Add in-process concurrency support to the PS worker (#123)

The major changes are:
- Use `PSThreadOptions.ReuseThread` for the `InitialSessionState` when creating `Runspace`, so that every `PowerShellManager` only creates one thread and then reuse it afterwards. The default behavior is to create a new thread every time `PowerShell.Invoke` is called.
- Update `RequestProcessor` to process `InvocationRequest` in asynchronously via tasks.
- Implement `PowerShellManagerPool` using `BlockingCollection`
   - make upper bound of the pool configurable via an environment variable `PSWorkerInProcConcurrencyUpperBound`
   - make the pool able to expand in a lazy way
   - checkout `PowerShellManager` via `CheckoutIdleWorker` on the main thread. Once getting an idle instance back, the main thread will queue a task to process an invocation request on a thread-pool thread and forget about it -- the main thread then can go ahead to process the next message.
- Update the `RpcLogger` and make every `PowerShellManager` have its own logger instance.
   - also update the way to set the `RequestId` and `InvocationId` for logger. The original way to setup the context only works for single-thread design.
- Update `MessagingStream` to use a `BlockingCollection` to hold all messages that are about to be written out, then use a single thread-pool thread to take out items and write them to the gRPC channel.
   - currently, the way we write out response/log messages is completely task-based/async, using a semaphore for synchronization. However, this approach doesn't guarantee the order of the message.
   - this is because there could be multiple tasks blocked on the semaphore, and releasing the semaphore allows a blocked task to enter the semaphore, but there is no guaranteed order, such as first-in-first-out, for blocked threads to enter the semaphore.
   - so, the unblocked task could be a random one, and thus change the arrival order of the message when writing the message to the gRPC channel.
- Remove the two system logging we have in our worker, because they drastically worsen the processing time per an invocation request when there are a lot in-coming invocation requests.
   - the logging for "TriggerMetadata" parameter is not that useful, and should be removed
   - the execution time logging is good to have, but not necessary, especially when it impact the throughput.

.gitignore

@@ -17,6 +17,9 @@ obj/
 # Visual Studio IDE directory
 .vs/
 
+# VSCode directories that are not at the repository root
+/**/.vscode/
+
 # Project Rider IDE files
 .idea.powershell/
 

src/Logging/ILogger.cs

@@ -11,5 +11,7 @@ namespace Microsoft.Azure.Functions.PowerShellWorker.Utility
     internal interface ILogger
     {
         void Log(LogLevel logLevel, string message, Exception exception = null, bool isUserLog = false);
+        void SetContext(string requestId, string invocationId);
+        void ResetContext();
     }
 }

src/Logging/RpcLogger.cs

@@ -12,34 +12,33 @@
 
 namespace Microsoft.Azure.Functions.PowerShellWorker.Utility
 {
-    internal class RpcLogger : ILogger, IDisposable
+    internal class RpcLogger : ILogger
     {
         private const string SystemLogPrefix = "LanguageWorkerConsoleLog";
         private readonly MessagingStream _msgStream;
         private readonly StringBuilder _systemLogMsg;
         private string _invocationId;
         private string _requestId;
 
-        public RpcLogger(MessagingStream msgStream)
+        internal RpcLogger(MessagingStream msgStream)
         {
             _msgStream = msgStream;
             _systemLogMsg = new StringBuilder();
         }
 
-        public IDisposable BeginScope(string requestId, string invocationId)
+        public void SetContext(string requestId, string invocationId)
         {
             _requestId = requestId;
             _invocationId = invocationId;
-            return this;
         }
 
-        public void Dispose()
+        public void ResetContext()
         {
             _requestId = null;
             _invocationId = null;
         }
 
-        public async void Log(LogLevel logLevel, string message, Exception exception = null, bool isUserLog = false)
+        public void Log(LogLevel logLevel, string message, Exception exception = null, bool isUserLog = false)
         {
             if (isUserLog)
             {
@@ -56,7 +55,7 @@ public async void Log(LogLevel logLevel, string message, Exception exception = n
                     }
                 };
 
-                await _msgStream.WriteAsync(logMessage);
+                _msgStream.Write(logMessage);
             }
             else
             {

src/Messaging/MessagingStream.cs

@@ -4,6 +4,7 @@
 //
 
 using System;
+using System.Collections.Concurrent;
 using System.Threading;
 using System.Threading.Tasks;
 
