configurations phases:

configurations are an important part of the xyz ecosystem, hence it is important for the developer to know how to use them and manipulate them.

XYZ configurations can be set on 3 phases:

[3] The default value: stored in Constants.js file in xyz-core
[2] selfConf and systemConf passed to the constructor of xyz-core at runtime
[1] via command line arguments

and each of them have priorities indicated by [x] in the list. This means that whatever you pass in something as command line argument will override selfConf and Constants.js. Let’s look at each them one by one:

The default configuration: Constants.js

Recall from the two simple services that we worked with in the getting started section. Let’s lunch one of them but this time, we are not going to pass any configuration to it:

let xyz = require('xyz-core')
let mathMS = new xyz({
  selfConf: {},
  systemConf: {}
})

// register any services

console.log(mathMS)

As you can see the system lunches perfectly with the default values defined in Constants.js. The default name of the service will be node-xyz-init and one HTTP server will be launched by default on port 4000.

Runtime configurations: selfConf and systemConf

As you expect, whatever you place in selfConf and systemConf at runtime will override the default values.

let mathMS = new xyz({
  selfConf: {
    transport: [{type: 'HTTP', port: 4010}],
    name: 'from-self-conf'
  },
  systemConf: {nodes: []}
})

console.log(mathMS)

pay close attention to the values printed after console.log(mathMS) and see how the port of transport and name have changed.

Command line arguments

One last way to change configurations is to use command line arguments. Normally, you would run an instance like:

$ node mathMs.js

But, we have seen in the getting started section that you can actually override the port value of a node using:

$ node math.ms.js --xyz-transport.0.port 5002

this is actually a global pattern for overriding the configurations. It goes like this: --xyz-([CONFIG.KEY])* [CONFIG.VALUE]

As an example, you can change the name of a service via command line using:

$ node math.ms.js --xyz-name sth-from-cli

If you run a service like this, you’ll see that:

____________________  GLOBAL ____________________
selfConfig:
  {
  "name": "sth-from-cli",
  "defaultSendStrategy": "xyz.service.send.first.find",
  "logLevel": "info",
  ....

Keys with more depth can also be manipulated using a ., just as you access normal data in an object:

$ node mathMs.js --xyz-cli.enable true

// analogous to
// selfConf: {
//    ...
//    cli: {enable : true }
//    ...

Or with the port case:

$ node mathMs.js --xyz-transport.0.port 6000

// analogous to
// selfConf: {
//    ...
//    transport: [{type: '...', port: 6000 }]
//    ...

A complete example could be as follows:

$ node mathMs.js --xyz-logLevel debug --xyz-seed 127.0.0.1:4000 --xyz-name math.ms.slave