How to change the log level during runtime in Quarkus

Question

I am looking for a way to change the log level of one or multiple classes/packages of a Quarkus app (JVM) during runtime. Is there an API I can use to programmatically change the levels, e.g. by exposing a REST API or does there already exist some other solution?

I am aware of https://quarkus.io/guides/logging but this only discusses changing the log levels statically via a JVM property or applications.properties.

score 5 · Accepted Answer · answered Aug 07 '20 at 11:44

Apparently Quarkus uses java.util.logging under the hood, so I created a simple REST resource like this:

import javax.ws.rs.*;
import java.util.logging.*;

@Path("/logging")
public class LoggingResource {

   private static Level getLogLevel(Logger logger) {
      for (Logger current = logger; current != null;) {
         Level level = current.getLevel();
         if (level != null)
            return level;
         current = current.getParent();
      }
      return Level.INFO;
   }

   @GET
   @Path("/{logger}")
   @Produces("text/plain")
   public String logger(@PathParam("logger") String loggerName, @QueryParam("level") String level) {
      // get the logger instance
      Logger logger = Logger.getLogger(loggerName);

      // change the log-level if requested
      if (level != null && level.length() > 0)
         logger.setLevel(Level.parse(level));

      // return the current log-level
      return getLogLevel(logger);
   }
}

Now I can get the current log level like this:

curl http://myserver:8080/logging/com.example.mypackage

And set the log level like this:

curl http://myserver:8080/logging/com.example.mypackage?level=DEBUG

Simple and perfect solution. Thanks – Hugo Dias Jul 01 '21 at 12:05 — Hugo Dias, Jul 01 '21 at 12:05

score 5 · Answer 2 · answered Oct 22 '20 at 02:30

For future readers: I created a Quarkus extension that can be seen here: https://github.com/quarkiverse/quarkiverse-logging-ui

And can be used by adding this dependency

      <dependency>
          <groupId>io.quarkiverse.loggingui</groupId>
          <artifactId>quarkus-logging-ui</artifactId>
          <version>0.0.2</version>
      </dependency>

How to change the log level during runtime in Quarkus

2 Answers2