Overview
The log stream provides real-time access to container output. Use it to debug startup issues, monitor live traffic, and observe application behavior during testing. Streaming is for live visibility; enable container logging (filesystem) when you also need persisted history.
Short notes (exam revision)
- CLI command:
az webapp log tail - Portal path: Web App → Monitoring → Log stream
- Shows the same real-time output in browser or terminal
- Press Ctrl+C to stop streaming in the CLI
- Scaled-out apps: stream shows output from all instances; each line includes an instance identifier
- Best for: startup failures, live debugging, short test sessions — not long-term retention alone
Stream logs with Azure CLI
Azure CLI
az webapp log tail \
--resource-group myResourceGroup \
--name myDocumentProcessorThe log stream displays new entries as they appear. Stop with Ctrl+C.
Stream logs in the Azure portal
- Open your web app in the Azure portal
- Under Monitoring, select Log stream
- Watch the same real-time container output in the browser viewer
Multi-instance tip
When the app is scaled out, log stream includes lines from every instance. Use the instance identifier on each line to correlate which replica produced a message.
Use cases
- Container won't start — watch pull/start errors as they happen after a redeploy
- Validate a fix live — hit an API endpoint and confirm expected log lines appear immediately
- Traffic spikes during a demo/test — observe request and error output across instances
- Port / bind mistakes — see platform vs app messages when the site returns errors after deploy
Exam tips
- Associate Log stream ↔
az webapp log tail - Know it is real-time, not a full historical archive
- Scaled-out = all instances; lines are tagged with instance id
- Enable filesystem logging first if you need to keep logs after the stream session ends
Related
- Configure container logs (
az webapp log config+/home/LogFiles/) - Diagnostic console (Kudu) for browsing persisted files and env vars