前面我们完成了一个CQRS模式的数据采集（录入）平台。可以预见：数据的产生是在线下各式各样的终端系统中，包括web、桌面、移动终端。那么，为了实现一个完整的系统，必须把前端设备通过某种网络连接形式与数据采集平台集成为一体。有两种方式可以实现需要的网络连接：Restful-api, gRPC。由于gRPC支持http/2通讯协议，支持持久连接方式及双向数据流。所以对于POS设备这样的前端选择gRPC作为网络连接方式来实现实时的操作控制应该是正确的选择，毕竟采用恒久连接和双向数据流效率会高很多。gRPC是google公司的标准，基于protobuffer消息：一种二进制序列化数据交换机制。gRPC的优势在这里就不再细说，读者可以参考前面有关gRPC的讨论博文。
下面是系统结构示意图：
这篇讨论焦点集中在gRPC的server,client两头的具体实现。刚才提过，gRPC是google公司的开源库，同时还提供了各种语言的客户端，有：java, C ,python,go ... 但就是没有scala的，只能找第三方的scala客户端了。现在市面可供选择的gRPC-scala-客户端有scalaPB和akka-grpc两个，akka-grpc是基于akka-stream和akka-http构建的，按理来说会更合适，但由于还是处于preview版本，以后再说吧，现在只有scalaPB可选了。scalaPB是一个比较成熟的gRPC客户端，在前面的博客里我们也进行了介绍和示范。下面我们就用scalaPB来实现上面这个例子的客户端-平台集成。
首先，gRPC是通过protobuffer进行序列化数据传输的。下面是这个例子的.proto定义文件：
代码语言：javascript复制syntax = "proto3";
import "google/protobuf/wrappers.proto";
import "google/protobuf/any.proto";
import "scalapb/scalapb.proto";
option (scalapb.options) = {
// use a custom Scala package name
// package_name: "io.ontherocks.introgrpc.demo"
// don't append file name to package
flat_package: true
// generate one Scala file for all messages (services still get their own file)
single_file: true
// add imports to generated file
// useful when extending traits or using custom types
// import: "io.ontherocks.hellogrpc.RockingMessage"
// code to put at the top of generated file
// works only with `single_file: true`
//preamble: "sealed trait SomeSealedTrait"
};
package com.datatech.pos.messages;
message PBVchState { //单据状态
string opr = 1; //收款员
int64 jseq = 2; //begin journal sequence for read-side replay
int32 num = 3; //当前单号
int32 seq = 4; //当前序号
bool void = 5; //取消模式
bool refd = 6; //退款模式
bool susp = 7; //挂单
bool canc = 8; //废单
bool due = 9; //当前余额
string su = 10; //主管编号
string mbr = 11; //会员号
int32 mode = 12; //当前操作流程：0=logOff, 1=LogOn, 2=Payment
}
message PBTxnItem { //交易记录
string txndate = 1; //交易日期
string txntime = 2; //录入时间
string opr = 3; //操作员
int32 num = 4; //销售单号
int32 seq = 5; //交易序号
int32 txntype = 6; //交易类型
int32 salestype = 7; //销售类型
int32 qty = 8; //交易数量
int32 price = 9; //单价（分）
int32 amount = 10; //码洋（分）
int32 disc = 11; //折扣率 (%)
int32 dscamt = 12; //折扣额：负值 net实洋 = amount dscamt
string member = 13; //会员卡号
string code = 14; //编号（商品、卡号...）
string acct = 15; //账号
string dpt = 16; //部类
}
message PBPOSResponse {
int32 sts = 1;
string msg = 2;
PBVchState voucher = 3;
repeated PBTxnItem txnitems = 4;
}
message PBPOSCommand {
int64 shopid = 1;
string commandname = 2;
string delimitedparams = 3; //for multiple parameters, use ; to delimit
}
service SendCommand {
rpc SingleResponse(PBPOSCommand) returns (PBPOSResponse) {};
rpc MultiResponse(PBPOSCommand) returns (stream PBPOSResponse) {};
}前端通过两种模式向平台发送指令PBPOSCommand: SingleResponse代表传统的request/response交互模式，MultiResponse,又或者server-streaming,代表前端发送一个指令，服务端返回一串Response, 或response-stream。Command和PBCommand、POSResponse和PBPOSResponse之间必须具备相互转换函数：
代码语言：javascript复制package com.datatech.pos.cloud
import Messages._
import com.datatech.pos.messages._
object PBConverter {
implicit class PBConverter(pbmsg: PBPOSCommand) {
def toPOSComand: POSMessage = pbmsg.commandname.toUpperCase match {
case "LOGON" => POSMessage(pbmsg.shopid,LogOn(pbmsg.delimitedparams))
case "LOGOFF" => POSMessage(pbmsg.shopid,LogOff)
...
