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/pom.xml

@@ -1,84 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
-  <modelVersion>4.0.0</modelVersion>
-
-  <groupId>worker</groupId>
-  <artifactId>worker</artifactId>
-  <version>1.0-SNAPSHOT</version>
-
-
-  <dependencies>
-    <dependency>
-      <groupId>org.json</groupId>
-      <artifactId>json</artifactId>
-      <version>20140107</version>
-    </dependency>
-
-    <dependency>
-        <groupId>redis.clients</groupId>
-        <artifactId>jedis</artifactId>
-        <version>2.7.2</version>
-        <type>jar</type>
-        <scope>compile</scope>
-    </dependency>
-
-    <dependency>
-        <groupId>org.postgresql</groupId>
-        <artifactId>postgresql</artifactId>
-        <version>9.4-1200-jdbc41</version>
-    </dependency>
-  </dependencies>
-
-  <build>
-    <plugins>
-      <plugin>
-        <groupId>org.apache.maven.plugins</groupId>
-        <artifactId>maven-jar-plugin</artifactId>
-        <version>2.4</version>
-        <configuration>
-          <finalName>worker</finalName>
-          <archive>
-            <manifest>
-              <addClasspath>true</addClasspath>
-              <mainClass>worker.Worker</mainClass>
-              <classpathPrefix>dependency-jars/</classpathPrefix>
-            </manifest>
-          </archive>
-        </configuration>
-      </plugin>
-      <plugin>
-        <groupId>org.apache.maven.plugins</groupId>
-        <artifactId>maven-compiler-plugin</artifactId>
-        <version>3.1</version>
-        <configuration>
-          <source>1.7</source>
-          <target>1.7</target>
-        </configuration>
-      </plugin>
-      <plugin>
-        <groupId>org.apache.maven.plugins</groupId>
-        <artifactId>maven-assembly-plugin</artifactId>
-        <executions>
-          <execution>
-            <goals>
-              <goal>attached</goal>
-            </goals>
-            <phase>package</phase>
-            <configuration>
-              <finalName>worker</finalName>
-              <descriptorRefs>
-                <descriptorRef>jar-with-dependencies</descriptorRef>
-              </descriptorRefs>
-              <archive>
-                <manifest>
-                  <mainClass>worker.Worker</mainClass>
-                </manifest>
-              </archive>
-            </configuration>
-          </execution>
-        </executions>
-      </plugin>
-    </plugins>
-  </build>
-</project>

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
+        }
+    }
+}

worker/src/main/java/worker/Worker.java

@@ -1,101 +0,0 @@
-package worker;
-
-import redis.clients.jedis.Jedis;
-import redis.clients.jedis.exceptions.JedisConnectionException;
-import java.sql.*;
-import org.json.JSONObject;
-
-class Worker {
-  public static void main(String[] args) {
-    try {
-      Jedis redis = connectToRedis("redis");
-      Connection dbConn = connectToDB("db");
-
-      System.err.println("Watching vote queue");
-
-      while (true) {
-        String voteJSON = redis.blpop(0, "votes").get(1);
-        JSONObject voteData = new JSONObject(voteJSON);
-        String voterID = voteData.getString("voter_id");
-        String vote = voteData.getString("vote");
-
-        System.err.printf("Processing vote for '%s' by '%s'\n", vote, voterID);
-        updateVote(dbConn, voterID, vote);
-      }
-    } catch (SQLException e) {
-      e.printStackTrace();
-      System.exit(1);
-    }
-  }
-
-  static void updateVote(Connection dbConn, String voterID, String vote) throws SQLException {
-    PreparedStatement insert = dbConn.prepareStatement(
-      "INSERT INTO votes (id, vote) VALUES (?, ?)");
-    insert.setString(1, voterID);
-    insert.setString(2, vote);
-
-    try {
-      insert.executeUpdate();
-    } catch (SQLException e) {
-      PreparedStatement update = dbConn.prepareStatement(
-        "UPDATE votes SET vote = ? WHERE id = ?");
-      update.setString(1, vote);
-      update.setString(2, voterID);
-      update.executeUpdate();
-    }
-  }
-
-  static Jedis connectToRedis(String host) {
-    Jedis conn = new Jedis(host);
-
-    while (true) {
-      try {
-        conn.keys("*");
-        break;
-      } catch (JedisConnectionException e) {
-        System.err.println("Failed to connect to redis - retrying");
-        sleep(1000);
-      }
-    }
-
-    System.err.println("Connected to redis");
-    return conn;
-  }
-
-  static Connection connectToDB(String host) throws SQLException {
-    Connection conn = null;
-
-    try {
-
-      Class.forName("org.postgresql.Driver");
-      String url = "jdbc:postgresql://" + host + "/postgres";
-
-      while (conn == null) {
-        try {
-          conn = DriverManager.getConnection(url, "postgres", "");
-        } catch (SQLException e) {
-          System.err.println("Failed to connect to db - retrying");
-          sleep(1000);
-        }
-      }
-
-      PreparedStatement st = conn.prepareStatement(
-        "CREATE TABLE IF NOT EXISTS votes (id VARCHAR(255) NOT NULL UNIQUE, vote VARCHAR(255) NOT NULL)");
-      st.executeUpdate();
-
-    } catch (ClassNotFoundException e) {
-      e.printStackTrace();
-      System.exit(1);
-    }
-
-    return conn;
-  }
-
-  static void sleep(long duration) {
-    try {
-      Thread.sleep(duration);
-    } catch (InterruptedException e) {
-      System.exit(1);
-    }
-  }
-}