Unable to access REST service deployed in docker swarm in AWS

Question

I used the cloud formation template provided by Docker for AWS setup & prerequisites to set up a docker swarm.

I created a REST service using Tibco BusinessWorks Container Edition and deployed it into the swarm by creating a docker service.
docker service create --name aka-swarm-demo --publish 8087:8085 akamatibco/docker_swarm_demo:part1
The service starts successfully but the CloudWatch logs show the below exception:

I have tried passing the JVM environment variable in the Dockerfile as :
ENV JAVA_OPTS= "-Dbw.rest.docApi.port=7778"
but it doesn't help.

The interesting fact is at the end the log says:
com.tibco.thor.frwk.Application - TIBCO-THOR-FRWK-300006: Started BW Application [SFDemo:1.0]
So I tried to access the application using CURL -
curl -X GET --header 'Accept: application/json' 'URL of AWS load balancer : port which I exposed while creating the service/resource URI'
But I am getting the below message:

The REST service works fine when I do docker run.
I have checked the Security Groups of the manager and load-balancer. The load-balancer has inbound open to all traffic and for the manager I opened HTTP connections.

I am not able to figure out if anything I have missed. Can anyone please help ?

Answer 1

As mentioned in Deploy services to swarm, if you read along, you will find the following:

PUBLISH A SERVICE’S PORTS DIRECTLY ON THE SWARM NODE
Using the routing mesh may not be the right choice for your application if you need to make routing decisions based on application state or you need total control of the process for routing requests to your service’s tasks. To publish a service’s port directly on the node where it is running, use the mode=host option to the --publish flag.

Note: If you publish a service’s ports directly on the swarm node using mode=host and also set published= this creates an implicit limitation that you can only run one task for that service on a given swarm node. In addition, if you use mode=host and you do not use the --mode=global flag on docker service create, it will be difficult to know which nodes are running the service in order to route work to them.

Publishing ports for services works different than for regular containers. The problem was; the image does not expose the port after running service create --publish and hence the swarm routing layer cannot reach the REST service. To resolve this use mode = host.

So I used the below command to create a service:
docker service create --name tuesday --publish mode=host,target=8085,published=8087 akamatibco/docker_swarm_demo:part1

Which eventually removed the exception.

Also make sure to configure the firewall settings of your load balancer so as to allow communications through desired protocols in order to access your applications deployed inside the container.
For my case it was HTTP protocol, enabling port 8087 on load balancer which served the purpose.