Create PDP Monitoring GUI Model

Monitorning GUI to monitor PDPs Statistics, including
Web and Rest Server by embeded jetty.

Issue-ID: POLICY-2311
Signed-off-by: Hengye <yehui.wang@est.tech>
Change-Id: I9bd0d50eaa7ae4dbd07d17389da2cf107e854c61

9 files changed, 912 insertions, 0 deletions

diff --git a/gui-pdp-monitoring/src/main/java/org/onap/policy/gui/pdp/monitoring/PdpMonitoringMain.java b/gui-pdp-monitoring/src/main/java/org/onap/policy/gui/pdp/monitoring/PdpMonitoringMain.java
new file mode 100644
index 0000000..34b2901
--- /dev/null
+++ b/gui-pdp-monitoring/src/main/java/org/onap/policy/gui/pdp/monitoring/PdpMonitoringMain.java
@@ -0,0 +1,170 @@
+/*-
+ * ============LICENSE_START=======================================================
+ *  Copyright (C) 2020 Nordix Foundation.
+ * ================================================================================
+ * Licensed 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.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.gui.pdp.monitoring;
+
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+import lombok.Getter;
+import lombok.ToString;
+import org.onap.policy.common.parameters.ValidationResult;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * The main class for Pdp Statistics Monitoring.
+ *
+ * @author Yehui Wang (yehui.wang@est.tech)
+ */
+@ToString
+public class PdpMonitoringMain {
+    // Logger for this class
+    private static final Logger LOGGER = LoggerFactory.getLogger(PdpMonitoringMain.class);
+
+    // Recurring string constants
+    private static final String PDP_MONITORING_PREFIX = "Pdp Monitoring GUI (";
+
+    // Services state
+    public enum ServicesState {
+        STOPPED, READY, INITIALIZING, RUNNING
+    }
+
+    @Getter
+    private ServicesState state = ServicesState.STOPPED;
+
+    // The parameters for the Server
+    private PdpMonitoringServerParameters parameters = null;
+
+    // The Pdp Monitoring services this class is running
+    private PdpMonitoringServer pdpMonitoringServer = null;
+
+    private CountDownLatch countDownLatch = new CountDownLatch(1);
+
+    /**
+     * Constructor, kicks off the GUI service.
+     *
+     * @param args The command line arguments for the RESTful service
+     */
+    public PdpMonitoringMain(final String[] args) {
+
+        // Server parameter parsing
+        final PdpMonitoringServerParameterParser parser = new PdpMonitoringServerParameterParser();
+
+        try {
+            // Get and check the parameters
+            parameters = parser.parse(args);
+        } catch (final PdpMonitoringServerParameterException e) {
+            throw new PdpMonitoringServerParameterException(PDP_MONITORING_PREFIX + this + ") parameter error, "
+                    + e.getMessage() + '\n' + parser.getHelp(PdpMonitoringMain.class.getName()), e);
+        }
+
+        if (parameters.isHelpSet()) {
+            throw new PdpMonitoringServerParameterException(parser.getHelp(PdpMonitoringMain.class.getName()));
+        }
+
+        // Validate the parameters
+        final ValidationResult validationResult = parameters.validate();
+        if (!validationResult.isValid()) {
+            throw new PdpMonitoringServerParameterException(
+                    PDP_MONITORING_PREFIX + this + ") parameters invalid, " + validationResult.getResult() + '\n'
+                            + parser.getHelp(PdpMonitoringMain.class.getName()));
+        }
+
+        state = ServicesState.READY;
+    }
+
+    /**
+     * Initialize the rest service.
+     */
+    public void init() {
+        LOGGER.info(PDP_MONITORING_PREFIX + "{}) starting at {} . . .", this, parameters.getBaseUri());
+
+        try {
+            state = ServicesState.INITIALIZING;
+
+            // Start the Pdp Monitoring service
+            pdpMonitoringServer = new PdpMonitoringServer(parameters);
+
+            // Add a shutdown hook to shut down the servlet services when the process is exiting
+            Runtime.getRuntime().addShutdownHook(new Thread(new PdpServicesShutdownHook()));
+
+            state = ServicesState.RUNNING;
+
+            if (parameters.getTimeToLive() == PdpMonitoringServerParameters.INFINITY_TIME_TO_LIVE) {
+                LOGGER.info(PDP_MONITORING_PREFIX + "{}) starting at {} . . .", this, parameters.getTimeToLive());
+            } else {
+                LOGGER.info(PDP_MONITORING_PREFIX + "{}) started", this);
+            }
+
+            // Find out how long is left to wait
+            long timeRemaining = parameters.getTimeToLive();
+            if (timeRemaining >= 0) {
+                countDownLatch.await(timeRemaining, TimeUnit.SECONDS);
+            } else {
+                countDownLatch.await();
+            }
+        } catch (final Exception e) {
+            LOGGER.warn(this + " failed with error", e);
+        } finally {
+            shutdown();
+        }
+
+    }
+
+    /**
+     * Explicitly shut down the services.
