I have a C# Lambda Function that works on the first execution but fails on the second. I created some logs to help me troubleshoot where the issue is but I'm struggling to figure out what is actually happening.
First Execution Log:
START RequestId: XXXXXXXXXXXXXXXXXXXXXXXXXXXXX Version: $LATEST
1. Connecion to Database is Open
2. Running Query: SELECT * FROM Employee3
3. Returning Results
4. Close connection
5. Close reader
6. Dispose cmd
7. Configure encoding and string to stream
END RequestId: XXXXXXXXXXXXXXXXXXXXXXXX
REPORT RequestId: XXXXXXXXXXXXXXXXXXXXXXXX Duration: 10097.73 ms Billed Duration: 10100 ms Memory Size: 128 MB Max Memory Used: 41 MB
Response: (i know this isn't valid JSON, which I am ultimately aiming for, but that will be the next item I tackle once I figure this out)
Connecion to Database is Open
Joe
Bob
Mary
Second Execution Log:
START RequestId: XXXXXXXXXXXXXXXXXXXXXXXXXXXXX Version: $LATEST
1. Connecion to Database is Open
2. Running Query: SELECT * FROM Employee3
Connection must be valid and open.: InvalidOperationException
at MySql.Data.MySqlClient.MySqlCommand.Throw(Exception ex)
at MySql.Data.MySqlClient.MySqlCommand.CheckState()
at MySql.Data.MySqlClient.MySqlCommand.ExecuteReader(CommandBehavior behavior)
at LambdaDBTest.Function.returnRows(MySqlConnection connection)
at LambdaDBTest.Function.FunctionHandler(Stream input, ILambdaContext context)
at lambda_method(Closure , Stream , Stream , ContextInfo )
END RequestId: XXXXXXXXXXXXXXXXXXXXXXXX
REPORT RequestId: XXXXXXXXXXXXXXXXXXXXXXXX Duration: 1203.12 ms Billed Duration: 1300 ms Memory Size: 128 MB Max Memory Used: 47 MB
The following is the code I am using:
using System;
using System.IO;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using MySql.Data.MySqlClient;
using Amazon.Lambda.Core;
using Amazon.Lambda.Serialization;
using System.Text;
// Assembly attribute to enable the Lambda function's JSON input to be converted into a .NET class.
[assembly: LambdaSerializerAttribute(typeof(Amazon.Lambda.Serialization.Json.JsonSerializer))]
namespace LambdaDBTest
{
public class Function
{
/// <summary>
/// A simple function that takes a string and does a ToUpper
/// </summary>
/// <param name="input"></param>
/// <param name="context"></param>
/// <returns></returns>
public Stream FunctionHandler(Stream input, ILambdaContext context)
{
var dbCon = DBConnection.Instance();
dbCon.Server = "AWS-URI";
dbCon.DatabaseName = "DBNAME";
dbCon.User = "DBUSER";
dbCon.Password = "DBPASS";
string textInput;
if (dbCon.IsConnect())
{
textInput = "Connecion to Database is Open";
LambdaLogger.Log("\n 1. " + textInput);
textInput += returnRows(dbCon.Connection);
}
else
{
textInput = "\n Connecion to Database is NOT Open";
}
dbCon.Close();
LambdaLogger.Log("\n 7. Configure encoding and string to stream\n");
input = new System.IO.MemoryStream(System.Text.Encoding.UTF8.GetBytes(textInput));
return input;
}
public static MemoryStream GenerateStreamFromString(string value)
{
return new MemoryStream(Encoding.UTF8.GetBytes(value ?? ""));
}
static string returnRows(MySqlConnection connection)
{
string output = null;
string query = @"SELECT * FROM Employee3";
LambdaLogger.Log("\n 2. Running Query: " + query);
var cmd = new MySqlCommand(query, connection);
var reader = cmd.ExecuteReader();
LambdaLogger.Log("\n 3. Returning Results");
while (reader.Read())
{
output += "\n" + (string)reader["Name"];
}
LambdaLogger.Log("\n 4. Close connection");
connection.Close();
LambdaLogger.Log("\n 5. Close reader");
reader.Close();
LambdaLogger.Log("\n 6. Dispose cmd");
cmd.Dispose();
return output + "\r";
}
}
}
So the code is very basic, and a bit of a cut and paste job using the MySql.Data 6.10.1-beta Nu-Get Package for MySQL and AWS Lambda.
I cannot understand why I am getting an issue when it executes on the first attempt but not the second. There is zero state saving in Lambda as I understand it.
Hopefully I'm doing something stupid or missing something obvious which I will be happy to be notified about. If you need additional information, let me know.
EDITED CODE:
So a fix was found as shown below:
public Stream FunctionHandler(Stream input, ILambdaContext context)
{
var dbCon = DBConnection.Instance();
dbCon.Server = "######.rds.amazonaws.com";
dbCon.DatabaseName = "#####";
dbCon.User = "#####";
dbCon.Password = "######";
string textInput;
if (dbCon.IsConnect())
{
textInput = "Connecion to Database is Open";
LambdaLogger.Log("\n 1. " + textInput);
textInput += returnRows(dbCon.Connection);
}
else
{
textInput = "\n Connecion to Database is NOT Open";
}
// LambdaLogger.Log("\n 7. Close Database connection");
//dbCon.Close();
LambdaLogger.Log("\n 8. Configure encoding and string to stream\n");
input = new System.IO.MemoryStream(System.Text.Encoding.UTF8.GetBytes(textInput));
return input;
}
public static MemoryStream GenerateStreamFromString(string value)
{
return new MemoryStream(Encoding.UTF8.GetBytes(value ?? ""));
}
static string returnRows(MySqlConnection connection)
{
string output = null;
string query = @"SELECT * FROM Employee3";
LambdaLogger.Log("\n 2. Running Query: " + query);
var cmd = new MySqlCommand(query, connection);
var reader = cmd.ExecuteReader();
LambdaLogger.Log("\n 3. Returning Results");
while (reader.Read())
{
output += "\n" + (string)reader["Name"];
}
// LambdaLogger.Log("\n 4. Close connection");
//connection.Close();
LambdaLogger.Log("\n 5. Close reader");
reader.Close();
// LambdaLogger.Log("\n 6. Dispose cmd");
//cmd.Dispose();
return output + "\r";
}
The process reader was frozen by Lambda, so whilst I did not need to need to close MySQL connection due to connection pooling of the .net MySQL Driver, i did in fact need to invoke reader.Close(); to kill the frozen process. Thank you Udo Held :)
