Improve handling of multiple policy in APEX PDP

Change-Id: Ic4adf5bd8876dc31fc93993298e90389baaa2c39
Issue-ID: POLICY-2883
Signed-off-by: a.sreekumar <ajith.sreekumar@bell.ca>

4 files changed, 182 insertions, 288 deletions

diff --git a/services/services-engine/src/main/java/org/onap/policy/apex/service/engine/main/ApexActivator.java b/services/services-engine/src/main/java/org/onap/policy/apex/service/engine/main/ApexActivator.java
index cadcc7ee8..3451c120c 100644
--- a/services/services-engine/src/main/java/org/onap/policy/apex/service/engine/main/ApexActivator.java
+++ b/services/services-engine/src/main/java/org/onap/policy/apex/service/engine/main/ApexActivator.java
@@ -2,7 +2,7 @@
  * ============LICENSE_START=======================================================
  *  Copyright (C) 2016-2018 Ericsson. All rights reserved.
  *  Modifications Copyright (C) 2019-2021 Nordix Foundation.
- *  Modifications Copyright (C) 2020 Bell Canada. All rights reserved.
+ *  Modifications Copyright (C) 2020-2021 Bell Canada. All rights reserved.
  * ================================================================================
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -22,35 +22,41 @@
 
 package org.onap.policy.apex.service.engine.main;
 
-import java.util.AbstractMap;
-import java.util.ArrayList;
 import java.util.LinkedHashMap;
-import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
-import java.util.Optional;
-import java.util.Set;
-import java.util.stream.Collectors;
 import lombok.Getter;
 import lombok.Setter;
 import org.onap.policy.apex.model.basicmodel.concepts.ApexException;
 import org.onap.policy.apex.model.basicmodel.concepts.ApexRuntimeException;
 import org.onap.policy.apex.model.basicmodel.concepts.AxArtifactKey;
+import org.onap.policy.apex.model.basicmodel.concepts.AxKeyInfo;
+import org.onap.policy.apex.model.basicmodel.concepts.AxKeyInformation;
 import org.onap.policy.apex.model.basicmodel.handling.ApexModelException;
 import org.onap.policy.apex.model.basicmodel.service.ModelService;
+import org.onap.policy.apex.model.contextmodel.concepts.AxContextAlbum;
+import org.onap.policy.apex.model.contextmodel.concepts.AxContextAlbums;
+import org.onap.policy.apex.model.contextmodel.concepts.AxContextSchema;
+import org.onap.policy.apex.model.contextmodel.concepts.AxContextSchemas;
 import org.onap.policy.apex.model.enginemodel.concepts.AxEngineModel;
+import org.onap.policy.apex.model.eventmodel.concepts.AxEvent;
+import org.onap.policy.apex.model.eventmodel.concepts.AxEvents;
+import org.onap.policy.apex.model.policymodel.concepts.AxPolicies;
+import org.onap.policy.apex.model.policymodel.concepts.AxPolicy;
 import org.onap.policy.apex.model.policymodel.concepts.AxPolicyModel;
+import org.onap.policy.apex.model.policymodel.concepts.AxTask;
+import org.onap.policy.apex.model.policymodel.concepts.AxTasks;
 import org.onap.policy.apex.model.policymodel.handling.PolicyModelMerger;
 import org.onap.policy.apex.service.engine.event.ApexEventException;
 import org.onap.policy.apex.service.engine.runtime.EngineService;
 import org.onap.policy.apex.service.engine.runtime.impl.EngineServiceImpl;
+import org.onap.policy.apex.service.parameters.ApexParameterConstants;
 import org.onap.policy.apex.service.parameters.ApexParameters;
 import org.onap.policy.apex.service.parameters.engineservice.EngineServiceParameters;
 import org.onap.policy.apex.service.parameters.eventhandler.EventHandlerParameters;
 import org.onap.policy.apex.service.parameters.eventhandler.EventHandlerPeeredMode;
 import org.onap.policy.common.parameters.ParameterService;
-import org.onap.policy.models.tosca.authorative.concepts.ToscaConceptIdentifier;
 import org.slf4j.ext.XLogger;
 import org.slf4j.ext.XLoggerFactory;
 
@@ -66,13 +72,12 @@ public class ApexActivator {
     // The logger for this class
     private static final XLogger LOGGER = XLoggerFactory.getXLogger(ApexActivator.class);
 
-    // The parameters of the Apex activator when running with multiple policies
     @Getter
     @Setter
-    private Map<ToscaConceptIdentifier, ApexParameters> apexParametersMap;
+    private ApexParameters apexParameters;
 
     @Getter
-    Map<ToscaConceptIdentifier, AxPolicyModel> policyModelsMap;
+    private AxPolicyModel policyModel;
 
