Observability of the Java Virtual Machine

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The JVM is one of the most observable runtimes. It provides us lots of tools for troubleshooting a JVM application in production. 1. Thread observability Threads are how the JVM actually does work. When something is wrong in production, the symptom is almost always a thread: stopped, blocked, leaking etc. Thread dumps work on any JVM with no  instrumentation, no agents, no restarts. <Example project link with /threaddump endpoint>         // (1) Deadlock — two threads grab the same pair of locks in opposite order.         new Thread(() -> grab(LOCK_A, LOCK_B), "deadlock-A-then-B").start();         new Thread(() -> grab(LOCK_B, LOCK_A), "deadlock-B-then-A").start(); http://localhost:8080/actuator/threaddump To list the JVMS, we can use the command below. PS C:\observe-jvm> jps -lv 25296 jdk.jcmd/sun.tools.jps.Jps -Dapplication.home=C:\Program Files\Microsoft\jdk-21.0.3.9-hotspot -Xms8m -Djdk.module.main=...
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Saga Nedir?

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"Saga", Domain Driven Design ve CQRS sözkonusu olduğunda sıklıkla duyduğumuz bir kavram. Saga, birden fazla Aggregate ile ilişkili bir "long-running business transaction" konusunda bize yardımcı olan bir yapı. Saga'lar Aggregate üzerinde doğrudan bir state değişikliği yapmıyor fakat oluşturduğu Command mesajları ile dolaylı olarak state değişikliğine sebep oluyor. Sagalar aynı zamanda Command nesnelerini ele alabilir ve Event'lere abone olabilir.
Kısacası Saga, CQRS implementasyonlarında sıklıkla karşımıza çıkan ve DDD terminolojisinde ApplicationService adı verilen kavramla ilgili bir yapı.

Bir sonraki yazıda örnek bir Saga implementasyonunu paylaşıyor olalım.


Bahadır Konu
bah(dot)konu(at)gmail(dot)com

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