fix: add uwsgi tweaks for closed connection

[Ian2012]

Description

This PR fixes the issue with closed connections which causes 502 responses.

Closed connection after POST request: unbit/uwsgi#2133. The fix: unbit/uwsgi#1097 (comment)

More information on uwsgi production deployments: https://www.bloomberg.com/company/stories/configuring-uwsgi-production-deployment/

The other tweaks are some community recommendations:

nginx/kubernetes-ingress#143 (comment)

This has been tested with multiple tweaks, here are the k6 results:

1. Default k8s deployments:

     data_received..................: 8.8 MB 64 kB/s
     data_sent......................: 294 kB 2.1 kB/s
     http_req_blocked...............: avg=54ms    min=455ns    med=1.13µs   max=802.08ms p(90)=2.17µs   p(95)=629.69ms
     http_req_connecting............: avg=11.24ms min=0s       med=0s       max=163.75ms p(90)=0s       p(95)=132.52ms
     http_req_duration..............: avg=3.9s    min=126.72ms med=146.21ms max=45.4s    p(90)=18.04s   p(95)=31.13s  
       { expected_response:true }...: avg=3.93s   min=126.72ms med=146.3ms  max=45.4s    p(90)=18.16s   p(95)=31.13s  
     http_req_failed................: 0.98%  ✓ 12       ✗ 1207 
     http_req_receiving.............: avg=23.08ms min=58.45µs  med=208.32µs max=234.44ms p(90)=129.57ms p(95)=137.2ms 
     http_req_sending...............: avg=176.7µs min=55.29µs  med=173.53µs max=523.46µs p(90)=246.48µs p(95)=268.91µs
     http_req_tls_handshaking.......: avg=20.57ms min=0s       med=0s       max=374.19ms p(90)=0s       p(95)=223.41ms
     http_req_waiting...............: avg=3.87s   min=126.29ms med=145.79ms max=45.4s    p(90)=17.94s   p(95)=31.01s  
     http_reqs......................: 1219   8.858423/s
     ✓ { status:200 }...............: 1037   7.535837/s
     ✗ { status:403 }...............: 0      0/s
     ✓ { status:502 }...............: 12     0.087204/s
     iteration_duration.............: avg=42.5s   min=5.82µs   med=21.17s   max=1m14s    p(90)=1m13s    p(95)=1m13s   
     iterations.....................: 161    1.16998/s
     vus............................: 3      min=3      max=100
     vus_max........................: 100    min=100    max=100


2. uwsgi tunning for http:

     data_received..................: 7.5 MB 61 kB/s
     data_sent......................: 293 kB 2.4 kB/s
     http_req_blocked...............: avg=80.47ms  min=394ns    med=1.11µs   max=1.07s    p(90)=3.96µs   p(95)=785.65ms
     http_req_connecting............: avg=13.88ms  min=0s       med=0s       max=174.52ms p(90)=0s       p(95)=137.79ms
     http_req_duration..............: avg=5.12s    min=126.99ms med=146.76ms max=53.41s   p(90)=24.29s   p(95)=37.64s  
       { expected_response:true }...: avg=5.12s    min=126.99ms med=146.76ms max=53.41s   p(90)=24.29s   p(95)=37.64s  
     http_req_failed................: 0.00%  ✓ 0        ✗ 1012 
     http_req_receiving.............: avg=13.22ms  min=61.54µs  med=211.79µs max=140.49ms p(90)=7.59ms   p(95)=128.48ms
     http_req_sending...............: avg=174.95µs min=68.78µs  med=167.24µs max=1.34ms   p(90)=237.97µs p(95)=258.95µs
     http_req_tls_handshaking.......: avg=26.69ms  min=0s       med=0s       max=503.98ms p(90)=0s       p(95)=242.62ms
     http_req_waiting...............: avg=5.11s    min=126.62ms med=146.3ms  max=53.41s   p(90)=24.29s   p(95)=37.64s  
     http_reqs......................: 1012   8.169564/s
     ✓ { status:200 }...............: 876    7.071677/s
     ✗ { status:403 }...............: 0      0/s
     ✗ { status:502 }...............: 0      0/s
     iteration_duration.............: avg=49.3s    min=5.59µs   med=21.47s   max=1m22s    p(90)=1m21s    p(95)=1m21s   
     iterations.....................: 126    1.017159/s
     vus............................: 3      min=3      max=100
     vus_max........................: 100    min=100    max=100



