RabbitMq Project

The purpose of this project is to show the use of RabbitMQ + NodeJs with a generic and simple to understand implementation.

What will be shown in this project?

How to send messages to a specific Exchange on RabbitMQ.
How to bind the Exchange to a queue.
How to consume messages form a specific Queue.
How to set up Dead Letters Exchanges and bind them to a queue.

Senario: Setting Up RabbitMQ

As we called senario, we need to handle it in the code by programming. It is only a perspective of our goal/implemented code.

amq-gen-id is generated by your app.

Queue Configuration(You’d better to use APIs):

Go to Queues Tab on RabbitMQ
Click on Add a new queue bellow the table with all queues
Create three new queues with the following configuration

Name: log_aiservice  
Durabillity: Durable  
Auto delete: No  
Arguments: Leave it empty  

Name: error_aiservice  
Durabillity: Durable  
Auto delete: No  
Arguments: Leave it empty  

Name: sub-aiservice  
Durabillity: Durable  
Auto delete: No  
Arguments:  x-dead-letter-routing-key= amq-gen-id_dead_letter , x-dead-letter-routing-key = sub-aiservice

Exchange Configuration

Go to Exchanges Tab on RabbitMQ
Click on Add a new Exchange bellow the table with all exchanges
Create two new Exchanges named AMQ-GEN-ID and amq-gen-id_dead_letter both with Type: topic | Durabillity: Durable | Auto delete: No | Internal: No and let Arguments empty.

Remember these configurations are default for the project, if you wish to change the names remember to adapt the project to them on the following steps!

Click on the new Exchange named AMQ-GEN-ID
Inside AMQ-GEN-ID click on Bindings
Create two new followed Bidings

To queue: sub-aiservice
Routing Key: aiservice
Arguments: Leave it empty

To queue: log_aiservice
Routing Key: aiservice
Arguments: Leave it empty

Now go back to Exchanges and go to amq-gen-id_dead_letter exchange Create a new Biding:

To queue: error_aiservice
Routing Key: sub-aiservice
Arguments: Leave it empty

Custom APIs rabbitmq-management

Based on the followed link let’s extract some tips:

APIs of rabbitmq-management

To make a request put in http://localhost:15672/api/{followed-api-names}

Might you need to leave username and password of guest at header request.

/whoami

Details of the currently authenticated user.

#gateway By Axios GET

/aliveness-test/vhost

Declares a test queue, then publishes and consumes a message. Intended for use by monitoring tools. If everything is working correctly, will return HTTP status 200 with body:

{"status":"ok"}

Note: the test queue will not be deleted (to to prevent queue churn if this is repeatedly pinged).

#gateway By Axios GET

/vhosts/yourDesireName

#gateway By Axios POST it without body on the initialization of your app.

/permissions/vhost/user

#gateway By Axios Get it to know if you have read, write, or configure access or not.

/policies/vhost/name

An individual policy. To PUT a policy, you will need a body looking something like this:

{"pattern":"amq.gen-*", "definition": {"amq-gen":"all"}, "priority":0, "apply-to": "all"}

pattern and definition are mandatory, priority and apply-to are optional.

#gateway By Axios PUT it with body and then check it if is there a old policy or not.

/vhosts

A list of all vhosts.

#gateway By Axios GET to find total count of vhosts.

/nodes

A list of nodes in the RabbitMQ cluster.

#gateway By Axios GET to find total count of nodes.

/queues/vhost

A list of all queues in a given virtual host.

#gateway By Axios GET to find total count of queues of a vhost.

/queues/vhost/name/contents

Contents of a queue. DELETE to purge. Note you can’t GET this.

#gateway By Axios DELETE to purge a name service queue. Do it on step of initilization.

/queues/vhost/name

An individual queue. To PUT a queue, you will need a body looking something like this:

{"auto_delete":false,"durable":true,"arguments":{},"node":"rabbit@smacmullen"}

All keys are optional. This API doesn’t have POST method supportation by RabbitMq.

When DELETEing a queue you can add the query string parameters if-empty=true and / or if-unused=true. These prevent the delete from succeeding if the queue contains messages, or has consumers, respectively.

#gateway By Axios PUT to review above json when you use amqplib.

/queues/vhost/name/get

Get messages from a queue. (This is not an HTTP GET as it will alter the state of the queue.) You should post a body looking like:

{"count":5,"requeue":true,"encoding":"auto","truncate":50000}

count controls the maximum number of messages to get. You may get fewer messages than this if the queue cannot immediately provide them.
requeue determines whether the messages will be removed from the queue. If requeue is true they will be requeued - but their redelivered flag will be set.
encoding must be either “auto” (in which case the payload will be returned as a string if it is valid UTF-8, and base64 encoded otherwise), or “base64” (in which case the payload will always be base64 encoded). If truncate is present it will truncate the message payload if it is larger than the size given (in bytes).
truncate is optional; all other keys are mandatory.

Please note that the get path in the HTTP API is intended for diagnostics etc - it does not implement reliable delivery and so should be treated as a sysadmin’s tool rather than a general API for messaging.

#gateway In the getMessageCount() method, adding this params: {“count”: 2048, “requeue”:false,“encoding”:“auto”}

Why we use #2048 ? find it by hashtag.

messagebrokers(A.R)