Suffering in silence, you check the logs for fresh telemetry.
You think: That can't be right.
-- Blindsight, Peter Watts
Blindsight is "observability through logging" where observability is defined as baked in high cardinality structured data with field types. The name is taken from Peter Watts' excellent first contact novel, Blindsight.
Blindsight is a logging library written in Scala that wraps SLF4J to add useful features that solve several outstanding problems with logging:
- Rendering structured logs in multiple formats through a format-independent AST and DSL .
- Expressing domain specific objects as arguments through type classes.
- Resolving operation-specific loggers through logger resolvers.
- Building up complex logging statements through fluent logging.
- Enforcing user supplied type constraints through semantic logging.
- Minimal-overhead tracing and causality tracking through flow logging.
- Providing thread-safe context to logs through context aware logging.
- Time-based and targeted diagnostic logging through conditional logging.
The only hard dependency is the SLF4J API, but the DSL functionality is only implemented for Logback with logstash-logback-encoder.
Blindsight is a pure SLF4J wrapper: it delegates all logging through to the SLF4J API and does not configure or manage the SLF4J implementation at all.
Versions are published for Scala 2.11, 2.12, and 2.13.
See Setup for how to install Blindsight.
Because Blindsight uses a very recent version of Logstash that depends on Jackson 2.11.0, you may need to update your dependencies for the jackson-scala-module if you're using Play or Akka.
libraryDependencies += "com.fasterxml.jackson.module" %% "jackson-module-scala" % "2.11.0"
Benchmarks are available here.
To use a Blindsight Logger:
import com.tersesystems.blindsight._
val logger = LoggerFactory.getLogger
logger.info("I am an SLF4J-like logger")or in block form for diagnostic logging:
logger.debug { debug => debug("I am an SLF4J-like logger") }import com.tersesystems.blindsight._
import com.tersesystems.blindsight.DSL._
logger.info("Logs with argument {}", bobj("array" -> Seq("one", "two", "three")))val dayOfWeek = "Monday"
val temp = 72
// macro expands this to:
// Statement("It is {} and the temperature is {} degrees.", Arguments(dayOfWeek, temp))
val statement: Statement = st"It is ${dayOfWeek} and the temperature is ${temp} degrees."
logger.info(statement)case class Lotto(
id: Long,
winningNumbers: List[Int],
winners: List[Winner],
drawDate: Option[java.util.Date]
) {
lazy val asBObject: BObject = "lotto" ->
("lotto-id" -> id) ~
("winning-numbers" -> winningNumbers) ~
("draw-date" -> drawDate.map(_.toString)) ~
("winners" -> winners.map(w => w.asBObject))
}
object Lotto {
implicit val toArgument: ToArgument[Lotto] = ToArgument { lotto => Argument(lotto.asBObject) }
}
val winners =
List(Winner(23, List(2, 45, 34, 23, 3, 5)), Winner(54, List(52, 3, 12, 11, 18, 22)))
val lotto = Lotto(5, List(2, 45, 34, 23, 7, 5, 3), winners, None)
logger.info("message {}", lotto) // auto-converted to structured outputlogger.fluent.info
.message("The Magic Words are")
.argument(Arguments("Squeamish", "Ossifrage"))
.logWithPlaceholders()// log only user events
logger.semantic[UserEvent].info(userEvent)
// Works well with refinement types
import eu.timepit.refined.api.Refined
import eu.timepit.refined.string._
import eu.timepit.refined._
logger.semantic[String Refined Url].info(refineMV(Url)("https://tersesystems.com"))import com.tersesystems.blindsight.flow._
implicit def flowBehavior[B]: FlowBehavior[B] = new SimpleFlowBehavior
val arg1: Int = 1
val arg2: Int = 2
val result:Int = logger.flow.trace(arg1 + arg2)logger.onCondition(booleanCondition).info("Only logs when condition is true")
logger.info.when(booleanCondition) { info => info("when true") }import DSL._
// Add key/value pairs with DSL and return a logger
val markerLogger = logger.withMarker(bobj("userId" -> userId))
// log with generated logger
markerLogger.info("Logging with user id added as a context marker!")
// can retrieve state markers
val contextMarkers: Markers = logger.markersThere's an example application at https://github.com/tersesystems/play-blindsight that integrates with Honeycomb Tracing using the flow logger:
See the documentation for more details.
Blindsight is released under the "Apache 2" license. See LICENSE for specifics and copyright declaration.
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