Key Features

Supported for every popular style

You can use tofu.logging in any style you want:

• Tagless Final style;
• Simple cats.effect.IO or (monix|zio).Task and ReaderT;
• ZIO and ZLayers — with the help of dedicated module tofu-zio-logging and ZLogs;
• Even with Futures (although it’s kinda in the past).

Concise syntax

With the implicit instance of Logging one can log messages with ease:

import tofu.logging._
import tofu.syntax.logging._

val error = new Throwable("Oh no.")

def log[F[_] : Logging : Monad] = for {
  _ <- info"Hi! I'm logging"
  _ <- warn"Hello again!"
  _ <- error"It's me, error!"
  _ <- errorCause"So sad, I've got an error"(error)
} yield ()

Structured and controllable

You can easily put any necessary values into the structure of the log message with Loggable; also you can fully control what is logged and what is not:

import derevo._
import tofu.logging._

@derive(Loggable)
case class Payment(id: String, @hidden cardNumber: String, amount: Long)

def log[F[_] : Logging : Monad](payment: Payment) = info"Got payment $payment"

Given that there’s a defined Loggable instance for this context and provided logger is context aware (e.g. created with contextual method), every logged message will contain information about context, for example:

{
  "message": "Got payment payment",
  "level": "INFO",
  "payment": {
    "id": "131234234",
    "amount": 432
  }
}

Note that card number is not present at all as it was @hidden.

Context support

Let’s say your effect type has some context — it could be trace id or some domain info:

import cats._
import cats.effect._

case class TraceId(id: Long)

type TracedIO[A] = ReaderT[TraceId, IO, A]

tofu.logging can extract it and automatically add into the structure of every log message:

class MyService[F[_] : Logging] {
  def sayHello: F[Unit] = info"Hello!"
}

val ioservice = new MyService[IO]
val tracedService = new MyService[TracedIO]

(Note the absence of anything related to context in MyService, logging doest it all itself.)

Now if we run tracedService.sayHello the log message structure will contain the trace id:

{
  "message": "Hello!",
  "level": "INFO",
  "trace.id": 64534
}

and if we run ioService.sayHello the message will be clean:

{
  "message": "Hello!",
  "level": "INFO"
}

More on that can be found on the dedicated recipe page.

What’s next

• You can read about core concepts here
• You can see the recipes and discover what you need to use logging here