Best Practices for Performance Testing

Last update: April 9, 2024

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Introduction

Performance testing is an important part of any AEM deployment. Depending on customer requirements, performance testing may be performed on the publish instances, author instances, or both.

This documentation outlines overall strategies and methodologies of performing performance tests and some of the tools that are made available by Adobe to help the process. Finally, read an analysis of the tools that are available in AEM 6 to assist with performance tuning, both from a code analysis and system configuration perspective.

Simulating Reality

When doing performance tests, make sure that you mimic a production environment as close as possible. While such a task can often be difficult, it is imperative to ensure the accuracy of these tests. When working on designing performance tests, it is important to take the following points into consideration:

Production-like content

Many performance measurements in AEM, such as query response time, can be impacted by the size of the content on the system. It is important to make sure that the test environment has as close of a copy of the production data as possible.

Production code

The AEM version and hotfixes deployed in production should be the same in the test environment. It is also important to test on the version of the code that is deployed to production.

Production-like hardware and network configuration

The tests are meaningless without an environment that resembles the production one as closely as possible. Ideally, the hardware specifications, network interfaces, load balancers, and CDN should be identical to production in the test environment.

Production load

Many performance issues are not seen until the system is under heavy load. Good performance tests should simulate the load that the production systems are under at their peak.

Setting Goals

Before starting on performance testing, it is necessary to set non-functional requirements to specify load and response times. If you are migrating from an existing system, make sure that response times are similar to your current production values. For load, it is best to take the current peak load and double it. Doing so ensures that the website can continue to perform well as it grows.

Tools

There are many commercially available performance testing tools on the market. When running a load generating tool, it is important to ensure that the computers which are performing the tests have sufficient network bandwidth. Otherwise, once the test machine reaches the limits of its connection, no additional load is generated on the environment under test.

Testing Tools

Adobe’s Tough Day tool can be used to generate load on AEM instances and collect performance data. Adobe’s AEM engineering team actually uses the tool to do load testing of the AEM product itself. The scripts executed in Tough Day are configured via property files and JMX XML files. For more information, see the Tough Day documentation.
AEM provides out of the box tools to quickly see problematic queries, requests, and error messages. For more information, see the Diagnosis Tools section of the Operations Dashboard documentation.
Apache provides a product called JMeter that can be used for performance and load testing, and functional behavior. It is open-source software and free to use, but has a smaller feature set than enterprise products and a steeper learning curve. JMeter can be found on Apache’s website at https://jmeter.apache.org/
Load Runner is an enterprise grade load testing product. A free evaluation version is available. More information can be found at https://www.microfocus.com/en-us/portfolio/performance-engineering/overview
Website load testing tools like Vercara can also be used.
When testing mobile or responsive websites, a separate set of tools must be used. They work by throttling network bandwidth, simulating slower mobile connections like 3G or EDGE. Among the more widely used tools include the following:
- Network Link Conditioner - it provides an easy to use UI and works at a fairly low level on the networking stack. It includes versions for OS X and iOS;
- Charles - a web debugging proxy application that in addition to several other uses, provides network throttling. Versions are provided for Windows, OS X, and Linux®.

Optimization Tools

Monitoring

The Monitoring Performance documentation is a good resource for tools and methods that can be used to diagnose issue and pinpoint areas for tuning.

Developer Mode in Touch UI

One of the new features in AEM 6’s touch UI is the Developer Mode. Just as authors can switch between edit and preview modes, developers can switch to developer mode in the author UI. Doing so lets you see the render time for each of the components on the page and to see stack traces of any errors. For more information on developer mode, see this CQ Gems presentation.

Using the rlog.jar to read the request logs

For a more comprehensive analysis of the request logs on an AEM system, rlog.jar can be used to search through and sort the request.log files that AEM generates. This jar file is included with an AEM installation in the /crx-quickstart/opt/helpers folder. For more information on rlog tool and the request log on general, see the Monitoring and Maintaining documentation.

The Explain Query Tool

The Explain Query tool in ACS AEM Tools can be used to view the indexes that are used when running a query. This tool is useful when optimizing slow running queries.

PageSpeed Tools

Google’s PageSpeed tools offer site analysis for adherence to best practices for page performance and a plugin that can be installed alongside the Dispatcher on an Apache instance for additional optimizations.
See the PageSpeed Tools Website.