3. bypass caddy:

     data_received..................: 7.3 MB 57 kB/s
     data_sent......................: 283 kB 2.2 kB/s
     http_req_blocked...............: avg=84.77ms min=482ns    med=1.34µs   max=1.06s    p(90)=649.33ms p(95)=828.55ms
     http_req_connecting............: avg=14.24ms min=0s       med=0s       max=179.46ms p(90)=128.01ms p(95)=135.28ms
     http_req_duration..............: avg=5.39s   min=127.55ms med=148.74ms max=53.64s   p(90)=23.57s   p(95)=38.36s  
       { expected_response:true }...: avg=5.41s   min=127.55ms med=148.83ms max=53.64s   p(90)=23.7s    p(95)=38.42s  
     http_req_failed................: 0.20%  ✓ 2        ✗ 974  
     http_req_receiving.............: avg=13.74ms min=66.73µs  med=242.25µs max=144.57ms p(90)=124.63ms p(95)=129.48ms
     http_req_sending...............: avg=198.3µs min=82.65µs  med=190.38µs max=502.94µs p(90)=272.23µs p(95)=294.56µs
     http_req_tls_handshaking.......: avg=30.71ms min=0s       med=0s       max=505.02ms p(90)=143.5ms  p(95)=307.52ms
     http_req_waiting...............: avg=5.38s   min=127.02ms med=148.31ms max=53.64s   p(90)=23.57s   p(95)=38.36s  
     http_reqs......................: 976    7.662723/s
     ✓ { status:200 }...............: 844    6.626371/s
     ✗ { status:403 }...............: 0      0/s
     ✓ { status:502 }...............: 2      0.015702/s
     iteration_duration.............: avg=51.28s  min=6.64µs   med=21.13s   max=1m26s    p(90)=1m25s    p(95)=1m25s   
     iterations.....................: 121    0.949989/s
     vus............................: 4      min=4      max=100
     vus_max........................: 100    min=100    max=100

4. uwsgi tunning for http + bypass caddy

     data_received..................: 7.6 MB 61 kB/s
     data_sent......................: 295 kB 2.4 kB/s
     http_req_blocked...............: avg=119.86ms min=513ns    med=1.13µs   max=1.39s    p(90)=18.46µs  p(95)=1.23s   
     http_req_connecting............: avg=13.61ms  min=0s       med=0s       max=178.55ms p(90)=0s       p(95)=133.92ms
     http_req_duration..............: avg=5.18s    min=127.19ms med=150.27ms max=53.06s   p(90)=23.8s    p(95)=38.92s  
       { expected_response:true }...: avg=5.18s    min=127.19ms med=150.27ms max=53.06s   p(90)=23.8s    p(95)=38.92s  
     http_req_failed................: 0.00%  ✓ 0        ✗ 1019 
     http_req_receiving.............: avg=13.21ms  min=66.79µs  med=216.67µs max=140.86ms p(90)=4.55ms   p(95)=129.38ms
     http_req_sending...............: avg=178.8µs  min=59.96µs  med=174.09µs max=623.01µs p(90)=246.63µs p(95)=269µs   
     http_req_tls_handshaking.......: avg=37.78ms  min=0s       med=0s       max=527.16ms p(90)=0s       p(95)=407.79ms
     http_req_waiting...............: avg=5.17s    min=126.89ms med=149.79ms max=53.06s   p(90)=23.8s    p(95)=38.92s  
     http_reqs......................: 1019   8.148496/s
     ✓ { status:200 }...............: 882    7.052967/s
     ✗ { status:403 }...............: 0      0/s
     ✗ { status:502 }...............: 0      0/s
     iteration_duration.............: avg=49.52s   min=4.59µs   med=21.22s   max=1m23s    p(90)=1m22s    p(95)=1m22s   
     iterations.....................: 127    1.015563/s
     vus............................: 2      min=2      max=100
     vus_max........................: 100    min=100    max=100