     // Event unmarshalers are used to receive events asynchronously into Apex
     private final Map<String, ApexEventUnmarshaller> unmarshallerMap = new LinkedHashMap<>();
@@ -93,10 +98,10 @@ public class ApexActivator {
     /**
      * Instantiate the activator for the Apex engine as a complete service.
      *
-     * @param parametersMap the apex parameters map for the Apex service
+     * @param parameters the apex parameters for the Apex service
      */
-    public ApexActivator(Map<ToscaConceptIdentifier, ApexParameters> parametersMap) {
-        apexParametersMap = parametersMap;
+    public ApexActivator(ApexParameters parameters) {
+        apexParameters = parameters;
     }
 
     /**
@@ -108,96 +113,131 @@ public class ApexActivator {
         LOGGER.debug("Apex engine starting as a service . . .");
 
         try {
-            ApexParameters apexParameters = apexParametersMap.values().iterator().next();
-            // totalInstanceCount is the sum of instance counts required as per each policy
-            int totalInstanceCount = apexParametersMap.values().stream()
-                .mapToInt(p -> p.getEngineServiceParameters().getInstanceCount()).sum();
-            apexParameters.getEngineServiceParameters().setInstanceCount(totalInstanceCount);
-            engineKey = apexParameters.getEngineServiceParameters().getEngineKey();
             instantiateEngine(apexParameters);
             setUpModelMarshallerAndUnmarshaller(apexParameters);
         } catch (final Exception e) {
-            LOGGER.debug(APEX_ENGINE_FAILED_MSG, e);
+            try {
+                terminate();
+            } catch (ApexException e1) {
+                LOGGER.error("Terminating the ApexActivator encountered error", e1);
+            }
             throw new ApexActivatorException(APEX_ENGINE_FAILED_MSG, e);
         }
 
         LOGGER.debug("Apex engine started as a service");
     }
 
-    private void setUpModelMarshallerAndUnmarshaller(ApexParameters apexParameters) throws ApexException {
-        policyModelsMap = new LinkedHashMap<>();
-        Map<String, EventHandlerParameters> inputParametersMap = new LinkedHashMap<>();
-        Map<String, EventHandlerParameters> outputParametersMap = new LinkedHashMap<>();
-        Set<Entry<ToscaConceptIdentifier, ApexParameters>> apexParamsEntrySet = new LinkedHashSet<>(
-            apexParametersMap.entrySet());
-        apexParamsEntrySet.stream().forEach(apexParamsEntry -> {
-            ApexParameters apexParams = apexParamsEntry.getValue();
-            List<String> duplicateInputParameters = new ArrayList<>(apexParams.getEventInputParameters().keySet());
-            duplicateInputParameters.retainAll(inputParametersMap.keySet());
-            List<String> duplicateOutputParameters = new ArrayList<>(apexParams.getEventOutputParameters().keySet());
-            duplicateOutputParameters.retainAll(outputParametersMap.keySet());
-
-            if (!(duplicateInputParameters.isEmpty() && duplicateOutputParameters.isEmpty())) {
-                LOGGER.error("I/O Parameters {}/{} for {}:{} are duplicates. So this policy is not executed.",
-                    duplicateInputParameters, duplicateOutputParameters, apexParamsEntry.getKey().getName(),
-                    apexParamsEntry.getKey().getVersion());
-                apexParametersMap.remove(apexParamsEntry.getKey());
-                return;
-            }
 
-            inputParametersMap.putAll(apexParams.getEventInputParameters());
-            outputParametersMap.putAll(apexParams.getEventOutputParameters());
-            // Check if a policy model file has been specified
-            if (apexParams.getEngineServiceParameters().getPolicyModel() != null) {
-                LOGGER.debug("deploying policy model to the apex engines . . .");
-                try {
-                    final String policyModelString = apexParams.getEngineServiceParameters().getPolicyModel();
-                    AxPolicyModel policyModel = EngineServiceImpl.createModel(engineKey, policyModelString);
-                    policyModelsMap.put(apexParamsEntry.getKey(), policyModel);
-                } catch (ApexException e) {
-                    throw new ApexRuntimeException("Failed to create the apex model.", e);
-                }
-            }
-        });
-        AxPolicyModel finalPolicyModel = aggregatePolicyModels(policyModelsMap);
+    private void instantiateEngine(ApexParameters apexParameters) throws ApexException {
+        if (null != apexEngineService && apexEngineService.getKey().equals(engineKey)) {
+            throw new ApexException("Apex Engine already initialized.");
+        }
+        // Create engine with specified thread count
+        LOGGER.debug("starting apex engine service . . .");
+        apexEngineService = EngineServiceImpl.create(apexParameters.getEngineServiceParameters());
+
+        // Create the engine holder to hold the engine's references and act as an event
+        // receiver
+        engineServiceHandler = new ApexEngineServiceHandler(apexEngineService);
+    }
+
+    private void setUpModelMarshallerAndUnmarshaller(ApexParameters apexParameters) throws ApexException {
+        AxPolicyModel model;
+        try {
+            final String policyModelString = apexParameters.getEngineServiceParameters().getPolicyModel();
+            model = EngineServiceImpl.createModel(apexParameters.getEngineServiceParameters().getEngineKey(),
+                policyModelString);
+        } catch (ApexException e) {
+            throw new ApexRuntimeException("Failed to create the apex model.", e);
+        }
 
