Log4j2

Dynamic Log Levels for Log4j2 hooks into Akka Management and provides a route where log levels can be read and set over HTTP.

Project Info

Requires Akka Management and that the application uses Log4j2 as logging backend.

The Akka dependencies are available from Akka’s library repository. To access them there, you need to configure the URL for this repository.

sbt

resolvers += "Akka library repository".at("https://repo.akka.io/maven")

Gradle

repositories {
    mavenCentral()
    maven {
        url "https://repo.akka.io/maven"
    }
}

Maven

<project>
  ...
  <repositories>
    <repository>
      <id>akka-repository</id>
      <name>Akka library repository</name>
      <url>https://repo.akka.io/maven</url>
    </repository>
  </repositories>
</project>

Additionally, add the dependencies as below.

sbt

val AkkaManagementVersion = "1.5.1"
libraryDependencies ++= Seq(
  "com.lightbend.akka.management" %% "akka-management-loglevels-log4j2" % AkkaManagementVersion,
  "com.lightbend.akka.management" %% "akka-management" % AkkaManagementVersion
)

Gradle

def versions = [
  AkkaManagementVersion: "1.5.1",
  ScalaBinary: "2.13"
]
dependencies {
  implementation "com.lightbend.akka.management:akka-management-loglevels-log4j2_${versions.ScalaBinary}:${versions.AkkaManagementVersion}"
  implementation "com.lightbend.akka.management:akka-management_${versions.ScalaBinary}:${versions.AkkaManagementVersion}"
}

Maven

<properties>
  <akka.management.version>1.5.1</akka.management.version>
  <scala.binary.version>2.13</scala.binary.version>
</properties>
<dependencies>
  <dependency>
    <groupId>com.lightbend.akka.management</groupId>
    <artifactId>akka-management-loglevels-log4j2_${scala.binary.version}</artifactId>
    <version>${akka.management.version}</version>
  </dependency>
  <dependency>
    <groupId>com.lightbend.akka.management</groupId>
    <artifactId>akka-management_${scala.binary.version}</artifactId>
    <version>${akka.management.version}</version>
  </dependency>
</dependencies>

Akka Management and akka-management-loglevels-log4j2 can be used with Akka 2.9.2 or later. You have to override the following Akka dependencies by defining them explicitly in your build and define the Akka version to the one that you are using. Latest patch version of Akka is recommended and a later version than 2.9.2 can be used.

sbt

val AkkaVersion = "2.9.2"
libraryDependencies ++= Seq(
  "com.typesafe.akka" %% "akka-stream" % AkkaVersion,
  "com.typesafe.akka" %% "akka-slf4j" % AkkaVersion
)

Gradle

def versions = [
  AkkaVersion: "2.9.2",
  ScalaBinary: "2.13"
]
dependencies {
  implementation "com.typesafe.akka:akka-stream_${versions.ScalaBinary}:${versions.AkkaVersion}"
  implementation "com.typesafe.akka:akka-slf4j_${versions.ScalaBinary}:${versions.AkkaVersion}"
}

Maven

<properties>
  <akka.version>2.9.2</akka.version>
  <scala.binary.version>2.13</scala.binary.version>
</properties>
<dependencies>
  <dependency>
    <groupId>com.typesafe.akka</groupId>
    <artifactId>akka-stream_${scala.binary.version}</artifactId>
    <version>${akka.version}</version>
  </dependency>
  <dependency>
    <groupId>com.typesafe.akka</groupId>
    <artifactId>akka-slf4j_${scala.binary.version}</artifactId>
    <version>${akka.version}</version>
  </dependency>
</dependencies>

With Akka Management started and this module on the classpath the module is automatically picked up and provides the following two HTTP routes:

Reading Logger Levels

A HTTP GET request to loglevel/log4j2?logger=[logger name] will return the log level of that logger.

Changing Logger Levels

Only enabled if akka.management.http.route-providers-read-only is set to false.

A HTTP PUT request to loglevel/log4j2?logger=[logger name]&level=[level name] will change the level of that logger on the JVM the ActorSystem runs on.

For example using curl:

curl -X PUT "http://127.0.0.1:8558/loglevel/log4j2?logger=com.example.MyActor&level=DEBUG"

Classic and Internal Akka Logger Level

Internal Akka actors and classic Akka does logging through the built in API there is an additional level of filtering using the akka.loglevel setting. If you have not set akka.loglevel to DEBUG (recommended) log entries from the classic logging API may never reach the logger backend at all.

The current level configured with akka.loglevel can be inspected with a GET request to loglevel/akka.

If management read-only is set to false PUT requests to loglevel/akka?level=[level name] will dynamically change that. Note that the allowed level for Akka Classic logging is a subset of the loglevels supported by SLF4j, valid values are OFF, DEBUG, INFO, WARNING and ERROR.

For example using curl:

curl -X PUT "http://127.0.0.1:8558/loglevel/akka?level=DEBUG"