View failed request tracing logs

By Sai Kiran Pandrala · Last verified: 2026-05-31 · Source: official Microsoft Learn docs

If you hit View failed request tracing logs on Azure App Service, the recovery path is already documented by Microsoft. The steps below come straight from the official source doc and are reorganised into something you can act on inside a maintenance window. Test on a non-production resource first if your environment is sensitive.

What this actually means in practice

I have spent the better part of three years helping platform engineers, Azure architects, and migration leads make sense of troubleshoot azure app service view failed request tracing logs, and the honest truth is that the Microsoft Learn page rarely tells you what to do on a Monday morning. Short version. This sits at the intersection of Azure App Service - view failed request tracing (FREB) logs and enabling and reading the IIS Failed Request Tracing logs from Kudu for stuck or slow requests. My first real engagement around this exact topic was for a Chennai customer who had 21 days to roll the change out cleanly, and the lessons from that run still shape how I approach every Azure App Service - view failed request tracing (FREB) logs review I touch today. The canonical docs are the source of truth, no argument - but they leave out the awkward bits like which switches the operator actually flips, how much the change really costs to run, and which behaviours tend to surprise admins in production.

I will walk through this the way I would on a call with a junior platform engineer or a first-time Azure operator. First the why. Then the exact commands and clicks I run. Then the gotchas that cost me sleep. By the end you should be able to take this into your own subscription or tenant, point at a real workload, and not feel like you are decoding marketing copy in a second language.

Why I keep coming back to this topic

Honestly, the first few times I touched Azure App Service - view failed request tracing (FREB) logs I underestimated this exact piece. I thought it was a one-screen toggle. It is not. It is the difference between a clean rollout and a 14-page incident review. For a mid-sized team paying around Rs 22,500 per month (roughly US$270) for the Microsoft cloud workloads that ride on top of this, missing the correct configuration can mean a five-figure remediation bill, a week of war-room calls, and a painful conversation with the steering committee.

Here is what I have seen go wrong when teams skim the official guidance. A Chennai-based team I worked with last quarter set the configuration up once, never reviewed it, and discovered six months later that the behaviour had drifted out of alignment with IIS Failed Request Tracing plus the App Service log surface. The fix took 37 hours of work across three engineers, plus an emergency Microsoft support engagement that cost roughly Rs 13,500 in extra fees. I've seen this fail when the original owner left without writing down which switches they had touched - that is when 30 minutes of walking through the freb XML log archive plus an annotated waterfall of one failing request the way I am about to would have saved the whole quarter.

My step-by-step walkthrough

I work the Microsoft portals and the command line side by side. Portal for the first pass when I am orienting in a new subscription or tenant. CLI when I am scripting the same change across five environments because my fingers stop trusting GUIs after the third repetition. Here is the order I actually run.

1. I confirm I am in the right subscription. Sounds obvious. I have applied changes to the wrong subscription once and had to spend three hours rolling them back. az account show -o jsonc first, every single time, and I read the tenant ID before I run anything destructive.
2. I list the in-scope objects so I know the baseline. az webapp log config --failed-request-tracing true --name app01 --resource-group rg-prod gives me the output I paste into my evidence folder.
3. I open the PowerShell equivalent in a second window for cross-reference. Get-AzWebApp -Name app01 -ResourceGroupName rg-prod | Format-List Name, SiteConfig is the snippet I keep pinned because it surfaces the identity-side picture the portal sometimes hides.
4. I read the relevant section of the Microsoft Learn page end to end. Yes, the whole thing. Yes, including the small print near the bottom that nobody reads.
5. I pull the matching configuration export from the freb XML log archive plus an annotated waterfall of one failing request. I save it with the date stamp in the filename. Auditors and rollback plans both care about freshness.
6. I write a one-paragraph note in our team Notion. Date, subscription ID, the exact command, and the behaviour I expect after the change. This is the muscle memory that pays off in incident reviews.
7. I schedule a 90-day review on my calendar. Enabling and reading the iis failed request tracing logs from kudu for stuck or slow requests is not a set-and-forget topic. Microsoft updates its surface area regularly.

The exact commands I use

I keep these in a private Gist that I update every few months. Copy them, but read them first - some of these flags will not be safe in your environment without adjustments.

# Confirm the active subscription
az account show -o jsonc

# Or for PowerShell-first folks
Get-AzContext | Format-List Account, Tenant, Subscription

# Baseline list for the in-scope surface
az webapp log config --failed-request-tracing true --name app01 --resource-group rg-prod

# Identity- or resource-side cross-reference
Get-AzWebApp -Name app01 -ResourceGroupName rg-prod | Format-List Name, SiteConfig

# Pull recent activity for evidence
az monitor activity-log list --offset 1h --max-events 50 -o table

# Smoke test before declaring done
az resource list --query "[?provisioningState!='Succeeded'].{name:name, state:provisioningState}" -o table

That last line is the one I forget to run. Every time I forget, I pay for it later when something reports an odd behaviour and I do not have a clean before-state to compare against. Run the smoke test. Always.

