span \
style="font-size:6.0pt;font-family:"Candara","sans-serif";color:#44546A;mso-fareast-language:EN-GB"> </span><o:p></o:p></p>
<p class="MsoNormal" style="text-autospace:none"><span \
style="font-size:8.0pt;font-family:"Candara","sans-serif";color:#44546A;mso-fareast-language:EN-GB">Voice \
Simplified Ltd (registered in England & Wales: 07171825) registered office: \
Curzon House, 2nd Floor, 24 High Street, Banstead, Surrey. SM7 \
2LJ.</span><o:p></o:p></p> <p class="MsoNormal" style="text-autospace:none"><span \
style="font-size:8.0pt;font-family:"Candara","sans-serif";color:#44546A;mso-fareast-language:EN-GB">The \
information in this email is confidential and may be legally privileged. It is \
intended solely for the addressee. Access to this email by anyone else \
</span><o:p></o:p></p> <p class="MsoNormal" style="text-autospace:none"><span \
style="font-size:8.0pt;font-family:"Candara","sans-serif";color:#44546A;mso-fareast-language:EN-GB">is \
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<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal" style="margin-bottom:12.0pt"><span \
style="font-size:12.0pt;font-family:"Times New \
Roman","serif";mso-fareast-language:EN-GB"><br> <br>
<o:p></o:p></span></p>
<pre>_______________________________________________<o:p></o:p></pre>
<pre>SIP Express Router (SER) and Kamailio (OpenSER) - sr-users mailing \
list<o:p></o:p></pre> <pre><a \
href="mailto:sr-users@lists.sip-router.org">sr-users@lists.sip-router.org</a><o:p></o:p></pre>
<pre><a href="http://lists.sip-router.org/cgi-bin/mailman/listinfo/sr-users">http://lists.sip-router.org/cgi-bin/mailman/listinfo/sr-users</a><o:p></o:p></pre>
</blockquote>
<p class="MsoNormal" style="margin-bottom:12.0pt"><span \
style="font-size:12.0pt;font-family:"Times New \
Roman","serif";mso-fareast-language:EN-GB"><o:p> </o:p></span></p>
<pre>-- <o:p></o:p></pre>
<pre>Daniel-Constantin Mierla - <a \
href="http://www.asipto.com">http://www.asipto.com</a><o:p></o:p></pre> <pre><a \
href="http://twitter.com/#!/miconda">http://twitter.com/#!/miconda</a> - <a \
href="http://www.linkedin.com/in/miconda">http://www.linkedin.com/in/miconda</a><o:p></o:p></pre>
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