Author Environment

Performing Tests

To conduct performance testing on the author environment, it is necessary that you simulate the experience of production authors. That is, the author installations must contain all the components, OSGi bundles, UI customization, custom indexes, and any other additions you have in place for the production author instances.

There are many automation frameworks available that are designed for performance and load testing. Custom scripts can be recorded in these tools and then played back to simulate a peak number of authors performing similar content creation and activation activities simultaneously. It is recommended you use the Tough Day tool to simulate activities like uploading thousands of assets or activating large numbers of pages.

For the types of environments that have requirements of heavy asset loading or page authoring, it is imperative to use tools like Tough Day. Doing so ensures that the environment operates efficiently under peak load. WebDAV is a tool that does not require scripting and can also be used to load large amounts of assets.

MongoDB Specific Steps

On systems with MongoDB backends, AEM provides several JMX MBeans that must be monitored when performing load or performance tests:

The Consolidated Cache Statistics MBean. It can be accessed directly by going to:

https://server:port/system/console/jmx/org.apache.jackrabbit.oak%3Aid%3D6%2Cname%3D%22Consolidated+Cache+statistics%22%2Ctype%3D%22ConsolidatedCacheStats%22

For the cache named Document-Diff, the hit rate should be over .90. If the hit rate falls below 90%, it is likely that you must edit your DocumentNodeStoreService configuration. Adobe product support can recommend optimal settings for your environment.

The Oak Repository Statistics Mbean. It can be accessed directly by going to:

https://server:port/system/console/jmx/org.apache.jackrabbit.oak%3Aid%3D16%2Cname%3D%22Oak+Repository+Statistics%22%2Ctype%3D%22RepositoryStats%22

The ObservationQueueMaxLength section shows the number of events in Oak’s observation queue over the last hours, minutes, seconds, and weeks. Find the largest number of events in the “per hour” section. Compare this number to the oak.observation.queue-length setting. If the highest number shown for the observation queue exceeds the queue-length setting:

Create a file named: com.adobe.granite.repository.impl.SlingRepositoryManager.cfg containing the parameter oak.observation.queue‐length=50000
Place it under the /crx-‐quickstart/install folder.

NOTE

See AEM 6.x | Performance Tuning Tips

The default setting is 10,000, but most deployments must raise it to 20,000 or 50,000.

Publish Environment

Performing Tests

The most important part of a deployment that must be subjected to load tests is the end user facing publish or Dispatcher environment.

Third-party automated testing tools can be used to test the performance of the website. These tools let you record steps that users go through on the site and run many of these sessions at the same time to simulate the load that is typical of a production website.

Most production websites have optimizations in place like Dispatcher caching and a content delivery network in place. When testing, make sure that these optimizations are available for the test environment as well. In addition to monitoring response times for the end users, monitor system metrics on the publish servers and dispatchers to ensure that the system is not constrained by hardware resources.

On a system that does not require a high level of personalization, the Dispatcher should cache most requests. As a result, the load on the publish instance should remain relatively flat. If a high level of personalization is required, it is recommended to use technologies such as iFrames or AJAX requests for the personalized content to allow as much Dispatcher caching as possible.

For basic tests, Apache Bench can be used to measure web server response times and help to create load for measuring things like memory leaks. See the example in the Monitoring documentation.

Troubleshooting Performance Issues

After running performance tests on the author instance, any issues must be investigated, diagnosed, and addressed. You can use several tools and techniques when performing analysis and addressing issues:

You can inspect the Request Performance log in the Operations Dashboard. This tool can be used to identify slow page requests
Analyze slow running queries with the Query Performance tool
Watch the error log for errors or warnings. For more information, see Logging.
Monitor system hardware resources such as memory and CPU utilization, disk I/O, or network I/O. These resources are often the causes of performance bottlenecks.
Optimize the architecture of the pages and how they are addressed to minimize the usage of URL parameters to allow for as much caching as possible.
Follow the Performance Optimization and Performance tuning tips documentation.
If issues are present with editing certain pages or components on author instances, use the TouchUI Developer Mode to inspect the page in question. Doing so provides a breakdown of each content area on the page, and its load time.
Minify all JS and CSS on the site. See this blog post.
Eliminate embedded CSS and JS from the components. They should be included and minified with the client-side libraries to minimize the number of requests required to render the page.
To inspect the server requests and see which are taking the longest, use browser tools like Chrome’s Network tab.

Once problem areas are identified, application code can be inspected for performance optimizations. Any out of the box AEM features that are not performing properly can be addressed with Adobe Support.

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