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https://issues.apache.org/jira/browse/TS-4149?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Leif Hedstrom updated TS-4149:
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Fix Version/s: (was: 6.2.0)
7.0.0
> Add milestone for activity before TS_EVENT_HTTP_SSN_START
> ---------------------------------------------------------
>
> Key: TS-4149
> URL: https://issues.apache.org/jira/browse/TS-4149
> Project: Traffic Server
> Issue Type: Improvement
> Reporter: Scott Beardsley
> Labels: yahoo
> Fix For: 7.0.0
>
> Attachments: nullmutex.png, usingmutex.png
>
>
> I ran into a pretty big performance issue in a plugin when it created a mutex
> in the TS_EVENT_HTTP_SSN_START hook. This caused a significant delay in
> processing the request. It ended up delaying sending the request to the
> origin by between 50 and 100ms at the 75%+ percentile! Here is a sample
> plugin which illustrates the problem:
> {noformat}
> #include <ts/ts.h>
> #include <cstddef>
> int globalHandler(TSCont continuation, TSEvent event, void * data) {
> TSHttpSsn session = static_cast< TSHttpSsn >(data);
> TSHttpSsnReenable(session, TS_EVENT_HTTP_CONTINUE);
> return 0;
> }
> void TSPluginInit(int argc, const char * * argv) {
> TSPluginRegistrationInfo info;
> info.plugin_name = const_cast< char * >(PLUGIN_TAG);
> // If we create a Mutex here there is huge, unaccounted for TTFB latency
> TSCont continuation = TSContCreate(globalHandler, TSMutexCreate());
> // the following will "fix" this problem assuming you don't actually
> need the mutex
> // TSCont continuation = TSContCreate(globalHandler, NULL);
> TSHttpHookAdd(TS_HTTP_SSN_START_HOOK, continuation);
> }
> {noformat}
> What is also bad about this performance problem is that it is not visible in
> any of the milestone metrics including ttms. It shows up as a delay between
> in TTFB on the client side. It caused a lot of confusion to not be able to
> see the latency in slow logs, thus this request to expose the time spent here
> to the milestones.
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