+     */
+    public void shutdown() {
+        if (pdpMonitoringServer != null) {
+            LOGGER.info(PDP_MONITORING_PREFIX + "{}) shutting down", this);
+            pdpMonitoringServer.shutdown(parameters.getPort(), parameters.getDefaultRestPort());
+        }
+        countDownLatch.countDown();
+        state = ServicesState.STOPPED;
+        LOGGER.info(PDP_MONITORING_PREFIX + "{}) shutting down", this);
+    }
+
+    /**
+     * This class is a shutdown hook for the Pdp services command.
+     */
+    private class PdpServicesShutdownHook implements Runnable {
+        /**
+         * {@inheritDoc}.
+         */
+        @Override
+        public void run() {
+            shutdown();
+        }
+    }
+
+    /**
+     * Main method, main entry point for command.
+     *
+     * @param args The command line arguments for the GUI
+     */
+    public static void main(final String[] args) {
+        try {
+            final PdpMonitoringMain main = new PdpMonitoringMain(args);
+            main.init();
+        } catch (final Exception e) {
+            LOGGER.error("start failed", e);
+        }
+    }
+}
diff --git a/gui-pdp-monitoring/src/main/java/org/onap/policy/gui/pdp/monitoring/PdpMonitoringServer.java b/gui-pdp-monitoring/src/main/java/org/onap/policy/gui/pdp/monitoring/PdpMonitoringServer.java
new file mode 100644
index 0000000..97d2deb
--- /dev/null
+++ b/gui-pdp-monitoring/src/main/java/org/onap/policy/gui/pdp/monitoring/PdpMonitoringServer.java
@@ -0,0 +1,92 @@
+/*-
+ * ============LICENSE_START=======================================================
+ *  Copyright (C) 2020 Nordix Foundation.
+ * ================================================================================
+ * Licensed 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.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.gui.pdp.monitoring;
+
+import lombok.NonNull;
+import org.eclipse.jetty.servlets.CrossOriginFilter;
+import org.onap.policy.common.endpoints.http.server.HttpServletServer;
+import org.onap.policy.common.endpoints.http.server.HttpServletServerFactoryInstance;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * This class is used to launch the services. It creates a Jetty embedded web server and runs the
+ * services.
+ *
+ * @author Yehui Wang (yehui.wang@est.tech)
+ */
+public class PdpMonitoringServer {
+    // Logger for this class
+    private static final Logger LOGGER = LoggerFactory.getLogger(PdpMonitoringServer.class);
+
+    // The HTTP server exposing JAX-RS resources defined in this application.
+    private HttpServletServer jerseyServer;
+
+    // The HTTP server exposing static resources defined in this application.
+    private HttpServletServer staticResourceServer;
+
+    /**
+     * Starts the HTTP server for the Pdp statistics monitoring on the default base URI and with the
+     * default REST packages.
+     */
+    public PdpMonitoringServer() {
+        this(new PdpMonitoringServerParameters());
+    }
+
+    /**
+     * Starts the HTTP server for the Pdp statistics monitoring GUI.
+     *
+     * @param parameters The Pdp parameters to use to start the server.
