AEM Performance Optimization CPU/HEAP Status

Problem Statement:

As a developer or user, I would like to make an informed decision by fetching the AEM system CPU/Heap status before or while running a process.

Introduction:

Use cases for developers:

  1. Infinite loops – a coding error
  2. Garbage collection is not handled – unclosed streams
  3. An exception like out of bound issue
  4. Heap size issue – saving loads of data or declaring/manipulating too many strings

Java MX Bean is an API that provides detailed information on JVM CPU/MEM (Heap) status.

A platform MXBean is a managed bean that conforms to the JMX Instrumentation Specification and only uses a set of basic data types. A JMX management application and the platform MBeanServer can interoperate without requiring classes for MXBean specific data types. The data types being transmitted between the JMX connector server and the connector client are open types and this allows interoperation across versions. See the specification of MXBeans for details.

Each platform MXBean is a PlatformManagedObject and it has a unique ObjectName for registration in the platform MBeanServer as returned by the getObjectName method.

As developer before running or while running any bulk process or schedulers, it’s always better to get system information.

ThrottledTaskRunnerStats Service:

Create ThrottledTaskRunnerStats service as shown below:

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();
}

ThrottledTaskRunnerImpl Service Implementation:

Create ThrottledTaskRunnerImpl service implementation as shown below:

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);
    }
}

CPU Status Servlet:

Create a CpuStatusServlet based on the path as shown below: 

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;
    }
}

Frontend:

Make a request to a servlet from frontend using AJAX call as shown below:

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>

The output of the status:

CPU Memory status result

For more information on Throttled Task runner-based performance optimization please visit:

  1. AEM Performance Optimization Scheduler
  2. AEM Performance Optimization Workflow
  3. AEM Performance Optimization Replication

AEM Performance Optimization Activation/Replication

Problem Statement:

AEM Bulk Replication allows you to activate a series of pages and/or assets.

How can we make sure workflow won’t impact AEM performance (CPU or Heap memory) / throttle the system?

Introduction:

AEM bulk replication or activation is performed on a series of pages and/or assets. We usually perform bulk replication on tree structures or lists of paths.

Use case:

  1. MSM (Multi-site management) – rolling out a series of pages or site
  2. Editable template – add/remove new components on template structure and activate existing pages
  3. Bulk Asset ingests into the system
  4. Bulk redirect//vanity path update

ACS Commons Throttled Task Runner is built on Java management API for managing and monitoring the Java VM and can be used to pause tasks and terminate the tasks based on stats.

Throttled Task Runner (a managed thread pool) provides a convenient way to run many AEM-specific activities in bulk it basically checks for the Throttled Task Runner bean and gets current running stats of the actual work being done.

OSGi Configuration:

The Throttled Task Runner is OSGi configurable, but please note that changing configuration while work is being processed results in resetting the worker pool and can lose active work.

Throttled Task Runner OSGi

Max threads: Recommended not to exceed the number of CPU cores. Default 4.

Max CPU %: Used to throttle activity when CPU exceeds this amount. Range is 0..1; -1 means disable this check.

Max Heap %: Used to throttle activity when heap usage exceeds this amount. Range is 0..1; -1 means disable this check.

Cooldown time: Time to wait for CPU/MEM cooldown between throttle checks (in milliseconds)

Watchdog time: Maximum time allowed (in ms) per action before it is interrupted forcefully.

JMX MBeans

Throttled Task Runner MBean

This is the core worker pool. All action managers share the same task runner pool, at least in the current implementation. The task runner can be paused or halted entirely, throwing out any unfinished work.

Throttled task runner JMX
Throttled task runner JMX

How to use ACS Commons throttled task runner

Add the following dependency to your pom

Create a custom service or servlet as shown below:

Throttled Replication

inside the custom workflow process method check for the Low CPU and Low memory before starting your task to avoid performance impact on the system.

For bulk replication (publish/unpublish/delete) assets or pages, please refer to the AEM Operation Replication Tool

For best practices on the AEM servlet please refer to the link.

AEM Servlet – Best Practices

Problem Statement:

What is the best way to write a Sling servlet?

