Friday, January 28, 2011

Debugging/Troubleshooting SQL performance/blocking issues

I picked up a good tip from one of our DBA's yesterday.  He uses sp_who2 to see which users have active threads/processes running against a particular database.  This stored proc returns the PIDs as well (Process ID number).  I had known about this previously.  What was new to me was he also used:

dbcc inputbuffer(pidNumberHere)

to get the database to tell him which stored proc was being executed by that PID.  That seems to me like a handy trick.  It certainly solved the problem I was having.

Thursday, January 27, 2011

WCF and Large Result sets

Dealing with oil resource data across several disparate systems and also trying to make our API's more generic and consistent, we use WCF a lot (web services with windows apps). We've had a couple of instances where we've had to tweak the config settings for either our publishers or our clients to return some large datasets over WCF.
For the most part, I have found the error messages relating to constrained WCF config settings refreshingly to the point.  They pretty much pointed me directly to the attribute in the file that I needed to change in order to fix my issue.
For memory related errors on the client, I found that juggling with the maxBufferPoolSize and maxReceivedMessageSize in my binding to help.  I moved the maxBufferPoolSize from 9999999 to 99999999, and changed the maxReceivedMessageSize to 350000000.  Sometimes after that I would get a timeout error on the client machine (depending on what kind of load the server was under).  So I'd have to make the timeout settings on the binding higher.
Obviously it helps when the publisher has the same values for the same attributes on its binding.

Tuesday, January 18, 2011

SMTP email issue with hosts file

I had an interesting issue last week.  I had a website with a contact page that uses SMTP sendmail to email a list of people whatever was entered on a form.  The curious thing about this issue was it would send emails to everyone in the list except email addresses that matched the domain name of the web site.  For example, it would send an email to, but it wouldn't send an email to, even though the server that was doing the sending was listed in the DNS as ''.

I tried changing the email provider by pointing the Email Host to a server that I knew accepted anonymous email pushes, but it did the opposite - sending the emails successfully for users from, but not sending them for!

After looking through various logs (including /var/log/maillog), it seemed like sendmail was getting confused as the log was trying to associate the email address ( with a user on the host and not finding the user.

sendmail failed error: localhost: user not found

I tried removing an entry in the /etc/hosts file that pointed the IP address to, but that didn't seem to work.  What I didn't realize until later (with the help of my hosting provider) is that this was the correct change to make, I just needed to restart two services after I made the change:
service network restart
service sendmail restart
Then my email worked perfectly.