[jira] [Commented] (TS-2364) Introduce slice notation to field syntax in log format

["ASF subversion and git services (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/TS-2364?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14231770#comment-14231770 ] 

ASF subversion and git services commented on TS-2364:
-----------------------------------------------------

Commit 8c618e58ecd37a853769d11dc4023ceb8f78e75e in trafficserver's branch refs/heads/master from [~sudheerv]
[ https://git-wip-us.apache.org/repos/asf?p=trafficserver.git;h=8c618e5 ]

[TS-2364] - Update logging documentation with log slicing feature


> Introduce slice notation to field syntax in log format
> ------------------------------------------------------
>
>                 Key: TS-2364
>                 URL: https://issues.apache.org/jira/browse/TS-2364
>             Project: Traffic Server
>          Issue Type: New Feature
>          Components: Logging
>            Reporter: Yunkai Zhang
>            Assignee: Yunkai Zhang
>             Fix For: 4.2.0
>
>         Attachments: 0001-TS-2364-Introduce-slice-notation-to-field-syntax-in-.V2.patch, 0001-TS-2364-Introduce-slice-notation-to-field-syntax-in-.patch
>
>
> Now, we have two kind of field syntax in log format:
> {code}
> (1) simple; syntax: '%<field>', for example: %<cqu>
> (2) container field, syntax '%<{field}container>', for example: %<{Referer}cqh>.
> {code}
> I'm going to introduce slice notation, so that we can easy to limit the length of filed's output. With slice notation, the filed syntax will looks like:
> {code}
> (1) '%<field[start:end]>'
> (2) '%<{field}container[start:end]>'
> {code}
> In both forms, slice notation can be omitted, which means the whole field. But with one limitation: slice notation makes sense only when the field is string type and it shouldn't be ip/timestamp which are converted to string from integer.
> We can see the syntax of slice notation from Python, Golang, it's pretty simple:
> {code}
> [start:end] //items start through end-1
> [start:]    //items start through the rest of the array
> [:end]      //items from the beginning through end-1
> [:]         //the whole array(by default)
> {code}
> For example, 
> {code}
> '%<cqh>'       //the whole characters of <cqh>.
> '%<cqh>[:]'    //the whole characters of <cqh>.
> '%<cqh[0:30]>' //the first 30 characters of <cqh>.
> '%<cqh[-10:]>' //the last 10 characters of <cqh>.
> '%<cqh[:-5]>'  //everything except the last 5 characters of <cqh>.
> {code}



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