Not able to See the logs in Azure function app.

Question

Not able to See the logs in Azure function app.

Urmila Purohit 60

We are using Azure API Managed service and Azure function app(consumption plan) and we are facing 429 error code in response. Due to consumption plan I am not able to enable the logs. Is there any way to enable the logs without changing the consumption plan?
What is the cause of 429 error code? How I can debug that

Khadeer Ali 5,990 Reputation points Microsoft External Staff Moderator

2025-05-12T12:28:24.29+00:00
Urmila Purohit

Thank you for reaching out.

We understand you're facing HTTP 429 errors (Too Many Requests) while using Azure API Management in front of an Azure Function App on the Consumption Plan and also having difficulty enabling logs due to the plan restrictions.

Logging on Consumption Plan is Possible with Application Insights Even on a Consumption Plan, you can absolutely enable detailed telemetry. Here’s how to do it confidently without changing your plan:

In your Function App, go to Settings → Application Insights and enable it.

Make sure you use the newer APPLICATIONINSIGHTS_CONNECTION_STRING (instead of the older APPINSIGHTS_INSTRUMENTATIONKEY) for future compatibility.

Once enabled, logs will be captured and accessible via the Application Insights resource in the Azure Portal.

You can also use Live Metrics Stream for real-time monitoring, which works reliably on Consumption Plans.

429 Error Root Cause: Throttling HTTP 429 means your request volume is exceeding some limit. Based on your setup, this could be due to:

Rate limiting at the Azure API Management layer (common cause)

Execution limits of the Function App (Consumption Plan) – which auto-scales but does have burst constraints.

Throttling from a downstream service (like Cosmos DB, third-party APIs, etc.)

To determine the exact cause:

Enable Diagnostic Logs in API Management and check if any rate-limit or quota policies are being applied.

Check the response headers in the 429 response (e.g., Retry-After, x-ratelimit-remaining) to see where the throttling is happening.

Use Application Insights queries like below to pinpoint which function or API path is triggering the 429s:

requests | where resultCode == "429" | summarize count() by bin(timestamp, 5m), operation_Name
If the 429s are caused by hard quotas on the Consumption Plan (which auto-scales but still has concurrency limits), there is no guaranteed fix on the Consumption Plan alone beyond optimizing and reducing the request load or using retries. In such cases, scaling to a Premium Plan may be the only reliable fix.
Urmila Purohit 60 Reputation points

2025-05-12T12:41:16.5066667+00:00

Hii Khadeer Ali,
Thanks for your answer
Application insight logs are already enable on function but they are not showing the logs related to traffic of API gateway. My requirement is to monitor the API gateway traffic logs of incoming and outgoing requests. Do you know how can I see the API gateway incoming/outgoing traffic logs?
Please let me know your answer.
Khadeer Ali 5,990 Reputation points Microsoft External Staff Moderator

2025-05-12T15:18:47.1833333+00:00
@Urmila Purohit ,

Although Application Insights is already enabled on the Function App, it does not capture logs related to the traffic at the API Management Gateway level. This is by design, as Application Insights is scoped to monitor the Function App's internal telemetry — such as function executions, exceptions, and dependencies — and not the traffic flowing through Azure API Management.

To fully monitor incoming and outgoing traffic on the API Gateway, including metrics like request/response size, status codes, latency, and throttling (e.g., 429s), you’ll need to:

Configure Diagnostic Logs for API Management to Send Data to Log Analytics

Go to your API Management resource in the Azure Portal.

Navigate to Diagnostic settings.

Choose relevant log categories (e.g., “Logs related to API Management Gateway” — which you already have selected).

Under Destination details, choose "Send to Log Analytics workspace".

Select or create a Log Analytics workspace and click Save.

Once set up, you can query gateway-level traffic logs using KQL in Log Analytics. Here's an example query to get started:

AzureDiagnostics | where ResourceType == "APIMGatewayLogs" | sort by TimeGenerated desc

This is the recommended and supported approach to monitor API gateway-level traffic in Azure. At this time, there is no supported method to stream these gateway logs directly to Application Insights.
Urmila Purohit 60 Reputation points

2025-05-13T04:07:22.09+00:00

Ok, got it. So, is there any other way to find out the root cause of error "429 Too Many Requests" ? because we have not set any rate limit.
Khadeer Ali 5,990 Reputation points Microsoft External Staff Moderator

2025-05-15T12:54:08.9033333+00:00

@Urmila Purohit ,

I wanted to check in and see if my earlier response addressed your question. If you still need assistance or have additional questions, feel free to reach out.
Khadeer Ali 5,990 Reputation points Microsoft External Staff Moderator

2025-05-20T12:21:17.98+00:00

@Urmila Purohit Just following up again to see if you were able to address your queries or if there's anything else I can assist you with.