@@ -12,47 +13,44 @@
 
 namespace Microsoft.Azure.Functions.PowerShellWorker.Messaging
 {
-    internal class MessagingStream : IDisposable
+    internal class MessagingStream
     {
-        private SemaphoreSlim _writeSemaphore = new SemaphoreSlim(1, 1);
-        private AsyncDuplexStreamingCall<StreamingMessage, StreamingMessage> _call;
-        private bool isDisposed;
+        private readonly AsyncDuplexStreamingCall<StreamingMessage, StreamingMessage> _call;
+        private readonly BlockingCollection<StreamingMessage> _msgQueue;
 
-        public MessagingStream(string host, int port)
+        internal MessagingStream(string host, int port)
         {
             Channel channel = new Channel(host, port, ChannelCredentials.Insecure);
             _call = new FunctionRpc.FunctionRpcClient(channel).EventStream();
-        }
 
-        public void Dispose()
-        {
-            if (!isDisposed)
-            {
-                isDisposed = true;
-                _call.Dispose();
-            }
+            _msgQueue = new BlockingCollection<StreamingMessage>();
+            Task.Run(WriteImplAsync);
         }
 
-        public StreamingMessage GetCurrentMessage() =>
-            isDisposed ? null : _call.ResponseStream.Current;
-
-        public async Task<bool> MoveNext() =>
-            !isDisposed && await _call.ResponseStream.MoveNext(CancellationToken.None);
-
-        public async Task WriteAsync(StreamingMessage message)
+        /// <summary>
+        /// Get the current message.
+        /// </summary>
+        internal StreamingMessage GetCurrentMessage() => _call.ResponseStream.Current;
+
+        /// <summary>
+        /// Move to the next message.
+        /// </summary>
+        internal async Task<bool> MoveNext() => await _call.ResponseStream.MoveNext(CancellationToken.None);
+
+        /// <summary>
+        /// Write the outgoing message to the buffer.
+        /// </summary>
+        internal void Write(StreamingMessage message) => _msgQueue.Add(message);
+
+        /// <summary>
+        /// Take a message from the buffer and write to the gRPC channel.
+        /// </summary>
+        private async Task WriteImplAsync()
         {
-            if(isDisposed) return;
-
-            // Wait for the handle to be released because we can't have
-            // more than one message being sent at the same time
-            await _writeSemaphore.WaitAsync();
-            try
-            {
-                await _call.RequestStream.WriteAsync(message);
-            }
-            finally
+            while (true)
             {
-                _writeSemaphore.Release();
+                StreamingMessage msg = _msgQueue.Take();
+                await _call.RequestStream.WriteAsync(msg);
             }
         }
     }

src/PowerShell/PowerShellManager.cs

@@ -28,6 +28,11 @@ internal class PowerShellManager
         /// </summary>
         internal Guid InstanceId => _pwsh.Runspace.InstanceId;
 
+        /// <summary>
+        /// Gets the associated logger.
+        /// </summary>
+        internal ILogger Logger => _logger;
+
         static PowerShellManager()
         {
             // Set the type accelerators for 'HttpResponseContext' and 'HttpResponseContext'.
@@ -48,6 +53,7 @@ internal PowerShellManager(ILogger logger)
             }
 
             var initialSessionState = InitialSessionState.CreateDefault();
+            initialSessionState.ThreadOptions = PSThreadOptions.ReuseThread;
             initialSessionState.EnvironmentVariables.Add(
                 new SessionStateVariableEntry("PSModulePath", FunctionLoader.FunctionModulePath, null));
 
@@ -154,16 +160,11 @@ internal Hashtable InvokeFunction(
                 // Gives access to additional Trigger Metadata if the user specifies TriggerMetadata
                 if(functionInfo.FuncParameters.Contains(AzFunctionInfo.TriggerMetadata))
                 {
-                    _logger.Log(LogLevel.Debug, "Parameter '-TriggerMetadata' found.");
                     _pwsh.AddParameter(AzFunctionInfo.TriggerMetadata, triggerMetadata);
                 }
 
-                Collection<object> pipelineItems = null;
-                using (ExecutionTimer.Start(_logger, "Execution of the user's function completed."))
-                {
-                    pipelineItems = _pwsh.AddCommand("Microsoft.Azure.Functions.PowerShellWorker\\Trace-PipelineObject")
-                                         .InvokeAndClearCommands<object>();
-                }
+                Collection<object> pipelineItems = _pwsh.AddCommand("Microsoft.Azure.Functions.PowerShellWorker\\Trace-PipelineObject")
+                                                        .InvokeAndClearCommands<object>();
 
                 var result = _pwsh.AddCommand("Microsoft.Azure.Functions.PowerShellWorker\\Get-OutputBinding")
                                     .AddParameter("Purge", true)

