Lightweight HTTP server with controllable performance

Lhotse is a lightweight HTTP server designed for controlled performance testing. It facilitates dictating the server's behavior, such as introducing specific latencies or generating responses of varying sizes. Developed to complement k6, Lhotse is an excellent tool for measuring k6's accuracy and assisting in its improvement and debugging.

Installation

Install Lhotse using Go:

go install github.com/oleiade/lhotse@latest

Usage & Examples

Lhotse provides functionalities such as latency simulation, data response control, and custom response generation.

Here are some examples:

Latency Control

Fixed Duration

Command:

time curl -X GET -i http://localhost:3434/latency/500ms

Output:

HTTP/1.1 200 OK
Allow: GET, OPTIONS
Date: Tue, 01 Nov 2022 18:15:37 GMT
Content-Length: 12
Content-Type: text/plain; charset=utf-8

waited 500ms

Latency Range

Command:

curl -X GET -i http://localhost:3434/latency/500ms-1s

Output:

HTTP/1.1 200 OK
Allow: GET, OPTIONS
Date: Tue, 01 Nov 2022 18:16:43 GMT
Content-Length: 19
Content-Type: text/plain; charset=utf-8

waited 610.839158ms

Data Response Control

Fixed Size

Command:

curl -X GET -i http://localhost:3434/data/8b

Output:

HTTP/1.1 200 OK
Allow: GET, OPTIONS
Date: Tue, 01 Nov 2022 18:14:12 GMT
Content-Length: 8
Content-Type: text/plain; charset=utf-8

TMtTCoaN

Size Range

Command:

curl -X GET -i http://localhost:3434/data/64b-128b

Output:

HTTP/1.1 200 OK
Allow: GET, OPTIONS
Date: Tue, 01 Nov 2022 18:13:02 GMT
Content-Length: 116
Content-Type: text/plain; charset=utf-8

whTHctcuAxhxKQFDaFpLSjFbcXoEFfRsWxPLDnJObCsNVlgTeMaPEZQleQYhYzRyJjPjzpfRFEgmotaFetHsbZRjxAwnwekrBEmfdzdcEkXBAkjQZLCt

Custom Response Control

Custom Status Code

Command:

curl -X GET -i http://localhost:3434/response?status=204

Output:

HTTP/1.1 204 No Content
Content-Type: text/plain
Date: Sun, 14 Jan 2024 10:17:35 GMT

Custom content-type

Command:

curl -i -X GET --header 'Content-Type: application/json' http://localhost:3434/response

Output:

HTTP/1.1 200 OK
Content-Type: application/json
Date: Sun, 14 Jan 2024 10:18:36 GMT
Content-Length: 49

{"content_type":"application/json","status":200}

API Reference

Latency Control

Endpoint /latency/{duration} simulates a response delay.

  GET /latency/${duration}

Parameter	Type	Description
duration	string	Specifies the delay before responding. Use {value}{unit} or {lowerBound}-{upperBound} format.

Data Volume Control

Endpoint /data/{size} controls the response size.

  GET /data/${size}

Parameter	Type	Description
size	string	Size of the payload produced by Lhotse. It can either be specified as a single size of the form {value}{unit}, or as a range {lowerBound}-{upperBound}. The value should always be an unsigned integer value. Valid units are b, kb, mb, and gb. When specifying a range, lowerBound needs to be less than upperBound, and as a result, the produced payload will be of a random size somewhere between those bounds.

Custom Response Control

Endpoint /response allows customization of the response.

  GET /response?status=${status}

Query Parameters

Parameter	Type	Description
status	string	Specifies the HTTP status code for the response.

Headers

Header	Type	Description
Content-Type	string	Determines the Content-Type of the response. Currently text/plain and application/json are supported.

Contributing

Contributions to Lhotse are welcome! Whether it's bug reports, feature requests, or code contributions, please feel free to contribute. For more details, see CONTRIBUTING.md.

License

Lhotse is open-sourced under the MIT License.