ionutzpi commented on code in PR #12: URL: https://github.com/apache/sling-org-apache-sling-discovery-base/pull/12#discussion_r2066192521
########## src/main/java/org/apache/sling/discovery/base/commons/TopologyReadinessHandler.java: ########## @@ -0,0 +1,166 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, + * software distributed under the License is distributed on an + * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY + * KIND, either express or implied. See the License for the + * specific language governing permissions and limitations + * under the License. + */ +package org.apache.sling.discovery.base.commons; + +import java.util.concurrent.atomic.AtomicReference; + +import org.apache.felix.hc.api.condition.SystemReady; +import org.osgi.service.component.annotations.Activate; +import org.osgi.service.component.annotations.Component; +import org.osgi.service.component.annotations.Deactivate; +import org.osgi.service.component.annotations.Reference; +import org.osgi.service.component.annotations.ReferenceCardinality; +import org.osgi.service.component.annotations.ReferencePolicy; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; +import org.osgi.service.component.ComponentContext; + +/** + * Coordinates topology changes based on system readiness state. + * This component ensures that topology changes only occur when the system is in a stable state, + * both during startup and shutdown sequences. + * + * The handler manages three main states: + * 1. STARTUP: Initial state when the system is starting up + * 2. READY: System is ready for normal operation and topology changes + * 3. SHUTDOWN: System is in the process of shutting down + * + * State Transitions: + * - System starts in STARTUP state + * - Transitions to READY state only when SystemReady service is bound + * - Transitions to SHUTDOWN state when: + * * SystemReady service is unbound + * * Component is deactivated + * + * Note: This component requires the Felix SystemReady service to function properly. + * The system will remain in STARTUP state until SystemReady service is bound, + * and will transition to SHUTDOWN state when the service is unbound. + */ +@Component(service = TopologyReadinessHandler.class, immediate = true) +public class TopologyReadinessHandler { + + private final Logger logger = LoggerFactory.getLogger(this.getClass()); + + /** + * Represents the possible states of the system with explicit transitions. + */ + private enum SystemState { + STARTUP { + @Override + protected SystemState[] getAllowedTransitions() { + return new SystemState[] { READY }; + } + }, + READY { + @Override + protected SystemState[] getAllowedTransitions() { + return new SystemState[] { SHUTDOWN }; + } + }, + SHUTDOWN { + @Override + protected SystemState[] getAllowedTransitions() { + return new SystemState[] { }; // No transitions allowed from SHUTDOWN + } + }; + + protected abstract SystemState[] getAllowedTransitions(); + } + + private final StateMachine stateMachine = new StateMachine(); + + @Reference(cardinality = ReferenceCardinality.MANDATORY, policy = ReferencePolicy.STATIC) + private volatile SystemReady systemReady; Review Comment: Done. Added target = "(tag=systemready)" on annotation to filter SystemReady service with this tag set. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: dev-unsubscr...@sling.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
