com.twitter.finatra.httpclient.HttpClient.scala Maven / Gradle / Ivy

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package com.twitter.finatra.httpclient

import com.fasterxml.jackson.databind.ObjectReader
import com.twitter.finagle.Service
import com.twitter.finagle.http.Message
import com.twitter.finagle.http.Request
import com.twitter.finagle.http.Response
import com.twitter.finagle.http.Status
import com.twitter.finagle.service.RetryPolicy
import com.twitter.inject.conversions.future._
import com.twitter.inject.utils.RetryUtils
import com.twitter.util.Future
import com.twitter.util.Try
import com.twitter.util.jackson.ScalaObjectMapper
import com.twitter.util.logging.Logging

/**
 * A simple HTTP client.
 *
 * @note Some servers won't handle requests properly if the Host header is not set
 * @param hostname the hostname that will be used for the Host header. Leave as default or set as "" to not set a Host header
 * @param httpService underlying `com.twitter.finagle.Service`. This [[HttpClient]] '''DOES NOT''' manage the lifecycle of httpService.
 * @param retryPolicy optional retry policy if the service fails to get a successful response
 * @param defaultHeaders headers to add to every request
 * @param mapper object mapper [[com.twitter.util.jackson.ScalaObjectMapper]]
 */
class HttpClient(
  hostname: String = "",
  httpService: Service[Request, Response],
  retryPolicy: Option[RetryPolicy[Try[Response]]] = None,
  defaultHeaders: Map[String, String] = Map(),
  mapper: ScalaObjectMapper)
    extends Logging {

  /* Public */

  def execute(request: Request): Future[Response] = {
    debug(request + " with headers: " + request.headerMap.mkString(", "))
    setHeaders(request)
    setHostname(request)

    retryPolicy match {
      case Some(policy) => RetryUtils.retryFuture(policy)(httpService(request))
      case _ => httpService(request)
    }
  }

  def executeJson[T: Manifest](request: Request, expectedStatus: Status = Status.Ok): Future[T] = {

    execute(request) flatMap { httpResponse =>
      if (httpResponse.status != expectedStatus) {
        Future.exception(new HttpClientException(httpResponse.status, httpResponse.contentString))
      } else {
        Future(parseMessageBody[T](httpResponse, mapper.reader[T]))
          .transformException { e =>
            new HttpClientException(httpResponse.status, s"${e.getClass.getName} - ${e.getMessage}")
          }
      }
    }
  }

  /* Private */

  private def setHostname(request: Request) = {
    if (hostname.nonEmpty) {
      request.headerMap.set("Host", hostname)
    }
  }

  private def setHeaders(request: Request): Unit = {
    if (defaultHeaders.nonEmpty) {
      for ((key, value) <- defaultHeaders) {
        request.headerMap.set(key, value)
      }
    }
  }

  private def parseMessageBody[T: Manifest](message: Message, reader: ObjectReader): T = {
    val inputStream = message.getInputStream()
    try {
      reader.readValue[T](inputStream)
    } finally {
      inputStream.close()
    }
  }
}