Logging

There are a selection of different diagnostics to assist with debugging an App Service app. The following table shows types, support, storage location and a description:

Type	Platform	Location	Description
Application logging	Windows, Linux	File system Blob storage	Logs generated by your application (Critical, Error, Warning, Information, Debug, Trace).
Deployment logging	Windows, Linux	File system	Deployment logs for debugging failed deployments.
Web server logging	Windows	File system Blob storage	Raw HTTP request data.
Detailed error messages	Windows	File system	Copies of the HTML debug pages that are displayed outside of production.
Failed request tracing	Windows	File system	Trace of failed requests, IIS components used, duration in each component, each failed request generates a separate XML/XSL report.

Configuration

Instructions for enabling optional logging.

Application

Windows
1. App Service logs
2. Application Logging (Filesystem) or (Blob) set to On
  - Filesystem is for short term logging (turned off after 12 hours)
  - Blob is for long-term logging and requires an Azure storage account
3. Set the log level (Disabled, Error, Warning, Information, Verbose)
4. Save
Linux/container
1. App Service logs
2. Quota (MB) - set disk quota for logs
3. Retention Period (Days - set number of days retention
4. Save

Web server

Only available on Windows

App Service logs
Web server logging
- Storage for blob storage (set storage container and Retention Period (Days))
- File System for file system (set Quota (MB) and Retention Period (Days))
Save

Streaming

Azure portal
- Log stream
CLI/Cloud Shell
- az webapp log tail --name appname --resource-group myResourceGroup

Usage

You can log to application logs using System.Diagnostics.Trace:

System.Diagnostics.Trace.TraceError("If you're seeing this, something bad happened");

Access

You can access your stored logs in different ways depending on the storage method:

Filesystem
- Linux: https://<app-name>.scm.azurewebsites.net/api/logs/docker/zip
- Windows: https://<app-name>.scm.azurewebsites.net/api/dump
Blob
- Use a client tool that works with Azure storage

Linux/container logs

The zip file at the address above contains both docker host and container logs. For scaled-out apps, the ZIP container logs for each instance individually.