Java and .NET Workers can co-exist

Added a docker-compose-javaworker.yml file and Dockerfile.j as well as restoring the worker Java source so there are two different versions now.

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

@@ -0,0 +1,102 @@
+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("Waiting for redis");
+        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("Waiting for db");
+          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);
+    }
+
+    System.err.println("Connected to db");
+    return conn;
+  }
+
+  static void sleep(long duration) {
+    try {
+      Thread.sleep(duration);
+    } catch (InterruptedException e) {
+      System.exit(1);
+    }
+  }
+}