Disable backend restart when web.config changes

[LarsAndreasEk]

Hi,

Can I disable the feature that restart the backend process whenever web.config is changed?

Best regards,
Lars Andreas

[shirhatti]

@LarsAndreasEk Just curious what you are trying to achieve here? It is unlikely we'll make this change, but I want to make sure we've given enough consideration to your request.

[LarsAndreasEk]

I have an app that needs to aggressively cache a lot of data into memory at startup. Takes about a minute. When it's deployed to IIS, we have a minute of downtime. I've considered various approaches, including taking the app in/out of the load balancer, blue/green deploy on a per machine basis with IIS web farm+URL rewrite, and so on. My idea at the time when I posted was this: - Have the IIS Application serve files from a static folder, which contains only the web.config with aspNetCore module config. - On deploy, place the new version of the app in a new folder somewhere else. Then modify the aspNetCore element web.config to point at the app's new location. - If touching the web.config wouldn't case the app to restart I could trigger an application pool recycle. Overlapped recycle would do its magic and let us deploy without that minute of downtime. I have, however, found a workaround: By placing the aspNetCore config in a separate file and referencing it from web.config via the configSource attribute, I'm able to modify that file without causing a restart. Thoughs? Suggestions for improvement? :)

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On Mon, 19 Jun 2017 at 23:10, Sourabh Shirhatti ***@***.***> wrote: @LarsAndreasEk <https://github.com/larsandreasek> Just curious what you are trying to achieve here? It is unlikely we'll make this change, but I want to make sure we've given enough consideration to your request. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#111 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAUbBV1YE91-H5KlF78zrMLgN2xyXQ3Eks5sFuOsgaJpZM4N483C> .

[shirhatti]

cc @pan-wang

[LarsAndreasEk]

Me being curious: What exactly is the mechanism that restarts an app when web.config is changed? Is the mechanism the same for asp.net core applications as for pre-core web apps?

[pan-wang]

For traditional asp.net application, both IIS and ASP.NET monitors the web.config. If there is a change, IIS will recycle the corresponding IIS application, ASP.NET will upload AppDomain (i.e., the managed application gets recycled). For ASP.NET, ASP.NET core module listen on IIS application recycle. Once the recycle, is triggered (e.g., Web.config change), Asp.net core module will notify the backend to exit to mimic the AppDomain unload behavior.

[pan-wang]

if you have to cache a lot of data for your app, you may want to use some cache service and run as an independent service. Your app just communicate with the cache service to retrieve the data.
using configSource can cheat the monitoring mechanism, but new configuration for your asp.net core app may not be adopted.

[LarsAndreasEk]

We've considered an external cache, but decided against it for performance reasons.

I'm trying to understand your last statement. In what way do you mean new configuration may not be adopted?

[LarsAndreasEk]

Also, any tips on how to achieve something similar for a traditional asp.net application/wcf?

[PonchoPowers]

See issue #84 which is a prime example of why we should be able to avoid a restart of the .NET Core process when the web.config file is changed.

[shirhatti]

Closing this issue as there's nothing actionable here. I suggested an alternative in #84 in how to possibly achieve what you're doing you want.