@unu/taube v5.4.2

🕊 Taube

Taube is a microservice communication framework that enforces compatibility between Clients and Servers.

It is designed to enforce RESTful API design and provide easy Queueing without complex setup. It also provides standardized Errors.

It aims to leverage existing tooling as much as possible such as DNS and service discovery from an external provider as well as existing transfer protocols that are well supported and maintained:

• HTTP (express)
• RESTful
• AMQP (RabbitMQ)

npm install @unu/taube

Table of Contents

1. Quick start guide
2. Client/Server
3. Environment variables
4. Monitoring and Signal Handling
5. Publisher/Subscriber
6. Queue/Worker
7. AMQP
8. Errors
9. Metrics
10. Writing unit tests for projects using Taube
11. Migrate from cote
12. Migrate to Taube v4
13. Unit tests

Quick start guide

One service acts as a Server providing data and another as a Client requesting data.

import taube from '@unu/taube'
taube.http.init()

const server = new taube.Server({})
server.get(
  `/scooters/:id`,
  {
    params: Joi.object().keys({
      id: Joi.string().required()
    })
  },
  async(req) => {
    return `Data for ${req.params.id}`
  }
)

Any Client can now request data:

import taube from '@unu/taube'

const client = new taube.Client({
  uri: 'http://scooter'
})

async function run() {
  await client.get('/scooters/123')
}

Client/Server

The Client and Server components mimic the standard way of sending and routing http request, using the correct RESTful verbs.

Client

Client component is a wrapper around got that exposes different http methods to send a request.

import taube from '@unu/taube'

const client = new taube.Client({
  uri: 'http://scooter'
})

the Client supports 4 http methods:

GET

const response = await client.get('/scooters',
                                { query: { type: 'UNU2' } }) // Query

POST

const response = await client.post('/scooters',
                                { vin: '123' }, // Body
                                { query: { type: 'UNU2' } }) // Query

PUT

const response = await client.put('/scooters/123',
                                 { online: true }, // body
                                 { query: { type: 'UNU2' } }) // Query

DELETE

const response = await client.delete('/scooters/123', { type: 'UNU2' })

NOTE: Passing in options with a query or searchParams option does overwrite any passed url query arguments:

// This will NOT pass `page`
client.get(`/?page=2`, { query: { type: 'UNU2' }})

Client Options

Server

Server is a wrapper around the express Router that can register routes. it also enforces validation for all routes.

The Server component require HTTP to be intialized. Add taube.http.init().

import taube from '@unu/taube'
taube.http.init()

const server = new taube.Server({})

The Server component support 4 methods, each method expects 3 required arguments passed in to it:

• path: the route (express style)
• validation: a Joi object describing how the body and/or params of the request must look like
• handler function

GET

  server.get(
    `/scooters/:id`,
    {
      params: Joi.object().keys({
        id: Joi.string().required()
      }),
      query: Joi.object().keys({
        type: Joi.string().required()
      })
    },
    async(req) => {
      // do something
    }
  )

POST

  server.post(
    `/scooters`,
    {
      body: Joi.object().keys({
        vin: Joi.string().required()
      })
    },
    async(req) => {
      // do something
    }
  )

PUT

  server.put(
    '/scooters/:id',
    {
      body: Joi.object().keys({
        online: Joi.boolean()
      }),
      params: Joi.object().keys({
        id: Joi.string().required()
      })
    },
    async(req) => {
      // do something
    }
  )

DELETE

  server.delete(
    `/scooters/:id`,
    {
      params: Joi.object().keys({
        id: Joi.string().required()
      })
    },
    async(req) => {
      // do something
    }
  )

Pagination

Taube supports pase-based pagination. A paginated route can be registered on the Server like this:

server.paginate(
  '/scooters',
  {},
  async(req) => {
    // req.query.page
    // req.query.limit
  }
)

This route also accepts Joi validation parameters. Validating the page and limit happens automatically and you don't need to manually validate those on the req.query object. Server expects the response returned from a paginated handler to be in this specific format. If you don't return it, a run-time error will be thrown.

{
  data: [] // array of the results,
  pagination: { // metadata about the pagination
    page: Number,
    limit: Number,
    totalDocs: Number,
    totalPages: Number,
    hasNextPage: Boolean,
    nextPage: Number,
    hasPrevPage: Boolean,
    prevPage: Number,
    pagingCounter: Number
  }
}

To make a request to a paginated route, you can use the Client in this way:

const response = await client.paginate('/scooters')

The client.paginate function accepts a second options object that describes the page and limit. By default Taube uses the values { page: 1, limit: 20 } if no options is passed in, otherwise uses the passed in values.

const response = await client.paginate('/scooters', { page: 3, limit: 10 })
// response.data
// response.pagination

Responders

The Server component require HTTP to be intialized. Add taube.http.init().

import taube from '@unu/taube'
taube.http.init()

const responder = new taube.Responder({
  key: 'users'
})

responder.on('get user', async({ prop1, prop2 }) => {
  return 'Bob'
})

Responder Options

Requesters

import taube from '@unu/taube'

// Creating the requester needs to be one of the first things in your application
// Assuming that a Responder with the given key is set up on the given uri
const requester = new taube.Requester({
  uri: 'http://localhost',
  key: 'users'
})

const res = await requester.send({
  type: 'get user',
  prop1: 'asd',
  prop2: 'asd'
})

Requester Options

The url option needs to include http or https without a / at the end.