+     * @return
+     */
+    public PdpMonitoringServer(@NonNull final PdpMonitoringServerParameters parameters) {
+
+        LOGGER.debug("Pdp Monitoring starting . . .");
+
+        jerseyServer = HttpServletServerFactoryInstance.getServerFactory().build("PDP Monitoring Rest Server", false,
+                parameters.getServerHost(), parameters.getDefaultRestPort(), parameters.getContextPath(), false, true);
+        jerseyServer.addServletPackage(parameters.getDefaultRestPath(), parameters.getRestPackage());
+        jerseyServer.addFilterClass(parameters.getDefaultRestPath(), CrossOriginFilter.class.getName());
+        jerseyServer.start();
+
+        staticResourceServer = HttpServletServerFactoryInstance.getServerFactory().buildStaticResourceServer(
+                "PDP Monitoring Html Server", false, parameters.getServerHost(), parameters.getPort(),
+                parameters.getContextPath(), true);
+        staticResourceServer.addServletResource(null,
+                PdpMonitoringServer.class.getClassLoader().getResource("webapp").toExternalForm());
+        staticResourceServer.start();
+
+        LOGGER.debug("Pdp Monitoring started");
+    }
+
+    /**
+     * Shut down the web server.
+     *
+     * @param htmlPort port number of static resource server
+     * @param restPort port number of jersey server
+     */
+    public void shutdown(int htmlPort, int restPort) {
+        LOGGER.debug("Pdp Monitoring . . .");
+        HttpServletServerFactoryInstance.getServerFactory().destroy(htmlPort);
+        HttpServletServerFactoryInstance.getServerFactory().destroy(restPort);
+        LOGGER.debug("Pdp Monitoring shut down");
+    }
+}
diff --git a/gui-pdp-monitoring/src/main/java/org/onap/policy/gui/pdp/monitoring/PdpMonitoringServerParameterException.java b/gui-pdp-monitoring/src/main/java/org/onap/policy/gui/pdp/monitoring/PdpMonitoringServerParameterException.java
new file mode 100644
index 0000000..8977d33
--- /dev/null
+++ b/gui-pdp-monitoring/src/main/java/org/onap/policy/gui/pdp/monitoring/PdpMonitoringServerParameterException.java
@@ -0,0 +1,47 @@
+/*-
+ * ============LICENSE_START=======================================================
+ *  Copyright (C) 2020 Nordix Foundation.
+ * ================================================================================
+ * Licensed 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.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.gui.pdp.monitoring;
+
+/**
+ * A run time exception used to report parsing and parameter input errors.
+ */
+public class PdpMonitoringServerParameterException extends IllegalArgumentException {
+    private static final long serialVersionUID = 6520231162404452427L;
+
+    /**
+     * Create an PdpMonitoringServerParameterException with a message.
+     *
+     * @param message the message
+     */
+    public PdpMonitoringServerParameterException(final String message) {
+        super(message);
+    }
+
+    /**
+     * Create an PdpMonitoringServerParameterException with a message and an exception.
+     *
+     * @param message the message
+     * @param throwable The exception that caused the exception
+     */
+    public PdpMonitoringServerParameterException(final String message, final Throwable throwable) {
+        super(message, throwable);
+    }
+}
diff --git a/gui-pdp-monitoring/src/main/java/org/onap/policy/gui/pdp/monitoring/PdpMonitoringServerParameterParser.java b/gui-pdp-monitoring/src/main/java/org/onap/policy/gui/pdp/monitoring/PdpMonitoringServerParameterParser.java
new file mode 100644
index 0000000..5d9d290
--- /dev/null
+++ b/gui-pdp-monitoring/src/main/java/org/onap/policy/gui/pdp/monitoring/PdpMonitoringServerParameterParser.java
@@ -0,0 +1,113 @@
+/*-
+ * ============LICENSE_START=======================================================
+ *  Copyright (C) 2020 Nordix Foundation.
+ * ================================================================================
+ * Licensed 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.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.gui.pdp.monitoring;
+
+import java.io.PrintWriter;
+import java.io.StringWriter;
+import java.util.Arrays;
+import org.apache.commons.cli.CommandLine;
+import org.apache.commons.cli.DefaultParser;
+import org.apache.commons.cli.HelpFormatter;
+import org.apache.commons.cli.Option;
+import org.apache.commons.cli.Options;
+import org.apache.commons.cli.ParseException;
+
+/**
+ * This class reads and handles command line parameters to the Pdp Statistics services.
+ *
+ * @author Yehui Wang (yehui.wang@est.tech)
+ */
+public class PdpMonitoringServerParameterParser {
+    // Apache Commons CLI options
+    private final Options options;
+
+    /**
+     * Construct the options for the Pdp monitoring services.
