Thrift Server Warmup

There may be occasions where we want to exercise specific code paths before accepting traffic to the server (e.g., for triggering JIT in the JVM). We can do this via server warmup.

Warmup

Finatra provides a warmup lifecycle callback function which will be executed in the correct phase of server startup, i.e, before the server’s external Thrift port is bound and thus before the TwitterServer Lifecycle Management /health endpoint responds with OK.

See here for more information on the lifecycle of a Finatra server.

To perform warmup, simply override this callback method and implement your logic. E.g.,

import DoEverythingModule
import com.twitter.finatra.thrift.ThriftServer
import com.twitter.finatra.thrift.routing.ThriftRouter
import com.twitter.finatra.thrift.filters._

object ExampleServerMain extends ExampleServer

class ExampleServer extends ThriftServer {

  override val modules = Seq(
    DoEverythingModule)

  override def configureThrift(router: ThriftRouter): Unit = {
    router
      .filter[LoggingMDCFilter]
      .filter[TraceIdMDCFilter]
      .filter[ThriftMDCFilter]
      .filter[AccessLoggingFilter]
      .filter[StatsFilter]
      .add[ExampleThriftController]
  }

  override protected def warmup(): Unit = {
    // YOUR WARMUP LOGIC HERE <----------------------------------------------
  }
}

c.t.finatra.thrift.routing.ThriftWarmup

Finatra provides a utility, c.t.finatra.thrift.routing.ThriftWarmup which will route requests to underlying service implementation configured by the ThriftRouter.

The most common way to use the c.t.finatra.thrift.routing.ThriftWarmup is via a constructor-arg to an implementation of a c.t.inject.utils.Handler.

The Finatra c.t.inject.serverTwitterServer provides a #handle[T <: Handler: Manifest] utility which simply instantiates a given c.t.inject.utils.Handler via the injector and invokes its #handle() function.

Combining the above, if we wanted to run an initial call through our Thrift service we could create the following handler:

import ExampleThriftController
import com.twitter.example.thriftscala.ExampleService.Add1
import com.twitter.finatra.thrift.routing.ThriftWarmup
import com.twitter.inject.Logging
import com.twitter.inject.utils.Handler
import com.twitter.util.{Await, Return, Throw, Try}
import javax.inject.Inject

class ExampleThriftWarmupHandler @Inject()(
 warmup: ThriftWarmup)
 extends Handler
 with Logging {

  /* Should be a ClientId that is white-listed to your service. */
  private val clientId = ClientId("client123")

  override def handle(): Unit = {
    try {
        clientId.asCurrent {
          warmup.send(
            method = Add1,
            args = Add1.Args(5)) { result: Try[Add1.SuccessType] =>
              result match {
                case Return(value) => assert(value == 6, "Warmup request failed.")
                case Throw(_) => assert(false, "Warmup request failed.")
              }
            }
        }
    } catch {
      case e: Throwable =>
        // Here we don't want a warmup failure to prevent server start-up --
        // this is important if your service will call downstream services
        // during warmup that could be temporarily down or unavailable.
        // We don't want that unavailability to cause our server to fail
        // warm-up and thus prevent the server from starting. So we simply
        // log the error message here.
        error(e.getMessage, e)
    }
    info("Warm-up done.")
  }
}

The handler above simply tries to call the Add1 endpoint of the server.

Warning

As noted above, be careful about exceptions which occur from calling endpoints on your service during warmup. Exceptions which escape the handler will potentially stop your server from starting and thus, you most likely do not want an exception from a warmup call to propagate out of the handler.

You would then run this handler in warmup() lifecycle callback E.g.,

E.g.,

import DoEverythingModule
import com.twitter.finatra.thrift.ThriftServer
import com.twitter.finatra.thrift.routing.ThriftRouter
import com.twitter.finatra.thrift.filters._

object ExampleServerMain extends ExampleServer

class ExampleServer extends ThriftServer {

  override val modules = Seq(
    DoEverythingModule)

  override def configureThrift(router: ThriftRouter): Unit = {
    router
      .filter[LoggingMDCFilter]
      .filter[TraceIdMDCFilter]
      .filter[ThriftMDCFilter]
      .filter[AccessLoggingFilter]
      .filter[StatsFilter]
      .add[ExampleThriftController]
  }

  override protected def warmup(): Unit = {
    handle[ExampleThriftWarmupHandler]() <----------------------------------------------
  }
}

More information

For more information, we encourage you to take a look at the full finatra/examples in the github source.