Add async overloads to SslOverTdsStream #27743

saurabh500 · 2018-03-05T21:06:26Z

Added ReadAsync and WriteAsync overloads to SslOverTdsStream in SqlClient so that the async apis over encrypted connection are full async instead of calling the Read and Write methods of SslOverTdsStream.

I also modified the SNITcpPacket to call into the Stream's WriteAsync APIs.

This impacts SSL connections to Sql server.
Tests done:

Tested the SqlClient Manual Tests.
Tested the EF tests.

saurabh500 · 2018-03-05T21:07:59Z

src/System.Data.SqlClient/src/System/Data/SqlClient/SNI/SslOverTdsStream.cs

@@ -48,6 +50,51 @@ public void FinishHandshake()
        /// <param name="count">Byte count</param>
        /// <returns>Bytes read</returns>
        public override int Read(byte[] buffer, int offset, int count)
+        {
+            return ReadInternal(buffer, offset, count, CancellationToken.None, false).GetAwaiter().GetResult();


@stephentoub I have tried to reuse code and use the same method for Read and ReadAsync. Looking forward to any feedback here.
From what I understand there should be no allocations due to this approach, but looking forward to your review.

stephentoub · 2018-03-05T21:08:06Z

src/System.Data.SqlClient/src/System/Data/SqlClient/SNI/SNIPacket.cs

+            uint status = TdsEnums.SNI_SUCCESS;
+            try
+            {
+                await stream.WriteAsync(_data, 0, _length, CancellationToken.None);


Nit: please add .ConfigureAwait(false) to the end of this

stephentoub · 2018-03-05T21:08:52Z

src/System.Data.SqlClient/src/System/Data/SqlClient/SNI/SNITcpHandle.cs

-                }
-            });
-
+                packet.WriteToStreamAsync(_stream, cb);


This could end up invoking callback while holding the lock. Is that ok?

I am looking into the need for the locks in Async Scenarios and running some tests to validate the removal of these locks only in case of async reads and writes.
SqlClient on Windows uses locks for some sync cases, however no locks are used for async scenarios and that parity can be applied to the Managed Networking stack of SqlClient as well.
If my validations don't show any regressions, then I will update the code with locks removed from async reads and writes.

corivera · 2018-03-05T21:09:07Z

src/System.Data.SqlClient/src/System/Data/SqlClient/SNI/SNITcpHandle.cs

-            SNIPacket newPacket = packet;
-
-            _writeTaskFactory.StartNew(() =>
+            SNIAsyncCallback cb = callback ?? _sendCallback;


Do these changes also need to be ported to NpHandle? If so, we might as well make a base class for both handles, since they only differ in the underlying streams they open/use.

I will change NpHandle as well.

corivera · 2018-03-05T21:09:12Z

src/System.Data.SqlClient/src/System/Data/SqlClient/SNI/SNIPacket.cs

@@ -249,7 +249,7 @@ public void ReadFromStreamAsync(Stream stream, SNIAsyncCallback callback, bool i
                options |= TaskContinuationOptions.LongRunning;
            }

-            stream.ReadAsync(_data, 0, _capacity).ContinueWith(t =>
+            stream.ReadAsync(_data, 0, _capacity, CancellationToken.None).ContinueWith(t =>


@corivera I will send out another PR changing the readAsync piece and making it use async await.

corivera · 2018-03-05T21:10:41Z

src/System.Data.SqlClient/src/System/Data/SqlClient/SNI/SslOverTdsStream.cs

                currentOffset += currentCount;
            }
        }

+


Extra space

stephentoub · 2018-03-05T21:10:43Z

src/System.Data.SqlClient/src/System/Data/SqlClient/SNI/SslOverTdsStream.cs

@@ -47,7 +49,50 @@ public void FinishHandshake()
        /// <param name="offset">Offset</param>
        /// <param name="count">Byte count</param>
        /// <returns>Bytes read</returns>
-        public override int Read(byte[] buffer, int offset, int count)
+        public override int Read(byte[] buffer, int offset, int count) =>
+            ReadInternal(buffer, offset, count, CancellationToken.None, false).GetAwaiter().GetResult();


It looks like previously this would have called the synchronous Read methods on the underlying stream, but now it's invoking the asynchronous ones and then blocking on the result. Why? That's generally not a good direction to go.

