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Tutorial - Debug APIs in Azure API Management using request tracing
Follow the steps of this tutorial to enable tracing and inspect request processing steps in Azure API Management.
api-management
dlepow
azure-api-management
tutorial
11/04/2024
danlep
devdivchpfy22

Tutorial: Debug your APIs using request tracing

[!INCLUDE api-management-availability-all-tiers]

This tutorial describes how to inspect (trace) request processing in Azure API Management. Tracing helps you debug and troubleshoot your API.

In this tutorial, you learn how to:

[!div class="checklist"]

  • Trace an example call in the test console
  • Review request processing steps
  • Enable tracing for an API

:::image type="content" source="media/api-management-howto-api-inspector/api-inspector-002.png" alt-text="Screenshot showing the API inspector." lightbox="media/api-management-howto-api-inspector/api-inspector-002.png":::

Prerequisites

[!INCLUDE api-management-tracing-alert]

Trace a call in the portal

Follow these steps to trace an API request in the test console in the portal. This example assumes that you imported a sample API in a previous tutorial. You can follow similar steps with a different API that you imported.

  1. Sign in to the Azure portal, and navigate to your API Management instance.

  2. Select APIs > APIs.

  3. Select Petstore API from your API list.

  4. Select the Test tab.

  5. Select the Find pet by ID operation.

  6. In the petId Query parameter, enter 1.

  7. Optionally check the value for the Ocp-Apim-Subscription-Key header used in the request by selecting the "eye" icon.

    [!TIP] You can override the value of Ocp-Apim-Subscription-Key by retrieving a key for another subscription in the portal. Select Subscriptions, and open the context menu (...) for another subscription. Select Show/hide keys and copy one of the keys. You can also regenerate keys if needed. Then, in the test console, select + Add header to add an Ocp-Apim-Subscription-Key header with the new key value.

  8. Select Trace.

Review trace information

  1. After the call completes, go to the Trace tab in the HTTP response.

  2. Select any of the following links to jump to detailed trace info: Inbound, Backend, Outbound, On error.

    :::image type="content" source="media/api-management-howto-api-inspector/response-trace-1.png" alt-text="Review response trace":::

    • Inbound - Shows the original request API Management received from the caller and the policies applied to the request. For example, if you added policies in Tutorial: Transform and protect your API, they appear here.

    • Backend - Shows the requests API Management sent to the API backend and the response it received.

    • Outbound - Shows the policies applied to the response before sending back to the caller.

    • On error - Shows the errors that occurred during the processing of the request and the policies applied to the errors.

    [!TIP] Each step also shows the elapsed time since the request is received by API Management.

Enable tracing for an API

The following high level steps are required to enable tracing for a request to API Management when using curl, a REST client such as Visual Studio Code with the REST Client extension, or a client app. Currently these steps must be followed using the API Management REST API:

  1. Obtain a debug token for tracing.
  2. Add the token value in an Apim-Debug-Authorization request header to the API Management gateway.
  3. Obtain a trace ID in the Apim-Trace-Id response header.
  4. Retrieve the trace corresponding to the trace ID.

Detailed steps follow.

Note

  • These steps require API Management REST API version 2023-05-01-preview or later. You must be assigned the Contributor or higher role on the API Management instance to call the REST API.
  • For information about authenticating to the REST API, see Azure REST API reference.

  1. Obtain a debug token - Call the API Management gateway's List debug credentials API. In the URI, enter "managed" for the instance's managed gateway in the cloud, or the gateway ID for a self-hosted gateway. For example, to obtain trace credentials for the instance's managed gateway, use a request similar to the following:

    POST https://management.azure.com/subscriptions/{subscriptionId}/resourceGroups/{resourceGroupName}/providers/Microsoft.ApiManagement/service/{serviceName}/gateways/managed/listDebugCredentials?api-version=2023-05-01-preview

    In the request body, pass the full resource ID of the API that you want to trace, and specify purposes as tracing. By default the token credential returned in the response expires after 1 hour, but you can specify a different value in the payload. For example:

    {
    "credentialsExpireAfter": "PT1H",
    "apiId": "/subscriptions/{subscriptionId}/resourceGroups/{resourceGroupName}/providers/Microsoft.ApiManagement/service/{serviceName}/apis/{apiId}",
    "purposes": ["tracing"]
}

    [!NOTE] The apiId can only be pulled from the full resource ID, not the name displayed in the portal.

