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Mark,
On 2/14/13 5:22 AM, Mark Thomas wrote:
> On 14/02/2013 02:22, Steve van Loben Sels wrote:
>> Greetings.
>>
>> I recently upgraded from Tomcat 6.0.36 to 7.0.35 with the native
>> APR connector, and I ran into a problem with numbers in my
>> access Log. I use the %D ("Time taken to process the request, in
>> millis") to measure the service delivery quality of the
>> application deployed to Tomcat, and it showed a large increase in
>> average response time after the upgrade. I had other independent
>> metrics in place that showed that the performance of the
>> application had actually improved, so I thought maybe that there
>> was instead a difference in how the request time was being
>> measured in the 6.0 and 7.0 releases.
>
> Correct.
>
>> By writing some test cases, I was able to see that the increase
>> in the measured time was due to time waiting to fill the internal
>> buffer while parsing the headers in that same code block. I'm
>> assuming that in the 6.0 server, the header data already buffered
>> and was immediately available whereas the 7.0 server was still
>> waiting on the client transmission. I tried increasing the
>> maxHttpHeaderSize since I see that the buffer size is directly
>> correlated to that value, but it had no effect on the behavior.
>
> The reason is that in Tomcat 6 start and end time for the request
> was measured at the point the request/response entered/left the
> AccessLogValve which is after the connector.
>
> In Tomcat 7 the access logging was refactored to take the full
> request time into account - mainly to align it with httpd.
>
>> For fun, I also tried out the other connector types. BIO
>> suffered from the same problem whereas the NIO connector
>> exhibited the old behavior. Unfortunately, I'm tied to the APR
>> connector for the SSL implementation.
>
> There is a bug in the NIO connector. The NIO connector is
> non-blocking while reading the headers and the start time gets
> reset every time another bit of the headers are read. That needs
> fixing.
>
>> I'm wondering, is there some knob I can turn to restore the old
>> behavior?
>
> Short answer. No.
>
>> I looked through all the documentation and the change log to see
>> if anything jumped out at me, but I couldn't come up with
>> anything. It looks as though the APR connector is treated more
>> or less as a black box. The time taken is an important metric
>> for me to determine that my application is meeting an SLA, so it
>> would be great to get it back to how it was working before.
>
> Long answer. Depending on exactly what you need you could either
> extend the existing AccessLogValve and modify how the request time
> is calculated or your could write a simple valve that logs what you
> need.
Or, write a Valve that wraps the AccessLogValve and sets the "start
time" there: that should restore the old Tomcat-6-style behavior, no?
- -chris
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