uwsgi cheaper killing workers processing requests

Question

I have a very basic flask application under uwsgi, managed by signals under supervisorctl. I use cheaper for scaling workers and ran into very disturbing situation. uwsgi is killing oldest worker, even when it is processing a request, causing 500.

How to prevent uwsgi from killing workers processing the request, for the sake of cheaping?

Any help/hints deeply appreciated. Found another similar post without response: UWSGI killing workers too fast

Config: uwsgi version: 2.0.4

# Auto-scaling
workers = 30
cheaper = 2
cheaper-step = 3
cheaper-algo = backlog
cheaper-overload = 2

Logs:

[pid: 15601|app: 0|req: 13/78] 10.83.9.61 () {28 vars in 368 bytes} [Fri Sep 30 02:00:34 2016] POST /xxxxxxxxxxxx => generated 257 bytes in 151 msecs (HTTP/1.1 200) 2 headers in 72 bytes (1 switches on core 0)
[pid: 15601|app: 0|req: 14/79] 10.83.9.61 () {28 vars in 368 bytes} [Fri Sep 30 02:00:35 2016] POST /xxxxxxxxxxxx => generated 186 bytes in 649 msecs (HTTP/1.1 200) 2 headers in 72 bytes (1 switches on core 0)
[pid: 15600|app: 0|req: 21/80] 10.83.9.62 () {28 vars in 369 bytes} [Fri Sep 30 03:30:08 2016] POST /xxxxxxxxxxxx => generated 186 bytes in 2696 msecs (HTTP/1.1 200) 2 headers in 72 bytes (3 switches on core 0)
Respawned uWSGI worker 1 (new pid: 21009)
Respawned uWSGI worker 4 (new pid: 21010)
Respawned uWSGI worker 5 (new pid: 21011)
[pid: 15601|app: 0|req: 15/81] 10.83.9.62 () {28 vars in 370 bytes} [Fri Sep 30 03:30:09 2016] POST /xxxxxxxxxxxx => generated 186 bytes in 3046 msecs (HTTP/1.1 200) 2 headers in 72 bytes (2 switches on core 0)
[pid: 15600|app: 0|req: 22/82] 10.83.9.63 () {28 vars in 370 bytes} [Fri Sep 30 03:30:10 2016] POST /xxxxxxxxxxxx => generated 0 bytes in 3347 msecs (HTTP/1.1 500) 2 headers in 127 bytes (7 switches on core 0)
worker 2 killed successfully (pid: 15600)       <------------- pid 15600 was interrupted, returned 500 (line above)
uWSGI worker 2 cheaped.
[pid: 15601|app: 0|req: 16/83] 10.83.9.62 () {28 vars in 369 bytes} [Fri Sep 30 03:30:12 2016] POST /xxxxxxxxxxxx => generated 0 bytes in 2560 msecs (HTTP/1.1 500) 2 headers in 127 bytes (3 switches on core 0)
[pid: 21010|app: 0|req: 19/84] 10.83.9.63 () {28 vars in 369 bytes} [Fri Sep 30 03:30:12 2016] POST /xxxxxxxxxxxx => generated 186 bytes in 2931 msecs (HTTP/1.1 200) 2 headers in 72 bytes (4 switches on core 0)
worker 3 killed successfully (pid: 15601)       <------------- pid 15601 was interrupted, returned 500 (line above)
uWSGI worker 3 cheaped.
[pid: 21011|app: 0|req: 22/85] 10.83.9.61 () {28 vars in 370 bytes} [Fri Sep 30 03:30:12 2016] POST /xxxxxxxxxxxx => generated 186 bytes in 3236 msecs (HTTP/1.1 200) 2 headers in 72 bytes (4 switches on core 0)
[pid: 21009|app: 0|req: 7/86] 10.83.9.61 () {28 vars in 370 bytes} [Fri Sep 30 03:30:12 2016] POST /xxxxxxxxxxxx => generated 0 bytes in 3532 msecs (HTTP/1.1 500) 2 headers in 127 bytes (4 switches on core 0)
worker 1 killed successfully (pid: 21009)       <------------- pid 15601 was interrupted, returned 500 (line above)
uWSGI worker 1 cheaped.
[pid: 21011|app: 0|req: 23/87] 10.83.9.63 () {28 vars in 369 bytes} [Fri Sep 30 03:30:15 2016] POST /xxxxxxxxxxxx => generated 186 bytes in 1614 msecs (HTTP/1.1 200) 2 headers in 72 bytes (1 switches on core 0)
Respawned uWSGI worker 1 (new pid: 21013)
Respawned uWSGI worker 2 (new pid: 21014)
Respawned uWSGI worker 3 (new pid: 21015)
[pid: 21011|app: 0|req: 24/88] 10.83.9.61 () {28 vars in 369 bytes} [Fri Sep 30 03:30:17 2016] POST /xxxxxxxxxxxx => generated 186 bytes in 2546 msecs (HTTP/1.1 200) 2 headers in 72 bytes (3 switches on core 0)
[pid: 21010|app: 0|req: 20/89] 10.83.9.62 () {28 vars in 370 bytes} [Fri Sep 30 03:30:15 2016] POST /xxxxxxxxxxxx => generated 0 bytes in 4845 msecs (HTTP/1.1 500) 2 headers in 127 bytes (6 switches on core 0)
worker 4 killed successfully (pid: 21010)       <------------- pid 15601 was interrupted, returned 500 (line above)
uWSGI worker 4 cheaped.
[pid: 21015|app: 0|req: 17/90] 10.83.9.61 () {28 vars in 369 bytes} [Fri Sep 30 03:30:18 2016] POST /xxxxxxxxxxxx => generated 186 bytes in 2402 msecs (HTTP/1.1 200) 2 headers in 72 bytes (3 switches on core 0)
worker 5 killed successfully (pid: 21011)       <------------- pid 15601 was interrupted, returned 500 (line above)

Answer 1

Bug fixed & merged in August 2016.

https://github.com/unbit/uwsgi/issues/1288

https://github.com/unbit/uwsgi/commit/f5dd0b855d0d21be62534dc98375fae2cd7c13f0