Establishe redis connection after its lost after a few minutes

Author: mbelsakACN

worker/src/Worker/Program.cs

@@ -17,17 +17,41 @@ public static int Main(string[] args)
             try
             {
                 var pgsql = OpenDbConnection("Server=db;Username=postgres;");
-                var redis = OpenRedisConnection("redis").GetDatabase();
+                var redisConn = OpenRedisConnection("redis");
+                var redis = redisConn.GetDatabase();
+
+                // Keep alive is not implemented in Npgsql yet. This workaround was recommended:
+                // https://github.com/npgsql/npgsql/issues/1214#issuecomment-235828359
+                var keepAliveCommand = pgsql.CreateCommand();
+                keepAliveCommand.CommandText = "SELECT 1";
 
                 var definition = new { vote = "", voter_id = "" };
                 while (true)
                 {
+                    // Reconnect redis if down
+                    if (redisConn == null || !redisConn.IsConnected) {
+                        Console.WriteLine("Reconnecting Redis");
+                        redis = OpenRedisConnection("redis").GetDatabase();
+                    }
                     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);
+                        // Reconnect DB if down
+                        if (!pgsql.State.Equals(System.Data.ConnectionState.Open))
+                        {
+                            Console.WriteLine("Reconnecting DB");
+                            pgsql = OpenDbConnection("Server=db;Username=postgres;");
+                        }
+                        else
+                        { // Normal +1 vote requested
+                            UpdateVote(pgsql, vote.voter_id, vote.vote);
+                        }
+                    }
+                    else
+                    {
+                        keepAliveCommand.ExecuteNonQuery();
                     }
                 }
             }
@@ -66,7 +90,7 @@ private static NpgsqlConnection OpenDbConnection(string connectionString)
 
             var command = connection.CreateCommand();
             command.CommandText = @"CREATE TABLE IF NOT EXISTS votes (
-                                        id VARCHAR(255) NOT NULL UNIQUE, 
+                                        id VARCHAR(255) NOT NULL UNIQUE,
                                         vote VARCHAR(255) NOT NULL
                                     )";
             command.ExecuteNonQuery();
@@ -84,7 +108,7 @@ private static ConnectionMultiplexer OpenRedisConnection(string hostname)
             {
                 try
                 {
-                    Console.Error.WriteLine("Connected to redis");
+                    Console.Error.WriteLine("Connecting to redis");
                     return ConnectionMultiplexer.Connect(ipAddress);
                 }
                 catch (RedisConnectionException)
@@ -123,4 +147,4 @@ private static void UpdateVote(NpgsqlConnection connection, string voterId, stri
             }
         }
     }
-}
+}