Salvo - my Apache Bench replacer

When I wrote Boom a few years ago, to replace Apache Bench (ab) in my work, Python was still maturing its async mechanisms, and gevent was a popular way to build an asynchronous HTTP client.

Fast forward 2020, asynchronous programming is now quite simple in Python and can be done natively, using async and await directives. I wrote Molotov, a load testing framework based on Python's asyncio and on the aiohttp client, and always wanted to rewrite Boom using Molotov, since it's just a very simple Molotov load test scenario: hitting a single HTTP(s) endpoint.

Instead of refactoring Boom, which is Python 2 compatible, I started a new tool called Salvo, which is Python 3 only. Salvo takes back Boom's command line interface and runs a Molotov script under the hood, and prints results the same way Boom is doing.

It's using a single process and runs as many concurrent "workers" as you want, which is enough to smoke test one endpoint. The philosophy is that anything more complex should be done using a full Molotov script.

To use Salvo, install it using pip and then send some load to an endpoint. Running with no option will perform a single hit

$ pip install salvo
$ salvo
-------- Server info --------

Server Software: ECS (bsa/EB12)

-------- Running 1 queries - concurrency 1 --------

[=================================================================>] 100%

-------- Results --------

Successful calls                    1
Total time                          0.4430 s
Average                             0.4430 s
Fastest                             0.4430 s
Slowest                             0.4430 s
Amplitude                           0.0000 s
Standard deviation                  0.000000
Requests Per Second                 2.26
Requests Per Minute                 135.44

-------- Status codes --------
Code 200                    1 times.

Want to build a more powerful load test ? Try Molotov !

You can then try to run more load. In the example below, we run 100 requests, across 10 concurrent workers:

$ salvo -n 10 -c 10
-------- Server info --------

Server Software: ECS (bsa/EB12)

-------- Running 10 queries - concurrency 10 --------

[=================================================================>] 100%

-------- Results --------

Successful calls                    100
Total time                          14.7801 s
Average                             0.1478 s
Fastest                             0.1049 s
Slowest                             0.5314 s
Amplitude                           0.4265 s
Standard deviation                  0.115398
Requests Per Second                 6.77
Requests Per Minute                 405.95

-------- Status codes --------
Code 200                    100 times.

Want to build a more powerful load test ? Try Molotov !

You can also use --duration to run the test for a given number of seconds, and use --json if you want to get the results in a JSON output.

In the example below, we also use --quiet to get only the JSON output, of a 10 seconds run using 10 workers:

$ salvo -d 10 -c 10 --json --quiet
{"count": 774, "total_time": 102.28760695457458, "rps": 7.566899090167683,
 "avg": 0.13215453094906277, "min": 0.10414314270019531,
 "max": 0.8381381034851074, "amp": 0.7339949607849121,
 "stdev": 0.09841954760413639,
 "rpm": 454.013945410061, "server": {"software": "ECS (bsa/EB18)"}}

Salvo has a few basic customization features (see --help) but I won't extend them, the plan is to keep it as simple as possible and invite developers that need more features to use Molotov.

I hope this tool will be useful. The repo is here:

Happy breaking!