Kitura slow or low request per second? - swift

Question

I've download Kitura 0.20 and created a new project for a benchmark on a swift build -c release
import Kitura
let router = Router()
router.get("/") {
request, response, next in
response.send("Hello, World!")
next()
}
Kitura.addHTTPServer(onPort: 8090, with: router)
Kitura.run()
and the score appear to be low compare to Zewo and Vapor which could hit 400k+ request/s?
MacBook-Pro:hello2 yanli$ wrk -t1 -c100 -d30 --latency http://localhost:8090
Running 30s test # http://localhost:8090
1 threads and 100 connections
Thread Stats Avg Stdev Max +/- Stdev
Latency 415.36us 137.54us 3.09ms 91.11%
Req/Sec 5.80k 2.47k 7.19k 85.71%
Latency Distribution
50% 391.00us
75% 443.00us
90% 513.00us
99% 0.93ms
16229 requests in 30.01s, 1.67MB read
Socket errors: connect 0, read 342, write 55, timeout 0
Requests/sec: 540.84
Transfer/sec: 57.04KB

Answer 1

I suspect you are running out of ephemeral ports. Your issue is probably the same as this one: 'ab' program freezes after lots of requests, why?
Kitura currently does not support HTTP keepalive, and so every request requires a new connection. One symptom of this is that regardless of how many seconds you attempt to drive load, you'll see a similar number of completed requests (16229 in your example).
On OS X, there are 16,384 ephemeral ports available by default, and these will be rapidly exhausted unless you tune the network settings.
[1] http://danielmendel.github.io/blog/2013/04/07/benchmarkers-beware-the-ephemeral-port-limit/
[2] https://rolande.wordpress.com/2010/12/30/performance-tuning-the-network-stack-on-mac-osx-10-6/
My approach has been to reduce the Maximum Segment Lifetime tunable (which defaults to 15000, or 15 seconds) and increase the range of available ports temporarily while benchmarking, for example:
sudo sysctl -w net.inet.tcp.msl=1000
sudo sysctl -w net.inet.ip.portrange.first=32768
<run benchmark>
sudo sysctl -w net.inet.tcp.msl=15000
sudo sysctl -w net.inet.ip.portrange.first=49152