1 answer

Your answer

Urmila Purohit 60 Reputation points

2025-05-12T12:41:16.5066667+00:00

Hii Khadeer Ali,
Thanks for your answer
Application insight logs are already enable on function but they are not showing the logs related to traffic of API gateway. My requirement is to monitor the API gateway traffic logs of incoming and outgoing requests. Do you know how can I see the API gateway incoming/outgoing traffic logs?
Please let me know your answer.
Khadeer Ali 5,990 Reputation points Microsoft External Staff Moderator

2025-05-12T15:18:47.1833333+00:00

@Urmila Purohit ,

Although Application Insights is already enabled on the Function App, it does not capture logs related to the traffic at the API Management Gateway level. This is by design, as Application Insights is scoped to monitor the Function App's internal telemetry — such as function executions, exceptions, and dependencies — and not the traffic flowing through Azure API Management.

To fully monitor incoming and outgoing traffic on the API Gateway, including metrics like request/response size, status codes, latency, and throttling (e.g., 429s), you’ll need to:

Configure Diagnostic Logs for API Management to Send Data to Log Analytics

Go to your API Management resource in the Azure Portal.

Navigate to Diagnostic settings.

Choose relevant log categories (e.g., “Logs related to API Management Gateway” — which you already have selected).

Under Destination details, choose "Send to Log Analytics workspace".

Select or create a Log Analytics workspace and click Save.

Once set up, you can query gateway-level traffic logs using KQL in Log Analytics. Here's an example query to get started:

AzureDiagnostics | where ResourceType == "APIMGatewayLogs" | sort by TimeGenerated desc

This is the recommended and supported approach to monitor API gateway-level traffic in Azure. At this time, there is no supported method to stream these gateway logs directly to Application Insights.
Urmila Purohit 60 Reputation points

2025-05-13T04:07:22.09+00:00

Ok, got it. So, is there any other way to find out the root cause of error "429 Too Many Requests" ? because we have not set any rate limit.
Khadeer Ali 5,990 Reputation points Microsoft External Staff Moderator

2025-05-15T12:54:08.9033333+00:00

@Urmila Purohit ,

I wanted to check in and see if my earlier response addressed your question. If you still need assistance or have additional questions, feel free to reach out.
Khadeer Ali 5,990 Reputation points Microsoft External Staff Moderator

2025-05-20T12:21:17.98+00:00

@Urmila Purohit Just following up again to see if you were able to address your queries or if there's anything else I can assist you with.

Answer 1

@Urmila Purohit ,

Thanks for the follow-up. I understand you're receiving 429 Too Many Requests errors, and you'd like to get to the bottom of it — especially since no explicit rate limiting has been configured.

We've looked into this, and I can confirm that these 429 responses are most likely being triggered due to platform-level throttling applied by Azure on the App Configuration Store or the hosting plan (e.g., API Management, Function App, etc.), even if no custom throttling policy is set.

Azure enforces internal quotas depending on the tier you're using — such as Free, Developer, or Standard. A 429 response typically indicates one of the following:

Request/throughput quota has been exceeded.
Bandwidth limit for the tier is hit.
Too many operations (like reads/writes to key-values) are occurring within a short time.
In some Function App plans (especially Consumption), cold starts or parallel executions may hit limits.

Even in the absence of user-defined rate limits, these service-level controls can lead to throttling.

To get a precise reason, I recommend:

Capturing the 429 response body — it often includes the specific reason for throttling.
Checking diagnostic logs on the App Configuration Store. Enabling and streaming logs to Log Analytics can help you monitor request volume, failures, and throttling patterns.
Reviewing the Request Quota Usage metric — this metric reflects how close you are to the tier limits.

If you’re using an API Management gateway, you can enable Diagnostic Logs related to Gateway Logs and stream them to Log Analytics to get a clearer view of incoming/outgoing traffic patterns.

If the 429s are frequent or impacting production:

Upgrade to the Premium tier – this removes most request/throughput limits.
Implement caching/retries – use SDKs or providers with built-in retry logic.
Distribute traffic load – scaling out across client instances can help.
Reduce config reads – e.g., cache configs locally and reduce polling frequency.

The same was documented here:
https://learn.microsoft.com/en-us/azure/azure-app-configuration/faq#my-application-receives-http-status-code-429-responses--why

Hope this helps. Do let us know if you have any further queries.

If this answers your query, do click Accept Answer and Yes for "Was this answer helpful." And if you have any further questions, let us know.

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Not able to See the logs in Azure function app.

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