EDUCAÇÃO E TECNOLOGIA

Overhead added by Garbage Collection Logging

Enabling Garbage collection logs on your application has certain advantages. In nutshell, Garbage collection logs will facilitate you to optimize Garbage Collection pause time, improve overall application’s response time, forecast production outages, reduce computing cost. Even though Garbage collection logs have these advantages, we weren’t sure what overhead does garbage collection logging add to the application. Thus we set out to conduct the below case study.

Environment

For our study we chose to use the open source spring boot pet clinic application. Pet Clinic is a poster child application that was developed to demonstrate the spring boot framework features.

We ran this application in OpenJDK 11. We deployed this application on the Amazon AWS t2.medium EC2 instance which has 16GB RAM and 2 CPUs. Test was orchestrated using Apache JMeter stress testing tool. We used AWS Cloudwatch to measure the CPU, Memory utilization. In nutshell here are the tools/technologies, we used to conduct this case study:

  • OpenJDK 11
  • AWS EC2
  • AWS Cloudwatch
  • Apache JMeter

Test Scenario

In this environment, we conducted 2 tests:

  1. Baseline Test – In this scenario we ran the pet clinic application without enabling garbage collection (GC) logs using the JMeter tool for 20 minutes with 200 concurrent users
  2. GC log Enabled Test – In this scenario we ran the pet clinic application with enabling garbage collection(GC) logs using the same JMeter script for 20 minutes with 200 concurrent users.

Note: If you don’t know how to enable GC log, see this post: ‘How to enable GC logs ?

Test Results

We captured average CPU and memory utilization from the AWS Cloudwatch and average response time and throughput from the JMeter tool. Data collected from both scenarios are summarized in the below table.

Data Collected Baseline test Enabled GC test
Avg CPU Usage 8.35% 10.10%
Avg Memory Usage 20.80% 20.50%
Avg Response Time 3901 ms 3881 ms
Avg Throughput 24.4/sec 24.5/sec

As you can see there is no noticeable difference in the CPU and Memory consumption. Similarly there is no noticeable difference in the average response and transaction throughput.

Conclusion

Thus based on our study we can conclude that there is no noticeable overhead in enabling the garbage collection log file. Given the benefits we get by enabling the Garbage collection log, you can consider enabling GC logging on all your production instances.