CODEWITHSUNDEEP
asp.netentity-frameworkazureasp.net-coreazure-blob-storage
Paul
Paul

Reputation: 3142

Understanding App Insights end to end for occassional long response times

Background: I have an ASP.NET Core App and have an API method that takes a file name of a blob that the frontend has uploaded to Azure Blob. It then needs to create a thumbnail version of the blob and return the name of the newly uploaded thumbnail Blob. Sometimes, for exactly the same file size it can take up to 40 seconds to complete. Mostly, it's around 400ms.

Below is the end to end from App Insights, I have a few things I don't understand:

1) The request duration is 37.5 s but yet the other operations add up to nowhere near this time

2) Why are there calls to master db? We are using EF6 with multiple contexts

3) The app is using an Azure App Service and SQL Azure. I don't understand why the response time is so inconsistent.

Any help would be much appreciated! enter image description here

Upvotes: 3

Views: 1248

Answers (2)

GaussZ
GaussZ

Reputation: 881

1.

The way the request timeline is displayed gives you only the time-span for the whole request (37.5s) and the individual time-spans for each dependency.

A dependency being another call that sends its run-time to the application insights. In your example each call to the database is automatically tracked as a dependency. The code running after each database call is not though.

So e.g. requesting a database entry which takes 200ms and then issuing a Thread.Sleep of 2 seconds and requesting another database entry which takes 300ms would result in a 2 second gap between the two database-call dependencies which will each be listed with 200/300ms respectively.

You can use TelemetryClient.TrackDependency to wrap parts of your own code into its own dependency. This way you will see your own code as an entry on the request timeline.

2.

Depending on your EntityFramework database-initialisier EF will connect to the master db on context creation. (E.g. to create the database if it does not exist).

3.

Try tracking your own code to find out what parts of it are slow. EF has a few performance issues to consider, try to understand the performance caveats of the libs you use. If your calls are inconsistently slow it might be an issue with resources being over-utilized or caches being emptied too early (like for EF warm vs. cold queries).

Upvotes: 1

Itay Podhajcer
Itay Podhajcer

Reputation: 2654

I've noticed multiple time that the first request after an application is deployed to Azure or after a long period that no requests were made to the application, it takes significantly longer to get a response. As far as I remember it was related to start-up time of the site (if you're using an App Service on Windows based underlying VM it still uses IIS as a reverse proxy).

I solved the issue by configuring health checks that occasionally perform requests to the app.

Also, in addition to Application Insights (which logs information only after the application has started), you can try the tools listed here to see more information.

Hope it helps!

Upvotes: 1

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