如何在OpenDaylight（Carbon）中为不同交换机部署不同应用？

Great question! In OpenDaylight Carbon, you can achieve this by leveraging the controller's event notification system to detect switch connections, then trigger application-specific configurations based on the switch's unique ID. Here's a detailed breakdown of how to implement this:

核心思路 #

ODL generates topology notifications whenever a switch connects or disconnects. We'll listen for the NodeAdded notification (fired when a switch first connects), extract the switch's ID (like openflow:1), and run deployment logic tailored to that specific switch.

步骤1：实现交换机连接事件监听 #

First, create a listener class that implements ODL's NotificationListener interface to catch NodeAdded events. This is where you'll add the logic to distinguish switches and trigger deployments.

import org.opendaylight.yang.gen.v1.urn.opendaylight.topology.notification.rev130819.NodeAdded;
import org.opendaylight.yangtools.yang.binding.NotificationListener;

public class SwitchDeploymentListener implements NotificationListener {

    @Override
    public void onNotification(NodeAdded notification) {
        // Extract the switch's unique ID (e.g., "openflow:1", "openflow:2")
        String switchId = notification.getNode().getNodeId().getValue();
        
        // Route to deployment logic based on switch ID
        switch (switchId) {
            case "openflow:1":
                deployL2SwitchApplication();
                break;
            case "openflow:2":
                deployCustomApplication();
                break;
            default:
                // Handle unrecognized switches (e.g., default deployment or no action)
                System.out.println("No deployment logic for switch: " + switchId);
                break;
        }
    }

    private void deployL2SwitchApplication() {
        // Logic to set up L2 switching for this switch
        // Example steps:
        // 1. Install a default flow to forward unknown MAC packets to the controller
        // 2. Register a PacketIn listener to learn MAC-port mappings
        // 3. Install flow entries for learned MAC addresses to enable layer-2 forwarding
        System.out.println("Deploying L2 Switch app to openflow:1");
    }

    private void deployCustomApplication() {
        // Logic for your custom application (e.g., ACL rules, QoS, routing)
        // Example steps:
        // 1. Install access control flow entries
        // 2. Configure group tables for traffic shaping
        System.out.println("Deploying custom app to openflow:2");
    }
}

步骤2：注册监听器到ODL框架 #

ODL uses Blueprint (OSGi) for component registration. Add this configuration to your application's blueprint.xml file to hook your listener into the controller's notification system:

<blueprint xmlns="http://www.osgi.org/xmlns/blueprint/v1.0.0"
           xmlns:odl="http://opendaylight.org/xmlns/blueprint/v1.0.0">

    <!-- Reference ODL's NotificationService to register our listener -->
    <reference id="notificationService" 
               interface="org.opendaylight.controller.md.sal.binding.api.NotificationService"/>

    <!-- Instantiate our custom listener -->
    <bean id="switchDeploymentListener" 
          class="com.your.package.name.SwitchDeploymentListener"/>

    <!-- Register the listener to receive NodeAdded notifications -->
    <odl:notification-listener ref="switchDeploymentListener"
                               notification-service="notificationService">
        <odl:notification-type type="org.opendaylight.yang.gen.v1.urn.opendaylight.topology.notification.rev130819.NodeAdded"/>
    </odl:notification-listener>

</blueprint>

步骤3：编写具体的应用部署逻辑 #

The deployL2SwitchApplication() and deployCustomApplication() methods are where you'll implement the actual functionality for each switch. For example:

• For the L2 switch app: Use ODL's FlowService to install flow entries that forward traffic based on MAC addresses. You'll also need to listen for PacketIn notifications to learn new MAC-port mappings.
• For your custom app: Install ACL rules, configure QoS meters, or set up routing policies using ODL's MD-SAL services.

关键注意事项 #

• Dependency Setup: Ensure your pom.xml includes dependencies for ODL modules like topology-notification, md-sal-binding, and openflowplugin to access the required APIs.
• Switch ID Format: The switch ID follows the pattern openflow:<dpid>, where <dpid> is the hexadecimal switch ID (e.g., openflow:1 corresponds to DPID 00:00:00:00:00:00:00:01).
• Reconnection Handling: If you need to handle switches disconnecting and reconnecting, add a listener for the NodeRemoved notification to clean up old flows or state before redeploying.
• Permissions: Make sure your application has the necessary ACL permissions in ODL to modify flow tables (e.g., grant flow:write access in the controller's etc/opendaylight/datastore/initial/config/ietf-netconf-acl.xml).

内容的提问来源于stack exchange，提问作者LostInTheFrequencyDomain