dhis2-devs team mailing list archive

[Lars Helge Øverland <larshelge@xxxxxxxxx>]

Hi Dave,

You are right, this code was getting a bit dated and used old-style jdbc
connections and result sets. I have re-factored the class your stack trace
refers to in trunk to use Spring JdbcTemplate which does resource handling
transparently. I did a quick analysis through eclipse and was able to fix a
few similar issues too. Many thanks for reporting this.

best regards,

Lars





On Thu, Apr 11, 2013 at 10:11 PM, Dave Trombley <dave.trombley@xxxxxxxxx>wrote:

>   Hi all -
>
>    Recently, some custom modifications we were doing for a DHIS2
> installation caused a server crash unexpectedly.   It turns out that
> we were not closing a ResultSet that we were creating directly from a
> JdbcTemplate, and this in turn was causing a c3p0 thread resource leak
> that would, over time, bring the entire service down.  (The endpoint
> error was something like "Maximum number of threads (200) created" in
> catalina.out...)
>
>    We were able to diagnose the problem and pinpoint the exact place
> in our custom source that the problem was at by setting the c3p0
> options 'debugUnreturnedConnectionStackTrace' and
> 'unreturnedConnectionTimeout' to appropriate values - these in concert
> cause a stack trace with the location of the created ResultSet to be
> emitted as log entries.  We fixed our mistake.
>
>    However, during this process, we were able to see another area of
> the code which got reported as not closing a resource as well, and on
> inspection it seems it was doing the exact thing we were - manually
> opening a ResultSet, and not closing it.  A partial stack trace from
> that event is attached.  Indeed, it seems like a number of methods in
> the SQL view actions do the same sort of thing...
>
>    I just wanted to bring this to your attention, as if it does
> actually represent a potential c3p0 leak it could cause server
> instability on potentially any DHIS2 installation on which that
> feature is used.  Our version of DHIS2 is heavily customized, so it's
> not exactly a test case, but I will be downloading stock 2.10 and 2.11
> codebases over the next few days to extensively test in this manner.
>
>    Are these known issues?   Is my reasoning here sound, or are there
> reasons that might this be a false positive?
>
> Best,
> -David
>
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