akka-grpc - 基于akka-http和akka-streams的scala gRPC开发工具
关于grpc，在前面的scalaPB讨论里已经做了详细的介绍：google gRPC是一种全新的RPC框架，在开源前一直是google内部使用的集成工具。gRPC支持通过http/2实现protobuf格式数据交换。protobuf即protocol buffer，是google发明的一套全新的序列化传输协议serialization-protocol，是二进制编码binary-encoded的，相对java-object，XML，Json等在空间上占有优势，所以数据传输效率更高。由于gRPC支持http/2协议，可以实现双向通讯duplex-communication，解决了独立request/response交互模式在软件编程中的诸多局限。这是在系统集成编程方面相对akka-http占优的一个亮点。protobuf格式数据可以很方便的转换成 json格式数据，支持对外部系统的的开放协议数据交换。这也是一些人决定选择gRPC作为大型系统微服务集成开发工具的主要原因。更重要的是：用protobuf和gRPC进行client/server交互不涉及任何http对象包括httprequest,httpresponse，很容易上手使用，而且又有在google等大公司内部的成功使用经验，用起来会更加放心。
虽然gRPC基于http/2协议在网络通讯效率和模式上有了很大的提升，但近段时间对gRPC使用的调研主要还是冲着protobuf来的。在http/1应用中对二进制文件的传输交换有诸多限制和不便，特别是效率方面的问题。在protobuf这种序列化模式中对任何类型的数据格式都一视同仁，可以很方便的实现图片等文件的上传下载。另一个原因是：http/2并不是一种普及的协议，并不适合作为一个开放数据平台的连接协议。再就是：虽然gRPC是基于http协议上的，但对于HttpRequest的调用却非常不便，需要通过interceptor来实现，不但麻烦而且有门槛。
实际上，在使用scalaPB的过程中一直在关注akka-grpc的发展，直到v1.01发布。这是一个正式版本，相信不会在模式、风格、语法上再有大的改变，应该值得试着使用了。
对akka-http用户来说，akka-grpc具有很大吸引（相对其它gRPC开放工具），因为它是基于akka-http的，看看下面grpc服务端的接口：
// Bind service handler servers to localhost:8080/8081
val binding = Http().bindAndHandleAsync(
serviceHandlers,
interface = host,
port = port,
connectionContext = HttpConnectionContext())
// report successful binding
binding.foreach { binding => println(s"gRPC server bound to: ${binding.localAddress}") }
binding
上面这段代码不就是akka-http里的吗。那么可以想象得到如果需要支持http+rpc混合模式的应用，akka-grpc将会发挥很大作用，这也是akka-http下一步的发展趋势。
至于akka-grpc基于akka-streams的特性，我并没有感到太大的兴趣。如上所述，我们的目标是实现一种开放数据平台的终端接入接口。akka-streams恰恰把总体方案限制在了内部系统集成模式，因为服务端客户端就是akka-streams的两端，是内部系统集成的场景。也许，在开发一套内部IT系统的过程中akka-grpc可以很趁手。
与scalaPB一样，akka-grpc也是通过编译IDL（.proto）文件用相应的插件（plugin）产生相关的scala类和服务函数代码。实际上akka-grpc产生代码的plugin还是采用scalaPB的插件，这个过程已经在scalaPB系列博客里详细介绍过了。
gRPC支持下面四种交互协议：
1、Unary：独立的一对client-request/server-response，是我们常用的http交互模式
2、Server-Streaming：client发出一个request后从server端接收一串多个response
3、Client-Streaming：client向server发送一串多个request后从server接收一个response
4、Bidirectional-Streaming：还是由client首先发送request启动连接，然后在这个连接上client/server双方可以不断交互信息。
在akka-grpc的官网上有很好的示范例子。我在例子的基础上增加了身份验证使用的示范。数据类型和服务函数用IDL定义的.proto文件内容如下：
syntax = "proto3";
//#options
option java_multiple_files = true;
//option java_package = "learn.akka.grpc";
//option java_outer_classname = "GreeterProto";
package learn.akka.grpc;
//#options
//#services
////////////////////////////////////// The greeting service definition.
