Package org.apache.juneau.rest.server.mcp

Class BasicMcpSubscriptionBroker

java.lang.Object

org.apache.juneau.rest.server.mcp.BasicMcpSubscriptionBroker

All Implemented Interfaces:

McpSubscriptionBroker, McpSubscriptions

public class BasicMcpSubscriptionBroker
extends Object
implements McpSubscriptionBroker

Default McpSubscriptionBroker: a ConcurrentHashMap-backed registry doing filtered fan-out.

Publish methods (resourceUpdated(java.lang.String), toolsListChanged(), promptsListChanged(), resourcesListChanged()) build one McpChangeEvent and iterate the live registry, offering the event only to subscriptions whose McpSubscriptionFilter.matches(McpChangeEvent) returns true — this never broadcasts unconditionally the way org.apache.juneau.rest.server.sse.SseBroadcaster#publish does.

Constructor Summary

Constructors

Constructor	Description
BasicMcpSubscriptionBroker(int queueSize)	Creates a new broker.

Method Summary

Modifier and Type	Method	Description
int	activeCount()	The number of currently registered (not yet closed) subscriptions.
void	closeAll()	Closes every currently registered subscription.
void	promptsListChanged()	Announces that the prompt list changed.
McpSubscription	register(String subscriptionId, McpSubscriptionFilter honoredFilter)	Registers a new subscription and returns its queue handle.
Optional<McpSubscription>	registerIfUnder(int max, String subscriptionId, McpSubscriptionFilter honoredFilter)	Atomically admission-checks against max and registers, closing the TOCTOU window a separate McpSubscriptionBroker.activeCount() check plus McpSubscriptionBroker.register(java.lang.String, org.apache.juneau.rest.server.mcp.McpSubscriptionFilter) call would leave open under concurrent callers (in particular against a JVM-wide shared broker instance, where unrelated callers race each other).
void	resourcesListChanged()	Announces that the resource list changed.
void	resourceUpdated(String uri)	Announces that a specific subscribed resource's content changed.
void	toolsListChanged()	Announces that the tool list changed.
void	unregister(String subscriptionId)	Deregisters and closes the subscription with the given id, if present.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

BasicMcpSubscriptionBroker

public BasicMcpSubscriptionBroker(int queueSize)

Creates a new broker.

Parameters:

queueSize - The per-subscription drop-oldest queue bound. Must be > 0.

Throws:

IllegalArgumentException - If queueSize is not > 0.

Method Details

register

public McpSubscription register(String subscriptionId,
 McpSubscriptionFilter honoredFilter)

Description copied from interface: McpSubscriptionBroker

Registers a new subscription and returns its queue handle. Uncapped: never rejects.

Specified by:

register in interface McpSubscriptionBroker

Parameters:

subscriptionId - The subscription identifier (the listen request's JSON-RPC id). Must not be null or empty.

honoredFilter - The capability-gated filter this subscription honors. Must not be null.

Returns:

The new subscription handle. Never null.

registerIfUnder

public Optional<McpSubscription> registerIfUnder(int max,
 String subscriptionId,
 McpSubscriptionFilter honoredFilter)

Description copied from interface: McpSubscriptionBroker

Atomically admission-checks against max and registers, closing the TOCTOU window a separate McpSubscriptionBroker.activeCount() check plus McpSubscriptionBroker.register(java.lang.String, org.apache.juneau.rest.server.mcp.McpSubscriptionFilter) call would leave open under concurrent callers (in particular against a JVM-wide shared broker instance, where unrelated callers race each other).

Re-registering an id that is already present is always allowed and never counted against max, matching McpSubscriptionBroker.register(java.lang.String, org.apache.juneau.rest.server.mcp.McpSubscriptionFilter)'s replace-on-same-id semantics (the previous subscription with that id is closed) — a replacement does not grow McpSubscriptionBroker.activeCount(), so it cannot be what pushes the registry over the cap.

Specified by:

registerIfUnder in interface McpSubscriptionBroker

Parameters:

max - The maximum number of concurrently active subscriptions to admit under (exclusive: a request is admitted only while McpSubscriptionBroker.activeCount() is strictly less than this, except for the same-id replacement case above).

subscriptionId - The subscription identifier (the listen request's JSON-RPC id). Must not be null or empty.

honoredFilter - The capability-gated filter this subscription honors. Must not be null.

Returns:

The new subscription handle, or Optional.empty() if the cap was reached and this was not a same-id replacement.

unregister

public void unregister(String subscriptionId)

Description copied from interface: McpSubscriptionBroker

Deregisters and closes the subscription with the given id, if present.

Specified by:

unregister in interface McpSubscriptionBroker

Parameters:

subscriptionId - The subscription identifier. A missing id is a no-op.

activeCount

public int activeCount()

Description copied from interface: McpSubscriptionBroker

The number of currently registered (not yet closed) subscriptions.

Specified by:

activeCount in interface McpSubscriptionBroker

Returns:

The active count.

closeAll

public void closeAll()

Description copied from interface: McpSubscriptionBroker

Closes every currently registered subscription.

Called when the server begins shutting down, so open subscriptions/listen streams complete promptly instead of holding the graceful drain open until its stop timeout. The default implementation does nothing, so custom brokers that predate this method keep working (their streams then end on the normal heartbeat/idle-timeout paths).

Specified by:

closeAll in interface McpSubscriptionBroker

resourceUpdated

public void resourceUpdated(String uri)

Description copied from interface: McpSubscriptions

Announces that a specific subscribed resource's content changed.

Specified by:

resourceUpdated in interface McpSubscriptions

Parameters:

uri - The exact resource URI that changed. Must not be null.

toolsListChanged

public void toolsListChanged()

Description copied from interface: McpSubscriptions

Announces that the tool list changed.

Specified by:

toolsListChanged in interface McpSubscriptions

promptsListChanged

public void promptsListChanged()

Description copied from interface: McpSubscriptions

Announces that the prompt list changed.

Specified by:

promptsListChanged in interface McpSubscriptions

resourcesListChanged

public void resourcesListChanged()

Description copied from interface: McpSubscriptions

Announces that the resource list changed.

Specified by:

resourcesListChanged in interface McpSubscriptions