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Page works sometimes, but sometimes no HTTP response, blank page

Antonio Walls
Greenhorn

Joined: Jun 12, 2012
Posts: 5
Hey smart people,

I just acquired a web application that has been functioning fine for over a year, with the most recent update in January. About a month ago, the page started acting finnicky, and sometimes will not load at all (blank white page) until it's refreshed several times. Obviously our userbase isn't very happy!

The page uses Struts/JSP/jQuery/MySQL 5.1.49 and is running on Tomcat 6.0.29. I'm not very experienced with most of these, but need to find a way to fix the problem. When the page fails to load, there's no HTTP response and the source is blank. The only thing that has changed to the webapp recently is 2 months ago we transferred the domain name registrar... (shouldn't affect anything?).

There is a slight difference in HTTP response headers when the page doesn't load:
Normal:
Content-Language en-US
Content-Type text/html;charset=ISO-8859-1

Blank:
Content-Type text/plain

Some days are worse than others, and generally the logs show more errors on those days (who would've guessed...). The main error is:
The Struts dispatcher cannot be found. This is usually caused by using Struts tags without the associated filter. Struts tags are only usable when the request has passed through its servlet filter, which initializes the Struts dispatcher needed for this tag. - [unknown location]
I know very little about Struts. The only reason I'm skeptical this is the issue is that this error is in the logs well before there were any problems. Granted there are MORE occurences of this error now, but it seems like we should've seen *some* problems before, but it was working perfectly.

NB: This is my first code forum post anywhere so my bad if I didn't provide enough info/it's not a good question, but I don't have a clue what to do and have spent a decent amount of time looking for a solution, both here and elsewhere!

Thanks for any info
Antonio Walls
Greenhorn

Joined: Jun 12, 2012
Posts: 5
Here's some additional details from the logs. These are the errors that have been occurring frequently, I'm not sure which are bad errors and which are more like warnings:

12 Jun 2012 13;37:40,658 WARN [User:] OgnlValueStack:49 - Error setting expression 'set[]' with value '[Ljava.lang.String;@1e74cb5'
ognl.ExpressionSyntaxException: Malformed OGNL expression: set[] [ognl.ParseException: Encountered " "]" "] "" at line 1, column 5.


12 Jun 2012 13;32:23,141 ERROR [User:] JDBCExceptionReporter:78 - Deadlock found when trying to get lock; try restarting transaction
12 Jun 2012 13;32:23,141 ERROR [User:] AbstractFlushingEventListener:301 - Could not synchronize database state with session
org.hibernate.exception.LockAcquisitionException: Could not execute JDBC batch update


The timestamp on the OGNL error is the only one that seems to coincide with when I see the problem, but it also occurs a lot when I don't see any issues. This could mean it's just unrelated, or that the errors are coming from our outside users on the webapp.
Bear Bibeault
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