Fortio

Fortio runs at a specified query per second (qps) and records an histogram of execution time and calculates percentiles (e.g. p99 ie the response time such as 99% of the requests take less than that number (in seconds, SI unit)).
It can run for a set duration, for a fixed number of calls, or until interrupted (at a constant target QPS, or max speed/load per connection/thread).

The name fortio comes from greek φορτίο which means load/burden.

Fortio is a fast, small (4Mb docker image, minimal dependencies), reusable, embeddable go library as well as a command line tool and server process, the server includes a simple web UI and REST API to trigger run and see graphical representation of the results (both a single latency graph and a multiple results comparative min, max, avg, qps and percentiles graphs).

Fortio also includes a set of server side features (similar to httpbin) to help debugging and testing: request echo back including headers, adding latency or error codes with a probability distribution, tcp echoing, tcp proxying, http fan out/scatter and gather proxy server, GRPC echo/health in addition to http, etc…

Fortio is quite mature and very stable with no known major bugs (lots of possible improvements if you want to contribute though!), and when bugs are found they are fixed quickly, so after 1 year of development and 42 incremental releases, we reached 1.0 in June 2018.

Fortio components can be used a library even for unrelated projects, for instance the log, stats, or fhttp utilities both client and server. As well as the newly integrated Dynamic Flags support (greatly inspired/imported initially from https://github.com/mwitkow/go-flagz but recently reimplemented using Go generics). Even more recent is the new jrpc JSON Remote Procedure Calls library package (docs).

If you want to connect to fortio using https and fortio to provide real TLS certificates, or to multiplex grpc and regular http behind a single port, check out Fortio Proxy.