Cloud Run and Revel Container

Question

I have a simple site built using revel containerized in a docker image. I'm trying to run this image in Cloud Run. Unfortunately when I go to the URL for the site, I see a 502 in the browser and this log line

2020/10/30 17:27:07 http: proxy error: dial tcp 0.0.0.0:16166: connect: connection refused

I would assume it had something to do with the port, but I tried mapping the port originally to 9898 and I still saw a random port number in the log line. Currently I have the port in my revel application set to ${PORT} as recommended by the GCP documentation.

I should mention I can deploy the container locally with no issues.

Dockerfile:

FROM golang:1.15 AS build
ENV CGO_ENABLED 0
ADD . /go/src/app

# Install revel framework
RUN go get -u github.com/revel/revel
RUN go get -u github.com/revel/cmd/revel
# Run revel app
EXPOSE ${PORT}
ENTRYPOINT revel run -a /go/src/app -p ${PORT} -m dev

Revel app.conf snippet:

# The IP address on which to listen.
http.addr = 0.0.0.0

# The port on which to listen.
http.port = ${PORT}

UPDATE: It was suggested to use the hardcoded port of 8080 and see if that works. I still see the 502. I tried running it locally again and it looks like revel is trying to set up on one port and then listenining as a reverse proxy on another. So unless I'm thinking this may be a revel issue and not a Cloud Run issue

docker run --publish 8080:8080 app
Revel executing: run a Revel application
Changed detected, recompiling
Parsing packages, (may require download if not cached)... Completed
INFO  02:34:24    app     run.go:34: Running revel server
INFO  02:34:24    app   plugin.go:9: Go to /@tests to run the tests.
Revel engine is listening on.. 0.0.0.0:44795

Time to recompile 8.0340966s
Revel proxy is listening, point your browser to : 8080

Notice the last line Revel proxy is listening, point your browser to : 8080 but also Revel engine is listening on.. 0.0.0.0:44795

Nothing jumps to me. But it seems like your container is trying to establish connection to 0.0.0.0:16166 for proxying purposes and it's failing. Why would revel do this? — Ahmet Alp Balkan
I'm unfamiliar with Revel but familiar with Cloud Run. The Cloud Run service wants to provide ${PORT} to your container but the service currently (always?) defaults this value to 8080. So, you need Revel to run on 8080 too. It's unclear why you specify ${PORT} in both the Dockerfile's revel run ... -p ${PORT} and app.conf since, presumably, the former overrides the later. You want to ensure that your container, when given an env var of ${PORT} will run (!) on ${PORT} but you should be able to hack this by replacing both ${PORT} with 8080 in your Dockerfile (!) — DazWilkin
Ensure that revel run uses 0.0.0.0 rather than localhost too. I suspect this is already true since you can run and access the container locally. — DazWilkin
Once built... if you can docker run ... --publish=8080:8080 ... and then curl localhost:8080, you should be good to deploy it to Cloud Run. — DazWilkin
I tried running on 8080 @DazWilkin, and it does work locally. But I do see now there is still a strange localhost port. I'm also new to revel and it seems like it's setting up and then listening on a reverse proxy at 8080 editing my answer with this — Sevvy325

Sevvy325 Sevvy325 · Accepted Answer · 2020-11-01T17:43:07

So after further investigation and discussion, it seems like when you run revel applications via revel run a proxy is set up on a random port and that connection was what was failing. Furthermore, the largest benefit of running via revel run is hot swapping of deployed code, which is unnecessary in a deployed context. So the solution here was to build the application via revel build and running that application that way so that only the application port is used for connections.

Cloud Run and Revel Container

1 Answers