Loading all assemblies on startup, not on first request? (Warmup)

[leak]

Is there a clean way to handle all the assembly loading that is usually done at the first request right at the start of the application?

I know there is an extension for IIS (http://blogs.iis.net/thomad/now-available-the-iis-7-5-application-warm-up-module) which does exactly that.

How would one do that with Kestrel? Is there something better than http-getting the own website?

[guardrex]

Just for reference for the IIS case, that will be addressed: aspnet/IISIntegration#161 This is the first issue asking for a warmup for Kestrel IIRC.

[davidfowl]

Sending a request doesn't load all assemblies (unless you wrote code to do that in your application).

[leak]

Well it does load the assemblies that are required for serving the initial request, thus "warming up" the application.
Also, yes, I am looking for this in a Kestrel context, not IIS.

[davidfowl]

You need another thing to ping your app. Kestrel is part of your process.

[schmitch]

well actually isn't this something that a production app should always do? load all assemblies? I mean it's a little bit akward to "ping" an application. In Java the first request is also a little bit slower, but not that slow, actually.

[davidfowl]

well actually isn't this something that a production app should always do?

No, why would you force load all of your assemblies? That could destroy your startup time. Assemblies always load lazily.

[schmitch]

eh I don't care for startup time I care for fast web requests. I mean startup time doesn't matter, but if your user loads some sites slower it does matter.

[davidfowl]

Then you can load your assemblies by calling into them or by force loading everything.

[schmitch]

I'm not sure what you mean by force loading? do you mean something like:

http://stackoverflow.com/questions/37895278/how-to-load-assemblies-located-in-a-folder-in-net-core-console-app

Sorry but that looks more like a hack to me.
Also calling into them is not suitable. I mean I have a pretty "dumb" application which does not call into any database (yet). And the first request takes like 2s-3s, thats extremly slow. while instant startup looks good on paper it's akward if there is a 2s penalty for the first request.
I know that there might be cases where this is good, but for many users I doubt it isn't. at least provide a way to warmup the whole vm while trading startup time, maybe via dotnet --warmup my_application.dll, I like a lot yet about .net core (and I'm a java/scala guy as you can see in my github account), but this is not really to my liking that I need to at least make a single request via curl http://localhost:5000 to my app before I can use it. you can't call it "dotnet run starts instantly", while the application loads and loads after it.

[davidfowl]

I don't know what to tell you, there's no code that will be baked into the framework that will force load all assemblies by default. If you desperately want this, you can write some logic to force load all assemblies in the application (which won't really do much BTW) and "warm" up your application by calling relevant parts of the code.

[muratg]

We are closing this issue because no further action is planned for this issue. If you still have any issues or questions, please log a new issue with any additional details that you have.

[nzain]

The warmup / first request problem becomes critical, when running on small devices. I'm developing a REST service for an embedded arm device (Cortex-A7) and the first request (that simply returns an integer) takes more than 7 seconds (!). Subsequent requests finish in ~1 millisecond (!).

I will fire up a thread to GET some of my own resource, since seven seconds is far above typical timeout / user acceptance.

[secretorange]

I also think this is a useful and common request. For example, we would prefer to bring in our servers behind a load balancer after they're "warm".

If a server registers and is suddenly hit by 1000s of requests it can cause problems if it's not ready to go.