Azure / Azure/azure-functions-host

Warmup trigger behavior on Dedicated plan scale out

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#9,737 10 comments 0 reactions 0 assignees View on GitHub
needs-discussion Needs: Triage (Functions)
Dominant language
C#
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Merged PRs (30d)
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Description

#### Is your question related to a specific version? If so, please specify: v4

#### What language does your question apply to? (e.g. C#, JavaScript, Java, All)
C#

#### Question
We have http trigger endpoints that serves as public apis and we have warmup trigger as well as to load the dependenciesfor the scale out operations.
But we are not seeing the correct behavior according to the [doc ](https://learn.microsoft.com/en-us/azure/azure-functions/functions-bindings-warmup?tabs=isolated-process%2Cnodejs-v4&pivots=programming-language-csharp).

According to the documentation, when we do the scale out we expect the warmup trigger to load first and not let any other request come in until the warmup finishes its job. But for us some http requests fires before the warmup in the new instance which makes the initial requests slow because the dependencies are not loaded properly and thus experiencing cold start.

Is there anything we have to do other than creating a warmup trigger or is it not guaranteed that warmup will be the first request for a new instance?

Contributor guide

Open the contributing guide

Research direction

Start by reading the linked Azure Functions warmup trigger documentation for v4 and C#, then inspect the host's scale-out and warmup request-ordering entry points. Done means establishing whether warmup is guaranteed before HTTP requests on Dedicated plan instances and documenting any required configuration or the observed limitation.

Written by the indexing model from the issue text.

Assessment

Tech stack
azure, csharp
Domain
backend, cloud
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
25/100

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