ConLog

A simple, contextual logging framework for Scala.

SBT Inclusion

The maven repo is part of the git repo so, thanks to github's raw URL support, you can point SBT at...

resolvers ++= Seq("Conlog Repository" at "https://raw.github.com/btab/ConLog/master/repo")

It's then a simple matter of adding the dependency (note the %% as this project follows the artifact naming convention of including the scala version against which it was compiled)...

libraryDependencies ++= Seq("com.bluetheta" %% "conlog" % "1.2")

Usage

Create a global logging object (probably in some root package of your project that's imported a lot to save on extra import statements)...

object Log extends com.bluetheta.conlog.Logger

Wire up one or more subscribers (otherwise logging will be a no-op)...

object Application extends App {
  Log.subscribe(SimpleLogReporter(System.out))
}

Log something...

Log.debug("memory usage at 20%")
Log.error("bad request")
Log.fatal("CPU overheat")
Log.info("processed 20/200 files")
Log.warn("option 3 is deprecated")

Provide a locator object. This concept emerged from the idea of parsing files and wanting to log a problem together with the location in the parsed file it occurred in. So for example...

case class SourceFileLine(line: String, lineNum: Int, file: File) extends com.bluetheta.conlog.LogLocator {
  def location = file.getPath + ":" + lineNum
}

val line = SourceFileLine(rawLine, 22, file)
Log.error("unable to parse declaration", line)

Log within a context. If a fullblown workflow engine is overkill for your project, this feature provides a non-threadsafe mechanism to place the global logger in a nestable context. It allows for logging as though the workflow of your application were divided up into tasks and sub-tasks without the rigour of actually doing so...

// we start in the RootContext
Log.pushContext("Scanning images") // ctx 1
// all logging here will have ctx 1
Log.pushContext("Scanning JPEGs")  // ctx2
// all logging here will have ctx 2 (inside ctx 1)
Log.popContext("59 JPEGs")         // exiting ctx2 with a summary
Log.popContext                     // exiting ctx1 with no summary
Log.popContext                     // will throw an error