Where can I find docker container logs for Azure App Service

Question

I do have a Docker container running a .net core 2 app.

The logging is configured using this code in Program.cs

public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
    WebHost.CreateDefaultBuilder(args)
        .ConfigureLogging((hostingContext, logging) =>
        {
            logging.AddConfiguration(hostingContext.Configuration.GetSection("Logging"));
            logging.AddConsole();
            logging.AddDebug();
        })
        .UseStartup<Startup>();

and the appsettings.json file

{
  "Logging": {
    "LogLevel": {
      "Default": "Information"
    }
  },
}

Logging seems to be Ok, when running Kestrel directly, I can see the logs in the terminal. Same thing, when containerized: the command docker logs shows what I want.

Troubles arise in production, when run in as a container in Azure Web App. I cannot find any consistent docker logs.

I made attempts to visit the Log file via FTP or via the url https://[mysite].scm.azurewebsites.net/api/logs/docker the log files are almost empty for example, https://[mysite].scm.azurewebsites.net/api/vfs/LogFiles/2018_09_09_RD0003FF74F63E_docker.log, only container starting lines are present

Also I do have the same lines in the usual portal interface.

The question is: do docker logs are automatically output in docker.log files in Azure Web App? Is there something that I am missing?

Solution 1

Firstly you need to enable container logs

[App Service] -> Monitoring -> App Service logs

Then you can see container logs in [App Service] -> Monitoring -> Log stream

UPD

Also you can find logs in KUDU

Then "Current Docker Logs"

Solution 2

I've been cursing this for a good while, and eventually found something that works for me.

First I enabled filesystem logging as per @dima_horror's answer.

Next I ran a command-line az webapp log tail --name myApp --resource-group myRg

That now seems to give me useful output (it gave me nothing prior to enabling filesystem logging).

Solution 3

Have you checked the logs in container settings? I followed this guide to deploy a container to Azure web app.

Solution 4

To add to the answers, if you're having trouble with deploying the image in your App Service and need logs for that specifically, you can get the docker logs for the provisioning phase of your container under Deployment Center, e.g.:

View more solutions

Comments

[Benoit Patra]

Yes as I wrote, I do have exactly the same lines, the docker run command and that's it. No other logs from the app itself.

[Mitch Stewart]

Do you see anything if you get the logs via CLI (docs.microsoft.com/en-us/azure/container-instances/…)?

[Benoit Patra]

You sure that az container commands are supposed to be used with Azure Web App? I cannot find the proper container, when I do az container list I do receive an empty array for answer. Looks like it is meant for Azure Container Instance

[Mitch Stewart]

I came across this article (docs.microsoft.com/en-us/azure/app-service/containers/…) and thought back to your question.

[Benoit Patra]

Actually, I just click off then on back and now I do have much more logs but I still cannot see the Application Logs I can only see Server logs

[ashur]

This is frustrating that you can't simply get logs in the portal - Log stream is mixing logs from Kudu and app logs :/

[David Carboni]

I've found a coping mechanism for this. az webapp log tail ... only provides a few lines of container output. Above those lines there's a URL which, providing you're authenticated with Azure, gives you more output. So: I first tail (to get the latest URL), then paste the link into my browser. It's a workaround (and a poor experience) but it's possible. I'd love to know if/when there's an easier way.

[Matthias Güntert]

az webapp log tail does not seem to work for linux app plans.

[kiloton]

is there any way to stream those to the Azure CLI as well?