Add .NET Core 2.1 versions

worker/dotnet/Dockerfile

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+FROM microsoft/dotnet:2.1-sdk as builder
+
+WORKDIR /Worker
+COPY Worker/Worker.csproj .
+RUN dotnet restore
+
+COPY /Worker .
+RUN dotnet publish -c Release -o /out Worker.csproj
+
+# app image
+FROM microsoft/dotnet:2.1-runtime
+
+WORKDIR /app
+ENTRYPOINT ["dotnet", "Worker.dll"]
+
+COPY --from=builder /out .

worker/dotnet/Worker/Data/IVoteData.cs

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+namespace Worker.Data
+{
+    public interface IVoteData
+    {
+        void Set(string voterId, string vote);
+    }
+}

worker/dotnet/Worker/Data/MySqlVoteData.cs

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+using Microsoft.Extensions.Logging;
+using Worker.Entities;
+
+namespace Worker.Data
+{
+    public class MySqlVoteData : IVoteData
+    {
+        private readonly VoteContext _context;        
+        private readonly ILogger _logger;
+
+        public MySqlVoteData(VoteContext context, ILogger<MySqlVoteData> logger)
+        {
+            _context = context;
+            _logger = logger;            
+        }
+
+        public void Set(string voterId, string vote)
+        {
+            var currentVote = _context.Votes.Find(voterId);
+            if (currentVote == null)
+            {
+                _context.Votes.Add(new Vote
+                {
+                    VoterId = voterId,
+                    VoteOption = vote
+                });
+            }
+            else if (currentVote.VoteOption != vote)
+            {
+                currentVote.VoteOption = vote;
+            }
+            _context.SaveChanges();
+        }
+    }
+}

worker/dotnet/Worker/Entities/Vote.cs

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+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
+
+namespace Worker.Entities
+{
+    [Table("votes")]
+    public class Vote
+    {
+        [Column("id")]
+        [Key]
+        public string VoterId { get; set; }
+
+        [Column("vote")]
+        public string VoteOption { get; set; }
+    }
+}

worker/dotnet/Worker/Entities/VoteContext.cs

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+using Microsoft.EntityFrameworkCore;
+
+namespace Worker.Entities
+{
+    public class VoteContext : DbContext
+    {
+        private static bool _EnsureCreated;
+        public VoteContext(DbContextOptions options) : base(options)
+        {
+            if (!_EnsureCreated)
+            {
+                Database.EnsureCreated();
+                _EnsureCreated = true;
+            }
+        }
+
+        public DbSet<Vote> Votes { get; set; }
+    }
+}

worker/dotnet/Worker/Messaging/IMessageQueue.cs

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+using NATS.Client;
+using Worker.Messaging.Messages;
+
+namespace Worker.Messaging
+{
+    public interface IMessageQueue
+    {
+        IConnection CreateConnection();
+
+        void Publish<TMessage>(TMessage message) where TMessage : Message;
+    }
+}

worker/dotnet/Worker/Messaging/MessageHelper.cs

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+using Newtonsoft.Json;
+using Worker.Messaging.Messages;
+using System.Text;
+
+namespace Worker.Messaging
+{
+    public class MessageHelper
+    {
+        public static byte[] ToData<TMessage>(TMessage message)
+            where TMessage : Message
+        {
+            var json = JsonConvert.SerializeObject(message);
+            return Encoding.Unicode.GetBytes(json);
+        }
+
+        public static TMessage FromData<TMessage>(byte[] data)
+            where TMessage : Message
+        {
+            var json = Encoding.Unicode.GetString(data);
+            return (TMessage)JsonConvert.DeserializeObject<TMessage>(json);
+        }
+    }
+}

worker/dotnet/Worker/Messaging/MessageQueue.cs

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+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.Logging;
+using NATS.Client;
+using Worker.Messaging.Messages;
+
+namespace Worker.Messaging
+{
+    public class MessageQueue : IMessageQueue
+    {
+        protected readonly IConfiguration _configuration;
+        protected readonly ILogger _logger;
+
+        public MessageQueue(IConfiguration configuration, ILogger<MessageQueue> logger)
+        {
+            _configuration = configuration;
+            _logger = logger;
+        }
+
+        public void Publish<TMessage>(TMessage message)
+            where TMessage : Message
+        {
+            using (var connection = CreateConnection())
+            {
+                var data = MessageHelper.ToData(message);
+                connection.Publish(message.Subject, data);
+            }
+        }
+
+        public IConnection CreateConnection()
+        {
+            var url = _configuration.GetValue<string>("MessageQueue:Url");
+            return new ConnectionFactory().CreateConnection(url);
+        }
+    }
+}

worker/dotnet/Worker/Messaging/Messages/Events/VoteCastEvent.cs

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+using System;
+
+namespace Worker.Messaging.Messages
+{
+    public class VoteCastEvent : Message
+    {
+        public override string Subject { get { return MessageSubject; } }
+
+        public string VoterId {get; set;}
+
+        public string Vote {get; set; }
+
+         public static string MessageSubject = "events.vote.votecast";
+    }
+}

