com.twitter.finagle.thrift.ClientId.scala Maven / Gradle / Ivy

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package com.twitter.finagle.thrift

import com.twitter.finagle.context.Contexts
import com.twitter.util.{Return, Throw}
import com.twitter.io.Buf

case class ClientId(name: String) {
  /**
   * Executes the given function with this ClientId set as the current
   * ClientId.  The current ClientId before executing this will be restored
   * on completion.
   */
  def asCurrent[T](f: => T): T = ClientId.let(Some(this))(f)
}

/**
 * `ClientId` provides the client identification of the incoming request if available.
 * It is set at the beginning of the request and is available throughout the life-cycle
 * of the request. It is iff the client has an upgraded finagle connection and has chosen
 * to specify the client ID in their codec.
 */
object ClientId {
  // As a matter of legacy, we need to support the notion of
  // an empty client id. Old version of contexts could serialize
  // the absence of a client id with an empty buffer.
  private[finagle] val clientIdCtx = new Contexts.broadcast.Key[Option[ClientId]]("com.twitter.finagle.thrift.ClientIdContext") {
    def marshal(clientId: Option[ClientId]): Buf = clientId match {
      case None => Buf.Empty
      case Some(ClientId(name)) => Buf.Utf8(name)
    }

    def tryUnmarshal(buf: Buf) = buf match {
      case buf if buf.isEmpty => Return.None
      case Buf.Utf8(name) => Return(Some(ClientId(name)))
      case invalid => Throw(new IllegalArgumentException("client id not a utf8 string"))
    }
  }

  private[this] val NoClientFn: () => Option[ClientId] = () => None

  def current: Option[ClientId] =
    Contexts.broadcast.getOrElse(clientIdCtx, NoClientFn)

  private[finagle] def let[R](clientId: ClientId)(f: => R): R =
    Contexts.broadcast.let(clientIdCtx, Some(clientId))(f)

  private[finagle] def let[R](clientId: Option[ClientId])(f: => R): R = {
    clientId match {
      case Some(id) => Contexts.broadcast.let(clientIdCtx, Some(id))(f)
      case None => Contexts.broadcast.letClear(clientIdCtx)(f)
    }
  }
}