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daniel-strmecki
Community Advisor and Adobe Champion
daniel-strmeckiCommunity Advisor and Adobe Champion
Community Advisor and Adobe Champion
November 6, 2024
Investigating

Add support for ETag in Dispatcher

  • November 6, 2024
  • 3 replies
  • 779 views
Request for Feature Enhancement (RFE) Summary: Since the Dispatcher doesn't support ETags it creates unnecessary traffic between the Dispatcher and the CDN by sending unchanged content.
Use-case: The page is cached on both CDN and Dispatcher. CDN sends a request to the Dispatcher with the f-None-Match header. The Dispatcher responds with HTTP 200 and the content in the body, even though the content hasn't changed and the CDN already has the latest version.
Current/Experienced Behavior: The Dispatcher is always returning HTTP 200 code when delivering cached content. Even when the cache ETag header value matches the value of the If-None-Match header in the request.
Improved/Expected Behavior: The expected behavior would be for the Dispatcher to return HTTP 304 code with no body when ETag matches the value of the If-None-Match header.
Environment Details (AEM version/service pack, any other specifics if applicable): Latest AEMaaCS - 2024.10.18311.20241017T104455Z
Customer-name/Organization name: Assa Abloy
Screenshot (if applicable):
Code package (if applicable):  

    3 replies

    kautuk_sahni
    Community Manager
    kautuk_sahniCommunity Manager
    Community Manager
    November 21, 2024

    @daniel-strmecki 

    Thanks for proposing this idea.
    This has been reported to the engineering under the internal reference SITES-27072. The product team will triage this request to verify feasibility based on the prioritization model. This post will be updated according to Jira's status.
    Kautuk Sahni
    radu_cotescu
    Adobe Employee
    radu_cotescuAdobe Employee
    Adobe Employee
    February 17, 2025

    This can be enabled at the project level with the help of the FileETag httpd directive [0].

     

    [0] - https://httpd.apache.org/docs/2.4/mod/core.html#fileetag

    daniel-strmecki
    Community Advisor and Adobe Champion
    daniel-strmeckiCommunity Advisor and Adobe ChampionAuthor
    Community Advisor and Adobe Champion
    February 17, 2025

    @radu_cotescu not exactly, this directive is used to generate ETags on Apache.

    When generating ETags on AEM, we would need to set "DeflateAlterETag NoChange" as per the Apache documentation: https://httpd.apache.org/docs/trunk/mod/mod_deflate.html#deflatealteretag

     

    However, when I set this nothing changes and I see the following entry in the logs "Apache configuration uses non-allowlisted directives". Therefore, this directive should be whitelisted by Adobe.

     

    BR,

    Daniel

     

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