logging

One of my current talks focuses on Observability in general and Distributed Tracing in particular, with an OpenTelemetry implementation. In the demo, I show how you can see the traces of a simple distributed system consisting of: the Apache APISIX API Gateway, a Kotlin app with Spring Boot, a Python app with Flask, and a Rust app with Axum. Earlier this year, I spoke and attended the Observability room at FOSDEM.

December was not a good time for Java developers and even less for Ops. The former had to repackage their apps with a fixed Log4J’s version, and the latter had to redeploy them - several times. Yet, every cloud has a silver lining. In my case, I learned about System.Logger. A good time to start using the new standard System.Logger API introduced in Java 9: https://t.co/SaBUnqEZqF. It works like SLF4J and by default logs using JUL but can use Log4J or any othet logging under the hood.

Last week, I wrote a post that described how to hack the Maven dependency resolution system. I admit it was a dirty hack, it’s even in the post name. But I got it wrong. Thanks Stéphane Nicoll for pointing it out: "It boils down to excluding the spring-boot-starter-logging in every Spring Boot starter"Since you've put every in bold, I assume you meant it. That's actually wrong and not what the documentation states.Here is an example: https://t.

Logging is one of the fundamental components of any application which runs in production. Yet, between performance and logging in critical environments, I’d favor the former. For that reason, modern logging frameworks should implement at least two requirements: Async appenders: the write operation shouldn’t be blocking the execution of the programLazy computation: the framework doesn’t run expensive computations until they are needed - or never if that’s the case.

Logging is a not a sexy subject but it’s important nonetheless. In the Java world, logging frameworks range from Log4J to SLF4J via Commons Logging and JDK logging (let’s exclude Log4J 2 for the time being). Though different in architecture and features, all of their API look the same. The logger has a method for each log level e.g.: debug(String message)info(String message)error(String message)etc. Levels are organized into a hierarchy.

Logging is for sure not a glamorous subject, but it’s a critical one - at least for DevOps and Ops teams. While there are plenty of material on the Web describing how to change your ASCII banner, there is not much on how to efficiently manage the log output. By default, Spring Boot will output log on the console and not use any file at all. However, it’s possible to tell Spring Boot to log in an output file. At the simplest level, the path where Spring Boot will put the spring.

I mainly write articles for two reasons: to understand something that is new to me or to document something I regularly have to explain to others. This article definitely falls in the second category: in order to celebrate the new 1.0.0 version of Logback, I’ve decided to write down once and for all how to properly use SLF4J with Maven since it seems there’s no shortage of questions about it.