+     */
+    public PdpMonitoringServerParameterParser() {
+        options = new Options();
+        options.addOption("h", "help", false, "outputs the usage of this command");
+        options.addOption(Option.builder("p").longOpt("port").desc("port to use for the Pdp Services REST calls")
+                .hasArg().argName("PORT").required(false).type(Number.class).build());
+        options.addOption(Option.builder("t").longOpt("time-to-live")
+                .desc("the amount of time in seconds that the server will run for before terminating").hasArg()
+                .argName("TIME_TO_LIVE").required(false).type(Number.class).build());
+    }
+
+    /**
+     * Parse the command line options.
+     *
+     * @param args the arguments
+     * @return parsed parameters
+     */
+    public PdpMonitoringServerParameters parse(final String[] args) {
+        CommandLine commandLine = null;
+        try {
+            commandLine = new DefaultParser().parse(options, args);
+        } catch (final ParseException e) {
+            throw new PdpMonitoringServerParameterException("invalid command line arguments specified", e);
+        }
+
+        final PdpMonitoringServerParameters parameters = new PdpMonitoringServerParameters();
+        final String[] remainingArgs = commandLine.getArgs();
+
+        if (commandLine.getArgs().length > 0) {
+            throw new PdpMonitoringServerParameterException(
+                    "too many command line arguments specified : " + Arrays.toString(remainingArgs));
+        }
+
+        if (commandLine.hasOption('h')) {
+            parameters.setHelpSet(true);
+        }
+        try {
+            if (commandLine.hasOption('p')) {
+                parameters.setPort(((Number) commandLine.getParsedOptionValue("port")).intValue());
+            }
+        } catch (final ParseException e) {
+            throw new PdpMonitoringServerParameterException("error parsing argument \"port\"", e);
+        }
+        try {
+            if (commandLine.hasOption('t')) {
+                parameters.setTimeToLive(((Number) commandLine.getParsedOptionValue("time-to-live")).longValue());
+            }
+        } catch (final ParseException e) {
+            throw new PdpMonitoringServerParameterException("error parsing argument \"time-to-live\"", e);
+        }
+
+        return parameters;
+    }
+
+    /**
+     * Get help information.
+     *
+     * @param mainClassName the main class name for the help output
+     * @return help string
+     */
+    public String getHelp(final String mainClassName) {
+        final StringWriter stringWriter = new StringWriter();
+        final PrintWriter stringPrintWriter = new PrintWriter(stringWriter);
+
+        final HelpFormatter helpFormatter = new HelpFormatter();
+        helpFormatter.printHelp(stringPrintWriter, 120, mainClassName + " [options...] ", "", options, 0, 0, "");
+
+        return stringWriter.toString();
+    }
+}
diff --git a/gui-pdp-monitoring/src/main/java/org/onap/policy/gui/pdp/monitoring/PdpMonitoringServerParameters.java b/gui-pdp-monitoring/src/main/java/org/onap/policy/gui/pdp/monitoring/PdpMonitoringServerParameters.java
new file mode 100644
index 0000000..614d47d
--- /dev/null
+++ b/gui-pdp-monitoring/src/main/java/org/onap/policy/gui/pdp/monitoring/PdpMonitoringServerParameters.java
@@ -0,0 +1,95 @@
+/*-
+ * ============LICENSE_START=======================================================
+ *  Copyright (C) 2020 Nordix Foundation.
+ * ================================================================================
+ * Licensed 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.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.gui.pdp.monitoring;
+
+import java.net.URI;
+import lombok.Getter;
+import lombok.Setter;
+import lombok.ToString;
+import org.onap.policy.common.parameters.BeanValidator;
+import org.onap.policy.common.parameters.ValidationResult;
+import org.onap.policy.common.parameters.annotations.Max;
+import org.onap.policy.common.parameters.annotations.Min;
+
+/**
+ * This class reads and handles command line parameters to the Pdp Monitoring services.
+ *
+ * @author Yehui Wang (yehui.wang@est.tech)
+ */
+@ToString
+@Getter
+@Setter
+public class PdpMonitoringServerParameters {
+    public static final int DEFAULT_PORT = 18999;
+    public static final int INFINITY_TIME_TO_LIVE = -1;
+
+    // Base URI the HTTP server will listen on
+    private static final String DEFAULT_SERVER_URI_ROOT = "http://0.0.0.0:";
+    private static final String DEFAULT_REST_PATH = "/papservices/*";
+    private static final String DEFAULT_CONTEXT_PATH = "/";
+    private static final String SERVER_HOST = "0.0.0.0";
+    private static final int DEFAULT_REST_PORT = 17999;
+    // Package that will field REST requests
+    private static final String DEFAULT_REST_PACKAGE = "org.onap.policy.gui.pdp.monitoring.rest";
+
+    // The services parameters
+    private boolean helpSet = false;
+
+    @Min(1024)
+    @Max(65534)
+    private int port = DEFAULT_PORT;
+
+    @Min(-1)
+    private long timeToLive = INFINITY_TIME_TO_LIVE;
+
+    /**
+     * Validate the parameters.
