Querying logs for Azure resources

Article
10/28/2024

In Azure Monitor Log Analytics, queries typically execute in the context of a workspace. A workspace may contain data for many resources, making it difficult to isolate data for a particular resource. Resources may additionally send data to multiple workspaces. To simplify this experience, the REST API permits querying Azure resources directly for their logs.

Response format

Azure resource queries produce the same response shape as queries targeting a Log Analytics workspace.

URL format

Consider an Azure resource with a fully qualified identifier:

/subscriptions/<sid>/resourceGroups/<rg>/providers/<providerName>/<resourceType>/<resourceName>

A query for this resource's logs against the direct API endpoint would go to the following URL:

https://api.loganalytics.azure.com/v1/subscriptions/<sid>/resourceGroups/<rg>/providers/<providerName>/<resourceType>/<resourceName>/query

A query to the same resource via ARM would use the following URL:

https://management.azure.com/subscriptions/<sid>/resourceGroups/<rg>/providers/<providerName>/<resourceType>/<resourceName>/providers/microsoft.insights/logs?api-version=2018-03-01-preview

Essentially, this URL is the fully qualified Azure resource plus the extension provider: /providers/microsoft.insights/logs.

Table access and RBAC

The microsoft.insights resource provider exposes a new set of operations for controlling access to logs at the table level. These operations have the following format for a table named tableName.

microsoft.insights/logs/<tableName>/read

This permission can be added to roles using the actions property to allow specified tables and the notActions property to disallow specified tables.

Workspace access control

Azure resource queries look over Log Analytics workspaces as possible data sources. However, administrators can lock access to the workspace via RBAC roles. By default, the API only returns results from workspaces the user has permissions to access.

Workspace administrators can use Azure resource queries without breaking existing RBAC. A boolean property on the workspace lets users with read permissions view logs for a specific Azure resource but not query the workspace which contains those logs.

This is the action for scoping access to Tables at the workspace level:

microsoft.operationalinsights/workspaces/query/<tableName>/read

Error responses

Here's a brief listing of common failure scenarios when querying Azure resources along with a description of symptomatic behavior.

Azure resource doesn't exist

HTTP/1.1 404 Not Found
{ 
    "error": { 
        "message": "The resource /subscriptions/7fd50ca7-1e78-4144-ab9c-0ec2faafa046/resourcegroups/test-rg/providers/microsoft.storage/storageaccounts/exampleResource was not found", 
        "code": "ResourceNotFoundError" 
    }
}

No access to resource

HTTP/1.1 403 Forbidden 
{
    "error": { 
        "message": "The provided credentials have insufficient access to  perform the requested operation", 
        "code": "InsufficientAccessError", 
        "innererror": { 
            "code": "AuthorizationFailedError",
            "message": "User '92eba38a-70da-42b0-ab83-ffe82cce658f' does not have access to read logs for this resource"
        }
    } 
}

No logs from resource, or no permission to workspace containing those logs

Depending on the precise combination of data and permissions, the response either contains a 200 with no resulting data, or throws a syntax error (4xx error).

Partial access

There are some scenarios where a user may have partial permissions to access a particular resource's logs. This is the case if the user is missing either:

Access to the workspace containing logs for the Azure resource.
Access to the tables reference in the query.

They see a normal response, with data sources the user doesn't have permissions to access silently filtered out. To see information about a user's access to an Azure resource, the underlying Log Analytics workspaces, and to specific tables, include the header Prefer: include-permissions=true with requests. This causes the response JSON to include a section like the following example:

{ 
    "permissions": { 
        "resources": [ 
            { 
                "resourceId": "/subscriptions/<id>/resourceGroups<id>/providers/Microsoft.Compute/virtualMachines/VM1", 
                "dataSources": [ 
                    "/subscriptions/<id>/resourceGroups<id>/providers/Microsoft.OperationalInsights/workspaces/WS1" 
                ] 
            }, 
            { 
                "resourceId": "/subscriptions/<id>/resourceGroups<id>/providers/Microsoft.Compute/virtualMachines/VM2", 
                "denyTables": [ 
                    "SecurityEvent", 
                    "SecurityBaseline" 
                ], 
                "dataSources": [ 
                    "/subscriptions/<id>/resourceGroups<id>/providers/Microsoft.OperationalInsights/workspaces/WS2",
                    "/subscriptions/<id>/resourceGroups<id>/providers/Microsoft.OperationalInsights/workspaces/WS3" 
                ] 
            } 
        ], 
        "dataSources": [ 
            { 
                "resourceId": "/subscriptions/<id>/resourceGroups<id>/providers/Microsoft.OperationalInsights/workspaces/WS1", 
                "denyTables": [ 
                    "Tables.Custom" 
                ] 
            }, 
            { 
                "resourceId": "/subscriptions/<id>/resourceGroups<id>/providers/Microsoft.OperationalInsights/workspaces/WS2" 
            } 
        ] 
    } 
}

The resources payload describes an attempt to query two VMs. VM1 sends data to workspace WS1, while VM2 sends data to two workspaces: WS2 and WS3. Additionally, the user doesn't have permission to query the SecurityEvent or SecurityBaseline tables for the resource.

The dataSources payload filters the results further by describing which workspaces the user can query. Here, the user doesn't have permissions to query WS3, and another table filtered out of WS1.

To clearly state what data such a query would return:

Logs for VM1 in WS1, excluding Tables. Custom from the workspace.
Logs for VM2, excluding SecurityEvent and SecurityBaseline, in WS2.

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