Ah, nevermind, I see you're switching in the implementation on using either the sync or async methods. Ok.

Could you name the argument to ReadInternal so that it's clear what the bool means, e.g. async: false instead of just false?

corivera · 2018-03-05T21:10:49Z

src/System.Data.SqlClient/src/System/Data/SqlClient/SNI/SslOverTdsStream.cs

@@ -195,6 +280,7 @@ public override long Seek(long offset, SeekOrigin origin)
            throw new NotSupportedException();
        }

+


Extra space

stephentoub · 2018-03-05T21:12:20Z

src/System.Data.SqlClient/src/System/Data/SqlClient/SNI/SslOverTdsStream.cs

+                        else
+                        {
+                            readBytes += _stream.Read(packetData, readBytes, TdsEnums.HEADER_LEN - readBytes);
+                        }


Nit: you could simplify this slightly, e.g.

readBytes += async ? await _stream.ReadAsync(packetData, readBytes, TdsEnums.HEADER_LEN - readBytes, token).ConfigureAwait(false) : _stream.Read(packetData, readBytes, TdsEnums.HEADER_LEN - readBytes);

stephentoub · 2018-03-05T21:13:45Z

src/System.Data.SqlClient/src/System/Data/SqlClient/SNI/SslOverTdsStream.cs

-                        readBytes += _stream.Read(packetData, readBytes, TdsEnums.HEADER_LEN - readBytes);
+                        if (async)
+                        {
+                            readBytes += await _stream.ReadAsync(packetData, readBytes, TdsEnums.HEADER_LEN - readBytes, token).ConfigureAwait(false);


This library targets netstandard2.0 rather than netcoreapp2.1, right? If it targeted the latter, it'd be nice to use the new Memory-based overloads, but I don't think it does.

Yes, SqlClient targets netstandard2.0. I would like to change it to target netcoreapp
I will open an issue to track the work. Then SqlClient can benefit more from the Memory Based overloads.

stephentoub · 2018-03-05T21:14:00Z

src/System.Data.SqlClient/src/System/Data/SqlClient/SNI/SslOverTdsStream.cs

+        /// <param name="count"></param>
+        /// <param name="token"></param>
+        /// <param name="async"></param>
+        /// <returns></returns>


Nit: you can delete all of these empty comments

saurabh500 · 2018-03-05T23:51:54Z

In the commit that I have pushed , I have added an additional change which removes locks in SNITcpHandle.cs during async reads and writes.
I tested the changes with our server based tests and Entity Framework's tests.
The removal of locks confirms with our implementation on Windows using Win32 APIs where no locks are acquired during async reads and writes.

saurabh500 · 2018-03-06T03:16:50Z

@stephentoub is this good with you?

stephentoub · 2018-03-06T03:38:54Z

src/System.Data.SqlClient/src/System/Data/SqlClient/SNI/SNIPacket.cs

+                SNILoadHandle.SingletonInstance.LastError = new SNIError(provider, SNICommon.InternalExceptionError, e);
+                status = TdsEnums.SNI_ERROR;
+            }
+            callback(this, status);


What's expected to happen if the callback throws an exception? Is that possible?

The callback is not expected to throw any exceptions and handles all the exception using a
try { } catch (Exception e) {} block and handling all the exception itself.

stephentoub · 2018-03-06T03:39:52Z

src/System.Data.SqlClient/src/System/Data/SqlClient/SNI/SNITcpHandle.cs

-            });
-
+                packet.WriteToStreamAsync(_stream, cb, SNIProviders.TCP_PROV);
+            }


Same question I had before... this is now potentially invoking cb while holding the lock... is that ok?

