attak
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Last updated 3 years ago by mvegeto .
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Attak Distributed Computing Framework

Next generation serverless functions

ATTAK is a full-stack framework for applications built on auto-scaling components.

We aim to be platform agnostic, beginning with support for Amazon Web Services and then Google Cloud.

Why use ATTAK

Companies like Amazon and Google create amazing building block services, but they don't put much focus on tools combining them. ATTAK blends many services together to create a fully featured application framework, and offers tools for complex local simulation, multi-function unit testing, and much more. It handles the setup for permissions, event triggers, etc., and lets you focus on your application rather than platform specifics.

Status

Pre-alpha.

Roadmap:

  • Alpha AWS compatibility summer 2017
  • Alpha Google compatibility late 2017

Readme and other documentation may be inaccurate or incomplete.

Contents

Quick Start

Install cli

npm install -g attak

Create an attak topology

Generate a simple boilerplate project by running:

attak init

Setup environment

Rename .env.example to .env and put in values as appropriate for your deploy. The required fields are:

  • AWS_ACCESS_KEY_ID
  • AWS_SECRET_ACCESS_KEY
  • AWS_ROLE_ARN

Topology simulation and debugging

Visit the ATTAK ui and run the simulation with the command displayed, which will look like:

attak simulate -i [simulation id]

If you want to run the topology without the UI debugger, simply run

attak simulate

Deploy the topology

ATTAK will deploy all processors and streams in the topology.

attak deploy

Examples

Basic functionality demos

Complex examples

Topologies

An topology is a structure that defines the features of your application. It declares the resources required (serverless functions, message queues, static hosting, authentication, etc.) and ATTAK will automatically setup the permissions and connections necessary.

Note: An ATTAK project is meant to be a node package, so we will require the project directory, and index.js (or whatever is specified in package.json as main) will be loaded as your topology.

Every topology needs a name, but all other parameters are optional. They include:

  • processors - event handler functions
  • schedule - trigger processors periodically
  • streams - connections between processors
  • static - static hosting configuration
  • api - handle HTTP requests

At its core, a topology is a description of one or more processors and the connections between them. Here's an example of a very simple topology. Processors is a key-value map between processor name and procesor definition, and streams is an array of processor connections.

module.exports = {
  name: 'attak-example',
  processors: {
    reverse: './processors/reverse',
    hello_world_spout: './processors/hello_world'
  },
  streams: [
    ['hello_world_spout', 'reverse']
  ]
}

ATTAK can build many different types of applications. For instance, here's a topology that sets up static hosting and an HTTP endpoint, but no streams.

module.exports = {
  name: 'static-example',
  static: './public',
  api: 'requestHandler',
  processors: {
    requestHandler: function(event, context, callback) {
      callback(null, "Amazing HTTP request response")
    }
  }
}

Processors

Processors are the basic unit of computation in ATTAK and represents configuration for a single process. A processor has a main "handler function" that is called in response to events, and it can be used to process data, emit events, invoke other processors, call other handler functions locally, or otherwise run code in response to events.

Handler functions

Handler functions are called with an event, context, and callback like other serverless frameworks. Unlike other frameworks, ATTAK handlers have context.emit(topic, message), which allows them to send out data across the topology. They may emit any number of events, and must call the callback when finished. Here's an example handler:

module.exports = {
  handler: function(event, context, callback) {
    console.log(event)
    context.emit('output topic', 'hello ' + event.name)
    callback()
  }
}

Emitting events

Processors can emit any number of events on any number of topics. Events can optionally contain data of any type.

handler: function(event, context, callback) {
  context.emit('processing started')
  context.emit('got event', event)

  // If emitting a lot, do it asynchronously
  context.emit('frequent', 'event', function(err) {
    console.log('done emitting')

    // The handler must call the callback. We can emit
    // errors if we have them
    if (err) {
      callback(err)
    } else {
      callback()
    }
  })
}

Inline handlers

Processor handler functions can be defined inline

module.exports = {
  processors: {
    inlineProcessor: function(event, context, callback) {
      // process the event...
      event.total += 1
      context.emit('topic name', {your: 'data'})
      callback()
    }
  }
}

Processor folders

If all processors are in a single folder, processors can be set to the folder path.

module.exports = {
  processors: './processors'
}

Dynamic definitions

If we want to dynamically generate processors, we have two options.

We can define a function that will return an key-value map of processor name to processor definitions:

module.exports = {
  processors: function() {
    var processors = []
    
    for (var iProcessor=0; iProcessor<10; ++iProcessor) {
      processors.push(
        function(event, context, callback) {
          ...your processor logic...
        }
      )
    }

    return processors
  }
}

Or we can define a function that takes a processor name and returns processor definitions:

module.exports = {
  processor: function(name) {
    return function(event, context, callback) {
        ...your processor logic...
    }
  }
}

Handler callback

The processor's callback argument is important for several reasons

It signals the end of asynchronous execution

Serverless functions (which processors run on) are billed by the millisecond. Calling the callback shuts down process execution, which also shuts down billing.

