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Posted to dev@tomcat.apache.org by bu...@apache.org on 2007/08/28 14:34:14 UTC
DO NOT REPLY [Bug 43228] New: - StandardWrapper#countAllocated isn't thread-safe
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Summary: StandardWrapper#countAllocated isn't thread-safe
Product: Tomcat 6
Version: 6.0.14
Platform: Other
OS/Version: other
Status: NEW
Severity: normal
Priority: P2
Component: Catalina
AssignedTo: tomcat-dev@jakarta.apache.org
ReportedBy: kanekotky@gmail.com
Hi,
I noticed that StandardWrapper#countAllocated isn't thread-safe.
So, StandardWrapper#unload cannot finish until nRetries will be 21(40 seconds)
because countAllocated won't be 0.
I made a patch.
Regards,
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DO NOT REPLY [Bug 43228] - StandardWrapper#countAllocated isn't thread-safe
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------- Additional Comments From kanekotky@gmail.com 2007-08-28 05:48 -------
> (40 seconds)
I'm sorry. It takes 2 seconds per Wrapper.
If Tomcat has 100-Wrappers and their countAllocated are incorrect, it takes 200
seconds to shutdown them.
Regards,
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DO NOT REPLY [Bug 43228] - StandardWrapper#countAllocated isn't thread-safe
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------- Additional Comments From remm@apache.org 2007-08-30 16:17 -------
Yes, HelloWorldExample does a number of expensive operations.
OTOH, the shutdown strategy is not optimal at all, and has a lot of ways to go
wrong. It should use the time where the connectors (or the webapp) were
shutdown, rather that an individual per servlet time.
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DO NOT REPLY [Bug 43228] - StandardWrapper#countAllocated isn't thread-safe
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------- Additional Comments From kanekotky@gmail.com 2007-08-29 22:09 -------
Created an attachment (id=20738)
--> (http://issues.apache.org/bugzilla/attachment.cgi?id=20738&action=view)
benchmark results with a simpler servlet
Hi Remy,
Did you mean that a significant overhead of HelloExampleServlet is
ResourceBundle.getBundle() or concatenating strings?
Anyway I did tests with a simpler Servlet.
testname, rps, 99% tile, cpu
original, 6777.25 [#/sec], 75 [ms], 86.90 [%]
patch, 6873.97 [#/sec], 60 [ms], 86.29 [%]
And I did same tests with Keep-Alive.
testname, rps, 99% tile, cpu
original, 10137.90 [#/sec], 60 [ms], 97.32 [%]
patch, 10130.51 [#/sec], 63 [ms], 96.46 [%]
As a result, I could not see the overhead of using AtomicInteger on Tomcat.
However, this issue is not so serious problem because countAllocated is not
used on other places and we have already gotten a workalound, so I consent this
issue is WONTFIX.
I will never reopen it. :-) thanks a lot.
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DO NOT REPLY [Bug 43228] - StandardWrapper#countAllocated isn't thread-safe
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------- Additional Comments From kanekotky@gmail.com 2007-08-29 05:25 -------
Created an attachment (id=20726)
--> (http://issues.apache.org/bugzilla/attachment.cgi?id=20726&action=view)
patch for document if needed
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DO NOT REPLY [Bug 43228] - StandardWrapper#countAllocated isn't thread-safe
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------- Additional Comments From kanekotky@gmail.com 2007-08-28 05:35 -------
Created an attachment (id=20720)
--> (http://issues.apache.org/bugzilla/attachment.cgi?id=20720&action=view)
patch against tc6.0.x
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DO NOT REPLY [Bug 43228] - StandardWrapper#countAllocated isn't thread-safe
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remm@apache.org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution| |WONTFIX
------- Additional Comments From remm@apache.org 2007-08-28 06:03 -------
As usual, I am not in favor of applying this sort of patch, given the possible
high synchronization vs the actual severity of the issue. Feel free to continue
using your patch if it works for you.
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DO NOT REPLY [Bug 43228] - StandardWrapper#countAllocated isn't thread-safe
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remm@apache.org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|REOPENED |RESOLVED
Resolution| |WONTFIX
------- Additional Comments From remm@apache.org 2007-08-29 07:15 -------
The HelloWorldExample has a significant overhead, unfortunately. As I said
previously, I don't think this patch is needed, sorry, especially since few
people see this as an issue. Please do not reopen the report, thanks.
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DO NOT REPLY [Bug 43228] - StandardWrapper#countAllocated isn't thread-safe
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kanekotky@gmail.com changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|RESOLVED |REOPENED
Resolution|WONTFIX |
------- Additional Comments From kanekotky@gmail.com 2007-08-29 05:22 -------
Hi Remy,
thanks for response.
I have respects for your carefulness about the performance.
IMO, AtomicInteger doesn't have synchronization problem and it's overhead is
really low.
I did performance benchmarks using Apache Bench between original and my patch .
Here are the summary of results.
Requests per second:
original 5743.66 [#/sec] (mean)
patch 5748.83 [#/sec] (mean)
99% Percentage of the requests served within a certain time (ms)
original 96
patch 80
Average CPU Usage
original 96.35%
patch 96.25%
Is this reasonable? How do you think?
BTW, the actual severity is that we cannot shutdown Tomcat quickly.
We can avoid this problem to set the StandardContext#unloadDelay as 0.
If this issue is WONTFIX, please note it on document instead.
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------- Additional Comments From kanekotky@gmail.com 2007-08-29 05:23 -------
Created an attachment (id=20725)
--> (http://issues.apache.org/bugzilla/attachment.cgi?id=20725&action=view)
benchmark results
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