5. uwsgi tunning for http + bypass caddy + master tunning

     data_received..................: 7.9 MB 56 kB/s
     data_sent......................: 289 kB 2.1 kB/s
     http_req_blocked...............: avg=75.86ms  min=497ns    med=1.11µs   max=1.01s    p(90)=2.38µs   p(95)=783.95ms
     http_req_connecting............: avg=12.8ms   min=0s       med=0s       max=160.49ms p(90)=0s       p(95)=132.87ms
     http_req_duration..............: avg=4.79s    min=127.11ms med=139.98ms max=49.17s   p(90)=20.99s   p(95)=34.38s  
       { expected_response:true }...: avg=4.79s    min=127.11ms med=139.98ms max=49.17s   p(90)=20.99s   p(95)=34.38s  
     http_req_failed................: 0.00%  ✓ 0        ✗ 1060 
     http_req_receiving.............: avg=15.28ms  min=67.16µs  med=214.68µs max=803.93ms p(90)=125ms    p(95)=129.97ms
     http_req_sending...............: avg=176.01µs min=70.15µs  med=170.95µs max=494.78µs p(90)=239.71µs p(95)=264.03µs
     http_req_tls_handshaking.......: avg=35.6ms   min=0s       med=0s       max=569.08ms p(90)=0s       p(95)=354.03ms
     http_req_waiting...............: avg=4.78s    min=126.69ms med=139.29ms max=49.17s   p(90)=20.87s   p(95)=34.38s  
     http_reqs......................: 1060   7.535613/s
     ✓ { status:200 }...............: 915    6.504798/s
     ✗ { status:403 }...............: 0      0/s
     ✗ { status:502 }...............: 0      0/s
     iteration_duration.............: avg=47.24s   min=5.78µs   med=21.1s    max=1m21s    p(90)=1m19s    p(95)=1m20s   
     iterations.....................: 135    0.959724/s
     vus............................: 4      min=4      max=100
     vus_max........................: 100    min=100    max=100

6. uwsgi tunning for HTTP + master tunning

     data_received..................: 8.6 MB 61 kB/s
     data_sent......................: 305 kB 2.2 kB/s
     http_req_blocked...............: avg=71.83ms  min=443ns    med=1.14µs   max=1.69s    p(90)=2.27µs   p(95)=782.48ms
     http_req_connecting............: avg=11.45ms  min=0s       med=0s       max=157.15ms p(90)=0s       p(95)=133.12ms
     http_req_duration..............: avg=4.14s    min=127.65ms med=139.88ms max=46.6s    p(90)=17.88s   p(95)=33.14s  
       { expected_response:true }...: avg=4.14s    min=127.65ms med=139.88ms max=46.6s    p(90)=17.88s   p(95)=33.14s  
     http_req_failed................: 0.00%  ✓ 0        ✗ 1184 
     http_req_receiving.............: avg=13.53ms  min=64.81µs  med=218.75µs max=261.77ms p(90)=124.93ms p(95)=129.08ms
     http_req_sending...............: avg=174.85µs min=52.74µs  med=173.39µs max=411.8µs  p(90)=235.25µs p(95)=255.89µs
     http_req_tls_handshaking.......: avg=27.81ms  min=0s       med=0s       max=1.15s    p(90)=0s       p(95)=268.69ms
     http_req_waiting...............: avg=4.12s    min=127.27ms med=139.42ms max=46.6s    p(90)=17.88s   p(95)=33.14s  
     http_reqs......................: 1184   8.443182/s
     ✓ { status:200 }...............: 1020   7.273687/s
     ✗ { status:403 }...............: 0      0/s
     ✗ { status:502 }...............: 0      0/s
     iteration_duration.............: avg=43.58s   min=6.57µs   med=21.03s   max=1m18s    p(90)=1m16s    p(95)=1m17s   
     iterations.....................: 153    1.091053/s
     vus............................: 3      min=3      max=100
     vus_max........................: 100    min=100    max=100

[jfavellar90]

@Ian2012 please include this link: https://www.bloomberg.com/company/stories/configuring-uwsgi-production-deployment/ which helps to understand better the changes to the tuning variables (it is mentioned in the github comment but not explicitly)

[Ian2012]

@jfavellar90 do we need to backport this one? And are we pursuing an upstream contribution?

[jfavellar90]

@Ian2012 I would say both, but let's proceed with the backports first