+     *
+     * @return the result of the validation
+     */
+    public ValidationResult validate() {
+        return new BeanValidator().validateTop(PdpMonitoringServerParameters.class.getSimpleName(), this);
+    }
+
+    public URI getBaseUri() {
+        return URI.create(DEFAULT_SERVER_URI_ROOT + port + DEFAULT_REST_PATH);
+    }
+
+    public String getRestPackage() {
+        return DEFAULT_REST_PACKAGE;
+    }
+
+    public String getContextPath() {
+        return DEFAULT_CONTEXT_PATH;
+    }
+
+    public String getServerHost() {
+        return SERVER_HOST;
+    }
+
+    public String getDefaultRestPath() {
+        return DEFAULT_REST_PATH;
+    }
+
+    public int getDefaultRestPort() {
+        return DEFAULT_REST_PORT;
+    }
+}
diff --git a/gui-pdp-monitoring/src/main/java/org/onap/policy/gui/pdp/monitoring/package-info.java b/gui-pdp-monitoring/src/main/java/org/onap/policy/gui/pdp/monitoring/package-info.java
new file mode 100644
index 0000000..d1595b8
--- /dev/null
+++ b/gui-pdp-monitoring/src/main/java/org/onap/policy/gui/pdp/monitoring/package-info.java
@@ -0,0 +1,27 @@
+/*-
+ * ============LICENSE_START=======================================================
+ *  Copyright (C) 2020 Nordix Foundation.
+ * ================================================================================
+ * Licensed 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.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ * ============LICENSE_END=========================================================
+ */
+
+/**
+ * Implements the PDP monitoring GUI.
+ *
+ * @author Yehui Wang (yehui.wang@est.tech)
+ */
+
+package org.onap.policy.gui.pdp.monitoring;
diff --git a/gui-pdp-monitoring/src/main/java/org/onap/policy/gui/pdp/monitoring/rest/EngineStatus.java b/gui-pdp-monitoring/src/main/java/org/onap/policy/gui/pdp/monitoring/rest/EngineStatus.java
new file mode 100644
index 0000000..5d2d38a
--- /dev/null
+++ b/gui-pdp-monitoring/src/main/java/org/onap/policy/gui/pdp/monitoring/rest/EngineStatus.java
@@ -0,0 +1,43 @@
+/*-
+ * ============LICENSE_START=======================================================
+ *  Copyright (C) 2020 Nordix Foundation.
+ * ================================================================================
+ * Licensed 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.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.gui.pdp.monitoring.rest;
+
+import lombok.Setter;
+
+
+/**
+ * A POJO class to record engine worker status.
+ *
+ * @author Yehui Wang (yehui.wang@est.tech)
+ *
+ */
+@Setter
+@SuppressWarnings("unused")
+class EngineStatus {
+    private String timestamp;
+    private String id;
+    private String status;
+    private String lastMessage;
+    private long upTime;
+    private long policyExecutions;
+    private String lastPolicyDuration;
+    private String averagePolicyDuration;
+}
diff --git a/gui-pdp-monitoring/src/main/java/org/onap/policy/gui/pdp/monitoring/rest/PdpMonitoringRestResource.java b/gui-pdp-monitoring/src/main/java/org/onap/policy/gui/pdp/monitoring/rest/PdpMonitoringRestResource.java
new file mode 100644
index 0000000..921c68c
--- /dev/null
+++ b/gui-pdp-monitoring/src/main/java/org/onap/policy/gui/pdp/monitoring/rest/PdpMonitoringRestResource.java
@@ -0,0 +1,277 @@
+/*-
+ * ============LICENSE_START=======================================================
+ *  Copyright (C) 2020 Nordix Foundation.
