Excellent idea!
gerry
On Fri, Dec 13, 2013 at 2:12 AM, Heiko Klein <Heiko.Klein@xxxxxx> wrote:
> Hi Jay,
>
> not sure if this is connected, but we've had similar problems with
> ncWMS/thredds some years ago http://www.unidata.ucar.edu/
> mailing_lists/archives/thredds/2010/msg00069.html
>
> WMS-clients will request many maps/tiles at once and this will give high
> server load if not cached. This might lead to canceled client requests. In
> addition, tomcat6 with ncWMS had a strange bug with requests cancelled by
> the client, leading to a server-crash at the end.
>
>
> We solved this by adding a apache 'mod-cache' in front of tomcat and made
> tomcat deliver all pages with cache-headers keeping pictures for 7 days in
> the cache. Server-load dropped nicely due to the cache, and tomcat doesn't
> get any more 'client abort exceptions' since those are swollowed by the
> cache.
>
> Heiko
>
>
> On 2013-12-11 23:33, Jay Alder wrote:
>
>> Hi, we’ve recently released a web application that uses TDS for mapping,
>> which is getting a lot of traffic. At one point the server stopped
>> responding altogether, which is a major problem. A quick restart of
>> tomcat got it going again, so I’m starting to dig into the logs. We
>> normally get the GET / request complete behavior, but occasionally we’ll
>> have:
>>
>> GET …url…
>> GET …url…
>> GET …url…
>> GET …url…
>> GET …url…
>> GET …url…
>> GET …url…
>> GET …url…
>>
>> meanwhile having a 100% CPU spike (with 12 CPUs) for a minute or more
>>
>> request compete
>> request compete
>> request compete
>> request cancelled by client
>> request cancelled by client
>> request compete
>> request compete
>>
>> While watching the logs the few times I’ve seen this occur it seems to
>> pull out of it ok. However the time the server failed, requests were
>> never returned. From the logs, requests came in for roughly 40 minutes
>> without being completed. Unfortunately do to the high visibility we
>> started to get emails from users and the press about the application no
>> longer working.
>>
>> Has anyone experienced this before and/or can you give guidance on how
>> to diagnose or prevent this?
>>
>> Here are some config settings:
>> CentOS 5.7
>> Java 1.6
>> TDS 4.3.17
>> only WMS is enabled
>> Java -Xmx set to 8Gb (currently taking 5.3, the dataset is 600 Gb of
>> 30-arcsecond grids for the continental US, 3.4 Gb per file)
>> For better or worse we are configured to use 2 instances of TDS to keep
>> the catalogs and configuration isolated. I’m not sure if this matters,
>> but I didn’t want to omit it. Since it is a live server I can’t easily
>> change to the preferred proxy configuration.
>>
>> I am trying not to panic yet. However, if the server goes unresponsive
>> again, staying calm may no longer be an option.
>>
>> Jay Alder
>> US Geological Survey
>> Oregon State University
>> 104 COAS Admin Building
>> Office Burt Hall 166
>> http://ceoas.oregonstate.edu/profile/alder/
>>
>>
>>
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>>
>>
> --
> Dr. Heiko Klein Tel. + 47 22 96 32 58
> Development Section / IT Department Fax. + 47 22 69 63 55
> Norwegian Meteorological Institute http://www.met.no
> P.O. Box 43 Blindern 0313 Oslo NORWAY
>
>
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>
--
Gerry Creager
NSSL/CIMMS
405.325.6371
++++++++++++++++++++++
“Big whorls have little whorls,
That feed on their velocity;
And little whorls have lesser whorls,
And so on to viscosity.”
Lewis Fry Richardson (1881-1953)