+        AxKeyInformation existingKeyInformation = null;
+        AxContextSchemas existingSchemas = null;
+        AxEvents existingEvents = null;
+        AxContextAlbums existingAlbums = null;
+        AxTasks existingTasks = null;
+        AxPolicies existingPolicies = null;
+        if (ModelService.existsModel(AxPolicyModel.class)) {
+            existingKeyInformation = new AxKeyInformation(ModelService.getModel(AxKeyInformation.class));
+            existingSchemas = new AxContextSchemas(ModelService.getModel(AxContextSchemas.class));
+            existingEvents = new AxEvents(ModelService.getModel(AxEvents.class));
+            existingAlbums = new AxContextAlbums(ModelService.getModel(AxContextAlbums.class));
+            existingTasks = new AxTasks(ModelService.getModel(AxTasks.class));
+            existingPolicies = new AxPolicies(ModelService.getModel(AxPolicies.class));
+        }
         // Set the policy model in the engine
-        apexEngineService.updateModel(engineKey, finalPolicyModel, true);
+        try {
+            apexEngineService.updateModel(apexParameters.getEngineServiceParameters().getEngineKey(), model, true);
+            policyModel = new AxPolicyModel(model);
+        } catch (ApexException exp) {
+            // Discard concepts from the current policy
+            if (null != existingKeyInformation) {
+                // Update model service with other policies' concepts.
+                ModelService.registerModel(AxKeyInformation.class, existingKeyInformation);
+                ModelService.registerModel(AxContextSchemas.class, existingSchemas);
+                ModelService.registerModel(AxEvents.class, existingEvents);
+                ModelService.registerModel(AxContextAlbums.class, existingAlbums);
+                ModelService.registerModel(AxTasks.class, existingTasks);
+                ModelService.registerModel(AxPolicies.class, existingPolicies);
+            } else {
+                ModelService.clear();
+            }
+            throw exp;
+        }
+        if (null != existingKeyInformation) {
+            // Make sure all concepts in previously deployed policies are retained in ModelService
+            // during multi policy deployment.
+            updateModelService(existingKeyInformation, existingSchemas, existingEvents, existingAlbums, existingTasks,
+                existingPolicies);
+        }
 
-        handleExistingMarshallerAndUnmarshaller(inputParametersMap, outputParametersMap);
-        setUpNewMarshallerAndUnmarshaller(apexParameters.getEngineServiceParameters(), inputParametersMap,
-            outputParametersMap);
+        setUpNewMarshallerAndUnmarshaller(apexParameters.getEngineServiceParameters(),
+            apexParameters.getEventInputParameters(), apexParameters.getEventOutputParameters());
 
         // Wire up pairings between marhsallers and unmarshallers
-        setUpMarshalerPairings(inputParametersMap);
+        setUpMarshalerPairings(apexParameters.getEventInputParameters());
 
         // Start event processing
-        startUnmarshallers(inputParametersMap);
+        startUnmarshallers(apexParameters.getEventInputParameters());
     }
 