service GreeterService {
//////////////////////
// Sends a greeting //
////////*****/////////
// HELLO //
////////*****/////////
rpc SayHello (HelloRequest) returns (HelloReply) {}
// Comment spanning
// on several lines
rpc ItKeepsTalking (stream HelloRequest) returns (HelloReply) {}
/*
* C style comments
*/
rpc ItKeepsReplying (HelloRequest) returns (stream HelloReply) {}
/* C style comments
* on several lines
* with non-empty heading/trailing line */
rpc StreamHellos (stream HelloRequest) returns (stream HelloReply) {}
}
service AuthService {
rpc GetAuthToken(UCredential) returns (JWToken) {}
}
//#services
//#messages
// The request message containing the user's name.
message HelloRequest {
string name = 1;
}
// The response message containing the greetings
message HelloReply {
string message = 1;
}
message UCredential {
string userid = 1;
string password = 2;
}
message JWToken {
string jwt = 1;
}
//#messages
注意：文件里增加了AuthService服务，函数和类型分别为：GetAuthToken, UCredential, JWToken
身份验证需要通过HttpHeader实现，所以产生的函数样板里必须提供使用HttpHeader的参数。这个可以通过在built.sbt里增加akkaGrpcCodeGeneratorSettings += "server_power_apis"就能做到。下面是在产生的sayHello函数款式基础上的实现示范代码：
override def sayHello(in: HelloRequest,header: Metadata): Future[HelloReply] = {
if (isAuthenticated(header)) {
println(s"sayHello to ${in.name}")
FastFuture.successful(HelloReply(s"Hello, ${in.name}"))
} else {
println(s"${in.name} Unauthorized!")
FastFuture.successful(HelloReply(s"Unauthorized! ${in.name}"))
}
}
header是客户端提交的HttpRequest，如下：
//#with-metadata
def singleRequestReply(jwt: String): Unit = {
sys.log.info("Performing request")
val reply = client.sayHello().addHeader("Bearer", jwt).invoke(HelloRequest("Alice"))
println(s"got single reply: ${Await.result(reply, 5.seconds).message}")
}
客户端向服务端提供了JWT header 作为身份凭证。
上面提到，虽然http/2推出已经不短时间了，但尚未得到普及性的认可。即使是低点版本的websocket，也只能在一小撮专业的应用中得到使用。所以，akka-grpc并没有提供对OAuth2规范身份验证的支持。在这个例子里我们就只能进行基本的身份证明（如店号、机器号等），但身份验证过程的安全性就不做任何加密操作了。首先，在IDL文件里增加对AuthService的描述，如下：
service AuthService {
rpc GetAuthToken(UCredential) returns (JWToken) {}
}
message UCredential {
string userid = 1;
string password = 2;
}
message JWToken {
string jwt = 1;
}
现在需要在系统里提供两套服务：authService和greeterService, 如下：
class gRPCServer(host: String, port: Int) {
def run(system: ActorSystem[_]): Future[Http.ServerBinding] = {
implicit val classic = system.toClassic
implicit val ec: ExecutionContext = system.executionContext
val greeterService: PartialFunction[HttpRequest, Future[HttpResponse]] =
learn.akka.grpc.GreeterServicePowerApiHandler.partial(new GreeterServices(system))
val authService: PartialFunction[HttpRequest, Future[HttpResponse]] =
learn.akka.grpc.AuthServicePowerApiHandler.partial(new AuthServices())
val serviceHandlers: HttpRequest => Future[HttpResponse] =
ServiceHandler.concatOrNotFound(greeterService, authService)
// Bind service handler servers to localhost:8080/8081
val binding = Http().bindAndHandleAsync(
serviceHandlers,
interface = host,
port = port,
connectionContext = HttpConnectionContext())
// report successful binding
binding.foreach { binding => println(s"gRPC server bound to: ${binding.localAddress}") }
binding
//#server
}
}
获取身份凭证jwt示范如下：
客户端：
val authenticator = AuthServiceClient(clientSettings)
val futJwt = authenticator.getAuthToken(UCredential("9013","123456"))
val jwt = Await.result(futJwt,5.seconds).jwt
println(s"got jwt: ${jwt}")
服务端：
class AuthServices() extends AuthServicePowerApi {
//#service-request-reply
override def getAuthToken(in: UCredential, header: Metadata): Future[JWToken] =
FastFuture.successful(JWToken("jwtstring"))
}
服务端的身份验证示范：
override def sayHello(in: HelloRequest,header: Metadata): Future[HelloReply] = {
if (isAuthenticated(header)) {
println(s"sayHello to ${in.name}")
FastFuture.successful(HelloReply(s"Hello, ${in.name}"))
} else {
println(s"${in.name} Unauthorized!")
