[jira] [Updated] (TS-2501) VariableExpander in header_rewrite is unnecessary expensive

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

     [ https://issues.apache.org/jira/browse/TS-2501?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Leif Hedstrom updated TS-2501:
------------------------------

    Issue Type: Improvement  (was: Bug)

> VariableExpander in header_rewrite is unnecessary expensive
> -----------------------------------------------------------
>
>                 Key: TS-2501
>                 URL: https://issues.apache.org/jira/browse/TS-2501
>             Project: Traffic Server
>          Issue Type: Improvement
>          Components: Plugins
>            Reporter: Leif Hedstrom
>            Assignee: Leif Hedstrom
>             Fix For: 4.2.0
>
>         Attachments: TS-2501.diff
>
>
> It seems that VariableExpander gets instantiated and executed on every add-header operator. However, this seems rather suboptimal for a number of reasons:
> 1. It might not even be necessary (i.e. there might not be any %<> strings in the "static" string.
> 2. Perhaps even more important, we look for these strings on every request, even though if they are there, they would always be in the same position on every request.
> One suggestion would be to incorporate the VariableExpander "state" as part of parsing the configuration on startup / reload. Maybe it gets complicated when there are other expansions, but it still feels we can pre-parse these strings and get some ideas of what needs to be expanded once, and not on every request.
> This is similar to how e.g. the regex_remap plugin works, it recalculates the positions and expansion once only.
> Thoughts?



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