package com.aem.operations.core.services;

import javax.management.InstanceNotFoundException;
import javax.management.ReflectionException;

/**
 * Private interface for exposing ThrottledTaskRunner stats
 * **/
public interface ThrottledTaskRunnerStats {
    /**
     * @return the % of CPU being utilized.
     * @throws InstanceNotFoundException
     * @throws ReflectionException
     */
    double getCpuLevel() throws InstanceNotFoundException, ReflectionException;

    /**
     * The % of memory being utilized.
     * @return
     */
    double getMemoryUsage();

    /***
     * @return the OSGi configured max allowed CPU utilization.
     */
    double getMaxCpu();

    /***
     * @return the OSGi configured max allowed Memory (heap) utilization.
     */
    double getMaxHeap();

    /**
     * @return the max number of threads ThrottledTaskRunner will use to execute the work.
     */
    int getMaxThreads();
}

package com.aem.operations.core.services.impl;

import java.lang.management.ManagementFactory;
import javax.management.Attribute;
import javax.management.AttributeList;
import javax.management.AttributeNotFoundException;
import javax.management.InstanceNotFoundException;
import javax.management.MBeanException;
import javax.management.MBeanServer;
import javax.management.MalformedObjectNameException;
import javax.management.ObjectName;
import javax.management.ReflectionException;
import javax.management.openmbean.CompositeData;
import com.aem.operations.core.services.ThrottledTaskRunnerStats;
import org.osgi.service.component.annotations.Activate;
import org.osgi.service.component.annotations.Component;
import org.osgi.service.component.annotations.Modified;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

@Component(service = ThrottledTaskRunnerStats.class, immediate = true, name = "Throttled Task Runner Service Stats")
public class ThrottledTaskRunnerImpl implements ThrottledTaskRunnerStats {

    private static final Logger LOGGER = LoggerFactory.getLogger(ThrottledTaskRunnerImpl.class);
    private final MBeanServer mbs = ManagementFactory.getPlatformMBeanServer();
    private ObjectName osBeanName;
    private ObjectName memBeanName;

    @Activate
    @Modified
    protected void activate() {
        try {
            memBeanName = ObjectName.getInstance("java.lang:type=Memory");
            osBeanName = ObjectName.getInstance("java.lang:type=OperatingSystem");
        } catch (MalformedObjectNameException | NullPointerException ex) {
            LOGGER.error("Error getting OS MBean (shouldn't ever happen) {}", ex.getMessage());
        }
    }

    @Override
    public double getCpuLevel() throws InstanceNotFoundException, ReflectionException {
        // This method will block until CPU usage is low enough
        AttributeList list = mbs.getAttributes(osBeanName, new String[]{"ProcessCpuLoad"});

        if (list.isEmpty()) {
            LOGGER.error("No CPU stats found for ProcessCpuLoad");
            return -1;
        }

        Attribute att = (Attribute) list.get(0);
        return (Double) att.getValue();
    }

    @Override
    public double getMemoryUsage() {
        try {
            Object memoryusage = mbs.getAttribute(memBeanName, "HeapMemoryUsage");
            CompositeData cd = (CompositeData) memoryusage;
            long max = (Long) cd.get("max");
            long used = (Long) cd.get("used");
            return (double) used / (double) max;
        } catch (AttributeNotFoundException | InstanceNotFoundException | MBeanException | ReflectionException e) {
            LOGGER.error("No Memory stats found for HeapMemoryUsage", e);
            return -1;
        }
    }

    @Override
    public double getMaxCpu() {
        return 0.75;
    }

    @Override
    public double getMaxHeap() {
        return 0.85;
    }

    @Override
    public int getMaxThreads() {
        return Math.max(1, Runtime.getRuntime().availableProcessors()/2);
    }
}

package com.aem.operations.core.servlets;

import java.io.IOException;
import java.io.PrintWriter;
import java.text.MessageFormat;
import javax.management.InstanceNotFoundException;
import javax.management.ReflectionException;
import javax.servlet.Servlet;
import javax.servlet.ServletException;
import com.aem.operations.core.services.ThrottledTaskRunnerStats;
import org.apache.sling.api.SlingHttpServletRequest;
import org.apache.sling.api.SlingHttpServletResponse;
import org.apache.sling.api.servlets.SlingAllMethodsServlet;
import org.osgi.service.component.annotations.Component;
import org.osgi.service.component.annotations.Reference;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import com.google.gson.Gson;
import com.google.gson.JsonObject;

@Component(service = { Servlet.class }, property = { "sling.servlet.paths=" + CpuStatusServlet.RESOURCE_PATH,
        "sling.servlet.methods=POST" })
public class CpuStatusServlet extends SlingAllMethodsServlet{

    private static final Logger LOGGER = LoggerFactory.getLogger(CpuStatusServlet.class);

    private static final long serialVersionUID = 1L;
    public static final String RESOURCE_PATH = "/bin/cpustatust";
    private static final String MESSAGE_FORMAT = "{0,number,#%}";

    @Reference
    private transient ThrottledTaskRunnerStats ttrs;

    @Override
    protected void doGet(SlingHttpServletRequest request, SlingHttpServletResponse response)
            throws ServletException, IOException {
        JsonObject jsonResponse = getSystemStats();
        try (PrintWriter out = response.getWriter()) {
            out.print(new Gson().toJson(jsonResponse));
        }
    }

    private JsonObject getSystemStats() {
        JsonObject json = new JsonObject();
        try {
            json.addProperty("cpu", MessageFormat.format(MESSAGE_FORMAT, ttrs.getCpuLevel()));
        } catch (InstanceNotFoundException | ReflectionException e) {
            LOGGER.error("Could not collect CPU stats {}", e.getMessage());
            json.addProperty("cpu", -1);
        }
        json.addProperty("mem", MessageFormat.format(MESSAGE_FORMAT, ttrs.getMemoryUsage()));
        json.addProperty("maxCpu", MessageFormat.format(MESSAGE_FORMAT, ttrs.getMaxCpu()));
        json.addProperty("maxMem", MessageFormat.format(MESSAGE_FORMAT, ttrs.getMaxHeap()));
        return json;
    }
}

function getStatus(showStatus) {
   $.ajax({
      // add the servlet path
      url: "/bin/cpustatust",
      method: "GET",
      async: true,
      cache: false,
      contentType: false,
      processData: false
   }).done(function (data) {
      if (data) {
         data = JSON.parse(data);
         $("#table-body").append(`<tr>
						<td>${data.cpu}/${data.maxCpu}</td>
			            <td>${data.mem}/${data.maxMem}</td>
		           		 </tr>`);
      } else {
         $(".modal").hide();
         showStatus = false;
         ui.notify("Error", "Unable to get the status", "error");
      }
   }).fail(function (data) {
      $(".modal").hide();
      showStatus = false;
      if (data && data.responseJSON && data.responseJSON.message) {
         ui.notify("Error", data.responseJSON.message, "error");
      } else {
         //add error message
         ui.notify("Error", "Unable to get the status", "error");
      }
   });
   if (showStatus) {
      setTimeout(() => {
         emptyResults();
         getStatus(true);
      }, 2000);
   }
}
function emptyResults() {
   $("#table-body").empty();
}

<table id="table-data">
   <thead id="table-head">
   <tr>
      <th>CPU Usage</th>
      <th>Memory (Heap) Usage</th>
   </tr>
   </thead>
   <tbody id="table-body">
   </tbody>
</table>