Hyperledger Composer cannot connect with dockerized Node.js app

Question

I am working in a POC using Hyperledger Composer v0.16.0 and Node.js SDK. I have deployed my Hyperledger Fabric instance following this developer tutorial and when I run locally my Node.js app via node server.js command it works correctly, I can retrieve participants, assets, etc.

However, when I Dockerize my Node.js app and I run the container for this app I am not able to reach the Hyperledger Fabric instance. So, how can I set the credentials to be able to reach my Hyperledger Fabric or another one since my Node.js app?

My Dockerfile looks like this:

FROM node:8.9.1
WORKDIR /usr/src/app
COPY package*.json ./
RUN npm install
COPY . .
EXPOSE 3000
CMD [ "npm", "start" ]

I run my docker/node.js image with this command:

docker run --network composer_default -p 3000:3000 -d myuser/node-web-app

Answer 1

There are 2 pitfalls to watch out for with Dockerizing your app. 1. Location of Cards and 2. Network Address of Fabric servers.

1. The Business Network Card(s) used by your app to connect to the Fabric. These cards are in a hidden folder under your default home folder eg /home/thatcher/.composer on a Linux machine. You need to 'pass' these into the container or share them with a shared volume as suggested by the previous answer. So running your container for the first time try adding this in the command -v ~/.composer:/home/<user>/.composer where is the name of the default user in your container. Be aware also that the folder on your Docker Host machine must allow write access to the UID of the user inside the container.

2. When you have sorted out the sharing of the cards you need to consider what connection information is in the card. It is quite likely that the Business Network Card you are using will be using localhost as the addresses of your Fabric servers, the port forwarding of the ports from your Docker host into the containers means that localhost is easy and works. However in your container localhost will redirect inside the container so will not see the Fabric. The arguments on the Docker command --network composer_default will set up your new container on the same Docker network as the Fabric Containers and so your Container could see the 'addresses' of the Fabric servers eg orderer.example.com but you card would then fail outside your container. The best way forward would be to put the IP Address number of your Docker Host machine into the connection.json file instead of localhost, and then your card would work inside and outside of your container.

Answer 2

So, credentials would be config info. The two ways to pass config info into a basic docker container are:

1. environment variables (-e)
2. mount a volumes (-v) with config info.

You can also have scripts that you install from Dockerfile that modify files and such.

The docker logs may give clues as to the exact problem or set of problems.

docker logs mynode

You can also enter a running container and snoop around using the command

docker exec -it mynode bash