I could remove the locks from async reads and writes. As a result none of the operations are now holding a lock. I had another change for removal of locks during async reads and writes being tested. I clubbed the change with this PR. Please see comment at #27743 (comment)

stephentoub · 2018-03-06T04:26:40Z

src/System.Data.SqlClient/src/System/Data/SqlClient/SNI/SNITcpHandle.cs

+            }
+            catch (IOException ioe)
+            {
+                return ReportErrorAndReleasePacket(packet, ioe);


Nit: these catch blocks could be consolidated, e.g.

catch (Exception e) when (e is ObjectDisposedException || e is SocketException || e is IOException) { return ReportErrorAndReleasePacket(packet, e); }

Sounds good.

saurabh500 · 2018-03-06T18:32:25Z

@dotnet-bot Test NETFX x86 Release Build please
Test Windows x64 Debug Build please

saurabh500 · 2018-03-06T23:06:17Z

NETFX x86 Release Build has been timing out

13:11:14   call xunit.console.exe System.Web.HttpUtility.Tests.dll  -noshadow -xml testResults.xml -notrait Benchmark=true -notrait category=nonnetfxtests -notrait category=nonwindowstests  -notrait category=OuterLoop -notrait category=failing
13:11:14   popd
13:11:14   ===========================================================================================================
13:11:14   xUnit.net Console Runner (64-bit Desktop .NET 4.0.30319.42000)
13:11:15     Discovering: System.Web.HttpUtility.Tests
13:11:15     Discovered:  System.Web.HttpUtility.Tests
13:11:15     Starting:    System.Web.HttpUtility.Tests
13:11:18     Finished:    System.Web.HttpUtility.Tests
13:11:18   === TEST EXECUTION SUMMARY ===
13:11:18      System.Web.HttpUtility.Tests  Total: 2363, Errors: 0, Failed: 0, Skipped: 0, Time: 0.686s
13:11:18   ----- end 13:11:18.71 ----- exit code 0 ----------------------------------------------------------
14:46:30 Cancelling nested steps due to timeout
14:46:30 Sending interrupt signal to process
14:46:40 After 10s process did not stop
[Pipeline] }

The changes in this PR only impact Linux and macOS.
I am merging this PR.

* Add async overloads for SslOverTdsStream for async operations * Remove Unused Code * Expression bodied syntax * Address CR comments and remove locks in async operations * Remove Read Locks * Remove async logs from NpHandle * Remove extra space * Consolidate the exceptions Commit migrated from dotnet/corefx@68cfdde

Saurabh Singh added 2 commits March 5, 2018 11:53

Add async overloads for SslOverTdsStream for async operations

28f6721

Remove Unused Code

6cda1bd

saurabh500 requested review from stephentoub, keeratsingh and geleems March 5, 2018 21:06

saurabh500 commented Mar 5, 2018

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stephentoub reviewed Mar 5, 2018

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Expression bodied syntax

080c5a6

corivera reviewed Mar 5, 2018

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src/System.Data.SqlClient/src/System/Data/SqlClient/SNI/SslOverTdsStream.cs Outdated

currentOffset += currentCount;

}

}

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corivera Mar 5, 2018

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Extra space

stephentoub reviewed Mar 5, 2018

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corivera reviewed Mar 5, 2018

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stephentoub reviewed Mar 5, 2018

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Saurabh Singh added 2 commits March 5, 2018 14:00

Address CR comments and remove locks in async operations

8348756

Remove Read Locks

d4d3798

saurabh500 self-assigned this Mar 5, 2018

Remove async logs from NpHandle

5803d47

corivera approved these changes Mar 6, 2018

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Remove extra space

c269d6f

corivera mentioned this pull request Mar 6, 2018

SNIPacket memory allocation perf improvement (revised) #27758

Merged

stephentoub reviewed Mar 6, 2018

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Consolidate the exceptions

51aec9f

saurabh500 merged commit 68cfdde into dotnet:master Mar 6, 2018

karelz added this to the 2.1.0 milestone Mar 10, 2018

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Add async overloads to SslOverTdsStream #27743

Add async overloads to SslOverTdsStream #27743

saurabh500 commented Mar 5, 2018

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stephentoub Mar 6, 2018 •

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saurabh500 Mar 6, 2018

saurabh500 commented Mar 6, 2018

saurabh500 commented Mar 6, 2018

		@@ -195,6 +280,7 @@ public override long Seek(long offset, SeekOrigin origin)
		throw new NotSupportedException();
		}

Add async overloads to SslOverTdsStream #27743

Add async overloads to SslOverTdsStream #27743

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saurabh500 commented Mar 5, 2018

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saurabh500 commented Mar 5, 2018

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saurabh500 commented Mar 6, 2018

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