chain-js

chain-js

A fork of chain-api implemented in Node using JSON-LD instead of HAL-JSON. This fork is non-functional in its current state; its purpose was merely to experiment with Node and JSON-LD implementations after having implemented chain-api with Django and HAL-JSON.

Usage

Docker is required.

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If you want a persistant data volume: in the docker/data folder, run ./build and ./create.

In the docker/debug folder: run ./build.

To run without persistant data, run ./run -i. To run with persistant data, run ./run -i --persist.

The server should be accessible at http://localhost:8080. Most of the frontend templates have not yet been created, so curl must be used. Only Site has been fully implemented. Some example usage follows:

Get a list of sites:

curl -H "Accept: application/json" http://localhost:8080/sites

Get JSON schema fro creating a site:

curl -H "Accept: application/json" http://localhost:8080/sites/create

Create a site:

curl -H "Accept: application/json" -H "Content-Type: application/json" http://localhost:8080/sites/create -d '{"name":"mysite"}'

Get a site:

curl -H "Accept: application/json" http://localhost:8080/sites/1

Edit a site:

curl -H "Accept: application/json" -H "Content-Type: application/json" http://localhost:8080/sites/1/edit -d '{"name":"yoursite"}'

Delete a site:

curl -H "Accept: application/json" -H "Content-Type: application/json" http://localhost:8080/sites/1/delete -d '{}'

Findings

Pros

1. JSON and JavaScript go hand-in-hand, and there was extensive library support available for JSON-Schema and JSON-LD, which were very compatible in their roles in specifying input formats and displaying linked output data, respectively.
   • JSON-LD demands schematic definitions of the fields (and the compiler enforces this demand), which is very favorable for designing intuitive data structures
   • JSON-LD has a number of interchangable formats for the same data structure (see the JSON-LD Playground for examples), which is convenient
   • JSON-LD's graph structures are much more powerful and more intuitive than HAL, which could be useful for implementing presence data, because presence data introduce cycles, which created problems in Chain-API.
2. Although I did not get a chance to implement the ZMQ or websocket sockets, JavaScript's callback and promise API's seem much more compatable with message queue frameworks in comparison to Python's delegate-based event handling API.

Cons

1. Model management: Django's model management is much better than the model management I attempted with Sequelize.js. I stopped working on the fork when the associations between model classes (ie many devices to 1 site) became difficult. Sequelize has custom methods it creates (ie site.getDevices().then(function() {...})) to find related resources. This made it difficult to generalize without getting very hackish very quickly.

Future Work

If this project is continued, options other than Sequelize.js should be explored for model management in order to clear up the association issues.