imam / amqphelp

AMQP helper

amqphelp

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(Currently) only can be use for Sribu and Sribulancer, might not be a package that you hope for :(

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To run simulation, do : npm run simulate -- ./simulation/files_to_be_simulated

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Ask-Answer

To ease back-and-forth communication between two entities, you can use ask and answer functionality.

Ask

If an entity need to 'ask' other entity to do/give something, you can use ask like this:

amqphelp.ask(entityToAsk, action, payload)

It will return a promise that will resolved after the entity that you asked responded to your 'ask'.

Answer

On the other end, the entity that being asked should answer. answer can be used like this:

amqphelp.answer(entityToAsk, callback)

In the callback we will give the payload that were given by the answer and you can give any values to the asker by returning anything in the callback.

amqphelp.answer(entityName, payload => {
    let payload_to_give_to_the_asker = anyfunction(payload);
    
    return payload_to_give_to_the_asker;
}

Model

We use an opiniated modeling system to ease the development when you want to connect to any database system and monitor any changes (create, update, delete) that they've been made and notify RabbitMq.

Service Name

Service name is an identifier in our modeling system. We use your package name in your package.json (process.env.npm_package_name) as service_name by default, but you can fire registerServiceName(service_name) if you want to change it.

//TODO:: Write about attacher, and custom attacher

Attacher

MongoDB

To use MongoDB with amqphelp, is as simple as:

amqphelp.model('mongo', payload_name, modelSchema, entitiesToSendTo)

For example, I want to send any changes that a mongodb model named employee made to an entity named boss. We can do

amqphelp.model('mongo', 'employee', modelSchema, ['boss'])

If my service_name is office, then every time employee changed, it will push these queues to RabbitMq:

create_employee_from_office_for_boss update_employee_from_office_for_boss delete_employee_from_office_for_boss

You can receive these with default receive method from amqphelp, but we made receiver class for more convenience use of this feature.

Populate

If you want to populate a document before sending it to RabbitMq, you can send an object contains name for entity to send's name and populate for the field that you want to be populated.

amqphelp.model('mongo', 'employee', modelSchema, [{name: 'boss', populate: ['companies']})]

Populate should be an array of path.

Receiving from model

To receive queues from a model, just extend amqphelp/app/helpers/receiver.js like this to the receiver entity.

class BossReceiver extends AmqpReceiver {
}

Then, attach that receiver class to your amqphelp entity.

amqphelp.modelReceive(new BossReceiver)

Settings

There are several settings that are required to register:

• receive_from, the name of entity that you receive the payload from
• payload_name, the name of payload that you'll be receiving
• service_name, the name of the current entity (default to your package name in your package.json)

You should register them in register method

class BossReceiver extends AmqpReceiver {

    register(){
        this.service_name = 'boss'
        this.receive_from = 'office';
        this.payload_name = 'employee';
    }

}

Managing payload

By default, when you're receiving any queues from model, we'll log the payload to console, and acknowledge that we've received the queue to RabbitMq. If you want to use the payload, you should add some/all of these methods according to your need: create, update, and delete, then call receiveCreate(callback), receiveUpdate(callback), or receiveDelete(callback).

Callback given to receive{Create|Update|Delete} would contain a payload as their first argument.

class BossReceiver extends AmqpReceiver{

    create(){
        this.receiveCreate(payload=>{
            //Things to do with the payload
        })
    }
    
    update(){
        this.receiveUpdate(payload=>{
            //Things to do with the payload
        })
    }

    delete(){
        this.receiveDelete(payload=>{
            //Things to do with the payload
        })
    }

}