Hemera-web

Http route mapping for Hemera microservices. Based on Express 4

• Depends on minimalist and new web framework Express 4
• Respect Body and Query payload as pattern
• Provide a REST like interface /:topic/:cmd to Hemera
• Transport small binary or text data in pattern
• Returns correct Hemera errors without stack traces

Usage

const hemera = new Hemera(nats)
hemera.use(require('hemera-web'), {
  port: 3000,
  host: '127.0.0.1',
  pattern: {} // fixed pattern or function (request) => { }
})

How to execute a server method ?

You can transport the pattern in different ways:

• As Query parameters
• As Payload from type JSON
• As Payload from type x-www-form-urlencoded
• topic and cmd can be declared in url parameters

Examples

• GET Request

http://localhost:3000?topic=math&cmd=add&a=1&b=2
http://localhost:3000/math/add?a=1&b=2

• POST Request

http://localhost:3000?topic=math&cmd=add
http://localhost:3000/math/add

Body:
{
  "a": 1,
  "b": 2
}

• application/x-www-form-urlencoded

http://localhost:3000?topic=math&cmd=add
http://localhost:3000/math/add

Payload: a=1&bd=2

Define default pattern

In Hemera:

const hemera = new Hemera(nats)
hemera.use(hemeraWeb, {
  port: 3000,
  host: '127.0.0.1',
  pattern: {
    topic: 'math'
  }
})
 
GET - http://localhost:3000?cmd=add&a=1&b=2

Error handling

In Hemera:

const CustomError = hemera.createError('CustomError')
 
hemera.add(
  {
    topic: 'math',
    cmd: 'add'
  },
  function(req, cb) {
    const error = new CustomError()
    error.statusCode = 404
    cb(error)
  }
)

Results in

Status Code: 404 - default (500)

{
  "error": {
    "name": "Error",
    "message": "test",
    "hops": [
      {
        "service": "math",
        "method": "a:1,b:2,cmd:add,topic:math",
        "app": "hemera-starptech",
        "ts": 299208574491
      }
    ]
  }
}

Show error stack for debugging

In Hemera:

const hemera = new Hemera(nats)
hemera.use(hemeraWeb, {
  port: 3000,
  host: '127.0.0.1',
  errors: { propBlacklist: [] }
})

Access to express web framework

const hemera = new Hemera(nats)
hemera.use(hemeraWeb, {
  port: 3000,
  host: '127.0.0.1'
})
hemera.ready(() => {
  const app = hemera.express
  // Define Auth layer ... use it as always
  app.use(passport.session())
})

Plugin decorators

• .express