Kemal error under docker

README.md

To reproduce

Spin up your docker environment, then run the following:

$ docker build -t my/kemaltest .
$ docker run -p 8080:8080 -it my/kemaltest

Run the following inside the container, and then hit the docker machine's IP on port 8080 in a browser. You should see a "Hello World" message.

/app # ./test

If you do, CTRL-C to stop kemal, then run again. Repeat, and eventually you should see the following error:

[production] Kemal is ready to lead at http://0.0.0.0:8080
accept: Invalid argument (Errno)
0x560bb97ebf75: run at /usr/lib/crystal/src/io/file_descriptor.cr 297:7
0x560bb978c606: main at /app/lib/kemal/src/kemal.cr 19:5
0x7f12462c8964: trap at /usr/lib/crystal/src/pointer.cr 129:6

Dockerfile

FROM alpine

ENV APP_PORT 8080
ENV KEMAL_ENV production

EXPOSE $APP_PORT

ENV PACKAGES="\
wget \
ca-certificates \
linux-headers \
openssl-dev \
git \
gcc \
tini \
"

RUN set -x && \
    apk update && \
    apk upgrade && \
    apk add --no-cache $PACKAGES

RUN echo "http://public.portalier.com/alpine/testing" >> /etc/apk/repositories && \
    wget -nv "http://public.portalier.com/alpine/julien%40portalier.com-56dab02e.rsa.pub" \
    -O /etc/apk/keys/julien@portalier.com-56dab02e.rsa.pub

RUN apk add --no-cache crystal shards

RUN echo "System Info: " && uname -a && /usr/bin/crystal -v && /usr/bin/crystal env

RUN mkdir /app

COPY . /app/
WORKDIR /app
RUN /usr/bin/crystal deps
RUN /usr/bin/crystal build test.cr --release
ENTRYPOINT /bin/sh

test.cr

require "kemal"

Kemal.config.port = 8080

get "/" do
  "Hello World!"
end

Kemal.run