    Get apiId:

    az apim api list --resource-group <resource-group> --service-name <service-name> -o table

    The debug credential is returned in the response, similar to the following:

    {
      "token": "aid=api-name&......."
}

  2. Add the token value in a request header - To enable tracing for a request to the API Management gateway, send the token value in an Apim-Debug-Authorization header. For example, to trace a call to the Petstore API that you imported in a previous tutorial, you might use a request similar to the following:

    curl -v https://apim-hello-world.azure-api.net/pet/1 HTTP/1.1 \
    -H "Ocp-Apim-Subscription-Key: <subscription-key>" \
    -H "Apim-Debug-Authorization: aid=api-name&......."

  3. Evaluate the response - The response can contain one of the following headers depending on the state of the debug token:

    • If the debug token is valid, the response includes an Apim-Trace-Id header whose value is the trace ID, similar to the following:

      Apim-Trace-Id: 0123456789abcdef....

    • If the debug token is expired, the response includes an Apim-Debug-Authorization-Expired header with information about expiration date.

    • If the debug token was obtained for a different API, the response includes an Apim-Debug-Authorization-WrongAPI header with an error message.

  4. Retrieve the trace - Pass the trace ID obtained in the previous step to the gateway's List trace API. For example, to retrieve the trace for the managed gateway, use a request similar to the following:

    POST https://management.azure.com/subscriptions/{subscriptionId}/resourceGroups/{resourceGroupName}/providers/Microsoft.ApiManagement/service/{serviceName}/gateways/managed/listTrace?api-version=2023-05-01-preview

    In the request body, pass the trace ID obtained in the previous step.

    {
    "traceId": "0123456789abcdef...."
}

    The response body contains the trace data for the previous API request to the gateway. The trace is similar to the trace you can see by tracing a call in the portal's test console.

Example .http file for VS Code REST Client extension

To help automate these steps with the Visual Studio Code REST Client extension, you can use the following example .http file:

@subscriptionId = // Your subscription ID
@resourceGroup = // Your resource group
@apimName = // Your API Management service name
@clientId = // Client ID from an app registration for authentication
@clientSecret = // Client secret from app registration
@externalHost = // The host name of the App Gateway or the fully qualified gateway URL
@subscriptionKey = // API Management subscription key
@apiEndPoint = // API URL
@requestBody = // Data to send
@tenantId = // Tenant ID
 
POST https://login.microsoftonline.com/{{tenandId}}/oauth2/token
content-type: application/x-www-form-urlencoded
 
grant_type=client_credentials&client_id={{clientId}}&client_secret={{clientSecret}}&resource=https%3A%2F%2Fmanagement.azure.com%2F
 
###
@authToken = {{login.response.body.$.access_token}}
###
# @name listDebugCredentials
POST https://management.azure.com/subscriptions/{{subscriptionId}}/resourceGroups/{{resourceGroup}}/providers/Microsoft.ApiManagement/service/{{apimName}}/gateways/managed/listDebugCredentials?api-version=2023-05-01-preview
Authorization: Bearer {{authToken}}
Content-Type: application/json
{
    "credentialsExpireAfter": "PT1H",
    "apiId": "/subscriptions/{{subscriptionId}}/resourceGroups/{{resourceGroup}}/providers/Microsoft.ApiManagement/service/{{apimName}}/apis/{{apiId}}",
    "purposes": ["tracing"]
}
 
###
@debugToken = {{listDebugCredentials.response.body.$.token}}
 
###
# @name callApi
curl -k -H "Apim-Debug-Authorization: {{debugToken}}" -H 'Host: {{externalHost}}' -H 'Ocp-Apim-Subscription-Key: {{subscriptionKey}}' -H 'Content-Type: application/json' '{{apiEndPoint}}' -d '{{requestBody}}'
 
###
@traceId = {{callApi.response.headers.Apim-Trace-Id}}
 
###
# @name getTrace
POST https://management.azure.com/subscriptions/{{subscriptionId}}/resourceGroups/{{resourceGroup}}/providers/Microsoft.ApiManagement/service/{{apimName}}/gateways/managed/listTrace?api-version=2024-06-01-preview
Authorization: Bearer {{authToken}}
Content-Type: application/json
 
{
    "traceId": "{{traceId}}"
}

For information about customizing trace information, see the trace policy.

Next steps

In this tutorial, you learned how to:

[!div class="checklist"]

  • Trace an example call in the test console
  • Review request processing steps
  • Enable tracing for an API

Advance to the next tutorial:

[!div class="nextstepaction"] Use revisions