FastFuture.successful(HelloReply(s"Unauthorized! ${in.name}"))
}
}
private def isAuthenticated(metadata: Metadata): Boolean = {
metadata.getText("bearer") match {
case Some(t) => t == "jwtstring"
case _ => false
}
}
好了，下面是本次示范的源代码：
project/plugins.sbt
addSbtPlugin("com.eed3si9n" % "sbt-assembly" % "0.14.9") addSbtPlugin("net.virtual-void" % "sbt-dependency-graph" % "0.9.2") addSbtPlugin("com.typesafe.sbt" % "sbt-native-packager" % "1.3.15") addSbtPlugin("com.lightbend.akka.grpc" % "sbt-akka-grpc" % "1.0.1") addSbtPlugin("com.lightbend.sbt" % "sbt-javaagent" % "0.1.5")
build.sbt
val AkkaVersion = "2.6.8" val AkkaPersistenceCassandraVersion = "1.0.1" val AkkaHttpVersion = "10.1.12" val elastic4sVersion = "7.6.0" lazy val akkaGrpcVersion = "1.0.1" enablePlugins(AkkaGrpcPlugin) lazy val `learn-akka-grpc` = project .in(file(".")) .settings( organization := "com.datatech", version := "1.0", scalaVersion := "2.13.2", scalacOptions in Compile ++= Seq("-deprecation", "-feature", "-unchecked", "-Xlog-reflective-calls", "-Xlint"), javacOptions in Compile ++= Seq("-Xlint:unchecked", "-Xlint:deprecation"), libraryDependencies ++= Seq( "com.typesafe.akka" %% "akka-actor-typed" % AkkaVersion, "com.typesafe.akka" %% "akka-stream" % AkkaVersion, "com.typesafe.akka" %% "akka-discovery" % AkkaVersion, "com.typesafe.akka" %% "akka-cluster-sharding-typed" % AkkaVersion, "com.typesafe.akka" %% "akka-persistence-typed" % AkkaVersion, "com.typesafe.akka" %% "akka-persistence-query" % AkkaVersion, "com.typesafe.akka" %% "akka-serialization-jackson" % AkkaVersion, "com.typesafe.akka" %% "akka-persistence-cassandra" % AkkaPersistenceCassandraVersion, "com.typesafe.akka" %% "akka-http" % AkkaHttpVersion, "com.typesafe.akka" %% "akka-http-spray-json" % AkkaHttpVersion, "com.typesafe.akka" %% "akka-slf4j" % AkkaVersion, "com.datastax.cassandra" % "cassandra-driver-core" % "3.6.0", "com.datastax.cassandra" % "cassandra-driver-extras" % "3.6.0", "com.sksamuel.elastic4s" %% "elastic4s-client-esjava" % elastic4sVersion, "ch.qos.logback" % "logback-classic" % "1.2.3", "com.pauldijou" %% "jwt-core" % "3.0.1", "org.json4s" %% "json4s-native" % "3.7.0-M4") ) enablePlugins(JavaAppPackaging) akkaGrpcCodeGeneratorSettings += "server_power_apis"
gRPCServer.scala
package learn.akka.grpc.demo import akka.actor.typed._ import akka.actor.typed.scaladsl._ import akka.actor.typed.scaladsl.adapter._ import akka.http.scaladsl._ import com.typesafe.config.ConfigFactory import akka.http.scaladsl.Http import akka.http.scaladsl.model._ import scala.concurrent._ import akka.grpc.scaladsl.ServiceHandler //#import //#server object gRPCServer { def main(args: Array[String]): Unit = { val hostPat = "(.*):(.