ionutzpi commented on code in PR #12: URL: https://github.com/apache/sling-org-apache-sling-discovery-base/pull/12#discussion_r2068034994
########## src/main/java/org/apache/sling/discovery/base/commons/TopologyReadinessHandler.java: ########## @@ -0,0 +1,163 @@ +/* + * 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, + target = "(tag=systemready)") + private volatile SystemReady systemReady; + + @Activate + protected void activate(ComponentContext context) { + logger.info("TopologyReadinessHandler activated - in STARTUP state"); + } + + @Deactivate + protected void deactivate(ComponentContext context) { + logger.info("TopologyReadinessHandler deactivated"); + stateMachine.transitionTo(SystemState.SHUTDOWN); + } + + public void bindSystemReady(SystemReady service) { + logger.debug("SystemReady service bound - transitioning to READY state"); + stateMachine.transitionTo(SystemState.READY); + } + + protected void unbindSystemReady(SystemReady service) { + logger.debug("SystemReady service unbound - transitioning to SHUTDOWN state"); + stateMachine.transitionTo(SystemState.SHUTDOWN); + } + + /** + * Initiate the shutdown process + */ + public void initiateShutdown() { Review Comment: Removed unnecessary method. ########## src/main/java/org/apache/sling/discovery/base/commons/TopologyReadinessHandler.java: ########## @@ -0,0 +1,163 @@ +/* + * 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, + target = "(tag=systemready)") + private volatile SystemReady systemReady; + + @Activate + protected void activate(ComponentContext context) { + logger.info("TopologyReadinessHandler activated - in STARTUP state"); + } + + @Deactivate + protected void deactivate(ComponentContext context) { + logger.info("TopologyReadinessHandler deactivated"); + stateMachine.transitionTo(SystemState.SHUTDOWN); + } + + public void bindSystemReady(SystemReady service) { + logger.debug("SystemReady service bound - transitioning to READY state"); + stateMachine.transitionTo(SystemState.READY); + } + + protected void unbindSystemReady(SystemReady service) { + logger.debug("SystemReady service unbound - transitioning to SHUTDOWN state"); + stateMachine.transitionTo(SystemState.SHUTDOWN); + } + + /** + * Initiate the shutdown process + */ + public void initiateShutdown() { + if (stateMachine.getCurrentState() == SystemState.READY) { + logger.info("Initiating shutdown process"); + stateMachine.transitionTo(SystemState.SHUTDOWN); + logger.info("Shutdown completed successfully"); + } + } + + /** + * Check if a topology change should be delayed based on system readiness + * @return true if the change should be delayed, false otherwise + */ + public boolean shouldDelayTopologyChange() { Review Comment: Done. -- This is an automated message from the Apache Git Service. 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