Azure WebApp DATAOUT流量突增问题排查求助

Hey Larry, let's break down how to track down that unexpected 230MB DATAOUT spike you saw at 9:48 ET. Even though you don't have large media files or FTP enabled, there are still a few key places to look in Azure's tooling:

• Dive into Azure Monitor HTTP logs
  Azure Monitor has all the HTTP request details you need—you just need to query the right logs. Head to the Logs section in your App Service resource, and run a query like this to zero in on the spike window:

  AzureDiagnostics
  | where Category == "AppServiceHTTPLogs"
  | where TimeGenerated between (datetime(202X-MM-DD 09:47)..datetime(202X-MM-DD 09:49))
  | summarize TotalBytesSent = sum(SentBytes) by CsUriStem, ClientIpAddress, HttpStatusCode
  | order by TotalBytesSent desc
  

  This will show you which request paths or client IPs are sending the most data. Look for things like:

  • A single client hitting one endpoint hundreds of times
  • A request returning an unusually large payload (even if you don't have big media, a broken endpoint might be dumping massive error stacks or raw database data)

• Check for application errors
  If your app threw unhandled exceptions around that time, it might be returning full stack traces or verbose error pages that add up to big bytes. Check your App Service's Log Stream or your app's internal logging system for errors at 9:48. Even a handful of errors with huge response bodies could hit that 230MB mark.

• Rule out Azure internal traffic
  Sometimes Azure's health checks, backup processes, or internal service calls can generate traffic, but they're usually consistent. You can filter out Azure's internal IP ranges in your log query to confirm if the spike came from external users.

• Verify background tasks/WebJobs
  If you're running WebJobs or scheduled tasks in your App Service, double-check if any of them ran at 9:48. A task that exports bulk data, calls an API and returns large responses, or syncs data externally could be the culprit.

• Check CDN/caching settings (if used)
  If you have Azure CDN set up, a cache purge or misconfigured TTL might have caused a flood of origin requests, all pulling data from your App Service and contributing to DATAOUT.

Start with the HTTP log query—it's the fastest way to narrow down exactly what's sending that data. Let me know if you find anything odd in the results!

内容的提问来源于stack exchange，提问作者LarryBud