Unit test async methods C#

Question

I've a problem)

I try to reproduсe something like several sp (stored procedure) calls in my c# code, but i want to do it in async way.

TSQL example: ( Execute sp @key = 15072000173475; Execute sp @key = 15072000173571; ... Execute sp @key = n;)

[TestClass]
public class UnitTestNomenclature {
    [TestMethod]
    public void ParallelSQLMethod() {
        Task scropeTasks = null;
        //real amount is more then 1500
        long[] keys = new long[] {15072000173475,15072000173571 ... n };

        try {
            var tasks = keys.Select( i =>  Task.Run(async () => { await RunStoredProc(i); }));
            scropeTasks =  Task.WhenAll(tasks);

            scropeTasks.Wait();
        } catch (Exception ex) {
            Debug.WriteLine("Exception: " + ex.Message);

            Debug.WriteLine("IsFaulted: " + scropeTasks.IsFaulted);
            foreach (var inx in scropeTasks.Exception.InnerExceptions) {
                Debug.WriteLine("Details: " + inx.Message);
            }
        }

        Assert.AreEqual(1, 1);
    }

    public async Task RunStoredProc(long scollNumbParam) {
        const string strStoredProcName = @"[dbo].[sp]";
        using (SqlConnection conn = new SqlConnection(@"data source=SERVER;initial catalog=Db;integrated security=True;Trusted_Connection=Yes;")) {
            await conn.OpenAsync();
            Debug.WriteLine("============================================ Connection is open: ==============================================");

            // info
            Debug.WriteLine(String.Format("Connection: {0}", conn.ClientConnectionId));
            Debug.WriteLine(String.Format("State: {0}", conn.State.ToString()));

            using (SqlCommand cmd = new SqlCommand(strStoredProcName, conn) { CommandTimeout = 120, CommandType = CommandType.StoredProcedure }) {

                SqlParameter scrParam = new SqlParameter() {
                    ParameterName = "@KEYKRT",
                    Value = scollNumbParam,
                    SqlDbType = SqlDbType.BigInt
                };
                cmd.Parameters.Add(scrParam);

                Debug.WriteLine("Start of Proccesing: " + scollNumbParam);
                await cmd.ExecuteNonQueryAsync().ConfigureAwait(false);
                Debug.WriteLine("End of Proccesing: " + scollNumbParam);

            }
        }

        Debug.WriteLine("============================================ Connection is closed: ==============================================");
    }
}

This's what i get in output window:

========== Connection is open: ========
Connection: 5be9c681-6eb5-422f-a22c-b49689a2d912
State: Open
Start of Proccesing: 15072000173475
========== Connection is open: ==========
Connection: cfb66041-6646-4b56-be1c-2afb26a18cb8
State: Open
Start of Proccesing: 15072000173571
.....
End of Proccesing: 15072000173475
=========== Connection is closed: =========
End of Proccesing: 15072000173571
=========== Connection is closed: =========

....

A timeout occurred while waiting for memory resources to execute the query in resource pool 'default' (2). Rerun the query.
Actual error number: 8645
Actual line number: 98

Also debug says that connection pool is overflowed I think main reason that connection doesn't appropriatly dispose, but how i can achive that with async?

If i try just open one connection before the async tasks are declared and pass this to my RunStoredProc method then i get connection doesn't support MultipleActiveResultSets

using (SqlConnection conn = new SqlConnection(@"data source=SERVER;initial catalog=Db;integrated security=True;Trusted_Connection=Yes;)) {

                    conn.OpenAsync();
                    var tasks = keys.Select(i => Task.Run(async () => { await RunStoredProc(i, conn); }));
                    scropeTasks = Task.WhenAll(tasks);

                    scropeTasks.Wait();
                }

                Debug.WriteLine("========== Connection is closed: ==========");

This's what i get in output window:

Connection: 5be9c681-6eb5-422f-a22c-b49689a2d912
State: Open
Start of Proccesing: 15072000173475
======= Connection is open: =============
Connection: cfb66041-6646-4b56-be1c-2afb26a18cb8
State: Open
Start of Proccesing: 15072000173571
========= Connection is open: =========

Answer 1

You have 1500 or so tasks all executing at the same time and also mixing async and blocking calls ( like .Wait) which can cause deadlocks.

Make the test async and try to avoid async void unless it is on an event handler.

Try iterating them in sequence. It will take longer but at least the connections will get disposed properly so as not to overload the resources. You could also consider doing them in reasonably sized batches.

[TestMethod]
public async Task ParallelSQLMethod() {
    //real amount is more then 1500
    var keys = new long[] { 
        15072000173475, 
        15072000173571, 
        //....., n
    };
    var tasks = keys.Select(i => RunStoredProc(i));
    var batchSize = 50; //Or smaller

    //run tasks in batches
    var sequence = tasks;
    while (sequence.Any()) {
        var batch = sequence.Take(batchSize);
        sequence = sequence.Skip(batchSize);

        await Task.WhenAll(batch);
    }
}