Akka（37）： Http：客户端操作模式

2024-04-09 04:48
文章标签 模式 操作 http 客户端 37 akka

本文主要是介绍Akka（37）： Http：客户端操作模式，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

   Akka-http的客户端连接模式除Connection-Level和Host-Level之外还有一种非常便利的模式：Request-Level-Api。这种模式免除了连接Connection的概念，任何时候可以直接调用singleRequest来与服务端沟通。下面我们用几个例子来示范singleRequest的用法：

  (for {response <- Http().singleRequest(HttpRequest(method=HttpMethods.GET,uri="http://localhost:8011/message"))message <- Unmarshal(response.entity).to[String]} yield message).andThen {case Success(msg) => println(s"Received message: $msg")case Failure(err) => println(s"Error: ${err.getMessage}")}.andThen {case _ => sys.terminate()}

这是一个GET操作：用Http().singleRequest直接把HttpRequest发送给服务端uri并获取返回的HttpResponse。我们看到，整组函数的返回类型都是Future[?]，所以用for-comprehension来把所有实际运算包嵌在Future运算模式内（context)。下面这个例子是客户端上传数据示范： 

  (for {entity <- Marshal("Wata hell you doing?").to[RequestEntity]response <- Http().singleRequest(HttpRequest(method=HttpMethods.PUT,uri="http://localhost:8011/message",entity=entity))message <- Unmarshal(response.entity).to[String]} yield message).andThen {case Success(msg) => println(s"Received message: $msg")case Failure(err) => println(s"Error: ${err.getMessage}")}.andThen {case _ => sys.terminate()}

以上是个PUT操作。我们需要先构建数据载体HttpEntity。格式转换函数Marshal也返回Future[HttpEntity]，所以也可以包含在for语句内。关注一下这个andThen，它可以连接一串多个monadic运算，在不影响上游运算结果的情况下实现一些副作用计算。

值得注意的是上面这两个例子虽然表现形式很简洁，但我们无法对数据转换过程中的异常及response的状态码等进行监控。所以我们应该把整个过程拆分成两部分：先获取response，再具体处理response,包括核对状态，处理数据等：

  case class Item(id: Int, name: String, price: Double)def getItem(itemId: Int): Future[HttpResponse] = for {response <- Http().singleRequest(HttpRequest(method=HttpMethods.GET,uri = s"http://localhost:8011/item/$itemId"))} yield responsedef extractEntity[T](futResp: Future[HttpResponse])(implicit um: Unmarshaller[ResponseEntity,T]) = {futResp.andThen {case Success(HttpResponse(StatusCodes.OK, _, entity, _)) =>Unmarshal(entity).to[T].onComplete {case Success(t) => println(s"Got response entity: ${t}")case Failure(e) => println(s"Unmarshalling failed: ${e.getMessage}")}case Success(_) => println("Exception in response!")case Failure(err) => println(s"Response Failed: ${err.getMessage}")}}extractEntity[Item](getItem(13))

现在这个extractEntity[Item](getItem(13))可以实现全过程的监控管理了。用同样的模式实现PUT操作： 

  def putItem(item: Item): Future[HttpResponse] =for {reqEntity <- Marshal(item).to[RequestEntity]response <- Http().singleRequest(HttpRequest(method=HttpMethods.PUT,uri="http://localhost:8011/item",entity=reqEntity))} yield responseextractEntity[Item](putItem(Item(23,"Item#23", 46.0))).andThen { case _ => sys.terminate()}

当然，我们还是使用了前面几篇讨论里的Marshalling方式来进行数据格式的自动转换： 

import de.heikoseeberger.akkahttpjson4s.Json4sSupport
import org.json4s.jackson
...
trait JsonCodec extends Json4sSupport {import org.json4s.DefaultFormatsimport org.json4s.ext.JodaTimeSerializersimplicit val serilizer = jackson.Serializationimplicit val formats = DefaultFormats ++ JodaTimeSerializers.all
}
object JsConverters extends JsonCodec
...import JsConverters._implicit val jsonStreamingSupport = EntityStreamingSupport.json().withParallelMarshalling(parallelism = 8, unordered = false)

