[jira] [Resolved] (SLING-7813) SlingHttpServletResponseImpl should log when setStatus is called after it is committed

["Julian Sedding (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SLING-7813?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Julian Sedding resolved SLING-7813.
-----------------------------------
       Resolution: Fixed
    Fix Version/s: Engine 2.6.12

Thanks for the review [~rombert]! I have merged the PR. Fixed with [commit bc9696b|https://gitbox.apache.org/repos/asf?p=sling-org-apache-sling-engine.git;a=commitdiff;h=bc9696b].

> SlingHttpServletResponseImpl should log when setStatus is called after it is committed
> --------------------------------------------------------------------------------------
>
>                 Key: SLING-7813
>                 URL: https://issues.apache.org/jira/browse/SLING-7813
>             Project: Sling
>          Issue Type: Improvement
>          Components: Engine
>    Affects Versions: Engine 2.6.12
>            Reporter: Julian Sedding
>            Assignee: Julian Sedding
>            Priority: Minor
>             Fix For: Engine 2.6.12
>
>          Time Spent: 0.5h
>  Remaining Estimate: 0h
>
> I have been debugging a scenario, where a response did not have the (in this case) expected status code {{500}} set by an error handling script, but instead the status code was {{200}}.
> It turns out that a rendering script calls {{#flushBuffer()}} on the response early on in order to optimize user experience. Later in the rendering chain a JSP causes a {{NullPointerException}}, triggering an error handler which calls {{#setStatus(500)}}. The {{#setStatus}} call is silently ignored.
> "Fixing" this problem would require buffering the entire response and ignoring any flush calls (be it {{#flushBuffer()}}, {{#getWriter().flush()}} or {{#getOutputStream().flush()}}). This would be a change in behaviour, a violation of the Servlet spec and performance issues waiting to happen. Thus I am ruling out this option.
> However, it would be helpful to improve "debuggability" of the problem. I propose to log a warning when {{#setStatus()}} is called. Additionally, if debug logging is enabled, I propose to log a stack trace to identify where the flush call originated (unless the flush was due to too many bytes written, which is not very helpful information).
> cc [~rombert]



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