• In Kubernetes the uri would be the name of the service (if in the same namespace) or the full dns (if not in the same namespace).
• In docker-compose the uri would be the service name.

Environment variables

Monitoring and Signal Handling

@unu/observability can be used to get readiness/liveness checks and signal handling for the taube http server.

import observability from '@unu/observability'

observability.monitoring.observeServer(taube.http.server, taube.http.app)

In order to gracefully handle Signal Handling and add liveness/readyness checks for AMQP, the following code can be used

import observability from '@unu/observability'

observability.monitoring.addOnSignalHook(taube.shutdown)

Publisher/Subscriber

The Publisher/Subscriber components can be used to connect to a AMQP enabled message broker. They provide the Publisher/Subscriber pattern to taube users.

To use these features you need to explicitly connect taube to a AMQP enabled message broker (e.g. RabbitMQ) using taube.amqp.init(). taube.amqp.init() can be called multiple times. It only has an effect once.

Taube handles reconnecting to RabbitMQ through a library. All requests during a connection outage are saved in memory and will be flushed after reconnecting. There is no timeout for this, it will save messages indefinitely.

A subscriber can be setup to listen to all events of a topic type:

const userSubscriber = new taube.Subscriber({
   key: 'users',
   brokerUri: 'amqp://guest:guest@localhost'
})

userSubscriber.on('users updated', async(data) => {
  try {
    console.log(data)
  } catch(err) {
    // Handle your errors or you will get unhandled rejections
  }
})

A Publisher is used to publish the corresponding events:

const publisher = new taube.Publisher({ key: 'users' })

publisher.publish(`users updated`, { data: {} })

Every Publisher/Subscriber creates a Channel to RabbitMQ. There is a maximum number of channels per connection which is defined by your RabbitMQ configuration. The default is 2047 per connection.

Technical implementation details

Overview of the process between Publisher and Subscriber including the RabbitMQ concepts

+-----------------------+-------------------------------------------+--------------------------+
|     Taube             |                RabbitMQ                   |            Taube         |
|                       |                                           |                          |
|                       |                                           |                          |
|                       |                      +---------------+    |     +------------------+ |
|                       |            topic a   |temporary queue| channel  | taube Subscriber | |
|                       |          +---------->+     -key      +----+---->+      -key        | |
|                       |          |           |     -topic a  |    |     +------------------+ |
| +---------------+  channel   +---+----+      +---------------+    |                          |
| |taube Publisher+-----+----->+exchange|                           |                          |
| +---------------+     |      |  -key  |                           |                          |
|                       |      +---+----+                           |                          |
|                       |          |                                |                          |
|                       |          |           +---------------+ channel  +------------------+ |
|                       |          +---------->+temporary queue+----+---->+ taube Subscriber | |
|                       |            topic b   |     -key      |    |     |      -key        | |
|                       |            topic a   |     -topic b  |    |     +------------------+ |
|                       |                      |     -topic a  |    |                          |
|                       |                      +---------------+    |                          |
|                       |                                           |                          |
+-----------------------+-------------------------------------------+--------------------------+

Concepts:

• exchange: An exchange is the place where the Publishers send their messages. Queues can "listen" on exchanges
• queue: A queue of messages that listens on an exchange. In Pub/Sub we use non persistant, non worker queues
• channels: Multiple lightweight connections that share a single TCP connection between a process and RabbitMQ

Process:

After both the Publisher and Subscriber have registered their components a publish works like this:

1. Publisher sends message to exchange
2. Exchange sends message too all queues that listen to that key and topic (key and route called in RabbitMQ)
3. All queues trigger their consumers (listeners), which in this case is the taube Subscriber

Queue/Worker

Taube supports RabbitMQ queue workers with exponential retries.

Every message will be retried multiple times and discarded if the last retry fails.

Every message will be retried after 1, 10, 60 seconds, 10 minutes and 24 hours. After that they are considered failed. An error handler can be passed for failed messages. If no error handler is passed, they are discarded.

The Queue/Worker is made up of two parts:

• The Queue component sends messages to the queue to be consumed
• The Worker component handles messages coming in the queue and consumes them

In order for the Queue/Worker component to be available, you need to pass brokerUri.

