The World Wide Web’s transmission system is built on HTTP. To ensure an application that uses the HTTP transmission works, you must monitor it constantly. This is where an HTTP monitor comes in.

In this tutorial, we’ll cover the fundamentals of HTTP monitors, including what they are, why they matter, and how to set one up.

What Is an HTTP Monitor?

An HTTP monitor is a tool that sends HTTP requests to a web application and servers and checks for API availability, response times, status and resource usage.

HTTP monitoring is a type of synthetic monitoring that also let you write automated scripts to simulate user behavior, take screenshots of the pages the script is navigating, track resource usage, response time and status.

However, HTTP monitor are basic in their configuration. They don’t let you run automated scripts but they are real easy to get started with. Just select the URL for which you want to run basic tests and the HTTP monitor will return the results like availability, response times, and status of the URL. This enables developers and system administrators to understand performance and health of web applications and infrastructure at a glance.

Why Monitor HTTP?

Web applications often depend on complex, interconnected systems, which can cause several problems like slow response times, errors, and failed requests. Without timely detection and resolution of these issues they can go unnoticed, leading to significant technical and financial debts for the company. Monitoring HTTP is vital to address these problems by:

• Simulating user environment: By monitoring HTTP requests, you can simulate user behavior in a synthetic environment. This feature let you test your application as if a real user would. Furthermore, you can also set your monitors to run the services as if it were running from different locations across the world. This feature lets you ensure that every user will have the same experience regardless of their location.
• Detecting website performance issues: Data collected by HTTP monitors can rapidly identify website performance issues and notify the technical teams to fix them before they impact end users. This proactive approach results in a better user experience and higher customer satisfaction. These notifications can be as specific as messages requesting improvements in server speed or the reduction of the volume of requests made to the server.
• Monitoring security: HTTP monitoring also plays a pivotal role during the development phase. HTTP monitors help developers identify web application issues and also potential security risks like cross-site scripting (XSS), SQL injection, and session hijacking. By constantly monitoring HTTP traffic, technical teams can spot suspicious behavior, such as persistent login failure or odd request patterns that usually point to an attempt to attack the web application.

Types of HTTP Monitors

There are various HTTP monitor types, each with unique features and functionalities. The right type for your use case will depend on the aspects of the HTTP traffic you want to track.

Availability Monitors

These monitors primarily focus on checking whether a website or web application is reachable and online. They send periodic HTTP requests to a specific URL or endpoint and analyze the response status code to determine if the server is up and running. Alerts are generated when the server responds with an unexpected status code or when the response time exceeds a defined threshold.

Performance Monitors

Performance monitors assess the responsiveness and speed of a website or application. They measure the time it takes for the server to respond to an HTTP request and may track factors like DNS resolution, connection time, time to first byte (TTFB), and content load time. These monitors help identify slow-loading pages, server bottlenecks, and network latency issues.

Content Monitors

Content monitors verify that specific content or elements on a webpage are present and correct. They can check for the presence of keywords, images, scripts, and other essential components to ensure that the page is rendering as expected. Content monitors are useful for detecting issues related to broken links, missing assets, or incorrect page rendering.

Security Monitors

Security monitors focus on detecting vulnerabilities and potential threats in web applications. They evaluate metrics, answer bodies, response codes, and the validity of SSL certificates. They also finds broken links or improperly set up SSL certificates. Security monitors help ensure that websites and applications are protected against malicious attacks.

Network Monitor

The last form of an HTTP monitor is a network monitor, which records and examines all network traffic, including HTTP traffic to detect suspicious network behavior. It also recognizes security threats, such as DDoS attacks or data breaches.

Key Metrics HTTP Monitors Measure

HTTP monitors measure several important metrics related to the functionality, accessibility, and security of web applications. Below are the most important ones:

