Access Go Api Hosted in Docker container - docker

Question

I have created a Go backend server that contains an api. All works well when running locally "go run server". I did however encounter issues when running it in docker. So I created a Dockerfile and run the linux container in networkmode host but can't access the api in the browser. If it's working I should be able to see a json response from http://localhost:8500/status. So I'm thinking I need permissions or add flags or more installation related scripts. I have been testing different flags and ports in docker but can't identify the issue. See code, dockerfile and command below.
Note: When I run the program locally on windows a security warning pops up, perhaps this is related to the issue?
I'm running docker desktop community v 2.2.0.5 stable.
Api code:
import (
"log"
"net/http"
conf "server/conf"
"github.com/gorilla/mux"
"github.com/jinzhu/gorm"
_ "github.com/jinzhu/gorm/dialects/mysql"
)
var db *gorm.DB
// Middleware used to add correct permissions for all requests
func middleware(next http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "application/json")
w.Header().Set("Access-Control-Allow-Origin", "*")
w.Header().Set("Access-Control-Allow-Headers", "Content-Type")
next.ServeHTTP(w, r)
})
}
func StartApi(config conf.Config, _db *gorm.DB) {
log.Println("Start Api")
db = _db
router := mux.NewRouter()
// Create
router.HandleFunc("/login", login).Methods("POST", "OPTIONS")
router.HandleFunc("/network", createNetwork).Methods("POST", "OPTIONS")
// Read
router.HandleFunc("/users/{networkName}", getUsers).Methods("GET", "OPTIONS")
router.HandleFunc("/streams/{networkName}", getStreams).Methods("GET", "OPTIONS")
router.HandleFunc("/status", showStatus).Methods("GET", "OPTIONS")
log.Println("API started at port " + config.Backend.Api_port) // api port is stored in config
log.Println(http.ListenAndServe(":"+config.Backend.Api_port, middleware(router)))
log.Println("Api done!") }
Dockerfile:
# Start from the latest golang base image
FROM golang:latest
WORKDIR /go/src/server
COPY ./src/server .
# Download packages
RUN go get .
# Compile code
#RUN go build -o server
RUN go install server
# Expose ports
EXPOSE 8500
EXPOSE 8600
#ENTRYPOINT ./server
CMD ["go", "run", "server"]
Docker-compose:
version : '3'
services:
react:
build: ./ReactFrontend/
container_name: ReactFrontend
tty: true
ports:
- 4000:3000
backend:
network_mode: host
build: ./GoBackend/
container_name: goserver
ports:
- 8500:8500
- 8600:8600
Docker command:
docker run --net=host goserver
Any help is appreciated,
Cheers!

Answer 1

So i solved it for now by:
As mentioned here:
https://docs.docker.com/compose/networking/
Add to docker-compose:
networks:
default:
external:
name: database_default
As mentioned here: Access to mysql container from other container
I can connect to database as < db_container_name >:3306 in backend.
To automate the process I created a .sh script for handling an extra setup config step on container start. However, due to my structure in my config.yml it was hard to update with just "sed" commands so I created a python program for updating all config data. The Dockerfile, docker-compose file, setup.sh and update_config.py file is shown below.
setup.sh:
#!/bin/bash
# Don't remove this!
# This file is used by dockerfile to replace configs
# Replace config on run
python3 update_config.py
# Start program
go run server
Dockerfile:
# Start from the latest golang base image
FROM golang:latest
WORKDIR /go/src/server
COPY ./src/server .
# Install python3 and yml compability
RUN apt-get update && apt-get install -y python3-pip
RUN python3 --version
RUN pip3 install PyYAML
# Download packages
RUN go get .
# Compile code
#RUN go build -o server
RUN go install server
# Expose ports
EXPOSE 8500
EXPOSE 8600
# ENV
ENV DB_HOST "mysql:3306"
#CHMOD setup
RUN chmod +x setup.sh
CMD ["./setup.sh"]
Docker-compose
version : '3'
services:
react:
build: ./ReactFrontend/
container_name: ReactFrontend
tty: true
ports:
- 4000:3000
backend:
build: ./GoBackend/
container_name: GoBackend
environment:
DB_HOST: mysql:3306 # Name or IP of DB container!
ports:
- 8500:8500
- 8600:8600
networks:
default:
external:
name: database_default
update_config.py:
import yaml
import os
"""
DONT REMOVE
This file is used in the dockerfile!
"""
fname = "/go/src/server/config.yml"
stream = open(fname, 'r')
data = yaml.safe_load(stream)
stream.close()
# Add more updates here!
if os.environ.get('DB_HOST') is not None:
data["database"]["ip"] = os.environ['DB_HOST']
# Updated data print
print("Updated Data", data)
# Write changes to config
stream = open(fname, 'w')
yaml.dump(data, stream)
stream.close()
Example docker command that now works if we only want container to run:
docker run -p 8500:8500 -p 8600:8600 --net database_default goserver
It is working fine! And we are avoiding using unnecessary host network mode!