Recreate worker as a .NET Core app

.gitignore

@@ -1 +1,4 @@
 *.pyc
+project.lock.json
+bin/
+obj/

worker/Dockerfile

@@ -1,19 +1,11 @@
-FROM java:openjdk-8-jdk-alpine
+FROM microsoft/dotnet:1.0.0-preview1
 
-RUN MAVEN_VERSION=3.3.3 \
- && cd /usr/share \
- && wget http://archive.apache.org/dist/maven/maven-3/$MAVEN_VERSION/binaries/apache-maven-$MAVEN_VERSION-bin.tar.gz -O - | tar xzf - \
- && mv /usr/share/apache-maven-$MAVEN_VERSION /usr/share/maven \
- && ln -s /usr/share/maven/bin/mvn /usr/bin/mvn
+WORKDIR /app
 
-WORKDIR /code
+ADD src/ /app/src/
 
-ADD pom.xml /code/pom.xml
-RUN ["mvn", "dependency:resolve"]
-RUN ["mvn", "verify"]
+RUN dotnet restore -v minimal src/ \
+    && dotnet publish -c Release -o ./ src/Worker/ \
+    && rm -rf src/ $HOME/.nuget/
 
-# Adding source, compile and package into a fat jar
-ADD src /code/src
-RUN ["mvn", "package"]
-
-CMD ["java", "-jar", "target/worker-jar-with-dependencies.jar"]
+CMD dotnet Worker.dll

worker/src/Worker/Program.cs

@@ -0,0 +1,115 @@
+using System;
+using System.Data.Common;
+using System.Linq;
+using System.Net;
+using System.Net.Sockets;
+using System.Threading;
+using Newtonsoft.Json;
+using Npgsql;
+using StackExchange.Redis;
+
+namespace Worker
+{
+    public class Program
+    {
+        public static int Main(string[] args)
+        {
+            try
+            {
+                var pgsql = OpenDbConnection("Server=db;Username=postgres;");
+                var redis = OpenRedisConnection("redis").GetDatabase();
+
+                var definition = new { vote = "", voter_id = "" };
+                while (true)
+                {
+                    string json = redis.ListLeftPopAsync("votes").Result;
+                    if (json != null)
+                    {
+                        var vote = JsonConvert.DeserializeAnonymousType(json, definition);
+                        Console.WriteLine($"Processing vote for '{vote.vote}' by '{vote.voter_id}'");
+                        UpdateVote(pgsql, vote.voter_id, vote.vote);
+                    }
+                }
+            }
+            catch (Exception ex)
+            {
+                Console.Error.WriteLine(ex.ToString());
+                return 1;
+            }
+        }
+
+        private static NpgsqlConnection OpenDbConnection(string connectionString)
+        {
+            var connection = new NpgsqlConnection(connectionString);
+            while (true)
+            {
+                try
+                {
+                    connection.Open();
+                    break;
+                }
+                catch (DbException)
+                {
+                    Console.Error.WriteLine("Failed to connect to db - retrying");
+                }
+            }
+
+            var command = connection.CreateCommand();
+            command.CommandText = @"CREATE TABLE IF NOT EXISTS votes (
+                                        id VARCHAR(255) NOT NULL UNIQUE, 
+                                        vote VARCHAR(255) NOT NULL
+                                    )";
+            command.ExecuteNonQuery();
+
+            return connection;
+        }
+
+        private static ConnectionMultiplexer OpenRedisConnection(string hostname)
+        {
+            // Use IP address to workaround hhttps://github.com/StackExchange/StackExchange.Redis/issues/410
+            var ipAddress = GetIp(hostname);
+            Console.WriteLine($"Found redis at {ipAddress}");
+
+            while (true)
+            {
+                try
+                {
+                    return ConnectionMultiplexer.Connect(ipAddress);
+                }
+                catch (RedisConnectionException)
+                {
+                    Console.Error.WriteLine("Failed to connect to redis - retrying");
+                    Thread.Sleep(1000);
+                }
+            }
+        }
+
+        private static string GetIp(string hostname)
+            => Dns.GetHostEntryAsync(hostname)
+                .Result
+                .AddressList
+                .First(a => a.AddressFamily == AddressFamily.InterNetwork)
+                .ToString();
+
+        private static void UpdateVote(NpgsqlConnection connection, string voterId, string vote)
+        {
+            var command = connection.CreateCommand();
+            try
+            {
+                command.CommandText = "INSERT INTO votes (id, vote) VALUES (@id, @vote)";
+                command.Parameters.AddWithValue("@id", voterId);
+                command.Parameters.AddWithValue("@vote", vote);
+                command.ExecuteNonQuery();
+            }
+            catch (DbException)
+            {
+                command.CommandText = "UPDATE votes SET vote = @vote WHERE id = @id";
+                command.ExecuteNonQuery();
+            }
+            finally
+            {
+                command.Dispose();
+            }
+        }
+    }
+}

worker/src/Worker/project.json

@@ -0,0 +1,24 @@
+{
+    "name": "Worker",
+    "buildOptions": {
+        "emitEntryPoint": true,
+        "warningsAsErrors": true
+    },
+    "dependencies": {
+        "StackExchange.Redis": "1.1.604-alpha",
+        "Npgsql": "3.1.3",
+        "Newtonsoft.Json": "9.0.1-beta1",
+        "Microsoft.NETCore.App": {
+            "type": "platform",
+            "version": "1.0.0-rc2-3002702"
+        }
+    },
+    "frameworks": {
+        "netcoreapp1.0": { }
+    },
+    "runtimeOptions": {
+        "configProperties": {
+            "System.GC.Server": true
+        }
+    }
+}