docker-engine

docker-engine

A Docker Engine API client for Node, driven at run-time by Docker's Swagger definition.

Why?

There are a number of excellent modules that allow you to connect to the Docker Engine API, but each of them caused me a problem in different ways. Whilst looking at making changes to these modules I realised that all a Docker API client needed was to use the Swagger file that Docker provides.

harbor-master: Has a minor issue with some endpoints. I investigated how to fix this and discovered that the API endpoint definitions use Joi; since Swagger files are maintained by Docker themselves, I felt that this was the wrong way to go.

dockerode: Dockerode also takes the approach of maintaining 'by hand' the connections between itself and the Docker API definitions. An example is the code required to implement the 'inspect container' endpoint. As with harbor-master I felt that this part of the module should be driven by the Swagger file.

docker-client: This module is driven the Swagger file. It's not dynamic--the client is generated with a code-generator that uses the Swagger file as input--but it would have been fine for my purposes. However, I was completely unable to get it to work with my local Docker Swarm. That's almost certain to be my fault, but I couldn't wait any longer, so had to move on. Note that because the client is generated it will be aligned with a specific version, whilst an approach that uses the Swagger file at run-time could be more dynamic.

Our Approach

Key to the approach we've taken here is:

• to use the Swagger file as a single source of truth to drive the creation of the client. And more specifically, to do this at run-time so that the same module can be used for any version of the Docker API, without needing to be continually updated;
• to use ES6 proxies to allow the client methods to be wrapped and so present different kinds of interfaces to developers. This makes it very easy to present harbor-master- or docker-client-compatible interfaces that still benefit from being Swagger-driven.

Future Work

The docker-modem module provides all of the connection code we would need for talking to the Docker API, handling TLS, duplex streaming, and so on. However, I wasn't quickly able to work out how to wire it in to docker-engine. This means that until docker-modem is incorporated the communication part of docker-engine is extremely basic.