如果我们需要对数据交换过程进行更细致的管控，用Host-Level-Api会更加适合。下面我们就针对Host-Level-Api构建一个客户端的工具库： 

class PooledClient(host: String, port: Int, poolSettings: ConnectionPoolSettings)(implicit sys: ActorSystem, mat: ActorMaterializer) {import sys.dispatcherprivate val cnnPool: Flow[(HttpRequest, Int), (Try[HttpResponse], Int), Http.HostConnectionPool] =Http().cachedHostConnectionPool[Int](host = host, port = port, settings = poolSettings)
//单一requestdef requestSingleResponse(req: HttpRequest): Future[HttpResponse] = {Source.single(req -> 1).via(cnnPool).runWith(Sink.head).flatMap {case (Success(resp), _) => Future.successful(resp)case (Failure(fail), _) => Future.failed(fail)}}
//组串requestdef orderedResponses(reqs: Iterable[HttpRequest]): Future[Iterable[HttpResponse]] = {Source(reqs.zipWithIndex.toMap).via(cnnPool).runFold(SortedMap[Int, Future[HttpResponse]]()) {case (m, (Success(r), idx)) => m + (idx -> Future.successful(r))case (m, (Failure(f), idx)) => m + (idx -> Future.failed(f))}.flatMap { m => Future.sequence(m.values) }}
}

下面是一种比较安全的模式：使用了queue来暂存request从而解决因发送方与接收方速率不同所产生的问题： 

class QueuedRequestsClient(host: String, port: Int, poolSettings: ConnectionPoolSettings)(qsize: Int = 10, overflowStrategy: OverflowStrategy = OverflowStrategy.dropNew)(implicit sys: ActorSystem, mat: ActorMaterializer) {import sys.dispatcherprivate val cnnPool: Flow[(HttpRequest,Promise[HttpResponse]),(Try[HttpResponse],Promise[HttpResponse]),Http.HostConnectionPool] =Http().cachedHostConnectionPool[Promise[HttpResponse]](host=host,port=port,settings=poolSettings)val queue =Source.queue[(HttpRequest, Promise[HttpResponse])](qsize, overflowStrategy).via(cnnPool).to(Sink.foreach({case ((Success(resp), p)) => p.success(resp)case ((Failure(e), p))    => p.failure(e)})).run()def queueRequest(request: HttpRequest): Future[HttpResponse] = {val responsePromise = Promise[HttpResponse]()queue.offer(request -> responsePromise).flatMap {case QueueOfferResult.Enqueued    => responsePromise.futurecase QueueOfferResult.Dropped     => Future.failed(new RuntimeException("Queue overflowed. Try again later."))case QueueOfferResult.Failure(ex) => Future.failed(ex)case QueueOfferResult.QueueClosed => Future.failed(new RuntimeException("Queue was closed (pool shut down) while running the request. Try again later."))}}
}

下面是这些工具函数的具体使用示范： 

  val settings = ConnectionPoolSettings(sys).withMaxConnections(8).withMaxOpenRequests(8).withMaxRetries(3).withPipeliningLimit(4)val pooledClient = new PooledClient("localhost",8011,settings)def getItemByPool(itemId: Int): Future[HttpResponse] = for {response <- pooledClient.requestSingleResponse(HttpRequest(method=HttpMethods.GET,uri = s"http://localhost:8011/item/$itemId"))} yield responseextractEntity[Item](getItemByPool(13))def getItemsByPool(itemIds: List[Int]): Future[Iterable[HttpResponse]] = {val reqs = itemIds.map { id =>HttpRequest(method = HttpMethods.GET, uri = s"http://localhost:8011/item/$id")}val rets = (for {responses <- pooledClient.orderedResponses(reqs)} yield responses)rets}val futResps = getItemsByPool(List(3,5,7))futResps.andThen {case Success(listOfResps) => {listOfResps.foreach { r =>r match {case HttpResponse(StatusCodes.OK, _, entity, _) =>Unmarshal(entity).to[Item].onComplete {case Success(t) => println(s"Got response entity: ${t}")case Failure(e) => println(s"Unmarshalling failed: ${e.getMessage}")}case _ => println("Exception in response!")}}}case _ => println("Failed to get list of responses!")}val queuedClient = new QueuedRequestsClient("localhost",8011,settings)()def putItemByQueue(item: Item): Future[HttpResponse] =for {reqEntity <- Marshal(item).to[RequestEntity]response <- queuedClient.queueRequest(HttpRequest(method=HttpMethods.PUT,uri="http://localhost:8011/item",entity=reqEntity))} yield responseextractEntity[Item](putItemByQueue(Item(23,"Item#23", 46.0))).andThen { case _ => sys.terminate()}

