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https://issues.apache.org/jira/browse/TS-506?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Leif Hedstrom resolved TS-506.
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Resolution: Fixed
This is resolved for now, with a change in the default configurations. Opening
a separate ticket to examine when we ought to do the writer lock, but can
target that for v3.1.
> Poor performance on proxied requests which are not cacheable.
> -------------------------------------------------------------
>
> Key: TS-506
> URL: https://issues.apache.org/jira/browse/TS-506
> Project: Traffic Server
> Issue Type: Bug
> Components: Cache
> Reporter: Leif Hedstrom
> Priority: Critical
> Fix For: 2.1.6
>
>
> This is a problem similar in behavior and how to reproduce as TS-505.
> I have a test setup using lighttpd (stock config, but with the port changed
> to port 82, and logging disabled). I've also disabled Keep-Alive on lighttpd,
> with a line like this in /etc/lighttpd/lighttpd.conf
> server.max-keep-alive-requests = 0
> I've created a small file (42 bytes) in /var/www/lighttpd/cl-test.html.
> I'm running Apache TS with a stock config ("gmake install") with the
> following configuration changes:
> records.config:
> ---------------
> CONFIG proxy.config.http.server_port INT 80
> CONFIG proxy.config.http.cache.required_headers INT 2
> CONFIG proxy.config.log2.logging_enabled INT 0
> remap.config:
> -------------
> map http://loki.ogre.com/lighttpd/ http://localhost:82/
> I'm "benchmarking" this using "ab" from a second host, running a command like
> ab -c 20 -n 10000 http://loki.ogre.com/lighttpd/cl-test.html
> Test 1: http caching is disabled with a records.config setting
> CONFIG proxy.config.http.cache.http INT 0
> Results:
> Requests per second: 9319.75 [#/sec] (mean)
> Time per request: 2.146 [ms] (mean)
> Time per request: 0.107 [ms] (mean, across all concurrent requests)
> Test 2: http caching enabled, records.config is
> CONFIG proxy.config.http.cache.http INT 0
> Results:
> Requests per second: 2967.59 [#/sec] (mean)
> Time per request: 6.739 [ms] (mean)
> Time per request: 0.337 [ms] (mean, across all concurrent requests)
> So, simply enabling the cache makes it process 3x less QPS and at 3x the
> latency. There is again no disk I/O on either of these tests.
> If I "combine" the worst case scenario, from TS-505 and this bug, and run the
> test with http.cache=1 (cache enabled) and have the lighttpd server send
> Connection: keep-alive responses, the performance plunges:
> Requests per second: 173.09 [#/sec] (mean)
> Time per request: 115.548 [ms] (mean)
> Time per request: 5.777 [ms] (mean, across all concurrent requests)
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