Skip to main content
Question

HTTPCaller Test Request Cache - Bug or Feature?

  • July 23, 2026
  • 1 reply
  • 41 views
robdegroot
Participant
Forum|alt.badge.img+2

Hi all,

 

When sending a test request with a HTTPCaller, the Test Response Preview shows the response. When you close this window and reopen it later after closing and re-opening the workspace (even on another date) this response is still there (cached?). Depending on the URL used, this can lead to an unreasonably large workspace file.

 

Is this an intended feature, or an oversight that can slow down workspace performance if a user isn’t aware of this?

If there is a benefit to being able to revisit this test response at a later date, maybe it’s a good idea to be able to enable/disable this feature entirely. Or at least be able to ‘clear’ this Test Response Preview.

 

Kind regards,

 

Rob de Groot

 

An example URL that leads to a +20MB size increase of your workspace if a test response preview is opened:

https://services1.arcgis.com/ug8NBKcLHVNmdmdt/arcgis/rest/services/Peilvakken/FeatureServer/0/query?where=1%3D1&outFields=*&outSR=4326&f=json

If you do this for multiple HTTPCallers it can add up quickly and decrease performance significantly.

Tested on FME Form 2024.2 and 2026.1.

    1 reply

    evieatsafe
    Safer
    • evieatsafeSafer
    • Safer
    • August 10, 2026

    Hi ​@robdegroot, thanks for flagging this! What you are seeing is by design. The response from Send Test Request is stored in the workspace so you can revisit it later without having to fire the request again. The tradeoff, as you have found, is that a large response can inflate your fmw file quite a bit depending on the request.

    Right now there is not a setting to disable this caching, or a quick way to clear an individual Test Response Preview, other than adding a new HTTPCaller and reconfiguring the transformer. Given the workspace size impact you are describing, especially with larger ArcGIS REST responses like the one you shared, this is worth flagging as a product improvement. I encourage you to submit an idea on the Community Ideas board requesting a way to enable, disable, or clear this caching. Other FME Community users can upvote it, and our product team reviews ideas for future inclusion in FME.

    Looks like the cache from the Send Test Request is also preserved when duplicating the transformer or copying it to different workspaces. 

    In the meantime, if file size becomes an issue, running Send Test Request only when you actually need to inspect a response and avoiding it on very large payloads will help keep things manageable. Another alternative is sampling by one record and running the transformer with data caching enabled, then seeing the response in the data preview table. This would avoid the Send Test Request entirely. 

    Let us know if you have any other questions!

    Happy to help - Evie

    Community Stats

    32,839
    Posts
    124,527
    Replies
    41,407
    Members
    Terms & ConditionsAccessibility statement
    A product of
    Safe Software respectfully acknowledges that we live, learn and work on the traditional and unceded territories of the Kwantlen, Katzie, and Semiahmoo First Nations.