HTTP - Troubleshooting

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Troubleshooting is the process to find and resolve issues that occur during the communication between a client and the server. In troubleshooting, we identify the problems that may affect the performance, security, or functionality and then resolve them. This chapter covers the common HTTP issues and how to resolve them, tools and their working for troubleshooting HTTP problems, and performance optimization techniques.

Tools for Troubleshooting

We can use tools like Browser Developer Tools, Curl, Postman, etc for troubleshooting HTTP issues. We have mentioned below the steps which we can use to troubleshoot HTTP issues using Browser Developer tools.

Browser Developer Tools

Modern browsers like Google Chrome, Firefox, Edge, and Safari include Browser Developer Tools (DevTools). It is easy to use which also allows users to view and analyze HTTP requests and responses, perform debugging of JavaScript, and evaluate performance. Here are some of the key features of DevTools:

• Network Tab: This tab displays all the request sent by the browser along with other details including: URL, methods, Status codes, Request and Response header, time and payload.
• Console Tab: It displays JavaScript errors, warnings, and custom messages added by developers. It can also be used to execute the JavaScript commands.
• Application Tab: It displays a view of cookies, local, session, and IndexedDB storage.

Using Browser DevTools

• Open any webpage you want to inspect.
• Then right click on the web page and select Inspect or press F12.
• Navigate to the Network tab.
• Reload the page to capture HTTP requests.
• Analyze requests by clicking on them to see headers, response bodies, and other details.

Example:

Suppose we are having 404 NOT FOUND error, then by using browser developers tool we can troubleshoot this error by following below mentioned steps:

• Right click on the web page and select Inspect or press F12.
• Open the Network tab in DevTools and reload the web page to get all the network requests.
• Search for a request with the Status Code 404. Click on that request to get request URL and check if the file/resource exist on the server and if the URL is correct.
• Check the response body for any error message.

Common HTTP Errors and Resolution

HTTP errors are the status codes, which indicates any problem that occurred during data transmission between client and server. HTTP errors can occur due to various reasons, such as client side issues, server side issues, network issues, or misconfigurations. Some of the common HTTP errors and their resolutions are mentioned below:

404 Not Found

HTTP 404 Not Found is a client error response code which indicates that the server cannot find the requested resource. This error can occur due to various reasons, such as:

• If the resource is not found.
• If the URL is incorrect.
• If the resource has been moved to some other place or deleted.
• Due to server misconfiguration.

Resolution:

We can follow below mentioned resolution techniques to overcome 404 NOT Found.

• First, verify if the entered URL is correct.
• Check the server logs for more information on the error.
• Verify if the requested resource exists on the server.

403 Forbidden

HTTP 403 Forbidden error indicates that server refuses to authorize the request. This error can occur due to various reasons, such as:

• When authentication or permissions is required and user have not provided the required information.
• Due to IP blocking or,
• Due to Server misconfiguration.

Resolution:

We can follow below mentioned resolution techniques to overcome 403 Forbidden error.

• Check if the user is authenticated and authorized.
• Verify if user has permissions for the requested resource or not.
• Check the server configuration for any IP blocking rules.

500 Internal Server Error

HTTP 500 Internal Server Error indicates that something went wrong on the server side while processing the request. This error can occur due to various reasons, such as:

• Due to server misconfiguration.
• if there is database connection issues.
• Due to resource exhaustion.

Resolution:

We can follow below mentioned resolution techniques to overcome 500 Internal Server Error.

• Check the server logs for detailed error information.
• Verify server configuration and make sure it is correct.
• Review server side code for any application errors, database connectivity, or configuration issues.

502 Bad Gateway

HTTP 502 Bad Gateway error indicates that a proxy server or gateway received an invalid response from an upstream server. This error can occur due to various reasons, such as:

• It can be caused because of network issues.
• Due to upstream server misconfiguration.
• If the upstream server is down or unreachable.

Resolution:

We can follow below mentioned resolution techniques to overcome 502 Bad Gateway error.

• Check upstream servers such as database for issues.
• Make sure that the network connectivity is stable.
• Check for proxies and load balancers. Make sure they are configured correctly.

503 Service Unavailable

HTTP 503 Service Unavailable error indicates that the server is currently unable to handle the request due to a temporary overload or maintenance. This error can occur due to various reasons, such as:

• Server overload
• Server maintenance
• Resource exhaustion

Resolution:

We can follow below mentioned resolution techniques to overcome 503 Service Unavailable.

• Check the server load and ensure it is within acceptable limits.
• Check if server configuration is correct.

408 Request Timeout

HTTP 408 Request Timeout error indicates that the server timed out waiting for the client to send a request. This error typically occurs when:

• The client takes too long to send the request.
• Network latency delays the transmission.
• Server timeout settings are too low for the client's response speed.

Resolution:

We can follow below mentioned resolution techniques to overcome 408 Request Timeout.

• Ensure that client sends the request on time avoiding any unnecessary delays.
• Generally network issues causes latency, so check for it.
• Change the server's timeout configuration by increasing it.
• Make request payload size optimal to reduce transmission time.

Performance Optimization Techniques

Here are some of the performance optimization techniques which can be used to improve the performance of web application.

Reduce Latency

Latency means the delay between a request sent and the response received. we can use below mentioned techniques to reduce the latency:

• Implement HTTP/2 or HTTP/3: HTTP/2 or HTTP/3 can make use of multiplexing to improve performance. It reduces the round trips and improving page load speed.
• By Using a CDN: CDNs(Content Delivery Network) reduces the gap between user and server, which decreases the latency. CDNs store cached data in multiple geographic locations.
• Optimize DNS resolution: Faster DNS servers can be used for reducing the time taken to translate domain names into IP addresses.

Caching

Cache stores the responses locally at client side or on intermediate servers. Since responses are stored locally, we can reduce the need of sending repetitive requests to the server. We can use below mentioned techniques for caching:

• Using HTTP Cache Headers: We can use HTTP cache headers such as Cache-Control, ETag, or Last-Modified headers. We can specify how long content should be cached using these headers.
• Use server side caching: We can Cache most frequent requested data in the memory. This can help in reducing database load.
• Use client side caching: We can also use client side caching to store the data locally on user's or client side. We can use browser caching or HTML5 storage APIs.

Minimize HTTP Requests

HTTP requests take time to process, so we can reduce the requests made to server. Minimizing the requests can speed up page load times. We have mentioned below the techniques for minimizing the HTTP requests.

• We can remove unnecessary comments or blank spaces to reduce the file size of CSS and Javascript.
• To reduce the number of requests, rather than separate files for CSS and Javascript, we can combine multiple CSS and Javascript files into one file.
• We can reduce the initial load time by loading images and other resources only when needed.

Persistent Connections

HTTP/1.1, introduced persistent connections which allowed multiple requests and responses to be sent over a single connection. This can help in reducing the overhead of establishing a new connection again and again. We can use below mentioned technique for persistent connections:

• Keep-Alive: We can use Keep-Alive header. It ensures that connections remain open for future requests.