}
}
implicit class POSResponseConvert(resp: POSResponse) {
def toPBPOSResponse: PBPOSResponse = new PBPOSResponse(
sts = resp.sts,
msg = resp.msg,
voucher = Some(resp.voucher.toPBVchState),
txnitems = resp.txnItems.map(_.toPBTxnItem)
)
}
implicit class VchStateConvert(state: VchStates) {
def toPBVchState: PBVchState = new PBVchState(
opr = state.opr, //收款员
jseq = state.jseq, //begin journal sequence for read-side replay
num = state.num, //当前单号
seq = state.seq, //当前序号
void = state.void, //取消模式
refd = state.refd, //退款模式
susp = state.susp, //挂单
canc = state.canc, //废单
due = state.due, //当前余额
su = state.su, //主管编号
mbr = state.mbr, //会员号
mode = state.mode //当前操作流程：0=logOff, 1=LogOn, 2=Payment
)
}
implicit class TxnItemConvert(item: TxnItem) {
def toPBTxnItem: PBTxnItem = new PBTxnItem(
txndate = item.txndate, //交易日期
txntime = item.txntime, //录入时间
opr = item.opr, //操作员
num = item.num, //销售单号
seq = item.seq, //交易序号
txntype = item.txntype, //交易类型
salestype = item.salestype, //销售类型
qty = item.qty, //交易数量
price = item.price, //单价（分）
amount = item.amount, //码洋（分）
disc = item.disc, //折扣率 (%)
dscamt = item.dscamt, //折扣额：负值 net实洋 = amount dscamt
member = item.member, //会员卡号
code = item.code, //编号（商品、卡号...）
acct = item.acct, //账号
dpt = item.dpt //部类
)
}
}然后可以开始实现平台端POS接口服务了：
代码语言：javascript复制package com.datatech.pos.cloud
import com.datatech.pos.messages._
import io.grpc.stub.StreamObserver
import PBConverter._
import akka.actor.ActorRef
import akka.pattern.ask
import scala.concurrent.duration._
import akka.util.Timeout
import Messages._
import scala.concurrent.{Await, Future}
import com.typesafe.config.ConfigFactory
import com.datatech.sdp
import sdp.logging._
class gRPCServices(writerRouter: ActorRef) extends SendCommandGrpc.SendCommand with LogSupport {
import gRPCServices._
import PBConverter._
var posConfig: com.typesafe.config.Config = _
var exetimeout: Int = 5
try {
posConfig = ConfigFactory.load("pos.conf").getConfig("pos.server")
exetimeout = posConfig.getInt("executimeout")
}
catch {
case excp : Throwable =>
log.warn(s"gRPCServices: ${excp.getMessage}")
exetimeout = 5
}
override def singleResponse(request: PBPOSCommand): Future[PBPOSResponse] = {
getPBResponse(writerRouter,request.toPOSComand, exetimeout)
}
override def multiResponse(request: PBPOSCommand, responseObserver: StreamObserver[PBPOSResponse]): Unit = ???