-    private AxPolicyModel aggregatePolicyModels(Map<ToscaConceptIdentifier, AxPolicyModel> policyModelsMap) {
-        // Doing a deep copy so that original values in policyModelsMap is retained
-        // after reduction operation
-        Set<Entry<ToscaConceptIdentifier, AxPolicyModel>> policyModelsEntries = policyModelsMap.entrySet().stream()
-            .map(entry -> new AbstractMap.SimpleEntry<>(entry.getKey(), entry.getValue())).collect(Collectors.toSet());
-        Optional<Entry<ToscaConceptIdentifier, AxPolicyModel>> finalPolicyModelEntry = policyModelsEntries.stream()
-            .reduce((entry1, entry2) -> {
-                try {
-                    entry1.setValue(
-                        PolicyModelMerger.getMergedPolicyModel(entry1.getValue(), entry2.getValue(), true, true));
-                } catch (ApexModelException exc) {
-                    LOGGER.error("Policy model for {} : {} has duplicates. So this policy is not executed.",
-                        entry2.getKey().getName(), entry2.getKey().getVersion(), exc);
-                    apexParametersMap.remove(entry2.getKey());
-                    policyModelsMap.remove(entry2.getKey());
-                }
-                return entry1;
-            });
-        AxPolicyModel finalPolicyModel = null;
-        if (finalPolicyModelEntry.isPresent()) {
-            finalPolicyModel = new AxPolicyModel(finalPolicyModelEntry.get().getValue());
+    private void updateModelService(AxKeyInformation existingKeyInformation,
+        AxContextSchemas existingSchemas, AxEvents existingEvents,
+        AxContextAlbums existingAlbums, AxTasks existingTasks,
+        AxPolicies existingPolicies) throws ApexModelException {
+
+        AxContextSchemas axContextSchemas = ModelService.getModel(AxContextSchemas.class);
+        AxEvents axEvents = ModelService.getModel(AxEvents.class);
+        AxContextAlbums axContextAlbums = ModelService.getModel(AxContextAlbums.class);
+        AxTasks axTasks = ModelService.getModel(AxTasks.class);
+        AxPolicies axPolicies = ModelService.getModel(AxPolicies.class);
+
+        Map<AxArtifactKey, AxContextSchema> newSchemasMap = axContextSchemas.getSchemasMap();
+        Map<AxArtifactKey, AxEvent> newEventsMap = axEvents.getEventMap();
+        Map<AxArtifactKey, AxContextAlbum> newAlbumsMap = axContextAlbums.getAlbumsMap();
+        Map<AxArtifactKey, AxTask> newTasksMap = axTasks.getTaskMap();
+        Map<AxArtifactKey, AxPolicy> newPoliciesMap = axPolicies.getPolicyMap();
+
+        StringBuilder errorMessage = new StringBuilder();
+        PolicyModelMerger.checkForDuplicateItem(existingSchemas.getSchemasMap(), newSchemasMap, errorMessage, "schema");
+        PolicyModelMerger.checkForDuplicateItem(existingEvents.getEventMap(), newEventsMap, errorMessage, "event");
+        PolicyModelMerger.checkForDuplicateItem(existingAlbums.getAlbumsMap(), newAlbumsMap, errorMessage, "album");
+        PolicyModelMerger.checkForDuplicateItem(existingTasks.getTaskMap(), newTasksMap, errorMessage, "task");
+        PolicyModelMerger.checkForDuplicateItem(existingPolicies.getPolicyMap(), newPoliciesMap, errorMessage,
+            "policy");
+        if (errorMessage.length() > 0) {
+            throw new ApexModelException(errorMessage.toString());
         }
-        return finalPolicyModel;
+
+        AxKeyInformation axKeyInformation = ModelService.getModel(AxKeyInformation.class);
+        Map<AxArtifactKey, AxKeyInfo> newKeyInfoMap = axKeyInformation.getKeyInfoMap();
+        // Now add all the concepts that must be copied over
+        newKeyInfoMap.putAll(existingKeyInformation.getKeyInfoMap());
+        newSchemasMap.putAll(existingSchemas.getSchemasMap());
+        newEventsMap.putAll(existingEvents.getEventMap());
+        newAlbumsMap.putAll(existingAlbums.getAlbumsMap());
+        newTasksMap.putAll(existingTasks.getTaskMap());
+        newPoliciesMap.putAll(existingPolicies.getPolicyMap());
     }
 
     private void setUpNewMarshallerAndUnmarshaller(EngineServiceParameters engineServiceParameters,
@@ -226,38 +266,6 @@ public class ApexActivator {
         }
     }
 
-    private void handleExistingMarshallerAndUnmarshaller(Map<String, EventHandlerParameters> inputParametersMap,
-        Map<String, EventHandlerParameters> outputParametersMap) {
-        // stop and remove any marshaller/unmarshaller that is part of a policy that is
-        // undeployed
-        marshallerMap.entrySet().stream()
-            .filter(marshallerEntry -> !outputParametersMap.containsKey(marshallerEntry.getKey()))
-            .forEach(marshallerEntry -> marshallerEntry.getValue().stop());
-        marshallerMap.keySet().removeIf(marshallerKey -> !outputParametersMap.containsKey(marshallerKey));
-        unmarshallerMap.entrySet().stream()
-            .filter(unmarshallerEntry -> !inputParametersMap.containsKey(unmarshallerEntry.getKey()))
-            .forEach(unmarshallerEntry -> unmarshallerEntry.getValue().stop());
-        unmarshallerMap.keySet().removeIf(unmarshallerKey -> !inputParametersMap.containsKey(unmarshallerKey));
-
-        // If a marshaller/unmarshaller is already initialized, they don't need to be
-        // reinitialized during model update.
-        outputParametersMap.keySet().removeIf(marshallerMap::containsKey);
-        inputParametersMap.keySet().removeIf(unmarshallerMap::containsKey);
-    }
-
-    private void instantiateEngine(ApexParameters apexParameters) throws ApexException {
-        if (null != apexEngineService && apexEngineService.getKey().equals(engineKey)) {
-            throw new ApexException("Apex Engine already initialized.");
-        }
-        // Create engine with specified thread count
-        LOGGER.debug("starting apex engine service . . .");
-        apexEngineService = EngineServiceImpl.create(apexParameters.getEngineServiceParameters());
-
-        // Create the engine holder to hold the engine's references and act as an event
-        // receiver
-        engineServiceHandler = new ApexEngineServiceHandler(apexEngineService);
-    }
-
     /**
      * Set up unmarshaler/marshaler pairing for synchronized event handling. We only
      * need to traverse the unmarshalers because the unmarshalers and marshalers are
@@ -275,8 +283,8 @@ public class ApexActivator {
                 // Check if the unmarshaler is synchronized with a marshaler
                 if (inputParameters.getValue().isPeeredMode(peeredMode)) {
                     // Find the unmarshaler and marshaler
-                    final ApexEventMarshaller peeredMarshaler = marshallerMap
-                        .get(inputParameters.getValue().getPeer(peeredMode));
+                    final ApexEventMarshaller peeredMarshaler =
+                        marshallerMap.get(inputParameters.getValue().getPeer(peeredMode));
 