src/PowerShell/PowerShellManagerPool.cs

@@ -4,7 +4,12 @@
 //
 
 using System;
+using System.Collections.Concurrent;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.Azure.Functions.PowerShellWorker.Messaging;
 using Microsoft.Azure.Functions.PowerShellWorker.Utility;
+using Microsoft.Azure.WebJobs.Script.Grpc.Messages;
 
 namespace Microsoft.Azure.Functions.PowerShellWorker.PowerShell
 {
@@ -15,37 +20,80 @@ namespace Microsoft.Azure.Functions.PowerShellWorker.PowerShell
     /// </summary>
     internal class PowerShellManagerPool
     {
-        private readonly ILogger _logger;
-        // Today we don't really support the in-proc concurrency. We just hold an instance of PowerShellManager in this field.
-        private PowerShellManager _psManager;
+        private readonly int _upperBound;
+        private readonly MessagingStream _msgStream;
+        private readonly BlockingCollection<PowerShellManager> _pool;
+        private int _poolSize;
 
         /// <summary>
         /// Constructor of the pool.
         /// </summary>
-        internal PowerShellManagerPool(ILogger logger)
+        internal PowerShellManagerPool(MessagingStream msgStream)
         {
-            _logger = logger;
+            string upperBound = Environment.GetEnvironmentVariable("PSWorkerInProcConcurrencyUpperBound");
+            if (string.IsNullOrEmpty(upperBound) || !int.TryParse(upperBound, out _upperBound))
+            {
+                _upperBound = 1;
+            }
+
+            _msgStream = msgStream;
+            _pool = new BlockingCollection<PowerShellManager>(_upperBound);
         }
 
         /// <summary>
         /// Initialize the pool and populate it with PowerShellManager instances.
-        /// When it's time to really implement this pool, we probably should instantiate PowerShellManager instances in a lazy way.
-        /// Maybe start from size 1 and increase the number of workers as needed.
+        /// We instantiate PowerShellManager instances in a lazy way, starting from size 1 and increase the number of workers as needed.
         /// </summary>
-        internal void Initialize()
+        internal void Initialize(string requestId)
         {
-            _psManager = new PowerShellManager(_logger);
+            var logger = new RpcLogger(_msgStream);
+
+            try
+            {
+                logger.SetContext(requestId, invocationId: null);
+                _pool.Add(new PowerShellManager(logger));
+                _poolSize = 1;
+            }
+            finally
+            {
+                logger.ResetContext();
+            }
         }
 
         /// <summary>
-        /// Checkout an idle PowerShellManager instance.
-        /// When it's time to really implement this pool, this method is supposed to block when there is no idle instance available.
+        /// Checkout an idle PowerShellManager instance in a non-blocking asynchronous way.
         /// </summary>
-        internal PowerShellManager CheckoutIdleWorker(AzFunctionInfo functionInfo)
+        internal PowerShellManager CheckoutIdleWorker(StreamingMessage request, AzFunctionInfo functionInfo)
         {
+            PowerShellManager psManager = null;
+            string requestId = request.RequestId;
+            string invocationId = request.InvocationRequest?.InvocationId;
+
+            // If the pool has an idle one, just use it.
+            if (!_pool.TryTake(out psManager))
+            {
+                // The pool doesn't have an idle one.
+                if (_poolSize < _upperBound &&
+                    Interlocked.Increment(ref _poolSize) <= _upperBound)
+                {
+                    // If the pool hasn't reached its bounded capacity yet, then
+                    // we create a new item and return it.
+                    var logger = new RpcLogger(_msgStream);
+                    logger.SetContext(requestId, invocationId);
+                    psManager = new PowerShellManager(logger);
+                }
+                else
+                {
+                    // If the pool has reached its bounded capacity, then the thread
+                    // should be blocked until an idle one becomes available.
+                    psManager = _pool.Take();
+                }
+            }
+
             // Register the function with the Runspace before returning the idle PowerShellManager.
-            FunctionMetadata.RegisterFunctionMetadata(_psManager.InstanceId, functionInfo);
-            return _psManager;
+            FunctionMetadata.RegisterFunctionMetadata(psManager.InstanceId, functionInfo);
+            psManager.Logger.SetContext(requestId, invocationId);
+            return psManager;
         }
 
         /// <summary>
@@ -57,6 +105,8 @@ internal void ReclaimUsedWorker(PowerShellManager psManager)
             {
                 // Unregister the Runspace before reclaiming the used PowerShellManager.
                 FunctionMetadata.UnregisterFunctionMetadata(psManager.InstanceId);
+                psManager.Logger.ResetContext();
+                _pool.Add(psManager);
             }
         }
     }