How to use express api gateway in a docker swarm mode? - docker

Question

I have a few simple REST api services implemented in Express.These services run in docker containers in a swarm mode.Also,I am trying to use express-api gateway with these services.The express api gateway also runs in a container as part of the docker swarm.Following is the Dockercompose file
version: "3"
services:
firstService:
image: chaitanyaw/firstrepository:first
deploy:
replicas: 3
restart_policy:
condition: on-failure
ports:
- '3000:3000'
networks:
- webnet
apiGateway:
image: firstgateway:latest
deploy:
restart_policy:
condition: on-failure
ports:
- '80:80'
networks:
- webnet
visualizer:
image: dockersamples/visualizer:latest
ports:
- 8080:8080
volumes:
- /var/run/docker.sock:/var/run/docker.sock
deploy:
placement:
constraints: [node.role == manager]
networks:
- webnet
networks:
webnet:
also, following is the gateway.config file
http:
port: 80
admin:
port: 9876
hostname: localhost
apiEndpoints:
api:
host: 192.168.99.100
paths: '/ip'
localApi:
host: 192.168.99.100
paths: '/'
serviceEndpoints:
httpbin:
url: 'https://httpbin.org'
services:
urls:
- 'http://192.168.99.100:3000/serviceonerequest'
- 'http://192.168.99.100:3000/servicetwo'
policies:
- basic-auth
- cors
- expression
- key-auth
- log
- oauth2
- proxy
- rate-limit
pipelines:
default:
apiEndpoints:
- api
policies:
# Uncomment `key-auth:` when instructed to in the Getting Started guide.
# - key-auth:
- proxy:
- action:
serviceEndpoint: httpbin
changeOrigin: true
customPipeline:
apiEndpoints:
- localApi
policies:
- proxy:
- action:
serviceEndpoint: services
changeOrigin: true
The ip '192.168.99.100' is the docker-machine ip.
If I run the stack using the above gateway.config file, everything works fine.
However,IF I replace
services:
urls:
- 'http://192.168.99.100:3000/serviceonerequest'
- 'http://192.168.99.100:3000/servicetwo'
with
services:
urls:
- 'http://services_firstService:3000/serviceonerequest'
- 'http://services_firstService:3000/servicetwo'
I get a bad gateway!
This docker swarm runs an overlay network "webnet".So,I must be able to use the service name as the hostname in the gateway.config file according to this link.
In the above working case with the use of IP the services become available 'outside' of the gateway which I do not desire.
What is wrong?

Answer 1

SO I have found where I was going wrong!Look at the compose file above!The service names are firstService (a capital S!).
Now, if I used
urls:
- 'http://services_firstService:3000/serviceonerequest'
- 'http://services_firstService:3000/servicetwo'
the API gateway would keep looking for services_firstservice (Note the small 's' in firstService) which obviously is not present in the overlay network!
Now,I changed the names to small case and it works just as expected!
Here is the new Docker-compose file
version: "3"
services:
firstservice:
image: chaitanyaw/firstrepository:first
deploy:
replicas: 3
restart_policy:
condition: on-failure
networks:
- webnet
apigateway:
image: firstgateway:latest
deploy:
restart_policy:
condition: on-failure
ports:
- '80:80'
networks:
- webnet
visualizer:
image: dockersamples/visualizer:latest
ports:
- 8080:8080
volumes:
- /var/run/docker.sock:/var/run/docker.sock
deploy:
placement:
constraints: [node.role == manager]
networks:
- webnet
networks:
webnet:
Also,here is the gateway.config file
http:
port: 80
admin:
port: 9876
hostname: localhost
apiEndpoints:
api:
host: 192.168.99.100
paths: '/ip'
localApi:
host: 192.168.99.100
paths: '/'
serviceEndpoints:
httpbin:
url: 'https://httpbin.org'
services:
urls:
- 'http://services_firstservice:3000/serviceonerequest'
- 'http://services_firstservice:3000/servicetwo'
policies:
- basic-auth
- cors
- expression
- key-auth
- log
- oauth2
- proxy
- rate-limit
pipelines:
default:
apiEndpoints:
- api
policies:
# Uncomment `key-auth:` when instructed to in the Getting Started guide.
# - key-auth:
- proxy:
- action:
serviceEndpoint: httpbin
changeOrigin: true
customPipeline:
apiEndpoints:
- localApi
policies:
- proxy:
- action:
serviceEndpoint: services
changeOrigin: true

Answer 2

From a Gateway perspective, there's nothing wrong in the configuration. As long the DNS name can be resolved correctly, the request should go through with no problem.
What I would try to do is to log in the Gateway container and try to ping the two services. If something goes wrong, then most likely the docker-compose.yml file has some problem.
I'd try to remove the network key, for example. The network is implicitly created so you do not really need that part.
Also — I do not think that the DNS name for the service is services_firstService; I'd try with firstService directly.
Cheers,
V.