                     // Connect the unmarshaler and marshaler
                     unmarshaller.connectMarshaler(peeredMode, peeredMarshaler);
@@ -298,22 +306,6 @@ public class ApexActivator {
     }
 
     /**
-     * Updates the APEX Engine with the model created from new Policies.
-     *
-     * @param apexParamsMap the apex parameters map for the Apex service
-     * @throws ApexException on errors
-     */
-    public void updateModel(Map<ToscaConceptIdentifier, ApexParameters> apexParamsMap) throws ApexException {
-        try {
-            ApexParameters apexParameters = apexParamsMap.values().iterator().next();
-            setUpModelMarshallerAndUnmarshaller(apexParameters);
-        } catch (final Exception e) {
-            LOGGER.debug(APEX_ENGINE_FAILED_MSG, e);
-            throw new ApexActivatorException(APEX_ENGINE_FAILED_MSG, e);
-        }
-    }
-
-    /**
      * Get the Apex engine worker stats.
      */
     public List<AxEngineModel> getEngineStats() {
@@ -338,19 +330,25 @@ public class ApexActivator {
             engineServiceHandler.terminate();
             engineServiceHandler = null;
         }
-
-        // Clear the services
-        ModelService.clear();
-        ParameterService.clear();
+        // Clear the services in case if this was the only policy running in the engine
+        ApexParameters apexParams = null;
+        if (ParameterService.contains(ApexParameterConstants.MAIN_GROUP_NAME)) {
+            apexParams = ParameterService.get(ApexParameterConstants.MAIN_GROUP_NAME);
+        }
+        if (null != apexParams
+            && apexParameters.getEventInputParameters().size() == apexParams.getEventInputParameters().size()) {
+            ModelService.clear();
+            ParameterService.clear();
+        }
     }
 
     /**
      * Shuts down all marshallers and unmarshallers.
      */
     private void shutdownMarshallerAndUnmarshaller() {
-        marshallerMap.values().forEach(ApexEventMarshaller::stop);
-        marshallerMap.clear();
         unmarshallerMap.values().forEach(ApexEventUnmarshaller::stop);
         unmarshallerMap.clear();
+        marshallerMap.values().forEach(ApexEventMarshaller::stop);
+        marshallerMap.clear();
     }
 }
diff --git a/services/services-engine/src/main/java/org/onap/policy/apex/service/engine/main/ApexEventUnmarshaller.java b/services/services-engine/src/main/java/org/onap/policy/apex/service/engine/main/ApexEventUnmarshaller.java
index fd6ac4489..fdc404c67 100644
--- a/services/services-engine/src/main/java/org/onap/policy/apex/service/engine/main/ApexEventUnmarshaller.java
+++ b/services/services-engine/src/main/java/org/onap/policy/apex/service/engine/main/ApexEventUnmarshaller.java
@@ -2,7 +2,7 @@
  * ============LICENSE_START=======================================================
  *  Copyright (C) 2016-2018 Ericsson. All rights reserved.
  *  Modifications Copyright (C) 2019-2020 Nordix Foundation.
- *  Modifications Copyright (C) 2020 Bell Canada. All rights reserved.
+ *  Modifications Copyright (C) 2020-2021 Bell Canada. All rights reserved.
  * ================================================================================
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -347,17 +347,16 @@ public class ApexEventUnmarshaller implements ApexEventReceiver, Runnable {
         // Order the stop
         stopOrderedFlag = true;
 
-        // Order a stop on the synchronous cache if one exists
-        if (consumerParameters != null && consumerParameters.isPeeredMode(EventHandlerPeeredMode.SYNCHRONOUS)
-            && consumer.getPeeredReference(EventHandlerPeeredMode.SYNCHRONOUS) != null) {
-            ((SynchronousEventCache) consumer.getPeeredReference(EventHandlerPeeredMode.SYNCHRONOUS)).stop();
-        }
-
         // Wait for thread shutdown
         while (unmarshallerThread != null && unmarshallerThread.isAlive()) {
             ThreadUtilities.sleep(UNMARSHALLER_SHUTDOWN_WAIT_INTERVAL);
         }
 