*)".r val (host, port) = args(0) match { case hostPat(h, p) => (h, p) case _ => ("localhost", "8080") } // important to enable HTTP/2 in ActorSystem's config val conf = ConfigFactory.parseString("akka.http.server.preview.enable-http2 = on") .withFallback(ConfigFactory.defaultApplication()) val system = ActorSystem[Nothing](Behaviors.empty, "grpc-server", conf) new gRPCServer(host,port.toInt).run(system) } } class gRPCServer(host: String, port: Int) { def run(system: ActorSystem[_]): Future[Http.ServerBinding] = { implicit val classic = system.toClassic implicit val ec: ExecutionContext = system.executionContext val greeterService: PartialFunction[HttpRequest, Future[HttpResponse]] = learn.akka.grpc.GreeterServicePowerApiHandler.partial(new GreeterServices(system)) val authService: PartialFunction[HttpRequest, Future[HttpResponse]] = learn.akka.grpc.AuthServicePowerApiHandler.partial(new AuthServices()) val serviceHandlers: HttpRequest => Future[HttpResponse] = ServiceHandler.concatOrNotFound(greeterService, authService) // Bind service handler servers to localhost:8080/8081 val binding = Http().bindAndHandleAsync( serviceHandlers, interface = host, port = port, connectionContext = HttpConnectionContext()) // report successful binding binding.foreach { binding => println(s"gRPC server bound to: ${binding.localAddress}") } binding //#server } }
GreeterServices.scala
package learn.akka.grpc.demo import akka.NotUsed import akka.actor.typed.ActorSystem import akka.http.scaladsl.util.FastFuture import akka.grpc.scaladsl._ import akka.stream.scaladsl.Sink import akka.stream.scaladsl.Source import learn.akka.grpc._ import scala.concurrent.{ExecutionContext, Future} //#import //#service-request-reply //#service-stream class GreeterServices(system: ActorSystem[_]) extends GreeterServicePowerApi { private implicit val sys: ActorSystem[_] = system private implicit val ec: ExecutionContext = system.executionContext override def sayHello(in: HelloRequest,header: Metadata): Future[HelloReply] = { if (isAuthenticated(header)) { println(s"sayHello to ${in.name}") FastFuture.successful(HelloReply(s"Hello, ${in.name}")) } else { println(s"${in.name} Unauthorized!") FastFuture.successful(HelloReply(s"Unauthorized! ${in.name}")) } } override def itKeepsTalking(in: Source[HelloRequest, NotUsed],header: Metadata): Future[HelloReply] = { if (isAuthenticated(header)) { println(s"sayHello to in stream...") in.runWith(Sink.seq).map(elements => HelloReply(s"Hello, ${elements.map(_.name).mkString(", ")}")) } else { println(s"Unauthorized!") in.runWith(Sink.seq).map(elements => HelloReply(s"Unauthorized, ${elements.map(_.name).mkString(", ")}")) } } override def itKeepsReplying(in: HelloRequest,header: Metadata): Source[HelloReply, NotUsed] = { if (isAuthenticated(header)) { println(s"sayHello to ${in.name} with stream of chars...") Source(s"Hello, ${in.name}".toList).map(character => HelloReply(character.toString)) } else { println(s"${in.name} Unauthorized!") Source(s"Unauthorized, ${in.name}".toList).map(character => HelloReply(character.toString)) } } override def streamHellos(in: Source[HelloRequest, NotUsed],header: Metadata): Source[HelloReply, NotUsed] = { if (isAuthenticated(header)) { println(s"sayHello to stream...") in.map(request => HelloReply(s"Hello, ${request.name}")) } else { println(s"Unauthorized!") in.map(request => HelloReply(s"Unauthorized, ${request.name}")) } } private def isAuthenticated(metadata: Metadata): Boolean = { metadata.getText("bearer") match { case Some(t) => t == "jwtstring" case _ => false } } } //#service-stream //#service-request-reply