下面是本次讨论的示范源代码：

服务端代码：

import akka.actor._
import akka.stream._
import akka.http.scaladsl.Http
import akka.http.scaladsl.server.Directives._import de.heikoseeberger.akkahttpjson4s.Json4sSupport
import org.json4s.jackson
trait JsonCodec extends Json4sSupport {import org.json4s.DefaultFormatsimport org.json4s.ext.JodaTimeSerializersimplicit val serilizer = jackson.Serializationimplicit val formats = DefaultFormats ++ JodaTimeSerializers.all
}
object JsConverters extends JsonCodecobject TestServer extends App with JsonCodec {implicit val httpSys = ActorSystem("httpSystem")implicit val httpMat = ActorMaterializer()implicit val httpEC = httpSys.dispatcherimport JsConverters._case class Item(id: Int, name: String, price: Double)val messages = path("message") {get {complete("hello, how are you?")} ~put {entity(as[String]) {msg =>complete(msg)}}}val items =(path("item" / IntNumber) & get) { id =>get {complete(Item(id, s"item#$id", id * 2.0))}} ~(path("item") & put) {entity(as[Item]) {item =>complete(item)}}val route = messages ~ itemsval (host, port) = ("localhost", 8011)val bindingFuture = Http().bindAndHandle(route,host,port)println(s"Server running at $host $port. Press any key to exit ...")scala.io.StdIn.readLine()bindingFuture.flatMap(_.unbind()).onComplete(_ => httpSys.terminate())}