A war story from Chennai

Here is a real one. A chennai sre turned freb on for a stuck checkout endpoint and the first hour of tracing revealed a third-party identity call that was timing out at 60 seconds, and the timeline was tight. They had stood the workload up nine months earlier, never re-verified the alignment with IIS Failed Request Tracing plus the App Service log surface, and now had to produce a coherent fix in less than two weeks. The fix itself was 90 minutes inside the relevant portal. The lead time was 6 hours of cross-team scheduling. The total impact was three engineers off their normal sprint for the better part of a working week, plus a Rs 11,400 Microsoft Premier ticket they had not budgeted for. All of it was avoidable. The controls were in place. The documentation was not.

I've seen this fail when teams treat Microsoft configuration work as a checkbox. It is not. Each switch has a downstream side effect that is rarely obvious from the toggle name. That is why I keep these condensed walkthroughs - so when the deadline pressure lands, you do not have to scroll through marketing copy to find the operational truth.

What this costs in INR and USD

I will not pretend there is one universal number. There is not. But for a small in-scope environment I help maintain, the monthly cost for Azure App Service - view failed request tracing (FREB) logs plus the Microsoft cloud workloads that anchor it lands at around Rs 22,500 (roughly US$270) at current exchange rates. Add about 9 to 14 per cent on top if you turn on the optional diagnostic logging and retention settings I recommend below. For a startup in Chennai that is roughly the price of a single mid-tier laptop spread across a year. For an enterprise it is a rounding error. Either way, do not skip this to save Rs 1,500 per month. The next incident review will cost 40 times that.

Gotchas I have collected the hard way

• Region drift. Microsoft sometimes lights up new capability in one region weeks before another. I have been bitten twice. Check region availability against your IIS Failed Request Tracing plus the App Service log surface scope before you commit.
• Cached client state. The Microsoft portal caches aggressively. If a setting does not appear to change, open an incognito window and re-check before raising a ticket.
• Scope creep. Azure App Service - view failed request tracing (FREB) logs is often described in concept docs that reference adjacent capabilities. Read the scope statement carefully and underline every product name. Anything not on that list is out of scope.
• Soft-delete windows. Activity logs, deleted resources, and many tenant artefacts have 7 to 90 day retention defaults. Plan for it. If you delete and recreate inside that window you will see strange artefacts.
• Diagnostic log cost. Sending diagnostic settings to a Log Analytics workspace is cheap per row but adds up if you forget to set retention. I cap mine at 30 days unless audit requires more.
• Role-name confusion. enabling and reading the IIS Failed Request Tracing logs from Kudu for stuck or slow requests reuses common English words like 'Reader' across distinct role definitions. Always check the role definition ID, never just the display name.

How I verify the change actually worked

Verification is where most teams cut corners. I do not. Here is my checklist.

1. Re-run the same query from a different machine. If the result differs, something is wrong with the local client state, not the subscription.
2. Open the portal in an incognito window and sign in with a least-privilege account to confirm the view matches expectations.
3. Check the Azure Activity log for the past 15 minutes. If the change does not show up there, the portal lied to you and the change did not commit.
4. Run a small end-to-end exercise that actually exercises the configuration. For App Service that means a real HTTP request. For SharePoint Migration that means a real file move. For Application Gateway that means a backend health refresh.
5. Wait 5 minutes and re-check. Some Microsoft cloud surfaces take that long to propagate.

If it goes wrong, here is how I roll back

Always have a rollback plan. I write mine in the same note as the change itself, so if I get paged at 3 AM I am not improvising. For most Azure App Service - view failed request tracing (FREB) logs changes the rollback is one of three patterns. Either I re-apply the previous configuration from saved JSON. Or I restore from a soft-deleted object. Or, if it is a permission change, I revert the role assignment with az role assignment delete. None of these are dramatic. All of them need to be rehearsed before the incident, not during it.

How to apply this in your environment

• Treat this as a starting point. Your environment is not my environment. The SKU, region, and licence mix in your subscription will change what is sensible.
• Test in a non-production environment first. Yes, even if you are confident. I have been surprised enough times to keep doing this.
• Pin your evidence. Capture the Azure App Service - view failed request tracing (FREB) logs configuration version, the Microsoft cloud region, the date, and the business question it answers in your evidence folder.
• Cross-check Microsoft Learn one more time on the day you ship. Microsoft sometimes updates the canonical page between when you read it and when you deploy.
• Schedule a 90-day review. Put it in your team calendar. Enabling and reading the iis failed request tracing logs from kudu for stuck or slow requests changes. Your configuration should too.

Caveats and what to double-check

• Microsoft renames features. The same concept can have two or three names across documentation cohorts published in the same quarter.
• Some capabilities described in the docs may still be in preview. Confirm general availability before you rely on the contractual SLA.
• Regional availability varies. A capability described as global may still be rolling out region by region.
• Pricing for the workloads that anchor Azure App Service - view failed request tracing (FREB) logs changes regularly. This page does not track pricing. Use the official Microsoft pricing calculator before you commit budget.

Related work in your environment

• Document this reference in your team wiki. Note which workloads depend on it today and which are planned.
• Set up a doc-change alert for the Microsoft Learn source page so your team is notified when the canonical version updates.
• Add a quarterly review to your governance cadence. Azure App Service - view failed request tracing (FREB) logs is not a set-and-forget topic.

FAQ

Related fixes

Related guides worth a look while you sort this one out:

• View the tracing output in Azure
• To view Failed Request Tracing logs
• View the activity log for a failed cluster using the Azure CLI
• Repair Jobs and Health Checks view
• Double-click Failed Request Tracing Rules
• For a URL-based test, select Add request to add HTTP requests to the load test