Simplify the code a bit using async/await

[papandreou]

I've had a bit of trouble wrapping my head around exactly what's going on in index.js. Adopting async/await seems to help a bit. Added some drive-by optimizations as well so more stuff is precomputed outside the middleware itself.

This makes the middleware function async, but it doesn't ever return a rejected promise because its body is wrapped in a try/catch. This should still be compatible with both vanilla express and express-promise-router.

Drive-by fixes #153

@AndrewKeig, this is a bit of an invasive refactoring, so I would appreciate a sign-off from you 😬 🤞

[AndrewKeig]

Hey, I’m cool with it as long as no impact on performance, see the load tests to confirm any issues

[AndrewKeig]

Also, maybe bump the major version as this might break old versions of node, thanks for supporting this by the way, much appreciated

[papandreou]

Tried running the load tests with node.js 16.14.2 before and after applying this change:

Before

[express-validation]$ ./load/post.sh 
Running 10s test @ http://localhost:3000/login
10 connections


┌─────────┬──────┬──────┬───────┬──────┬─────────┬─────────┬───────┐
│ Stat    │ 2.5% │ 50%  │ 97.5% │ 99%  │ Avg     │ Stdev   │ Max   │
├─────────┼──────┼──────┼───────┼──────┼─────────┼─────────┼───────┤
│ Latency │ 2 ms │ 2 ms │ 5 ms  │ 7 ms │ 2.43 ms │ 1.06 ms │ 28 ms │
└─────────┴──────┴──────┴───────┴──────┴─────────┴─────────┴───────┘
┌───────────┬────────┬────────┬─────────┬─────────┬─────────┬────────┬────────┐
│ Stat      │ 1%     │ 2.5%   │ 50%     │ 97.5%   │ Avg     │ Stdev  │ Min    │
├───────────┼────────┼────────┼─────────┼─────────┼─────────┼────────┼────────┤
│ Req/Sec   │ 1794   │ 1794   │ 3625    │ 3721    │ 3363.82 │ 561.74 │ 1794   │
├───────────┼────────┼────────┼─────────┼─────────┼─────────┼────────┼────────┤
│ Bytes/Sec │ 858 kB │ 858 kB │ 1.73 MB │ 1.78 MB │ 1.61 MB │ 269 kB │ 858 kB │
└───────────┴────────┴────────┴─────────┴─────────┴─────────┴────────┴────────┘

Req/Bytes counts sampled once per second.
# of samples: 11

0 2xx responses, 37000 non 2xx responses
37k requests in 11.02s, 17.7 MB read

After

[express-validation]$ ./load/post.sh 
Running 10s test @ http://localhost:3000/login
10 connections


┌─────────┬──────┬──────┬───────┬──────┬────────┬─────────┬───────┐
│ Stat    │ 2.5% │ 50%  │ 97.5% │ 99%  │ Avg    │ Stdev   │ Max   │
├─────────┼──────┼──────┼───────┼──────┼────────┼─────────┼───────┤
│ Latency │ 2 ms │ 2 ms │ 5 ms  │ 7 ms │ 2.4 ms │ 1.05 ms │ 26 ms │
└─────────┴──────┴──────┴───────┴──────┴────────┴─────────┴───────┘
┌───────────┬────────┬────────┬─────────┬─────────┬─────────┬────────┬────────┐
│ Stat      │ 1%     │ 2.5%   │ 50%     │ 97.5%   │ Avg     │ Stdev  │ Min    │
├───────────┼────────┼────────┼─────────┼─────────┼─────────┼────────┼────────┤
│ Req/Sec   │ 1804   │ 1804   │ 3667    │ 3833    │ 3420.9  │ 623.18 │ 1804   │
├───────────┼────────┼────────┼─────────┼─────────┼─────────┼────────┼────────┤
│ Bytes/Sec │ 863 kB │ 863 kB │ 1.75 MB │ 1.83 MB │ 1.63 MB │ 298 kB │ 862 kB │
└───────────┴────────┴────────┴─────────┴─────────┴─────────┴────────┴────────┘

Req/Bytes counts sampled once per second.
# of samples: 10

0 2xx responses, 34206 non 2xx responses
34k requests in 10.02s, 16.4 MB read

[papandreou]

Released in 4.0.0 🚀