客户端源代码： 

import akka.actor._
import akka.http.scaladsl.settings.ConnectionPoolSettings
import akka.stream._
import akka.stream.scaladsl._
import akka.http.scaladsl.Http
import akka.http.scaladsl.model._import scala.util._
import de.heikoseeberger.akkahttpjson4s.Json4sSupport
import org.json4s.jacksonimport scala.concurrent._
import akka.http.scaladsl.unmarshalling.Unmarshal
import akka.http.scaladsl.unmarshalling._
import akka.http.scaladsl.marshalling.Marshalimport scala.collection.SortedMap
import akka.http.scaladsl.common._trait JsonCodec extends Json4sSupport {import org.json4s.DefaultFormatsimport org.json4s.ext.JodaTimeSerializersimplicit val serilizer = jackson.Serializationimplicit val formats = DefaultFormats ++ JodaTimeSerializers.all
}
object JsConverters extends JsonCodecclass PooledClient(host: String, port: Int, poolSettings: ConnectionPoolSettings)(implicit sys: ActorSystem, mat: ActorMaterializer) {import sys.dispatcherprivate val cnnPool: Flow[(HttpRequest, Int), (Try[HttpResponse], Int), Http.HostConnectionPool] =Http().cachedHostConnectionPool[Int](host = host, port = port, settings = poolSettings)def requestSingleResponse(req: HttpRequest): Future[HttpResponse] = {Source.single(req -> 1).via(cnnPool).runWith(Sink.head).flatMap {case (Success(resp), _) => Future.successful(resp)case (Failure(fail), _) => Future.failed(fail)}}def orderedResponses(reqs: Iterable[HttpRequest]): Future[Iterable[HttpResponse]] = {Source(reqs.zipWithIndex.toMap).via(cnnPool).runFold(SortedMap[Int, Future[HttpResponse]]()) {case (m, (Success(r), idx)) => m + (idx -> Future.successful(r))case (m, (Failure(f), idx)) => m + (idx -> Future.failed(f))}.flatMap { m => Future.sequence(m.values) }}
}
class QueuedRequestsClient(host: String, port: Int, poolSettings: ConnectionPoolSettings)(qsize: Int = 10, overflowStrategy: OverflowStrategy = OverflowStrategy.dropNew)(implicit sys: ActorSystem, mat: ActorMaterializer) {import sys.dispatcherprivate val cnnPool: Flow[(HttpRequest,Promise[HttpResponse]),(Try[HttpResponse],Promise[HttpResponse]),Http.HostConnectionPool] =Http().cachedHostConnectionPool[Promise[HttpResponse]](host=host,port=port,settings=poolSettings)val queue =Source.queue[(HttpRequest, Promise[HttpResponse])](qsize, overflowStrategy).via(cnnPool).to(Sink.foreach({case ((Success(resp), p)) => p.success(resp)case ((Failure(e), p))    => p.failure(e)})).run()def queueRequest(request: HttpRequest): Future[HttpResponse] = {val responsePromise = Promise[HttpResponse]()queue.offer(request -> responsePromise).flatMap {case QueueOfferResult.Enqueued    => responsePromise.futurecase QueueOfferResult.Dropped     => Future.failed(new RuntimeException("Queue overflowed. Try again later."))case QueueOfferResult.Failure(ex) => Future.failed(ex)case QueueOfferResult.QueueClosed => Future.failed(new RuntimeException("Queue was closed (pool shut down) while running the request. Try again later."))}}
}
object ClientRequesting extends App {import JsConverters._implicit val sys = ActorSystem("sysClient")implicit val mat = ActorMaterializer()implicit val ec = sys.dispatcherimplicit val jsonStreamingSupport = EntityStreamingSupport.json().withParallelMarshalling(parallelism = 8, unordered = false)case class Item(id: Int, name: String, price: Double)def extractEntity[T](futResp: Future[HttpResponse])(implicit um: Unmarshaller[ResponseEntity,T]) = {futResp.andThen {case Success(HttpResponse(StatusCodes.OK, _, entity, _)) =>Unmarshal(entity).to[T].onComplete {case Success(t) => println(s"Got response entity: ${t}")case Failure(e) => println(s"Unmarshalling failed: ${e.getMessage}")}case Success(_) => println("Exception in response!")case Failure(err) => println(s"Response Failed: ${err.getMessage}")}}(for {response <- Http().singleRequest(HttpRequest(method=HttpMethods.GET,uri="http://localhost:8011/message"))message <- Unmarshal(response.entity).to[String]} yield message).andThen {case Success(msg) => println(s"Received message: $msg")case Failure(err) => println(s"Error: ${err.getMessage}")}  //.andThen {case _ => sys.terminate()}(for {entity <- Marshal("Wata hell you doing?").to[RequestEntity]response <- Http().singleRequest(HttpRequest(method=HttpMethods.PUT,uri="http://localhost:8011/message",entity=entity))message <- Unmarshal(response.entity).to[String]} yield message).andThen {case Success(msg) => println(s"Received message: $msg")case Failure(err) => println(s"Error: ${err.getMessage}")} //.andThen {case _ => sys.terminate()}def getItem(itemId: Int): Future[HttpResponse] = for {response <- Http().singleRequest(HttpRequest(method=HttpMethods.GET,uri = s"http://localhost:8011/item/$itemId"))} yield responseextractEntity[Item](getItem(13))def putItem(item: Item): Future[HttpResponse] =for {reqEntity <- Marshal(item).to[RequestEntity]response <- Http().singleRequest(HttpRequest(method=HttpMethods.PUT,uri="http://localhost:8011/item",entity=reqEntity))} yield responseextractEntity[Item](putItem(Item(23,"Item#23", 46.0))).andThen { case _ => sys.terminate()}val settings = ConnectionPoolSettings(sys).withMaxConnections(8).withMaxOpenRequests(8).withMaxRetries(3).withPipeliningLimit(4)val pooledClient = new PooledClient("localhost",8011,settings)def getItemByPool(itemId: Int): Future[HttpResponse] = for {response <- pooledClient.requestSingleResponse(HttpRequest(method=HttpMethods.GET,uri = s"http://localhost:8011/item/$itemId"))} yield responseextractEntity[Item](getItemByPool(13))def getItemsByPool(itemIds: List[Int]): Future[Iterable[HttpResponse]] = {val reqs = itemIds.map { id =>HttpRequest(method = HttpMethods.GET, uri = s"http://localhost:8011/item/$id")}val rets = (for {responses <- pooledClient.orderedResponses(reqs)} yield responses)rets}val futResps = getItemsByPool(List(3,5,7))futResps.andThen {case Success(listOfResps) => {listOfResps.foreach { r =>r match {case HttpResponse(StatusCodes.OK, _, entity, _) =>Unmarshal(entity).to[Item].onComplete {case Success(t) => println(s"Got response entity: ${t}")case Failure(e) => println(s"Unmarshalling failed: ${e.getMessage}")}case _ => println("Exception in response!")}}}case _ => println("Failed to get list of responses!")}val queuedClient = new QueuedRequestsClient("localhost",8011,settings)()def putItemByQueue(item: Item): Future[HttpResponse] =for {reqEntity <- Marshal(item).to[RequestEntity]response <- queuedClient.queueRequest(HttpRequest(method=HttpMethods.PUT,uri="http://localhost:8011/item",entity=reqEntity))} yield responseextractEntity[Item](putItemByQueue(Item(23,"Item#23", 46.0))).andThen { case _ => sys.terminate()}}






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