[jira] [Updated] (TS-4149) Add milestone for activity before TS_EVENT_HTTP_SSN_START

["Leif Hedstrom (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/TS-4149?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Leif Hedstrom updated TS-4149:
------------------------------
    Component/s: TS API
                 Logging

> 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
>          Components: Logging, TS API
>            Reporter: Scott Beardsley
>            Assignee: Bryan Call
>              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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