API gateway for microservice with Kong

API gateway with Kong

Introduction

I have implemented a JWT microservice. But I need an API gateway to redirect the outside HTTP request to the inner network. We need a server to receive an HTTP request and then redirect to the corresponding microservice. How do we know the actual IP address in our network? One is to hard-code the IP address in the API gateway. You can also use service discovery to register your microservice IP address. So you can dynamically start service or shutdown service. In this tutorial, I use consul as my service discovery registry.

Service discovery

Let’s talk about service discovery first. There are 2 types of service discovery. One is client-side, another is server-side. Client-side means you get the actual IP address of a microservice from the service discovery registry first, then use that IP address to access the microservice. Server-side means you send a request to the service discovery registry, and it will help you to query the corresponding microservice then send back the microservice response to you.

Code

I use consul as service registry and Kong as API gateway and use docker-compose to set up my docker containers.

docker-compose.yml

	version: "3.5"
	services:
	jwt_service:
	container_name: jwt_service
	build :
	context : ./jwt
	target: deploy
	environment:
	SECRETKEY: asdf
	localIP: 192.168.18.5
	PORT: 8087
	consul_url: consul:8500
	networks:
	net:
	ipv4_address: 192.168.18.5
	expose :
	- 8087
	depends_on:
	- consul
	consul :
	container_name : consul
	image: consul
	networks:
	net:
	ipv4_address: 192.168.18.4
	expose:
	- 8500
	- 8600/udp
	ports:
	- "8700:8500"
	kong:
	image: kong:latest
	volumes:
	- ./kong.yml:/usr/local/kong/declarative/kong.yml
	environment:
	- KONG_DATABASE=off
	- KONG_DECLARATIVE_CONFIG=/usr/local/kong/declarative/kong.yml
	- KONG_PROXY_ACCESS_LOG=/dev/stdout
	- KONG_ADMIN_ACCESS_LOG=/dev/stdout
	- KONG_PROXY_ERROR_LOG=/dev/stderr
	- KONG_ADMIN_ERROR_LOG=/dev/stderr
	- KONG_ADMIN_LISTEN=0.0.0.0:8001, 0.0.0.0:8444 ssl
	- KONG_DNS_RESOLVER=192.168.18.4:8600
	ports:
	- "8000:8000"
	- "8443:8443"
	- "127.0.0.1:8001:8001"
	- "127.0.0.1:8444:8444"
	networks:
	- net
	networks:
	net:
	driver: bridge
	ipam:
	config:
	- subnet: 192.168.18.0/24
	gateway: 192.168.18.1

view raw api-gatway-docker-compose.yml hosted with ❤ by GitHub

We need to edit the config file for the Kong API gateway. I set the DNS resolver to the consul. I use the docker bridge network to assign a static IP directly to each microservice container. If we didn’t assign a static IP, we use the service name to represent the IP address of each container. When we access that IP, we will get the actual IP of that container from docker. You can think that we use docker as a DNS resolver. But we use consul as DNS resolver! So it won’t know what is the actual IP address of the service name. Make sure to assign a static IP to microservice! This is how I make it. If you have another good method to do it, please tell me!

kong.yml

	_format_version: "2.1"
	_transform: false
	services:
	- name: jwt-service
	url: http://jwt_service.service.dc1.consul
	routes:
	- name: jwt-route
	paths:
	- /jwt

view raw api-gateway-kong.yml hosted with ❤ by GitHub

We set the URL to the service name that we register to the consul.

Then I can access my microservice with path /jwt !

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If you have any problems, feel free to ask me!

You can find me here 👉 tim.chenbw@gmail.com

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