Evaluate response status code and failure metrics

Response Status Codes

When interacting with Azure Cosmos DB, various HTTP status codes can be returned as part of the response. These codes help us understand the outcome of the request and take appropriate actions based on the success or failure of the operation. Here are some important status codes:

• 200 – Success: This status code indicates that the request was successful, and the response body contains the requested data.
• 201 – Created: This code is returned when a new resource is successfully created in Azure Cosmos DB, such as a new document or collection.
• 202 – Accepted: It signifies that the request has been accepted for further processing, but the operation is not yet completed. This can occur in scenarios like bulk import of data, where the completion might take some time.
• 204 – No Content: This status code indicates that the request was successful, but there is no content to return. For example, when deleting a resource, the server may return a 204 status code to confirm successful deletion.
• 400 – Bad Request: This code is returned when the request is malformed, missing required parameters, or has invalid data. It indicates an issue with the client’s request.
• 401 – Unauthorized: When the request lacks valid authentication credentials, this status code is returned. It suggests that the client needs to authenticate before retrying the request.
• 404 – Not Found: This code is returned when the requested resource is not found in Azure Cosmos DB. It implies that the resource does not exist or the provided URL is incorrect.

Failure Metrics

To track and evaluate failure metrics related to requests made to Azure Cosmos DB, we can consider the following factors:

• Status Code Analysis: Monitoring the distribution of different status codes received from Azure Cosmos DB can provide insights into the success and failure rates. This can be done by tracking the frequencies of different status codes over time.
• Error Messages: Analyzing error messages and their frequency can help understand the common causes of failures. Azure Cosmos DB provides detailed error messages that can assist in diagnosing the issues.
• Retry Metrics: Tracking the number of retries performed for failed requests can indicate the reliability of the application. Excessive retries might indicate persistent failures, while successful retries imply temporary or transient issues.
• Latency Analysis: Monitoring the response times of requests can help identify slow-performing queries or operations. High latency might indicate bottlenecks or inefficiencies in the application design.
• Availability Percentage: Calculating the availability percentage of Azure Cosmos DB can give an overview of the system’s reliability. It is typically measured as the percentage of successful requests over a given time period.

Example Code

To retrieve the status code from a response in a code snippet using the Azure Cosmos DB SDK for .NET, you can use the following code:

using Microsoft.Azure.Cosmos;
using System;

// Retrieve and print the status code
Console.WriteLine($"Response Status Code: {response.StatusCode}");
}
catch (Exception ex)
{
Console.WriteLine($"An error occurred: {ex.Message}");
}
finally
{
// Dispose the CosmosClient to release resources
cosmosClient.Dispose();
}
}


In the above code, we create a `CosmosClient` instance using the endpoint URL and authentication key. We then get the required database and container objects. Finally, we read an item using its ID and retrieve the status code from the response by accessing the `StatusCode` property of the `ItemResponse` object.

By analyzing response status codes and failure metrics, we can gain insights into the overall performance and reliability of applications using Azure Cosmos DB. This information helps in troubleshooting issues, optimizing the application design, and ensuring a smooth user experience.