}
object gRPCServices {
import scala.concurrent.ExecutionContext.Implicits.global
def getPBResponse(ref: ActorRef, cmd: POSMessage, executimeout: Int = 5): Future[PBPOSResponse] = {
implicit val timeout = Timeout(executimeout second)
val futRes: Future[POSResponse] = ask(ref, cmd).mapTo[POSResponse]
futRes.map(_.toPBPOSResponse)
}
}现在需要把gRPCService与POS系统集成为一体，这样前端发来的PBCommand转换成Command后经POSAgent转发给集群分片writerRouter，writeRouter再发给writer去进行具体的操作处理，完后把POSResponse转换成PBPOSResponse通过service再返回前端：
代码语言：javascript复制 def getPBResponse(ref: ActorRef, cmd: POSMessage, executimeout: Int = 5): Future[PBPOSResponse] = {
implicit val timeout = Timeout(executimeout second)
val futRes: Future[POSResponse] = ask(ref, cmd).mapTo[POSResponse]
futRes.map(_.toPBPOSResponse)
}可以看到上面使用了ask()模式来进行双向沟通。这个ref是一个中间信息交互actor （POSAgent）：
代码语言：javascript复制 var config = ConfigFactory.parseString("akka.remote.netty.tcp.port="" port """)
.withFallback(ConfigFactory.parseString("akka.remote.netty.tcp.hostname="" host """))
.withFallback(ConfigFactory.parseString("cassandra-journal.contact-points=["" host ""]"))
.withFallback(ConfigFactory.parseString("cassandra-snapshot-store.contact-points=["" host ""]"))
if (!seednodes.isEmpty)
config = config.withFallback(ConfigFactory.parseString("akka.cluster.seed-nodes=[" seednodes "]"))
//roles can be deployed on this node
config = config.withFallback(ConfigFactory.parseString("akka.cluster.roles = [poswriter]"))
.withFallback(ConfigFactory.load())
val posSystem = ActorSystem(systemName, config)
posSystem.actorOf(ClusterMonitor.props, "cps-cluster-monitor")
posSystem.actorOf(ActionReader.readerProps(showSteps),"reader")
val readerRouter = posSystem.actorOf(ReaderRouter.props(showSteps),"reader-router")
WriterShard.deployShard(posSystem)(ReaderInfo(readerRouter,writeOnly),showSteps)
val posHandler = ClusterSharding(posSystem).shardRegion(WriterShard.shardName)
val posref = posSystem.actorOf(WriterRouter.props(posHandler), "writer-router")
val passer = posSystem.actorOf(POSAgent.props(posref), "pos-agent")
val svc = SendCommandGrpc.bindService(new gRPCServices(passer), posSystem.dispatcher)
runServer(svc)
...
package com.datatech.pos.cloud
import akka.actor._
import com.datatech.sdp
import sdp.logging._
import Messages._
object POSAgent {
def props(pos: ActorRef) = Props(new WriterRouter(pos))
}
class POSAgent(posHandler: ActorRef) extends Actor with LogSupport {
var _sender: ActorRef = _
override def receive: Receive = {
case msg @ POSMessage(_,_) =>
_sender = sender()
posHandler ! msg
case resp: POSResponse => _sender ! resp
}
}
...
package com.datatech.pos.cloud
import akka.actor._
import com.datatech.sdp
import sdp.logging._
import Messages._
object WriterRouter {
def props(pos: ActorRef) = Props(new WriterRouter(pos))
}
class WriterRouter(posHandler: ActorRef) extends Actor with LogSupport {
var _sender: ActorRef = _
override def receive: Receive = {
case msg @ POSMessage(_,_) =>
_sender = sender()
posHandler ! msg
case resp: POSResponse => _sender ! resp
// log.info(s"*********response from server: $resp *********")
}
}前端是gRPC的客户端。我们构建一个来测试后台控制逻辑：
代码语言：javascript复制package poc.client
import scala.concurrent.Future
import com.datatech.pos.messages._
import com.datatech.pos.messages.SendCommandGrpc
import io.grpc.netty.{NegotiationType, NettyChannelBuilder}
object POCClient {
def main(args: Array[String]): Unit = {
val channel = NettyChannelBuilder
.forAddress("192.168.11.189",50051)
.negotiationType(NegotiationType.PLAINTEXT)
.build()
/*
//build connection channel
val channel = io.grpc.ManagedChannelBuilder
.forAddress("192.168.11.189",50051)
.usePlaintext(true)
.build()
val pbCommand = PBPOSCommand(1022,"LogOn","888")
//async call
val asyncStub = SendCommandGrpc.blockingStub(channel)
val futResponse: Future[PBPOSResponse] = asyncStub.singleResponse(pbCommand)
