Analysis of Openflowplugin ContextChain Creation and Lifecycle Management

The article examines the second part of the Openflowplugin source code analysis, focusing on the core logic that creates the ContextChain for a newly connected switch after the handshake phase.

When a switch connects, ContextChainHolderImpl.deviceConnected invokes ContextChainHolderImpl.createContextChain , which builds a unique ContextChain object to manage the switch's lifecycle within Openflowplugin.

1. Create DeviceContext

The method calls deviceManager.createContext(connectionContext) to obtain a DeviceContext . It registers a mastership watcher, configures the packet‑in filter, creates an OutboundQueueHandler , a DeviceContextImpl , and an OpenflowProtocolListenerFullImpl to handle all messages from the switch.

final DeviceContext deviceContext = deviceManager.createContext(connectionContext);
deviceContext.registerMastershipWatcher(this);

2. Create RpcContext

Using the previously created deviceContext , the code calls rpcManager.createContext(deviceContext) to obtain an RpcContext and registers the same mastership watcher.

final RpcContext rpcContext = rpcManager.createContext(deviceContext);
rpcContext.registerMastershipWatcher(this);

3. Create StatisticsContext

The method creates a StatisticsContext via statisticsManager.createContext(deviceContext, ownershipChangeListener.isReconciliationFrameworkRegistered()) , registers a watcher, and also creates a MultipartWriterProvider to write operational YANG data to the device.

final StatisticsContext statisticsContext = statisticsManager.createContext(deviceContext, ownershipChangeListener.isReconciliationFrameworkRegistered());
statisticsContext.registerMastershipWatcher(this);

4. Create RoleContext

A RoleContext is created with roleManager.createContext(deviceContext) , a RoleContextImpl and a SalRoleServiceImpl are instantiated to manage master/slave role assignment.

final RoleContext roleContext = roleManager.createContext(deviceContext);
roleContext.registerMastershipWatcher(this);

5. Assemble ContextChain

After the four individual contexts are ready, a ContextChainImpl is instantiated. Each context is wrapped in a GuardedContextImpl and added via addContext . The chain registers a device‑removed handler, stores the chain in ContextChainHolderImpl.contextChainMap , and finally registers services with contextChain.registerServices(singletonServiceProvider) .

@Override
public
void addContext(@Nonnull final T context) {
    contexts.add(new GuardedContextImpl(context));
}

6. Master/Slave Election

The article notes that after the ContextChain is built, the next crucial step is the call to contextChain.registerServices , which triggers the master/slave role election among multiple controllers in a cluster.

Summary

In summary, once a switch completes the Openflow handshake, Openflowplugin creates four specialized contexts (Device, Rpc, Statistics, Role), aggregates them into a ContextChain , and prepares the switch for further operations, including high‑availability master/slave role election.