HTTP Server Tests

HTTP Server tests measure the availability and performance of HTTP services. Any HTTP service that is exposed to the internet (or intranet, if Enterprise Agents are deployed in your internal network) can be tested. HTTP Server Tests measure the availability, response time, and throughput of a web server.

The HTTP Server test is performed as a series of steps (or phases):

DNS: The domain part of the test target URL is resolved to an IP address.
Connect: A TCP 3-way handshake is performed.
SSL (optional): Security mechanisms are negotiated.
Send: An HTTP request is sent.
Receive: An HTTP response is waited for and received.
HTTP: The HTTP response code is validated.
Content verification (optional): Verification of the received content is performed by matching it against a regular expression.

HTTP Server tests support various authentication protocols, custom headers, as well as SSL options.

When the HTTP Server test detects an issue, the results pinpoint the phase of a request in which the issue occurred. To assist the analysis, information from lower layers is included in this test type. These include agent-to-server network and BGP routing tests.

Use Cases for HTTP Server Tests

Ensuring website availability and performance
Monitoring HTTP services served from multiple data-centers concurrently
Validating CDN performance and delivery speed

HTTP Server Metrics

HTTP Server Tests collect metrics that capture the entire lifecycle of an HTTP/HTTPS request, from DNS resolution to receiving the server’s response. The metrics are:

Availability (%): Percentage of successful HTTP requests, typically defined as requests returning a 2xx or 3xx status code.
Response Time (ms): Total time to complete the HTTP request, encompassing DNS resolution, TCP connection, SSL handshake (if HTTPS), sending the request, waiting for the server’s response, and receiving the response.
Throughput (MB/s): The data transfer rate, measured in megabytes per second, calculated as the Wire Size (bytes transferred) divided by the Receive Time (time from first byte to last byte of the response payload). It reflects the efficiency of data delivery from the server.
Redirect Time (ms): The time spent processing HTTP redirects (e.g., 301, 302 status codes), from receiving a redirect response to initiating the request to the new URL, including any additional DNS resolution, connection, or SSL handshake for the redirected endpoint.
Connect Time (ms): Time to establish a TCP connection to the server.
DNS Time (ms): Time to resolve the target domain’s DNS record.
SSL Time (ms): Time to complete the SSL/TLS handshake (only for HTTPS endpoints).
Wait Time (ms): Time waiting for the server to begin responding (e.g., time to first byte, reflecting server processing).
Receive Time (ms): Time to receive the full response from the server.
Wire Size (bytes): The total size of the HTTP response data transferred over the network, including headers and body, measured in bytes.
Response Code: The HTTP status code returned by the server (e.g., 200 OK, 404 Not Found, 500 Internal Server Error), indicating the outcome of the HTTP request.
Error Details: Specific errors encountered, such as HTTP status codes (e.g., 404 Not Found, 500 Internal Server Error), DNS failures, or timeouts.

Error Types for HTTP Server Tests

Error Type

Error Definition

DNS

Failure to resolve a domain name to one or more IP addresses using DNS

Connect

Failure to complete a TCP 3-way handshake (SYN, SYN-ACK, ACK)

SSL (if test target using SSL/TLS)

Failure to complete SSL/TLS negotiation

Send

Failure to complete sending of an HTTP GET or POST request

Receive

Failure to receive a valid and complete HTTP response

HTTP

Receiving an HTTP response code that is not (default) 2XX or 3XX, or not the desired HTTP status code of the response as configured in Advanced Settings of the test

Content (optional)

Failure to match returned content to an expression in the Verify Content field