import scala.concurrent.ExecutionContext.Implicits.global
futResponse.foreach(result => println(result)) */
val pbCommand = PBPOSCommand(1022,"LogOn","888")
val syncStub1: SendCommandGrpc.SendCommandBlockingClient = SendCommandGrpc.blockingStub(channel)
val response1: PBPOSResponse = syncStub1.singleResponse(pbCommand)
println(s"${response1.msg}")
val pbCommand2 = PBPOSCommand(1022,"LogOff","")
//sync call
val syncStub: SendCommandGrpc.SendCommandBlockingClient = SendCommandGrpc.blockingStub(channel)
val response: PBPOSResponse = syncStub.singleResponse(pbCommand2)
println(s"${response.msg}")
scala.io.StdIn.readLine()
channel.shutdown()
}
}这里有几点必须注意：
1、protobuffer对象的强名称必须一致。在客户端用了同一个posmessages.proto定义文件：
代码语言：javascript复制syntax = "proto3";
import "google/protobuf/wrappers.proto";
import "google/protobuf/any.proto";
import "scalapb/scalapb.proto";
option (scalapb.options) = {
// use a custom Scala package name
// package_name: "io.ontherocks.introgrpc.demo"
// don't append file name to package
flat_package: true
// generate one Scala file for all messages (services still get their own file)
single_file: true
// add imports to generated file
// useful when extending traits or using custom types
// import: "io.ontherocks.hellogrpc.RockingMessage"
// code to put at the top of generated file
// works only with `single_file: true`
//preamble: "sealed trait SomeSealedTrait"
};
package com.datatech.pos.messages;
message PBVchState { //单据状态
string opr = 1; //收款员
int64 jseq = 2; //begin journal sequence for read-side replay
int32 num = 3; //当前单号
int32 seq = 4; //当前序号
bool void = 5; //取消模式
bool refd = 6; //退款模式
bool susp = 7; //挂单
bool canc = 8; //废单
bool due = 9; //当前余额
string su = 10; //主管编号
string mbr = 11; //会员号
int32 mode = 12; //当前操作流程：0=logOff, 1=LogOn, 2=Payment
}
message PBTxnItem { //交易记录
string txndate = 1; //交易日期
string txntime = 2; //录入时间
string opr = 3; //操作员
int32 num = 4; //销售单号
int32 seq = 5; //交易序号
int32 txntype = 6; //交易类型
int32 salestype = 7; //销售类型
int32 qty = 8; //交易数量
int32 price = 9; //单价（分）
int32 amount = 10; //码洋（分）
int32 disc = 11; //折扣率 (%)
int32 dscamt = 12; //折扣额：负值 net实洋 = amount dscamt
string member = 13; //会员卡号
string code = 14; //编号（商品、卡号...）
string acct = 15; //账号
string dpt = 16; //部类
}
message PBPOSResponse {
int32 sts = 1;
string msg = 2;
PBVchState voucher = 3;
repeated PBTxnItem txnitems = 4;
}
message PBPOSCommand {
int64 shopid = 1;
string commandname = 2;
string delimitedparams = 3;
}
service SendCommand {
rpc SingleResponse(PBPOSCommand) returns (PBPOSResponse) {};
rpc MultiResponse(PBPOSCommand) returns (stream PBPOSResponse) {};
}注意package com.datatech.pos.messages, 这项在服务端和客户端必须一致。
2、另外就是客户端的channelbuilder：在scalaPB例子里使用的是ManagedChannelBuilder，这是一个实验阶段的东东：
代码语言：javascript复制 //build connection channel
val channel = io.grpc.ManagedChannelBuilder
.forAddress("132.232.229.60",50051)
.usePlaintext(true)
.build()要用gRPC中正式的channelbuilder：
代码语言：javascript复制 val channel = NettyChannelBuilder
.forAddress("192.168.11.189",50051)
.negotiationType(NegotiationType.PLAINTEXT)
.build()上面这个NettyChannelBuilder的设置与那个io.grpc.ManagedChannelBuilder功能相等。但NettyChannelBuilder还具备更多的设置参数，如ssl/tls设置。
3、还有：因为客户端是按照顺序来发送操作指令的，每发一个指令，等待返回结果后才能再发下一个指令。所以必须使用同步客户端调用函数blockingStub。
下面是本次示范的一些配置文档：
project/plugins.sbt
代码语言：javascript复制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.thesamet" % "sbt-protoc" % "0.99.21")
libraryDependencies = "com.thesamet.scalapb" %% "compilerplugin" % "0.9.0-M6"build.sbt
代码语言：javascript复制name := "pos-on-cloud"
version := "0.1"
scalaVersion := "2.12.8"
scalacOptions = "-Ypartial-unification"
val akkaVersion = "2.5.23"
libraryDependencies := Seq(
"com.typesafe.akka" %% "akka-cluster-metrics" % akkaVersion,
"com.typesafe.akka" %% "akka-cluster-sharding" % akkaVersion,
"com.typesafe.akka" %% "akka-persistence" % akkaVersion,