The Queue component can be used to enqueue any data that can be used with JSON.stringify:

const { Queue } = taube.QueueWorkerExponentialRetries

const queue = new taube.Queue('example-queue-1', {
   brokerUri: 'amqp://guest:guest@localhost'
})
await queue.enqueue({ some: 'data' })

The Worker component will consume these messages:

const { Worker } = taube.QueueWorkerExponentialRetries

const worker = new Worker('example-queue-1', {
  brokerUri: 'amqp://guest:guest@localhost',
  worker: {
    prefetch: 2 // change worker prefetch value
  }
  errorHandler: ({
    error, message, payload, instance
  }) =>
    // e.g. send to Sentry
    console.error(
      error, // the thrown error
      message, // the original RabbitMQ message
      payload, // the containing payload
      instance // the Worker instance, can be used to get the name: instance.name
    )
})
await worker.consume((data, headers, message) => {
  console.log(data) // Actual payload
  console.log(headers) // Headers
  console.log(message) // Original AMQPlib meta object with additional data
})

The optional errorHandler will be called if all retries failed.

Connect to existing exchanges

The Worker component can bind to an existing exchange. You can pass any routing key using standard topic routing key specification: https://www.rabbitmq.com/tutorials/tutorial-five-python.html

You can use this to for example tie it to the standard MQTT exchange amq.topic:

const worker1 = new Worker('some-worker-name', {
    brokerUri: 'amqp://guest:guest@localhost',
    extraKeyBindings: [
      {
        exchange: 'amq.topic',
        routingKey: '#.telemetry',
      },
    ],
  })

Multiple bindings can be passed.

Beware that the MQTT plugin turns / into . This means for example that the MQTT topic VIN123/telemetry/sensor-a becomes the routing key VIN123.telemetry.sensor-a.

See https://www.rabbitmq.com/mqtt.html#implementation for more information on MQTT behavior.

Binary mode

By default the Worker and Queue component will assume the data is JSON compatible.

The Queue component will JSON.stringify everything that is enqueued and the worker component will JSON.parse everything that is consumed.

You can disable this behavior by passing the option json: false into either the Queue or the Worker:

const worker1 = new Worker('some-worker-name', {
    brokerUri: 'amqp://guest:guest@localhost',
    json: false
  })

This can be useful when for example parsing Protocol Buffers.

AMQP

Taube exposes an AMQP interface directly. You can get an active channel using:

const channel = await taube.amqp.channel({
  brokerUri: consts.brokerUri,
  ...amqpConnectionOptions // optional
})

You can pass in optional properties alongside brokerUri according to these specs.

This cannel exposes the mode-amqp-connection-manager channel wrapper interface. It can be used to for example publish messages directly to an exchange:

await channel.publish('amq.topic', '.2G.Rx.IMEI12345', Buffer.from('test'))

Technical Details

This setup is based upon https://www.brianstorti.com/rabbitmq-exponential-backoff/

In summary, failed messages are put on retry queues with a specific TTL (e.g. queue-1.RETRY1000 for 1 second). Those retry queues do not have a consumer and messages on it will always end up on the dead letter exchange. In our case, that exchange is the primary exchange again.

This way we make sure that messages are re-processed.

Errors

Errors component can be used to throw an error with proper HTTP statusCode.

This can handle all kinds of HTTP 4XX and 5XX errors.

To use this module, you need to import Errors module from taube and use the proper error constructor or statusCode.

new Errors[constructorName || statusCode] ([message, data])

Create a new error object with the given error message.

• constructorName : constructor name of error
• statusCode : the stautsCode which is Number

And there are two ways of throwing a taube error instance.

Throwing an error using constructor name

import { Errors } from '@unu/taube'

// joi/celebrate validation error
if(VALIDATION_FAILURE) {
  const message = 'validation failed'
  const data = { validation: '"scooterVin" is required'}  // validation failure message from joi/celebrate
  throw new Errors.BadRequest(message, data)
}

Throwing an error using statusCode

import { Errors } from '@unu/taube'

// your code
if(!scooter) {
  const message = 'validation failed'
  const data = { validation: '"scooterVin" is required'}
  throw new Errors[400](message, data)
}

And the requester will receive an error like below.

function errorHandler(err, req, res, next) {
  const { name, statusCode, message, data } = err
  // name: BadRequest
  // statusCode: 400
  // message: 'validation failed'
  // data: { validation: '"scooterVin" is required'}
}

You can find more example codes from the example/Errors folder.

List of all constructors

Metrics

Taube can expose Prometheus metrics of the underlying express server.

This will expose common RED (Request, Error rate, Duration of requests), and USE (Utilisation, Saturation, and Error rate) metrics.

