RabbitMQ®

For Elastisys Managed Services Customers

You can order Managed RabbitMQ® by filing a service ticket. Here are the highlights:

• Business continuity: three replicas.
• Disaster recovery:
  • Backup scope includes user definitions, vhost definitions, topology definitions.
  • Backup does NOT include messages -- RabbitMQ core Maintainers discourage this.
  • A full backup is taken every day between 0:00 am and 6:00 am CET. The backup retention period is 30 days unless otherwise requested by the customer.
• Monitoring, security patching and incident management: included.

For more information, please read ToS Appendix 3 Managed Additional Service Specification.

RabbitMQ on Welkin Deployment Model
This help you build a mental model on how to access RabbitMQ as an Application Developer and how to connect your application to RabbitMQ.

This page will help you succeed in connecting your application to a RabbitMQ-based message queue which meets your security and compliance requirements.

Accessing a RabbitMQ Cluster

Before continuing, make sure you have access to the Kubernetes API, as describe here.

Make sure to install the RabbitMQ client on your workstation. On Ubuntu, this can be achieved as follows:

sudo apt install rabbitmq-server

Accessing the Management UI

RabbitMQ provides the management plugin which allows control over everything within it, including messaging topology and access control.

Your administrator will set up a Secret inside Welkin containing the credentials of the default admin user, which is all you need to access your RabbitMQ cluster. The Secret has the following shape:

apiVersion: v1
kind: Secret
metadata:
  name: ${RABBITMQ_CLUSTER}-default-user
  namespace: ${RABBITMQ_NAMESPACE}
stringData:
  username: ${RABBITMQ_ADMIN_USERNAME}
  password: ${RABBITMQ_ADMIN_PASSWORD}

Danger

The Secret is very precious! Prefer not to persist any information extracted from it, as shown below.

To access the management UI, proceed as follows:

1. Retrieve the admin default username and password.

   export RABBITMQ_CLUSTER=     # Get this from your administrator
   export RABBITMQ_NAMESPACE=   # Get this from your administrator
   
   echo -n "RabbitMQ admin username: "
   kubectl -n "${RABBITMQ_NAMESPACE}" get secret "${RABBITMQ_CLUSTER}-default-user" -o jsonpath="{.data.username}" | base64 --decode && echo
   
   echo -n "RabbitMQ admin password: "
   kubectl -n "${RABBITMQ_NAMESPACE}" get secret "${RABBITMQ_CLUSTER}-default-user" -o jsonpath="{.data.password}" | base64 --decode && echo
   

   Danger

   Do not configure your application with the RabbitMQ default admin username and password. Since the application will get too much permission, this will likely violate your access control policy.

2. Start the port-forwarding:

   kubectl port-forward -n "${RABBITMQ_NAMESPACE}" "svc/${RABBITMQ_CLUSTER}" 15672
   

3. Open the admin dashboard (at http://localhost:15672) and log in using the credentials retrieved in step 1.

4. Create an application username, password and vhost, and store these in variables as named below:

   APP_USER=
   APP_PASS=
   APP_VHOST=
   

Create an Application Secret

First, check that you are on the right Welkin cluster, in the right application namespace:

kubectl get nodes
kubectl config view --minify --output 'jsonpath={..namespace}'; echo

Now, create a Kubernetes Secret in your application namespace to store the AMPQ URL:

cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: Secret
metadata:
    name: app-amqp-secret
type: Opaque
stringData:
    AMQP_URL: amqp://${APP_USER}:${APP_PASS}@${RABBITMQ_CLUSTER}.${RABBITMQ_NAMESPACE}/${APP_VHOST}
EOF

Expose AMQP URL to Your Application

To expose the AMQP URL to your application, follow one of the following upstream documentation:

• Create a Pod that has access to the secret data through a Volume
• Define container environment variables using Secret data

Using a RabbitMQ Cluster

Best practices for using RabbitMQ in Welkin.

Note

RabbitMQ is built as a plugin based system, by default only a limited set of plugins are enabled, contact your service-specific administrator about enabling the ones you require.

Cluster Division

RabbitMQ is a multi tenant system and has the concept of virtual host or vhost which provides logical separation of resources within it. Each vhost acts as their own RabbitMQ cluster and have their own connection, channels, exchanges, queues, and bindings.

Messages cannot flow directly between exchanges and queues in different vhosts, instead if that is required there must be a client that consumes messages in one vhost and then publishes messages in another vhost. This can also be realised with two plugins:

• Federation plugin - Provides federated exchanges and queue which connect to an upstream cluster or vhost, allowing consumers to access message from the upstream source.

• Shovel plugin - Provides a client which connect both to an upstream and downstream cluster or vhost, consuming and publishing messages between them.

Connection and Channel Management

In RabbitMQ connections and channels are intended to and optimised to be long-lived. Therefore one should avoid connection and channel churn by using and reusing them for as long as possible.

Each connection and channel consumes resources and should therefore be kept at a minimal number as required by the application. It is important to close unused connections and channels to free their resources.

Consumers and publishers should use separate connections and channels to allow RabbitMQ to better manage clients when under high pressure, allowing consumers to catch up by restricting publishers.

Recovering from connection failures should use automatic or recommended methods when provided by the client library, custom recovery methods need to be carefully made to not put too much pressure on RabbitMQ.

Reliable Messaging

The messaging protocol AMQP provide two mechanisms for client to manage reliable messaging:

• Consumer Acknowledgements - Ensure that the client has properly received a message. RabbitMQ will redeliver message left unacknowledged.

• Publisher Confirms - Ensures that the server has properly received a message. RabbitMQ may delay confirms when under to high pressure to be able to handle the load.

Additionally RabbitMQ has different queue types and modes that affect the reliability of messaging as will be explained in the next section.

Queue Selection

RabbitMQ supports three different types of queues which all have different pro's and con's:

• Classic Queues - Best for high performance with transient messages.

This is the standard choice for transient queues and messages since they consume little resources and offer high performance.

Danger

Classic queues are not replicated by default and should not be used with replication since mirrored classic queues are deprecated.

Durable classic queues are tied to the server they are created on and will become unavailable if that server is unavailable.

• Quorum Queues - Best for high availability with durable messages.

This is the standard choice for durable queues and messages since they are replicated by default and offer high availability.

Warning

Similar to connections and channels quorum queues are intended to be long-lived, avoid scenarios where quorum queues are frequently removed and redeclared as it may lock internal resources within RabbitMQ.

Keep the queues small and use multiple queues when possible for best performance.

• Stream Queues - Best for high volume with durable messages.

This is the standard choice for high volume durable queues and messages since they store messages as a persistent replicated log. This allows for messages to persist after they are consumed to be recalled or replayed, or with the stream protocol efficiently processed in batches.

Warning

When using stream queues you must set reasonable retention to keep them from filling up RabbitMQ as it will prevent it from accepting new messages.

Also note that messages in RabbitMQ are not backed up in the case of disaster.

Follow the Go-Live Checklist

You should be all set. Before going into production, don't forget to go through the go-live checklist.

Welkin RabbitMQ Release Notes

Check out the release notes for the RabbitMQ cluster that runs in Welkin environments!

Further Reading

• RabbitMQ Management UI
• AMQP URL spec
• AMQP Clients
• Kubernetes Secrets