worker/dotnet/Worker/Messaging/Messages/Message.cs

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+using System;
+
+namespace Worker.Messaging.Messages
+{
+    public abstract class Message
+    {
+        public string CorrelationId { get; set; }  
+        
+        public abstract string Subject { get; }      
+
+        public Message()
+        {
+            CorrelationId = Guid.NewGuid().ToString();
+        }
+    }
+}

worker/dotnet/Worker/Program.cs

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+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
+using System;
+using Worker.Data;
+using Worker.Entities;
+using Worker.Messaging;
+using Worker.Workers;
+
+namespace Worker
+{
+    class Program
+    {
+        static void Main(string[] args)
+        {
+            var config = new ConfigurationBuilder()
+                .AddJsonFile("appsettings.json")
+                .Build();
+
+            var loggerFactory = new LoggerFactory()
+                .AddConsole();
+
+            var services = new ServiceCollection()
+                .AddSingleton(loggerFactory)
+                .AddLogging()
+                .AddSingleton<IConfiguration>(config)
+                .AddTransient<IVoteData, MySqlVoteData>()
+                .AddTransient<IMessageQueue, MessageQueue>()
+                .AddSingleton<QueueWorker>()
+                .AddDbContext<VoteContext>(builder => builder.UseMySQL(config["VoteData:ConnectionString"]));
+
+            var provider = services.BuildServiceProvider();
+            var worker = provider.GetService<QueueWorker>();
+            worker.Start();
+        }
+    }
+}

worker/dotnet/Worker/Worker.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>netcoreapp2.1</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <None Remove="appsettings.json" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Content Include="appsettings.json">
+      <CopyToPublishDirectory>PreserveNewest</CopyToPublishDirectory>
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </Content>
+  </ItemGroup>  
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.EntityFrameworkCore" Version="2.0.3" />
+    <PackageReference Include="Microsoft.Extensions.Configuration.EnvironmentVariables" Version="2.1.1" />
+    <PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="2.1.1" />
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="2.1.1" />
+    <PackageReference Include="Microsoft.Extensions.Logging" Version="2.1.1" />
+    <PackageReference Include="Microsoft.Extensions.Logging.Console" Version="2.1.1" />
+    <PackageReference Include="MySql.Data.EntityFrameworkCore" Version="8.0.12" />
+    <PackageReference Include="NATS.Client" Version="0.8.1" />
+  </ItemGroup>
+
+</Project>

worker/dotnet/Worker/Workers/QueueWorker.cs

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+using System;
+using System.Threading;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.Logging;
+using NATS.Client;
+using Worker.Data;
+using Worker.Messaging;
+using Worker.Messaging.Messages;
+
+namespace Worker.Workers
+{
+    public class QueueWorker
+    {
+        private static ManualResetEvent _ResetEvent = new ManualResetEvent(false);
+        private const string QUEUE_GROUP = "save-handler";
+
+        private readonly IMessageQueue _messageQueue;
+        private readonly IConfiguration _config;
+        private readonly IVoteData _data;
+        protected readonly ILogger _logger;
+
+        public QueueWorker(IMessageQueue messageQueue, IVoteData data, IConfiguration config, ILogger<QueueWorker> logger)
+        {
+            _messageQueue = messageQueue;
+            _data = data;
+            _config = config;
+            _logger = logger;
+        }
+
+        public void Start()
+        {       
+            _logger.LogInformation($"Connecting to message queue url: {_config.GetValue<string>("MessageQueue:Url")}");
+            using (var connection = _messageQueue.CreateConnection())
+            {
+                var subscription = connection.SubscribeAsync(VoteCastEvent.MessageSubject, QUEUE_GROUP);
+                subscription.MessageHandler += SaveVote;
+                subscription.Start();
+                _logger.LogInformation($"Listening on subject: {VoteCastEvent.MessageSubject}, queue: {QUEUE_GROUP}");
+
+                _ResetEvent.WaitOne();
+                connection.Close();
+            }
+        }
+
+        private void SaveVote(object sender, MsgHandlerEventArgs e)
+        {
+            _logger.LogDebug($"Received message, subject: {e.Message.Subject}");
+            var voteMessage = MessageHelper.FromData<VoteCastEvent>(e.Message.Data);
+            _logger.LogInformation($"Processing vote for '{voteMessage.Vote}' by '{voteMessage.VoterId}'");
+            try
+            {
+                _data.Set(voteMessage.VoterId, voteMessage.Vote);
+                _logger.LogDebug($"Succesffuly processed vote by '{voteMessage.VoterId}'");
+            }
+            catch (Exception ex)
+            {
+                _logger.LogError($"Vote processing FAILED for '{voteMessage.VoterId}', exception: {ex}");
+            }
+            
+        }
+    }
+}

worker/dotnet/Worker/appsettings.json

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+{
+  "MessageQueue": {
+    "Url": "nats://message-queue:4222"
+  },
+  "VoteData": {
+    "ConnectionString": "Server=mysql;Port=4000;Database=votes;User=root;SslMode=None"
+  },
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information"
+    }
+  },
+  "AllowedHosts": "*"
+}