+ * ================================================================================
+ * Licensed 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.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.gui.pdp.monitoring.rest;
+
+import com.google.gson.Gson;
+import com.google.gson.reflect.TypeToken;
+import java.util.ArrayList;
+import java.util.Date;
+import java.util.HashMap;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import javax.ws.rs.Consumes;
+import javax.ws.rs.GET;
+import javax.ws.rs.Path;
+import javax.ws.rs.Produces;
+import javax.ws.rs.QueryParam;
+import javax.ws.rs.core.MediaType;
+import javax.ws.rs.core.Response;
+import lombok.EqualsAndHashCode;
+import lombok.Getter;
+import org.onap.policy.common.endpoints.event.comm.bus.internal.BusTopicParams;
+import org.onap.policy.common.endpoints.http.client.HttpClient;
+import org.onap.policy.common.endpoints.http.client.HttpClientConfigException;
+import org.onap.policy.common.endpoints.http.client.HttpClientFactoryInstance;
+import org.onap.policy.common.utils.coder.CoderException;
+import org.onap.policy.common.utils.coder.StandardCoder;
+import org.onap.policy.models.pdp.concepts.Pdp;
+import org.onap.policy.models.pdp.concepts.PdpEngineWorkerStatistics;
+import org.onap.policy.models.pdp.concepts.PdpGroups;
+import org.onap.policy.models.pdp.concepts.PdpStatistics;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * The class represents the root resource exposed at the base URL<br>
+ * The url to access this resource would be in the form {@code <baseURL>/rest/....} <br>
+ * For example: a GET request to the following URL
+ * {@code http://localhost:18989/papservices/rest/?hostName=localhost&port=12345}
+ *
+ * <b>Note:</b> An allocated {@code hostName} and {@code port} query parameter must be included in
+ * all requests. Datasets for different {@code hostName} are completely isolated from one another.
+ *
+ * @author Yehui Wang (yehui.wang@est.tech)
+ */
+@Path("monitoring/")
+@Produces({MediaType.APPLICATION_JSON})
+@Consumes({MediaType.APPLICATION_JSON})
+public class PdpMonitoringRestResource {
+    // Get a reference to the logger
+    private static final Logger LOGGER = LoggerFactory.getLogger(PdpMonitoringRestResource.class);
+    // Set up a map separated by host and engine for the data
+    private static final Map<String, HashMap<String, List<Counter>>> cache = new HashMap<>();
+
+    // Set the maximum number of stored data entries to be stored for each engine
+    private static final int MAX_CACHED_ENTITIES = 50;
+
+    private static Gson gson = new Gson();
+
+    /**
+     * Query Pdps.
+     *
+     * @param useHttps use Http or not
+     * @param hostname hostname the host name of the engine service to connect to.
+     * @param port port the port number of the engine service to connect to.
+     * @param username user name
+     * @param password password
+     * @return a Response object containing Pdps in JSON
+     * @throws HttpClientConfigException exception
+     */
+    @GET
+    public Response getPdps(@QueryParam("useHttps") final String useHttps,
+            @QueryParam("hostname") final String hostname, @QueryParam("port") final int port,
+            @QueryParam("username") final String username, @QueryParam("password") final String password)
+            throws HttpClientConfigException {
+
+        return Response
+                .ok(getHttpClient(useHttps, hostname, port, username, password, "policy/pap/v1/pdps").get().getEntity(),
+                        MediaType.APPLICATION_JSON)
+                .build();
+    }
+
+    /**
+     * Query Pdp statistics.
+     *
+     * @param useHttps use Http or not
+     * @param hostname the host name of the engine service to connect to.
+     * @param port the port number of the engine service to connect to.