+        // Order a stop on the synchronous cache if one exists
+        if (consumerParameters != null && consumerParameters.isPeeredMode(EventHandlerPeeredMode.SYNCHRONOUS)
+            && consumer.getPeeredReference(EventHandlerPeeredMode.SYNCHRONOUS) != null) {
+            ((SynchronousEventCache) consumer.getPeeredReference(EventHandlerPeeredMode.SYNCHRONOUS)).stop();
+        }
         LOGGER.exit("shut down Apex event unmarshaller");
     }
 }
diff --git a/services/services-engine/src/main/java/org/onap/policy/apex/service/engine/main/ApexMain.java b/services/services-engine/src/main/java/org/onap/policy/apex/service/engine/main/ApexMain.java
index 5707c95ad..65c2acffa 100644
--- a/services/services-engine/src/main/java/org/onap/policy/apex/service/engine/main/ApexMain.java
+++ b/services/services-engine/src/main/java/org/onap/policy/apex/service/engine/main/ApexMain.java
@@ -2,7 +2,7 @@
  * ============LICENSE_START=======================================================
  *  Copyright (C) 2016-2018 Ericsson. All rights reserved.
  *  Modification Copyright (C) 2019-2021 Nordix Foundation.
- *  Modifications Copyright (C) 2020 Bell Canada. All rights reserved.
+ *  Modifications Copyright (C) 2020-2021 Bell Canada. All rights reserved.
  * ================================================================================
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -24,26 +24,20 @@ package org.onap.policy.apex.service.engine.main;
 
 import java.util.Arrays;
 import java.util.Base64;
-import java.util.LinkedHashMap;
 import java.util.List;
-import java.util.Map;
 import java.util.Map.Entry;
-import java.util.TreeMap;
+import java.util.stream.Collectors;
 import lombok.Getter;
 import lombok.Setter;
 import org.onap.policy.apex.core.engine.EngineParameters;
 import org.onap.policy.apex.model.basicmodel.concepts.ApexException;
-import org.onap.policy.apex.model.basicmodel.concepts.AxArtifactKey;
-import org.onap.policy.apex.model.basicmodel.service.ModelService;
-import org.onap.policy.apex.model.contextmodel.concepts.AxContextAlbum;
-import org.onap.policy.apex.model.contextmodel.concepts.AxContextAlbums;
 import org.onap.policy.apex.model.enginemodel.concepts.AxEngineModel;
-import org.onap.policy.apex.model.policymodel.concepts.AxPolicyModel;
+import org.onap.policy.apex.service.parameters.ApexParameterConstants;
 import org.onap.policy.apex.service.parameters.ApexParameterHandler;
 import org.onap.policy.apex.service.parameters.ApexParameters;
+import org.onap.policy.apex.service.parameters.engineservice.EngineServiceParameters;
 import org.onap.policy.apex.service.parameters.eventhandler.EventHandlerParameters;
 import org.onap.policy.common.parameters.ParameterService;
-import org.onap.policy.models.tosca.authorative.concepts.ToscaConceptIdentifier;
 import org.slf4j.ext.XLogger;
 import org.slf4j.ext.XLoggerFactory;
 
@@ -58,14 +52,12 @@ public class ApexMain {
     private static final XLogger LOGGER = XLoggerFactory.getXLogger(ApexMain.class);
 
     // The Apex Activator that activates the Apex engine
+    @Getter
     private ApexActivator activator;
 
     // The parameters read in from JSON for each policy
     @Getter
-    private Map<ToscaConceptIdentifier, ApexParameters> apexParametersMap;
-
-    //engineParameters are aggregated in case of multiple policies
-    private EngineParameters aggregatedEngineParameters;
+    private ApexParameters apexParameters;
 
     private ApexParameterHandler apexParameterHandler = new ApexParameterHandler();
 
@@ -77,73 +69,27 @@ public class ApexMain {
      * Instantiates the Apex service.
      *
      * @param args the command line arguments
+     * @throws ApexException the apex exception.
      */
-    public ApexMain(final String[] args) {
+    public ApexMain(final String[] args) throws ApexException {
         LOGGER.entry("Starting Apex service with parameters " + Arrays.toString(args) + " . . .");
-        apexParametersMap = new LinkedHashMap<>();
-        aggregatedEngineParameters = new EngineParameters();
         try {
-            apexParametersMap.put(new ToscaConceptIdentifier(), populateApexParameters(args));
+            apexParameters = populateApexParameters(args);
         } catch (ApexException e) {
             LOGGER.error(APEX_SERVICE_FAILED_MSG, e);
             return;
         }
-        apexParameterHandler.registerParameters(apexParametersMap.values().iterator().next());
-        // Now, create the activator for the Apex service
-        activator = new ApexActivator(apexParametersMap);
-
-        // Start the activator
-        try {
-            activator.initialize();
-            setAlive(true);
-        } catch (final ApexActivatorException e) {
-            LOGGER.error("start of Apex service failed, used parameters are " + Arrays.toString(args), e);
-            return;
-        }
-
-        // Add a shutdown hook to shut everything down in an orderly manner
-        Runtime.getRuntime().addShutdownHook(new ApexMainShutdownHookClass());
-        LOGGER.exit("Started Apex");
-    }
-
-    /**
-     * Instantiates the Apex service for multiple policies.
-     *
-     * @param policyArgumentsMap the map with command line arguments as value and policy-id as key
-     * @throws ApexException on errors
-     */
-    public ApexMain(Map<ToscaConceptIdentifier, String[]> policyArgumentsMap) throws ApexException {
-        apexParametersMap = new LinkedHashMap<>();
-        aggregatedEngineParameters = new EngineParameters();
-        for (Entry<ToscaConceptIdentifier, String[]> policyArgsEntry: policyArgumentsMap.entrySet()) {
-            try {
-                apexParametersMap.put(policyArgsEntry.getKey(), populateApexParameters(policyArgsEntry.getValue()));
-            } catch (ApexException e) {
-                LOGGER.error("Invalid arguments specified for policy - " + policyArgsEntry.getKey().getName() + ":"
-                    + policyArgsEntry.getKey().getVersion(), e);
-            }
-        }
-        if (apexParametersMap.isEmpty()) {
-            LOGGER.error(APEX_SERVICE_FAILED_MSG);
-            return;
-        }
+        aggregateParametersAndRegister();
 
