file-logger.md

id	title
file-logger	File Logger

logger layer with configuration from config provider:

import zio.logging.fileLogger
import zio.{ ConfigProvider, Runtime }

val configProvider: ConfigProvider = ???

val logger = Runtime.removeDefaultLoggers >>> Runtime.setConfigProvider(configProvider) >>> fileLogger()

logger layer with given configuration:

import zio.logging.{ fileLogger, FileLoggerConfig }
import zio.Runtime

val config: FileLoggerConfig = ???

val logger = Runtime.removeDefaultLoggers >>> fileLogger(config)

there are other versions of file loggers:

• zio.logging.fileJsonLogger - output in json format
• file async:
  • zio.logging.fileAsynLogger - output in string format
  • zio.logging.fileAsyncJsonLogger - output in json format

Configuration

the configuration for file logger (zio.logging.FileLoggerConfig) has the following configuration structure:

logger {
  # log format, default value: LogFormat.default
  format = "%label{timestamp}{%fixed{32}{%timestamp}} %label{level}{%level} %label{thread}{%fiberId} %label{message}{%message} %label{cause}{%cause}"
  
  # URI to file
  path = "file:///tmp/console_app.log"
    
  # charset configuration, default value: UTF-8
  charset = "UTF-8"

  # auto flush batch size, default value: 1
  autoFlushBatchSize = 1

  # if defined, buffered writer is used, with given buffer size
  # bufferedIOSize = 8192
  
  # if defined, file log rolling policy is used
  rollingPolicy {
    type = TimeBasedRollingPolicy # time based file rolling policy based on date - currently only this one is supported
  }
  
  # log filter
  filter {
    # see filter configuration
    rootLevel = INFO
  }
}

see also log format configuration and filter configuration

Examples

You can find the source code here

File Logger

package zio.logging.example

import zio.config.typesafe.TypesafeConfigProvider
import zio.logging.fileLogger
import zio.{ Config, ConfigProvider, ExitCode, Runtime, Scope, ZIO, ZIOAppDefault, ZLayer }

object FileApp extends ZIOAppDefault {

  val configString: String =
    s"""
       |logger {
       |  format = "%timestamp{yyyy-MM-dd'T'HH:mm:ssZ} %fixed{7}{%level} [%fiberId] %name:%line %message %cause"
       |  path = "file:///tmp/file_app.log"
       |  rollingPolicy {
       |    type = TimeBasedRollingPolicy
       |  }
       |}
       |""".stripMargin

  val configProvider: ConfigProvider = TypesafeConfigProvider.fromHoconString(configString)

  override val bootstrap: ZLayer[Any, Config.Error, Unit] =
    Runtime.removeDefaultLoggers >>> Runtime.setConfigProvider(configProvider) >>> fileLogger()

  override def run: ZIO[Scope, Any, ExitCode] =
    for {
      _ <- ZIO.logInfo("Start")
      _ <- ZIO.fail("FAILURE")
      _ <- ZIO.logInfo("Done")
    } yield ExitCode.success
}

Expected file name: file_app-2023-03-05.log

Expected file content:

2023-03-05T12:37:31+0100 INFO    [zio-fiber-4] zio.logging.example.FileApp:40 Start
2023-03-05T12:37:31+0100 ERROR   [zio-fiber-0] zio-logger:  Exception in thread "zio-fiber-4" java.lang.String: FAILURE
        at zio.logging.example.FileApp.run(FileApp.scala:41)