+     * @param username user name
+     * @param password password
+     * @param id PdpGroupName/PdpSubGroup/PdpIntanceID
+     * @return a Response object containing the Pdp status and context data in JSON
+     * @throws HttpClientConfigException exception
+     * @throws CoderException Coder exception
+     */
+    @GET
+    @Path("statistics/")
+    public Response getStatistics(@QueryParam("useHttps") final String useHttps,
+            @QueryParam("hostname") final String hostname, @QueryParam("port") final int port,
+            @QueryParam("username") final String username, @QueryParam("password") final String password,
+            @QueryParam("id") final String id) throws HttpClientConfigException, CoderException {
+
+        PdpGroups pdpGroups = getHttpClient(useHttps, hostname, port, username, password, "policy/pap/v1/pdps").get()
+                .readEntity(PdpGroups.class);
+        String groupName;
+        String subGroup;
+        String instanceId;
+        String[] idArray = id.split("/");
+        if (idArray.length == 3) {
+            groupName = idArray[0];
+            subGroup = idArray[1];
+            instanceId = idArray[2];
+        } else {
+            throw new IllegalArgumentException("Cannot parse groupName, subGroup and instanceId from " + id);
+        }
+
+        Pdp pdp = pdpGroups.getGroups().stream().filter(group -> group.getName().equals(groupName))
+                .flatMap(group -> group.getPdpSubgroups().stream().filter(sub -> sub.getPdpType().equals(subGroup)))
+                .flatMap(sub -> sub.getPdpInstances().stream()
+                        .filter(instance -> instance.getInstanceId().equals(instanceId)))
+                .filter(Objects::nonNull).findFirst().orElseThrow();
+
+        final StatisticsResponse responseObject = new StatisticsResponse();
+
+        // Engine Service data
+        responseObject.setEngineId(pdp.getInstanceId());
+        responseObject.setServer(hostname);
+        responseObject.setPort(Integer.toString(port));
+        responseObject.setHealthStatus(pdp.getHealthy().name());
+        responseObject.setPdpState(pdp.getPdpState().name());
+
+        String statisticsEntity = getHttpClient(useHttps, hostname, port, username, password,
+                "policy/pap/v1/pdps/statistics/" + id + "?recordCount=1").get().readEntity(String.class);
+        Map<String, Map<String, List<PdpStatistics>>> pdpStats = gson.fromJson(statisticsEntity,
+                new TypeToken<Map<String, Map<String, List<PdpStatistics>>>>() {}.getType());
+
+        final List<EngineStatus> engineStatusList = new ArrayList<>();
+
+        if (!pdpStats.isEmpty()) {
+            PdpStatistics pdpStatistics = pdpStats.get(groupName).get(subGroup).get(0);
+            responseObject.setTimeStamp(pdpStatistics.getTimeStamp().toString());
+            responseObject.setPolicyDeployCount(pdpStatistics.getPolicyDeployCount());
+            responseObject.setPolicyDeploySuccessCount(pdpStatistics.getPolicyDeploySuccessCount());
+            responseObject.setPolicyDeployFailCount(pdpStatistics.getPolicyDeployFailCount());
+            responseObject.setPolicyExecutedCount(pdpStatistics.getPolicyExecutedCount());
+            responseObject.setPolicyExecutedSuccessCount(pdpStatistics.getPolicyExecutedSuccessCount());
+            responseObject.setPolicyExecutedFailCount(pdpStatistics.getPolicyExecutedFailCount());
+
+            // Engine Status data
+            for (final PdpEngineWorkerStatistics engineStats : pdpStatistics.getEngineStats()) {
+                try {
+                    final EngineStatus engineStatusObject = new EngineStatus();
+                    engineStatusObject.setTimestamp(pdpStatistics.getTimeStamp().toString());
+                    engineStatusObject.setId(engineStats.getEngineId());
+                    engineStatusObject.setStatus(engineStats.getEngineWorkerState().name());
+                    engineStatusObject.setLastMessage(new Date(engineStats.getEngineTimeStamp()).toString());
+                    engineStatusObject.setUpTime(engineStats.getUpTime());
+                    engineStatusObject.setPolicyExecutions(engineStats.getEventCount());
+                    engineStatusObject.setLastPolicyDuration(gson.toJson(
+                            getValuesFromCache(id, engineStats.getEngineId() + "_last_policy_duration",
+                                    pdpStatistics.getTimeStamp().getTime(), engineStats.getLastExecutionTime()),
+                            List.class));
+                    engineStatusObject.setAveragePolicyDuration(
+                            gson.toJson(getValuesFromCache(id, engineStats.getEngineId() + "_average_policy_duration",
+                                    pdpStatistics.getTimeStamp().getTime(),
+                                    (long) engineStats.getAverageExecutionTime()), List.class));
+                    engineStatusList.add(engineStatusObject);
+                } catch (final RuntimeException e) {
+                    LOGGER.warn("Error getting status of engine with ID " + engineStats.getEngineId() + "<br>", e);
+                }
+            }
+        } else {
+            responseObject.setTimeStamp("N/A");
+            responseObject.setPolicyDeployCount("N/A");
+            responseObject.setPolicyDeploySuccessCount("N/A");
+            responseObject.setPolicyDeployFailCount("N/A");
+            responseObject.setPolicyExecutedCount("N/A");
+            responseObject.setPolicyExecutedSuccessCount("N/A");
+            responseObject.setPolicyExecutedFailCount("N/A");
+        }
+
+        responseObject.setStatus(engineStatusList);
+        return Response.ok(new StandardCoder().encode(responseObject), MediaType.APPLICATION_JSON).build();
+    }
+
+    private HttpClient getHttpClient(String useHttps, String hostname, int port, String username, String password,
+            String basePath) throws HttpClientConfigException {
+        BusTopicParams busParams = new BusTopicParams();
+        busParams.setClientName("pdp-monitoring");
+        busParams.setHostname(hostname);
+        busParams.setManaged(false);
+        busParams.setPassword(password);
+        busParams.setPort(port);
+        busParams.setUseHttps(useHttps.equals("https"));
+        busParams.setUserName(username);
+        busParams.setBasePath(basePath);
+        return HttpClientFactoryInstance.getClientFactory().build(busParams);
+    }
+
+    /**
+     * This method takes in the latest data entry for an engine, adds it to an existing data set and
+     * returns the full map for that host and engine.