-        // Set the aggregated engineParameters which will be used later while creating the engine
-        ApexParameters apexParameters = apexParametersMap.values().iterator().next();
-        apexParameters.getEngineServiceParameters().setEngineParameters(aggregatedEngineParameters);
-        apexParameterHandler.registerParameters(apexParameters);
         // Now, create the activator for the Apex service
-        activator = new ApexActivator(apexParametersMap);
+        activator = new ApexActivator(apexParameters);
 
         // Start the activator
         try {
             activator.initialize();
-            apexParametersMap = activator.getApexParametersMap();
             setAlive(true);
         } catch (final ApexActivatorException e) {
-            LOGGER.error(APEX_SERVICE_FAILED_MSG, e);
-            activator.terminate();
-            return;
+            throw new ApexException("start of Apex service failed, used parameters are " + Arrays.toString(args), e);
         }
 
         // Add a shutdown hook to shut everything down in an orderly manner
@@ -151,75 +97,6 @@ public class ApexMain {
         LOGGER.exit("Started Apex");
     }
 
-    /**
-     * Updates the APEX Engine with the model created from new Policies.
-     *
-     * @param policyArgsMap the map with command line arguments as value and policy-id as key
-     * @throws ApexException on errors
-     */
-    public void updateModel(Map<ToscaConceptIdentifier, String[]> policyArgsMap) throws ApexException {
-        // flag that determines if any policy received in PDP_UPDATE is already deployed in the engine
-        boolean isAnyPolicyDeployed = policyArgsMap.keySet().stream().anyMatch(apexParametersMap::containsKey);
-        apexParametersMap.clear();
-        aggregatedEngineParameters = new EngineParameters();
-        AxContextAlbums albums = ModelService.getModel(AxContextAlbums.class);
-        Map<AxArtifactKey, AxContextAlbum> albumsMap = new TreeMap<>();
-        for (Entry<ToscaConceptIdentifier, String[]> policyArgsEntry : policyArgsMap.entrySet()) {
-            findAlbumsToHold(albumsMap, policyArgsEntry.getKey());
-            try {
-                apexParametersMap.put(policyArgsEntry.getKey(), populateApexParameters(policyArgsEntry.getValue()));
-            } catch (ApexException e) {
-                LOGGER.error("Invalid arguments specified for policy - {}:{}", policyArgsEntry.getKey().getName(),
-                    policyArgsEntry.getKey().getVersion(), e);
-            }
-        }
-        // Set the aggregated engineParameters
-        ApexParameters apexParameters = apexParametersMap.values().iterator().next();
-        apexParameters.getEngineServiceParameters().setEngineParameters(aggregatedEngineParameters);
-        ParameterService.clear();
-        apexParameterHandler.registerParameters(apexParameters);
-        try {
-            if (albumsMap.isEmpty() && !isAnyPolicyDeployed) {
-                // clear context since none of the policies' context albums has to be retained
-                // this could be because all policies have a major version change,
-                // or a full set of new policies are received in the update message
-                activator.terminate();
-                // ParameterService is cleared when activator is terminated. Register the parameters again in this case
-                apexParameterHandler.registerParameters(apexParameters);
-                activator = new ApexActivator(apexParametersMap);
-                activator.initialize();
-                setAlive(true);
-            } else {
-                albums.setAlbumsMap(albumsMap);
-                activator.setApexParametersMap(apexParametersMap);
-                activator.updateModel(apexParametersMap);
-            }
-        } catch (final ApexException e) {
-            LOGGER.error(APEX_SERVICE_FAILED_MSG, e);
-            activator.terminate();
-            throw new ApexException(e.getMessage());
-        }
-    }
-
-    /**
-     * Find the context albums which should be retained when updating the policies.
-     *
-     * @param albumsMap the albums which should be kept during model update
-     * @param policyId the policy id of current policy
-     */
-    private void findAlbumsToHold(Map<AxArtifactKey, AxContextAlbum> albumsMap, ToscaConceptIdentifier policyId) {
-        for (Entry<ToscaConceptIdentifier, AxPolicyModel> policyModelsEntry : activator.getPolicyModelsMap()
-            .entrySet()) {
-            // If a policy with the same major version is received in PDP_UPDATE,
-            // context for that policy has to be retained. For this, take such policies' albums
-            if (policyModelsEntry.getKey().getName().equals(policyId.getName())
-                && policyModelsEntry.getKey().getVersion().split("\\.")[0]
-                    .equals(policyId.getVersion().split("\\.")[0])) {
-                albumsMap.putAll(policyModelsEntry.getValue().getAlbums().getAlbumsMap());
-            }
-        }
-    }
-
     private ApexParameters populateApexParameters(String[] args) throws ApexException {
         // Check the arguments
         final ApexCommandLineArguments arguments = new ApexCommandLineArguments();
@@ -263,11 +140,32 @@ public class ApexMain {
                 ehParameterEntry.getValue().setName(ehParameterEntry.getKey());
             }
         }
-        aggregateEngineParameters(axParameters.getEngineServiceParameters().getEngineParameters());
         return axParameters;
     }
 
