Using the 'http_load' Command for HTTP Benchmarking (with examples)

The http_load command is a powerful tool for testing the throughput of a web server by running multiple HTTP fetches in parallel. This command is particularly useful for benchmarking and evaluating how a web server handles a specific load. Whether you are a developer conducting server performance tests, a systems administrator ensuring your servers are properly equipped to handle traffic, or a QA engineer validating server response times, http_load provides a flexible and efficient way to simulate different traffic patterns and load scenarios. Below, we explore several use cases of the http_load command and illustrate how it can be used in various benchmarking scenarios.

Use case 1: Emulate 20 requests based on a given URL list file per second for 60 seconds

Code:

http_load -rate 20 -seconds 60 path/to/urls.txt

Motivation:

In web performance testing, it is essential to understand how a server behaves under a specific load over time. This example demonstrates how to simulate a constant load of 20 requests per second for a duration of 60 seconds using URLs listed in a file. This scenario is particularly valuable when you want to measure the stability and responsiveness of your web server under a controlled, steady stream of requests.

Explanation:

• -rate 20: This argument specifies that the command should emulate a load of 20 HTTP requests per second. This setup helps assess whether your server can handle a constant request rate effectively.
• -seconds 60: This defines the duration of the test, which is set to 60 seconds. Running the test for a minute allows a sufficient period to gather an average performance measure.
• path/to/urls.txt: This is the path to a text file containing the list of URLs against which the requests will be made. The file should include a URL per line.

Example output:

857 fetches, 0 max parallel, 280451 bytes, in 60 seconds
278 median ms connect, 58332 bytes
58.16 mean bytes/source
14.28 fetches per second

Use case 2: Emulate 5 concurrent requests based on a given URL list file for 60 seconds

Code:

http_load -parallel 5 -seconds 60 path/to/urls.txt

Motivation:

This use case focuses on stress testing by emulating multiple parallel connections to the web server. Understanding how your server handles concurrency is vital for identifying potential bottlenecks which could cause performance degradation. This example is practical for assessing if there are resource limitations when serving multiple clients concurrently.

Explanation:

• -parallel 5: This indicates that 5 requests will be made concurrently throughout the test duration. It helps simulate real-world scenarios where multiple users access the server simultaneously.
• -seconds 60: This provides the duration over which these parallel requests are made, ensuring consistent stress on the server.
• path/to/urls.txt: The path to a file listing the URLs to be fetched concurrently as part of the test.

Example output:

1200 fetches, 5 max parallel, 498050 bytes, in 60 seconds
842 median ms connect, 12355 bytes
80.08 mean bytes/source
20.00 fetches/sec

Use case 3: Emulate 1000 requests at 20 requests per second, based on a given URL list file

Code:

http_load -rate 20 -fetches 1000 path/to/urls.txt

Motivation:

Benchmarking how a server performs while processing a fixed total number of requests rather than over a fixed duration provides insights into completeness and stability under varied loads. This scenario emulates a scenario where you want to ensure that your server sustains a steady load until a total of 1000 requests have been processed.

Explanation:

• -rate 20: Emulates a load of 20 HTTP requests per second, allowing the server to demonstrate its efficiency in handling a consistent influx of requests.
• -fetches 1000: Sets a limit of 1000 total requests to be performed in the test, establishing a goal for the number of interactions.
• path/to/urls.txt: The file path that contains the URLs to be accessed during the test.

Example output:

1000 fetches, 0 max parallel, 350000 bytes, in 50 seconds
198 median ms connect, 35000 bytes
50.00 mean bytes/source
20.00 fetches/sec

Use case 4: Emulate 1000 requests at 5 concurrent requests at a time, based on a given URL list file

Code:

http_load -parallel 5 -fetches 1000 path/to/urls.txt

Motivation:

In environments where traffic is unpredictable, understanding how servers behave when pushed to their concurrency limits is crucial. This use case involves simulating a scenario where 1000 requests are made, with 5 requests processed concurrently at any given time, to examine how well a server can manage high volumes of simultaneous interactions.

Explanation:

• -parallel 5: Configures the test to handle 5 requests concurrently, reflecting real-world usage where multiple clients access the service simultaneously.
• -fetches 1000: Specifies that the test will consist of a total of 1000 requests, establishing a clear target for assessing server throughput capabilities.
• path/to/urls.txt: This specifies the file containing URLs that will be used in the test, allowing for varied endpoints and request types to be evaluated.

Example output:

994 fetches, 5 max parallel, 670008 bytes, in 100 seconds
320 median ms connect, 13401 bytes
134.01 mean bytes/source
10.00 fetches/sec

Conclusion:

The http_load tool offers versatile options for simulating different HTTP request loads, making it a valuable asset in web server benchmarking and performance testing. Each use case discussed provides insights into various aspects of server performance including concurrency handling, sustained load management, and capacity limitations. By tailoring the number of requests, duration, and concurrency, users can employ http_load to gain critical performance insights and ensure their servers are optimized to handle the anticipated traffic efficiently.