[GitHub] markusthoemmes commented on a change in pull request #3347: Generic Pooling REST Client

[GitBox <gi...@apache.org>]

markusthoemmes commented on a change in pull request #3347: Generic Pooling REST Client
URL: https://github.com/apache/incubator-openwhisk/pull/3347#discussion_r170910847
 
 

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 File path: common/scala/src/main/scala/whisk/http/PoolingRestClient.scala
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 @@ -0,0 +1,154 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package whisk.http
+
+import scala.concurrent.Future
+import scala.concurrent.Promise
+import scala.util.{Failure, Success}
+
+import akka.actor.ActorSystem
+import akka.http.scaladsl.Http
+import akka.http.scaladsl.Http.HostConnectionPool
+import akka.http.scaladsl.marshallers.sprayjson.SprayJsonSupport._
+import akka.http.scaladsl.marshalling._
+import akka.http.scaladsl.model._
+import akka.http.scaladsl.unmarshalling._
+import akka.stream.ActorMaterializer
+import akka.stream.OverflowStrategy
+import akka.stream.QueueOfferResult
+import akka.stream.scaladsl._
+
+import spray.json._
+
+/**
+ * This class only handles the basic communication to the proper endpoints.
+ *  It is up to its clients to interpret the results. It is built on akka-http
+ *  host-level connection pools; compared to single requests, it saves some time
+ *  on each request because it doesn't need to look up the pool corresponding
+ *  to the host. It is also easier to add an extra queueing mechanism.
+ */
+class PoolingRestClient(protocol: String, host: String, port: Int, queueSize: Int)(implicit system: ActorSystem) {
+  require(protocol == "http" || protocol == "https", "Protocol must be one of { http, https }.")
+
+  implicit val context = system.dispatcher
+  implicit val materializer = ActorMaterializer()
+
+  // Creates or retrieves a connection pool for the host.
+  private val pool = if (protocol == "http") {
+    Http().cachedHostConnectionPool[Promise[HttpResponse]](host = host, port = port)
+  } else {
+    Http().cachedHostConnectionPoolHttps[Promise[HttpResponse]](host = host, port = port)
+  }
+
+  private val poolPromise = Promise[HostConnectionPool]
+
+  // Additional queue in case all connections are busy. Should hardly ever be
+  // filled in practice but can be useful, e.g., in tests starting many
+  // asynchronous requests in a very short period of time.
+  private val requestQueue = Source
+    .queue(queueSize, OverflowStrategy.dropNew)
+    .via(pool.mapMaterializedValue { x =>
+      poolPromise.success(x); x
+    })
+    .toMat(Sink.foreach({
+      case ((Success(response), p)) => p.success(response)
+      case ((Failure(error), p))    => p.failure(error)
+    }))(Keep.left)
+    .run
+
+  // Prepares a request with the proper headers.
+  def mkRequest0(method: HttpMethod,
+                 uri: Uri,
+                 body: Future[MessageEntity],
+                 headers: List[HttpHeader] = List()): Future[HttpRequest] = {
 
 Review comment:
   Please use `List.empty` instead. Much less garbage and more clear.

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