Pubsub Interface/Driver walkthrough

This guide provides an overview of the pubsub interface, including details on its structure and functionality. Additionally, it offers instructions on adding a new driver and utilizing providers other than the default provider Dapr.

Pubsub interface and Driver walkthrough

Pubsub's connection interface looks like

// Connection is the interface that wraps pubsub methods.
type Connection interface {
    // Publish single message over a specific topic/channel
    Publish(ctx context.Context, message interface{}, topic string) error

    // Close connections
    CloseConnection() error

    // Update an existing connection with new configuration
    UpdateConnection(ctx context.Context, config interface{}) error
}

As an example, the Dapr driver implements these three methods to publish message, close connection, and update connection respectively. Please refer to dapr.go to understand the logic that goes in each of these methods. Additionally, the Dapr driver also implements func NewConnection(_ context.Context, config interface{}) (connection.Connection, error) method that returns a new client for dapr.

How to add new drivers

Note: For example, if we want to add a new driver to use foo instead of Dapr as a tool to publish violations.

A driver must implement the Connection interface and a new func NewConnection(_ context.Context, config interface{}) (connection.Connection, error) method that returns a client for the respective tool.

This newly added driver's NewConnection method must be used to create a new pubSubs object in provider.go. For example,

var pubSubs = newPubSubSet(map[string]InitiateConnection{
  dapr.Name: dapr.NewConnection,
  "foo": foo.NewConnection,
},
)

How to use different providers

To enable audit to use this driver to publish messages, a connection configMap with appropriate config and provider is needed. For example,

apiVersion: v1
kind: ConfigMap
metadata:
  name: audit
  namespace: gatekeeper-system
data:
  provider: "foo"
  config: |
    {
      <config needed for foo connection>
    }

The data.provider field must exist and must match one of the keys of the pubSubs map that was defined earlier to use the corresponding driver. The data.config field in the configuration can vary depending on the driver being used. For dapr driver, data.config must be {"component": "pubsub"}.