+     *
+     * @param uri the pdp uri
+     * @param id the engines id
+     * @param timestamp the timestamp of the latest data entry
+     * @param latestValue the value of the latest data entry
+     * @return a list of {@code Counter} objects for that engine
+     */
+    private synchronized List<Counter> getValuesFromCache(final String uri, final String id, final long timestamp,
+            final long latestValue) {
+
+        Map<String, List<Counter>> engineStatus = cache.computeIfAbsent(uri, k -> new HashMap<>());
+
+        List<Counter> valueList = engineStatus.computeIfAbsent(id, k -> new SlidingWindowList<>(MAX_CACHED_ENTITIES));
+
+        valueList.add(new Counter(timestamp, latestValue));
+
+        return valueList;
+    }
+
+    /**
+     * A list of values that uses a FIFO sliding window of a fixed size.
+     */
+    @EqualsAndHashCode(callSuper = true)
+    public class SlidingWindowList<V> extends LinkedList<V> {
+        private static final long serialVersionUID = -7187277916025957447L;
+
+        private final int maxEntries;
+
+        public SlidingWindowList(final int maxEntries) {
+            this.maxEntries = maxEntries;
+        }
+
+        @Override
+        public boolean add(final V elm) {
+            if (this.size() > (maxEntries - 1)) {
+                this.removeFirst();
+            }
+            return super.add(elm);
+        }
+    }
+
+    /**
+     * A class used to storing a single data entry for an engine.
+     */
+    @Getter
+    public class Counter {
+        private final long timestamp;
+        private final long value;
+
+        public Counter(final long timestamp, final long value) {
+            this.timestamp = timestamp;
+            this.value = value;
+        }
+    }
+
+}
diff --git a/gui-pdp-monitoring/src/main/java/org/onap/policy/gui/pdp/monitoring/rest/StatisticsResponse.java b/gui-pdp-monitoring/src/main/java/org/onap/policy/gui/pdp/monitoring/rest/StatisticsResponse.java
new file mode 100644
index 0000000..ada722f
--- /dev/null
+++ b/gui-pdp-monitoring/src/main/java/org/onap/policy/gui/pdp/monitoring/rest/StatisticsResponse.java
@@ -0,0 +1,48 @@
+/*-
+ * ============LICENSE_START=======================================================
+ *  Copyright (C) 2020 Nordix Foundation.
+ * ================================================================================
+ * Licensed 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.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ * ============LICENSE_END=========================================================
+ */
+
+package org.onap.policy.gui.pdp.monitoring.rest;
+
+import java.util.List;
+import lombok.Setter;
+
+/**
+ * A POJO class to record Pdp statistics.
+ *
+ * @author Yehui Wang (yehui.wang@est.tech)
+ *
+ */
+@Setter
+@SuppressWarnings("unused")
+class StatisticsResponse {
+    private String engineId;
+    private String server;
+    private String port;
+    private String healthStatus;
+    private String pdpState;
+    private String timeStamp;
+    private Object policyDeployCount;
+    private Object policyDeploySuccessCount;
+    private Object policyDeployFailCount;
+    private Object policyExecutedCount;
+    private Object policyExecutedSuccessCount;
+    private Object policyExecutedFailCount;
+    private List<EngineStatus> status;
+}