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OpenTelemetry is fast gaining ground in the APM industry. What exactly is it?

1. If you just want to publish metrics from your Java app, with no code changes:

1a. You get the java agent jar and start your app with -javaagent. This is the same as any of the various APM agents available, such as the Elastic APM Java agent (which I work on). The Elastic APM Java agent has other startup options, such as remote attaching instead of only using javaagent

1b. You need to have the metrics collected by some server that understands the output format and ideally allows display of the metrics in some useful way (for example Elastic APM)

2. If you want to add custom instrumentation to your app:

2a. You include opentelemetry-api as a dependency, and add code using that API. When executed this won't publish metrics as the API backend is a no-op

2b. To publish metrics, you can include opentelemetry-sdk as a dependency, or simply start your app with any OpenTelemetry compatible java agent (such as the OpenTelemetry one, or the Elastic APM Java agent).

Now on to all the usual newsletter list of links, tips, tools, news and articles, and as usual I've extracted all the tips into this month's tips page including the Java agent tips

A note from this newsletter's sponsor

News

Java performance tuning related news

• Records Patterns, Performance and Serialization - Records already showing optimal performance
• Nice benchmarks looking at various locking algorithms. Reentrant lock (unfair mode) does very well, fair Reentrant locks have a very high cost
• Don't use URL objects as keys
• JMC agent let's you add custom JDK Flight Recorder (JFR) events to a running JVM without restarting or rebuilding the app

Tools

Java performance tuning related tools

• Enables SQL queries against JFR recording files
• Unique (for a single host) nanosecond timestamps
• A ForkJoinPool benchmarker with a dedicated benchmarking thread factory
• The CRaC (Coordinated Restore at Checkpoint) Project researches coordination of Java programs with mechanisms to checkpoint (make an image of, snapshot) a Java instance while it is executing. Restoring from the image could be a solution to some of the problems with the start-up and warm-up times

Articles

• Continuous Performance Regression Testing with JfrUnit (Gunnar Morling/p99conf)
• How Object Reuse Can Reduce Latency and Improve Performance (Per-Ake Minborg/DZone)
• Investigating Java Heap memory and Native memory leaks (Iranna Patil/Medium)

Jack Shirazi

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