uWSGI and Zuul: every other request fails

Question

I have a setup (microservices) in which Zuul gateway (localhost) is in front of a flask REST API app (localhost:8080) served with uWSGI.

When I try to reach the API via gateway (e.g. curl http://localhost/api/endpoint), every other request fails (HTTP 500). There are no logs on the API side and here's an extract from the very dense gateway's exception log:

com.netflix.zuul.exception.ZuulException: Forwarding error
...
Caused by: com.netflix.client.ClientException: null
...
Caused by: java.lang.RuntimeException: org.apache.http.NoHttpResponseException: localhost:8080 failed to respond

Though, it works perfectly fine (every requests is handled as expected) when I reach the API directly (e.g. curl http://localhost:8080/api/endpoint).

Another interesting thing is that it works when I try to reach the API via gateway if flask's development server is used instead of uWSGI.

Here's my uWSGI settings:

[uwsgi]
wsgi-file = api.py
callable = app
uid = api
gid = api
master = true

processes = 2
threads = 2
http-timeout = 300
socket-timeout = 300
harakiri = 300

http = 0.0.0.0:8080
socket = /tmp/uwsgi.socket
chmod-sock = 664
vacuum = true
die-on-term = true

wsgi-disable-file-wrapper = true

log-date = %%Y-%%m-%%d %%H:%%M:%%S
logformat-strftime = true
logformat = %(ftime) | uWSGI    | %(addr) (%(proto) %(status)) | %(method) %(uri) | %(pid):%(wid) | Returned %(size) bytes in %(msecs) ms to %(uagent)

Versions are spring-cloud-netflix-zuul-2.1.1.RELEASE.jar and uwsgi==2.0.17.1.

Wireshark inspection shows TCP 8080 -> 80 [RST] Seq=123 Win=0 Len=0

Any idea what may be the issue here?

Answer 1

Solved by putting NGINX on top of uWSGI.

NGINX listens on port 8080 and talks to uWSGI over an unix socket so nothing changed from Zuul's point of view.