In order to expose these metrics you will have to set TAUBE_EXPOSE_PROMETHEUS_METRICS. They are exposed at /-/taube-metrics and all have the prefix taube_.

See underlying library for details.

Writing unit tests for projects using taube

Currently does not support Publisher/Subscriber unit testing. Those unit tests will require a usable AMQP message broker connection initialized using taube.amqp.init(). You will need to call taube.shutdown() in

taube auto detects running in NODE_ENV=test and overwrites all requesters with uri = http://localhost. This means all Responders can easily be mocked. See test/unit-test.test.js for an example. It also uses a random port then which ensures that all Requesters and Responders in a process can only contact each other.

You can also force this by setting TAUBE_UNIT_TESTS

Contributing to the taube project

In order to run the unit tests, you need to run docker-compose up inside .test/. Then run npm run test-verbose to run the unit tests.

This project has a unit test line coverage of 100% and everything below that fails the ci jobs.

A few tests need to run before any other. These tests are prefixed by 0.X. Do not change their order.

Migrate from cote

You will have to install taube at version 2. npm install @unu/taube@2 to follow this part.

Version 0.X is designed to have a clear migration path to remove cote. Taube 0.X is a drop in replacement for cote. Without configuration it functions as a wrapper to cote and keeps using cote for communication. It also sets up http Responders, which means the service using Taube can be targeted by Taube Requesters.

There is 3 modes you can run taube in while migrating from cote to taube.

1. Mode 1: Still use cote. Requesters/Responders and Publisher/Subscribers still use cote for communication
2. Mode 2: Use taube, but still provide cote. Requesters will use HTTP and Subscribers AMQP. But Responders will still provide cote and Publishers will still publish using cote.
3. Mode 3: Disable cote. cote components will no longer be created.

These settings can be tuned per component type:

The following is a proposed migration path:

1. Replace all require('cote') with require('@unu/taube')
2. Make sure your tests pass
3. Pick a service
4. Make sure it has a resolvable dns (e.g. add a Kubernetes service to it)
5. Enable the taube services you want to use selectively. It is prefferable to activate one of the two options per iteration.
   1. For Requester/Responder HTTP: Add the environment variable TAUBE_HTTP_ENABLED=true to the service
   2. For AMQP Publisher/Subscribers: Initialize amqp pub/sub using the method described in Publisher/Subscriber
6. Make sure your tests pass
7. Go to 3 until no more services

Additional Environment Variables

Requesters and Responders

In order to activate HTTP for all Taube Requesters in a service you need to provide TAUBE_HTTP_ENABLED=true (if you are using it in a service inside stack, then this is already turned on).

Additional Responder Options

Additional Requester Options

Publisher/Subscriber

In order to use RabbitMQ based pub/sub, you need to explicitly activate it using and TAUBE_AMQP_ENABLED and connect taube to a AMQP enabled message broker (e.g. RabbitMQ) using taube.amqp.init().

Migrate to Taube v4

With Version 4.0.0 some breaking changes were introduced:

Remove taube.init() function.

Remove this function call to migrate to v4.

Added taube.http.init() to initialize HTTP based services.

This will be required for most Services. Add it after requiring taube in your index.js:

import taube from '@unu/taube'
taube.http.init() // This was added

Removed TAUBE_AMQP_URI usage and moved to a per-component broker connection

Every Queue, Worker, QueueWorkerExponentialRetries.Worker, QueueWorkerExponentialRetries.Queue, Subscriber and Publisher can now have its own AMQP connection.

This means that for all these components the new brokerUri option has to be passed.

The TAUBE_AMQP_URI environment variable is not used anymore and can be removed.

// QueueWorkerExponentialRetries components

new taube.QueueWorkerExponentialRetries.Worker('queue name', {
  brokerUri: 'amqp://guest:guest@localhost'
})

new taube.QueueWorkerExponentialRetries.Queue('queue name', {
  brokerUri: 'amqp://guest:guest@localhost'
})

// Classic Queue/Worker components
new taube.Queue({
  key: 'process',
  brokerUri: 'amqp://guest:guest@localhost'
})

new taube.Worker({
  key: 'process',
  brokerUri: 'amqp://guest:guest@localhost'
})

// Classic Publisher/Subscriber components
new taube.Subscriber({
  key: 'scooter',
  brokerUri: 'amqp://guest:guest@localhost'
})

new taube.Publisher({
  key: 'scooter',
  brokerUri: 'amqp://guest:guest@localhost'
})

Unit tests

In order to run unit tests locally, you need a running RabbitMQ instance with MQTT:

docker run -p 5672:5672 -p 15672:15672 -p 1883:1883 -e RABBITMQ_DEFAULT_USER=guest -e RABBITMQ_DEFAULT_PASS=guest r.unueng.com/cloud/rabbitmq-plugins:3.9-1

After it is running you can run npm run test-dev.