Note: Emitting data is an asynchronous operation and takes some time. If a processor emits data and then immediately calls the callback, process execution will not halt until all emits are complete.

It allows the handler function to report errors without crashing.

Callbacks are one way to report errors. Error handling is an important topic, so it has it's own section.

Logs

Processor logs are recorded and stored according to the platform being used. For example, AWS Lambda logs can be found in AWS CloudWatch.

More logging features and details coming soon.

Error handling

Debugging issues on a distributed topology is difficult. When a processor has an error we want to figure out what the stack/context/event data were, and we may even want to know the states of other previous processors.

ATTAK has a built in error handling system. Errors are recorded, retries are configurable,

By default, errors are not replayed, but rather recorded into an errors queue. By default the queue lasts for 24 hours, but can be configured to persist into DynamoDB or other datastores.

reported errors

The handler callback can be called with an error as the first parameter to report an error.

handler: (event, context, callback) {
  try {
    throw new Error 'purposefully caused error'
  } catch(err) {
    callback(err)
  }
}

This will allow ATTAK to record the error and stop execution as fast as possible. Emits that were still processing before the error will be allowed to finish.

Streams

Streams setup the flow of data between processors. Behind the scenes, a stream configures ATTAK to send emitted data through a distributed queue (Kinesis Streams, for example) to another processor.

Static definitions

Since streams are simply connections between two processors, they can be defined very simply as an array

streams: [
  // Simple stream from source to destination
  ['sourceProcessor', 'destProcessor'],

  // There can be unlimited streams from a given processor
  ['sourceProcessor', 'otherProcessor'],

  // There can also be unlimited streams into a given processor
  ['otherProcessor', 'finalProcessor'],
 
  // Loops are fine too
  ['finalProcessor', 'sourceProcessor'],

  // Listen for events on a specific topic
  ['finalProcessor', 'otherProcessor', 'finalProcessorTopic'],
]

Streams can also be defined as an object structure, which allows for more options to be defined:

module.exports = {
  name: 'stream-example'
  streams: [
    {
      from: 'processor1',
      to: 'processor2',
      shards: 50
    }
  ]
}

Dynamic definitions

Streams can be defined dynamically by providing a function for your topology's streams parameter. The function is called as the topology is loaded, and should return an array of stream definitions (in either array or object format)

  streams: function() {
    var streams = []

    for (var iStream=0; iStream<NUM_PROCESSORS; ++iStream) {
      streams.push({
        to: `processor${iStream}`,
        from: `processor${iStream == NUM_PROCESSORS - 1 ? 0 : iStream + 1}`
      })
    }

    return streams
  }

Schedule

ATTAK can trigger processors on a schedule. Schedules can be define in cron-like pattens or by specifying a call frequency.

  module.exports = {
    name: 'scheduled',
    schedule: [
      {
        name: 'every_2_minutes_cron',
        type: 'cron',
        value: '*/2 * * * ? *',
        processor: 'onEvent'
      },
      {
        name: 'every_minute_rate',
        type: 'rate',
        value: '1 minute',
        processor: 'onEvent'
      }
      {
        name: 'twice_a_day_rate',
        type: 'rate',
        value: '12 hours',
        processor: 'onEvent'
      }
    ],
    processors: {
      onEvent: function(event, context, callback) {
        console.log("INSIDE SCHEDULED EVENT HANDLER", event)
        callback(null, {ok: true})
      }
    }
  }

Static

ATTAK can configure your files to be hosted statically on services like s3. It will also assist with setting up things like federated authentication (sending users through a google authentication flow for AWS Cognito credentials, for instance).

Directory hosting

Setting up basic static hosting is easy:

  module.exports = {
    // Uploads all files in public and makes them publicly viewable
    static: './public'
  }

Authentication

This feature is under active development, but an example looks something like:

  static: {
    // Expose files inside the build directory
    dir: './build',
    permissions: {
      // Setup permissions for the front end to invoke processor1
      invoke: ['processor1']
    },
    auth: {
      federated: {
        // Setup a federated google auth flow using an api key
        google: {
          key: '...'
        }
      }
    }
  },

API

ATTAK processors can be used to handle http requests. To do this, specify one of your processors in the api parameter

module.exports = {
  name: 'api-example',
  api: 'requestHandler'
  processors: {
    requestHandler: function(event, context, callback) {
      callback null, {
        body: 'ATTAK!',
        statusCode: 200,
        headers: {
          'Content-Type': 'text'
        }
      }
    }
  }
}

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