Simple REST API backed by PostgreSQL.

Export the following environment variables. For the running PostgreSQL instance on localhost,

APP_DB_HOST
APP_DB_USERNAME
APP_DB_PASSWORD
APP_DB_NAME

For the port the API server listens to:

$ export APP_PORT=8010

go test -v
=== RUN   TestEmptyTable
--- PASS: TestEmptyTable (0.01s)
=== RUN   TestGetNonExistentProduct
--- PASS: TestGetNonExistentProduct (0.02s)
=== RUN   TestCreateProduct
--- PASS: TestCreateProduct (0.00s)
=== RUN   TestGetProduct
--- PASS: TestGetProduct (0.00s)
=== RUN   TestUpdateProduct
--- PASS: TestUpdateProduct (0.01s)
=== RUN   TestDeleteProduct
--- PASS: TestDeleteProduct (0.01s)
PASS
ok

go build
./simple-api

Local testing, pass built-in environment variables and use localhost for the DB:

$ docker build . -t simple-api-img --build-arg APP_DB_HOST="localhost" --build-arg APP_DB_USERNAME=${APP_DB_USERNAME} --build-arg APP_DB_PASSWORD=${APP_DB_PASSWORD} --build-arg APP_DB_NAME=${APP_DB_NAME}  --build-arg APP_PORT=${APP_PORT}

To run, use the localhost network:

$ docker run --network=host simple-api-img

Running via host bridge

Configure PostgreSQL to listen on docker host bridge address retrieved via

$ ip addr show docker0

Typically by adding the following line to the /etc/postgresql//main/pg_hba.conf file:

local   all             all             172.17.0.1/16           scram-sha-256

and listening on the bridge IPs by adding a line like the following to the /etc/postgresql//main/postgresql.conf file:

listen_addresses = 'localhost,127.17.0.1'

Note that this is less secure and should only be used in testing. Then restart the PostgreSQL service:

sudo systemctl restart postgresql.service

Build image with host.docker.internal DB host location:

$ docker build . -t simple-api-img --build-arg APP_DB_HOST="host.docker.internal" --build-arg APP_DB_USERNAME=${APP_DB_USERNAME} --build-arg APP_DB_PASSWORD=${APP_DB_PASSWORD} --build-arg APP_DB_NAME=${APP_DB_NAME}  --build-arg APP_PORT=${APP_PORT}

Note that this method demonstrates local testing only. A production environment requires proper secrets management in conjunction with secret storage typically offered by CI/CD devops tools.

And launch with the local host gateway

$ docker run --add-host host.docker.internal:host-gateway -p $APP_PORT:$APP_PORT simple-api-img

To clean up and free disk space, use

$ docker system prune -a

Sign up to Docker hub and create a repository named simple-api.

Build a docker image contacting the DB via host.minikube.internal, tag it, login and push the image:

$ docker build . -t simple-api-img --build-arg APP_DB_HOST="host.minikube.internal" --build-arg APP_DB_USERNAME=${APP_DB_USERNAME} --build-arg APP_DB_PASSWORD=${APP_DB_PASSWORD} --build-arg APP_DB_NAME=${APP_DB_NAME}  --build-arg APP_PORT=${APP_PORT}
$ docker tag simple-api-img <username>/simple-api:1.0.0.minikube
$ docker login
$ docker push <username>/simple-api:1.0.0.minikube

After installing minikube, start, test status and open the dashboard UI via

$ minikube start --driver=docker
$ minikube status
$ kubectl cluster-info
$ minikube dashboard

The service can then be tested using the following steps.

Launch service with

kubectl apply -f simple-api.yaml

Identify the service URL via

$ minikube service simple-api-service --url

Use this URL to generate requests against the service by setting the environment variables APP_HOST and APP_PORT. The outbound requests do not generate an external IP address for the NodePort service type and would require a tunnel to do so.

To simplify testing, change the PostgreSQL configuration to accept connections from the APP_HOST IP address by adding this line to the /etc/postgresql//main/pg_hba.conf file

host	all		all		192.168.0.1/16		scram-sha-256

and changing the listen_addresses in the /etc/postgresql//main/postgresql.conf file to:

listen_addresses = '*'

This is insecure and should be done only for development and testing, or be coupled with a firewall configuration, for example through cloud security groups. Then restart the PostgreSQL service:

sudo systemctl restart postgresql.service

To clean up, delete the service and minikube cluster, and if needed halt the postgresql service

$ kubectl delete -f simple-api.yaml
$ minikube delete --all
$ docker system prune -a