Requirement:

What is recommended way to register a sling servlet?

Introduction:

Servlets and scripts are themselves resources in Sling and thus have a resource path: this is either the location in the resource repository, the resource type in a servlet component configuration or the “virtual” bundle resource path (if a script is provided inside a bundle without being installed into the JCR repository).

OSGi DS – SlingServletResourceTypes

OSGi DS 1.4 (R7) component property type annotations for Sling Servlets (recommended)

  • Component as servlet based on OSGi R7/8
  • Provide resourcetype, method and extensions
  • ServiceDescription for the servlet
package com.mysite.core.servlets;

import com.day.cq.commons.jcr.JcrConstants;
import org.apache.sling.api.SlingHttpServletRequest
import org.apache.sling.api.SlingHttpServletResponse;
import org.apache.sling.api.resource.Resource;
import org.apache.sling.api.servlets.HttpConstants;
import org.apache.sling.api.servlets.SlingAllMethodsServlet;
import org.apache.sling.api.servlets.SlingSafeMethodsServlet;
import org.apache.sling.servlets.annotations.SlingServletResourceTypes;
import org.osgi.service.component.annotations.Component;
import org.osgi.service.component.propertytypes.ServiceDescription;
import javax.servlet.Servlet;
import javax.servlet.ServletException;
import java.io.IOException;

@Component(service = { Servlet.class })
@SlingServletResourceTypes(resourceTypes = "mysite/components/page", methods = HttpConstants.METHOD_GET, extensions = "txt")
@ServiceDescription("Simple Demo Servlet")
public class SimpleServlet extends SlingSafeMethodsServlet {

	private static final long serialVersionUID = 1L;

	@Override
	protected void doGet(final SlingHttpServletRequest req, final SlingHttpServletResponse resp)
			throws ServletException, IOException {
		final Resource resource = req.getResource();
		resp.setContentType("text/plain");
		resp.getWriter().write("Title = " + resource.getValueMap().get(JcrConstants.JCR_TITLE));
	}
}

Simple OSGi DS 1.2 annotations

Registering Servlet by path

  • Component as servlet based on OSGi R7/8
  • Servlet paths, metod and other details
package com.mysite.core.servlets;

import com.drew.lang.annotations.NotNull;
import org.apache.sling.api.SlingHttpServletRequest;
import org.apache.sling.api.SlingHttpServletResponse;
import org.apache.sling.api.servlets.SlingSafeMethodsServlet;
import org.osgi.service.component.annotations.Component;
import org.osgi.service.component.annotations.ConfigurationPolicy;
import javax.servlet.Servlet;
import javax.servlet.ServletException;
import java.io.IOException;

@Component(service = { Servlet.class }, configurationPolicy = ConfigurationPolicy.REQUIRE, property = {
        "sling.servlet.paths=" + PathBased.RESOURCE_PATH, "sling.servlet.methods=GET" })
public class PathBased extends SlingSafeMethodsServlet {
    static final String RESOURCE_PATH = "/bin/resourcepath";

    @Override
    protected void doGet(@NotNull SlingHttpServletRequest request, @NotNull SlingHttpServletResponse response)
            throws ServletException, IOException {
    }
}
@SlingServlet(
    resourceTypes = "/apps/my/type",
    selectors = "hello",
    extensions = "html",
    methods = "GET")
public class MyServlet extends SlingSafeMethodsServlet {

    @Override
    protected void doGet(SlingHttpServletRequest request, SlingHttpServletResponse response) throws ServletException, IOException {
        ...
    }
}

Configuration Policy – Required

  • configurationPolicy is mandatory to avoid calling any servlet or services outside particular environment
  • Its always recommended to run certain services like datasource to work only in authors
<strong>File Name - com.mysite.core.servlets.PathBased</strong>
<?xml version="1.0" encoding="UTF-8"?>
<jcr:root xmlns:sling="http://sling.apache.org/jcr/sling/1.0" xmlns:jcr="http://www.jcp.org/jcr/1.0"
          jcr:primaryType="sling:OsgiConfig"/>

Project Structure

References:

https://sling.apache.org/documentation/the-sling-engine/servlets.html