• Response time: The time a website needs to return an HTTP response, thus measuring the responsiveness of an application. Ideally, the response time should be less than 2 seconds. A higher response time could indicate slower server, network latency, unoptimized code, higher third party dependencies or larger content size.
• Availability: The time a web service is accessible to users. This metric is crucial for assuring the dependability and accessibility of web applications. Many organizations aim for availability percentages in the high 90s or even 99.9% (often referred to as “three nines” availability).
• Response payload: The data returned by the HTTP server. This metric measures the content, format, and elements of a payload. It lets you know if there is anything wrong with the data returned by the web server.
• Error rate: The percentage of HTTP queries that receive error responses during a specific operation. It helps find problems affecting the web service’s functioning. For example, the error rate could be the number of HTTP 500 Internal Server Errors when a user tries to login to a website. A critical application like financial system demands the error rate be 0 however a less critical application can have a higher error rate.
• Throughput: The volume of HTTP queries a server handles in a predetermined time. This metric is important to ensure servers manage the anticipated load and traffic. For example, a target throughput of 100 Mbps or higher might be reasonable for a medium-sized website.
• Request rate: The speed at which a server procceses HTTP requests in a particular time frame. It is used for spotting usage trends and confirming that servers can support the anticipated load. 50 to 100 requests per second (RPS) can be considered acceptable for many standard websites
• DNS lookup time: The time it takes for a DNS (Domain Name System) query to be resolved and translated into an IP address. Domain Name System Operations Analysis and Research Center (DNS-OARC) suggests that an average DNS lookup time should be around 20-120 milliseconds. Anything outside this range can indicate issues with network latency and website redirections.
• TLS handshake time: The time taken for a secure connection to be established between a client (such as a web browser) and a server using the TLS protocol. Higher traffic, certificate issues and slow handshakes can increase the TLS handshake time. As a guideline, aim for a TLS handshake time of around 1-2 seconds or less is often considered acceptable.
• Time to First Byte: The time taken for a user’s browser to receive the first byte of data from a web server after making an HTTP request. It can indicate poor network connection, unoptimized code or database queries and higher 3rd part dependencies. A TTFB of 200-300 milliseconds or less is often considered acceptable for a well-optimized website.
• HTTP response codes: The three-digit numbers returned by a web server to indicate the outcome of an HTTP request made by a client (such as a web browser). Codes other than the ones within the 200 range often indicates that your response was not successful.

Top HTTP Monitors

There are several HTTP monitoring tools available, each with its own features and capabilities. Some of the most popular include Sematext Synthetics, Datadog, Dynatrace, Pingdom, Uptrends.

If you want to know more about these tools, read our detailed take on synthetic monitoring tools.

How to Create an HTTP Monitor with Sematext Synthetics

Creating an HTTP Monitor is a great way to ensure a website performs well and is always available to users. To help you understand the process, we will use Sematext Synthetics.

Synthetics is a synthetic monitoring tool that allows you to the availability and performance of your APIs and Web URLs from multiple locations. HTTP monitors send a single request to a specified URL within a specified interval. They record the response body and headers and various metrics including average response time, page load time, time to first byte. You can also monitor your SSL certificates, get notified when your certificate is about to expire or changes, perform certificate authority checks and make sure your website is secure.

Here’s how you can use Synthetic to work with HTTP monitors:

Create an HTTP Monitor

To create an HTTP monitor with Sematext, follow the steps below:

1. Create a Sematext Synthetics app for the region that best suits your needs.
   

   

2. Click the New Monitor button on the top right corner of the page, choose HTTP Monitor, then click Continue.
   

   

3. Specify the URL you want to send requests periodically and set the time interval and locations to run the monitor.
4. Configure your HTTP request by setting the Authentication mechanism, header, query params, body and cookies if needed.
5. Supply the conditions to trigger alerts through the Conditions section.
   

   

6. You can also validate SSL certificates and get notified when SSL certificate is expiring or a change is detected.
   

   

7. Click the Create button on the top right corner of the page. Your HTTP monitor will run periodically based on the interval you’ve set.
8. You can edit, disable, clone your HTTP monitors at any time from the Monitors overview page.
   

   

You can also create public status pages and incidents to share the status and response time of your services with your customers and share status updates during planned maintenance or outages.

View the Analytics of an HTTP Monitor

Once the HTTP monitor is set up and running, it will send a single HTTP request with its configured request settings to the specified URL. The monitor will record the response data such as headers, body, error (if any), and various timings. This information can be accessed through multiple places:

1. The Overview section of your Sematext Synthetics app.
   

   

2. The overview page within the HTTP monitor.
   

   

3. The Runs tab within the HTTP monitor.
   

   

Conclusion

An HTTP monitor’s ability to detect issues early, mitigate potential disruptions, and ultimately deliver a seamless user experience makes it a critical tool forensuring the reliability, performance, and responsiveness of web servers and applications. With the right HTTP monitoring strategy in place, organizations can confidently navigate the intricacies of web performance, fortify their digital offerings, and forge lasting connections with users, all while ensuring their web services consistently deliver the utmost quality and reliability.

If you’re interested in adding an HTTP monitor to your monitoring strategy, check out Sematext Synthetics. It offers a 14-day free trial for you to test all its capabilites.

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