AuthServices.scala
package learn.akka.grpc.demo import akka.http.scaladsl.util.FastFuture import akka.grpc.scaladsl._ import learn.akka.grpc._ import scala.concurrent.Future class AuthServices() extends AuthServicePowerApi { //#service-request-reply override def getAuthToken(in: UCredential, header: Metadata): Future[JWToken] = FastFuture.successful(JWToken("jwtstring")) }
AuthServiceClient.scala
package learn.akka.grpc.demo import scala.concurrent.Await import scala.concurrent.Future import scala.concurrent.duration._ import scala.util.Try import akka.Done import akka.NotUsed import akka.actor.ActorSystem import akka.grpc.GrpcClientSettings import akka.stream.scaladsl.Source import learn.akka.grpc._ object AuthGreeterClient { def main(args: Array[String]): Unit = { implicit val sys = ActorSystem("grpc-client") implicit val ec = sys.dispatcher val clientSettings = GrpcClientSettings.fromConfig(GreeterService.name) val client = GreeterServiceClient(clientSettings) val authenticator = AuthServiceClient(clientSettings) val futJwt = authenticator.getAuthToken(UCredential("9013","123456")) val jwt = Await.result(futJwt,5.seconds).jwt println(s"got jwt: ${jwt}") singleRequestReply(jwt) streamingRequest(jwt) streamingReply(jwt) streamingRequestReply(jwt) sys.scheduler.scheduleAtFixedRate(1.second, 1.second)(new Runnable { override def run(): Unit = Try(singleRequestReply(jwt)) }) //#with-metadata def singleRequestReply(jwt: String): Unit = { sys.log.info("Performing request") val reply = client.sayHello().addHeader("Bearer", jwt).invoke(HelloRequest("Alice")) println(s"got single reply: ${Await.result(reply, 5.seconds).message}") } //#with-metadata def streamingRequest(jwt: String): Unit = { val requests = List("Alice", "Bob", "Peter").map(HelloRequest(_)) val reply = client.itKeepsTalking().addHeader("Bearer", jwt).invoke(Source(requests)) println(s"got single reply for streaming requests: ${Await.result(reply, 5.seconds).message}") } def streamingReply(jwt: String): Unit = { val responseStream = client.itKeepsReplying().addHeader("Bearer", jwt).invoke(HelloRequest("Alice")) val done: Future[Done] = responseStream.runForeach(reply => println(s"got streaming reply: ${reply.message}")) Await.ready(done, 1.minute) } def streamingRequestReply(jwt: String): Unit = { val requestStream: Source[HelloRequest, NotUsed] = Source .tick(100.millis, 1.second, "tick") .zipWithIndex .map { case (_, i) => i } .map(i => HelloRequest(s"Alice-$i")) .take(10) .mapMaterializedValue(_ => NotUsed) val responseStream: Source[HelloReply, NotUsed] = client.streamHellos().addHeader("Bearer", jwt).invoke(requestStream) val done: Future[Done] = responseStream.runForeach(reply => println(s"got streaming reply: ${reply.message}")) Await.ready(done, 1.minute) } } }