"com.lightbend.akka" %% "akka-stream-alpakka-cassandra" % "1.0.1",
"org.mongodb.scala" %% "mongo-scala-driver" % "2.6.0",
"com.lightbend.akka" %% "akka-stream-alpakka-mongodb" % "1.0.1",
"com.typesafe.akka" %% "akka-persistence-query" % akkaVersion,
"com.typesafe.akka" %% "akka-persistence-cassandra" % "0.97",
"com.datastax.cassandra" % "cassandra-driver-core" % "3.6.0",
"com.datastax.cassandra" % "cassandra-driver-extras" % "3.6.0",
"ch.qos.logback" % "logback-classic" % "1.2.3",
"io.monix" %% "monix" % "3.0.0-RC2",
"org.typelevel" %% "cats-core" % "2.0.0-M1",
"io.grpc" % "grpc-netty" % scalapb.compiler.Version.grpcJavaVersion,
"com.thesamet.scalapb" %% "scalapb-runtime" % scalapb.compiler.Version.scalapbVersion % "protobuf",
"com.thesamet.scalapb" %% "scalapb-runtime-grpc" % scalapb.compiler.Version.scalapbVersion
)
PB.targets in Compile := Seq(
scalapb.gen() -> (sourceManaged in Compile).value
)
enablePlugins(JavaAppPackaging)resouces/application.conf
代码语言：javascript复制akka.actor.warn-about-java-serializer-usage = off
akka.log-dead-letters-during-shutdown = off
akka.log-dead-letters = off
akka.remote.use-passive-connections=off
akka {
loglevel = INFO
actor {
provider = "cluster"
}
remote {
log-remote-lifecycle-events = on
netty.tcp {
hostname = "127.0.0.1"
# port set to 0 for netty to randomly choose from
port = 0
}
}
cluster {
seed-nodes = [
"akka.tcp://cloud-pos-server@172.27.0.8:2551"
,"akka.tcp://cloud-pos-server@172.27.0.7:2551"
]
log-info = off
sharding {
role = "poswriter"
passivate-idle-entity-after = 30 m
}
}
persistence {
journal.plugin = "cassandra-journal"
snapshot-store.plugin = "cassandra-snapshot-store"
}
}
cassandra-journal {
contact-points = [
"172.27.0.8",
"172.27.0.7",
"172.27.0.15"
]
}
cassandra-snapshot-store {
contact-points = [
"172.27.0.8",
"172.27.0.7",
"172.27.0.15"
]
}
# Enable metrics extension in akka-cluster-metrics.
akka.extensions=["akka.cluster.metrics.ClusterMetricsExtension"]
akka.actor.deployment {
/reader-router/readerRouter = {
# Router type provided by metrics extension.
router = cluster-metrics-adaptive-group
# Router parameter specific for metrics extension.
# metrics-selector = heap
# metrics-selector = load
# metrics-selector = cpu
metrics-selector = mix
#
routees.paths = ["/user/reader"]
cluster {
max-nr-of-instances-per-node = 10
max-total-nr-of-instances = 1000
enabled = on
#set to on when there is a instance of routee created
#on the same node as the router
#very important to set this off, could cause missing msg in local cluster
allow-local-routees = on
}
}
}
dbwork-dispatcher {
# Dispatcher is the name of the event-based dispatcher
type = Dispatcher
# What kind of ExecutionService to use
executor = "fork-join-executor"
# Configuration for the fork join pool
fork-join-executor {
# Min number of threads to cap factor-based parallelism number to
parallelism-min = 2
# Parallelism (threads) ... ceil(available processors * factor)
parallelism-factor = 2.0
# Max number of threads to cap factor-based parallelism number to
parallelism-max = 10
}
# Throughput defines the maximum number of messages to be
# processed per actor before the thread jumps to the next actor.
# Set to 1 for as fair as possible.
throughput = 100
}resources/logback.xml
代码语言：javascript复制<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
<encoder>
<Pattern>
%d{yyyy-MM-dd HH:mm:ss} [%thread] %-5level %logger{36} - %msg%n
</Pattern>
</encoder>
</appender>
<logger name="com.datatech" level="info"
additivity="false">
<appender-ref ref="STDOUT" />
</logger>
<logger name="com.datatech.sdp" level="info"
additivity="false">
<appender-ref ref="STDOUT" />
</logger>
<root level="warn">
<appender-ref ref="STDOUT" />
</root>
</configuration>resources/pos.conf
代码语言：javascript复制pos {
server {
debug = false
cqlport = 9042
readinterval = 1000
executimeout = 5
}
}