-    private void aggregateEngineParameters(EngineParameters engineParameters) {
+    private void aggregateParametersAndRegister() throws ApexException {
+        ApexParameters aggregatedParameters = null;
+        if (ParameterService.contains(ApexParameterConstants.MAIN_GROUP_NAME)) {
+            aggregatedParameters = ParameterService.get(ApexParameterConstants.MAIN_GROUP_NAME);
+        } else {
+            aggregatedParameters = new ApexParameters();
+            aggregatedParameters.setEngineServiceParameters(new EngineServiceParameters());
+            apexParameterHandler.registerParameters(aggregatedParameters);
+        }
+        List<String> duplicateInputParameters = aggregatedParameters.getEventInputParameters().keySet().stream()
+            .filter(apexParameters.getEventInputParameters()::containsKey).collect(Collectors.toList());
+        List<String> duplicateOutputParameters = aggregatedParameters.getEventOutputParameters().keySet().stream()
+            .filter(apexParameters.getEventOutputParameters()::containsKey).collect(Collectors.toList());
+        if (!(duplicateInputParameters.isEmpty() && duplicateOutputParameters.isEmpty())) {
+            throw new ApexException(
+                "start of Apex service failed because this policy has the following duplicate I/O parameters: "
+                    + duplicateInputParameters + "/" + duplicateOutputParameters);
+        }
+        aggregatedParameters.getEventInputParameters().putAll(apexParameters.getEventInputParameters());
+        aggregatedParameters.getEventOutputParameters().putAll(apexParameters.getEventOutputParameters());
+        EngineParameters aggregatedEngineParameters =
+            aggregatedParameters.getEngineServiceParameters().getEngineParameters();
+        EngineParameters engineParameters = apexParameters.getEngineServiceParameters().getEngineParameters();
         aggregatedEngineParameters.getTaskParameters().addAll(engineParameters.getTaskParameters());
         aggregatedEngineParameters.getExecutorParameterMap().putAll(engineParameters.getExecutorParameterMap());
         aggregatedEngineParameters.getContextParameters().getSchemaParameters().getSchemaHelperParameterMap()
@@ -346,8 +244,9 @@ public class ApexMain {
      * The main method.
      *
      * @param args the arguments
+     * @throws ApexException the apex exception.
      */
-    public static void main(final String[] args) {
+    public static void main(final String[] args) throws ApexException {
         new ApexMain(args);
     }
 }
diff --git a/services/services-engine/src/main/java/org/onap/policy/apex/service/parameters/ApexParameterHandler.java b/services/services-engine/src/main/java/org/onap/policy/apex/service/parameters/ApexParameterHandler.java
index 9a07b4ad5..673d9cab5 100644
--- a/services/services-engine/src/main/java/org/onap/policy/apex/service/parameters/ApexParameterHandler.java
+++ b/services/services-engine/src/main/java/org/onap/policy/apex/service/parameters/ApexParameterHandler.java
@@ -2,7 +2,7 @@
  * ============LICENSE_START=======================================================
  *  Copyright (C) 2016-2018 Ericsson. All rights reserved.
  *  Modifications Copyright (C) 2019 Nordix Foundation.
- *  Modifications Copyright (C) 2020 Bell Canada. All rights reserved.
+ *  Modifications Copyright (C) 2020-2021 Bell Canada. All rights reserved.
  * ================================================================================
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -73,8 +73,6 @@ public class ApexParameterHandler {
      */
     public ApexParameters getParameters(final ApexCommandLineArguments arguments) throws ParameterException {
 
-        ParameterService.clear();
-
         ApexParameters parameters = null;
         String toscaPolicyFilePath = arguments.getToscaPolicyFilePath();
         // Read the parameters