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Version: ZIO 2.x


LogStage is a zero-cost structural logging framework for Scala & Scala.js.


Some key features of LogStage:

  1. LogStage extracts structure from ordinary string interpolations in your log messages with zero changes to code.
  2. LogStage uses macros to extract log structure, it is faster at runtime than a typical reflective structural logging frameworks
  3. Log contexts
  4. Console, File, and SLF4J sinks included, File sink supports log rotation,
  5. Human-readable output and JSON output included,
  6. Method-level logging granularity. Can configure methods com.example.Service.start and com.example.Service.doSomething independently,
  7. Slf4J adapters: route legacy Slf4J logs into LogStage router


In order to use this library, we need to add the following line in our build.sbt file:

// LogStage core library
libraryDependencies += "io.7mind.izumi" %% "logstage-core" % "1.0.8"

There are also some optional modules:

libraryDependencies ++= Seq(
// Json output
"io.7mind.izumi" %% "logstage-rendering-circe" % "1.0.8",
// Router from Slf4j to LogStage
"io.7mind.izumi" %% "logstage-adapter-slf4j" % "1.0.8",
// LogStage integration with DIStage
"io.7mind.izumi" %% "distage-extension-logstage" % "1.0.8",
// Router from LogStage to Slf4J
"io.7mind.izumi" %% "logstage-sink-slf4j " % "1.0.8",


Let's try a simple example of using LogStage:

import izumi.fundamentals.platform.uuid.UUIDGen
import logstage.LogZIO.log
import logstage.{IzLogger, LogIO2, LogZIO}
import zio.{Has, URIO, _}

object LogStageExample extends zio.App {
val myApp = for {
_ <-"I'm logging with logstage!")
userId = UUIDGen.getTimeUUID()
_ <-"Current $userId")
_ <-"I'm logging within the same fiber!")
f <-"I'm logging within a new fiber!").fork
_ <- f.join
} yield ()

val loggerLayer: ULayer[Has[LogIO2[IO]]] =

override def run(args: List[String]): URIO[zio.ZEnv, ExitCode] =

The output of this program would be something like this:

I 2021-07-26T21:27:35.164 (LogStageExample.scala:8)  …mpty>.LogStageExample.myApp [14:zio-default-async-1] fiberId=Id(1627318654646,1) I'm logging with logstage!
I 2021-07-26T21:27:35.252 (LogStageExample.scala:10) <.LogStageExample.myApp.8 [14:zio-default-async-1] fiberId=Id(1627318654646,1) Current userId=93546810-ee32-11eb-a393-11bc5b145beb
I 2021-07-26T21:27:35.266 (LogStageExample.scala:11) <.L.myApp.8.10 [14:zio-default-async-1] fiberId=Id(1627318654646,1) I'm logging within the same fiber!
I 2021-07-26T21:27:35.270 (LogStageExample.scala:12) <.L.m.8.10.11 [16:zio-default-async-2] fiberId=Id(1627318655269,2) I'm logging within a new fiber!