XEvent Profiler initial event handlers (#456)

* Bump SMO to 140.2.5 to pick-up private XEvent binaries

* Pick up SMO binaries from the build lab

* Add ProfilerService class placeholder

* Update SMO nuget package to include DB Scoped XEvents

* Stage changes

* Stage changes

* Update SMO to use RTM dependencies and remove separate SqlScript package

* Stage changes

* Iterate on profiler service

* Fix post-merge break in localization

* More refactoring

* Continue iterating on profiler

* Add test profiler listener

* Address a couple of the code review feedback

* Fix AppVeyor build break

* Use self-cleaning test file

src/Microsoft.SqlTools.ServiceLayer/Profiler/Contracts/ProfilerEvent.cs

@@ -0,0 +1,78 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using System.Collections.Generic;
+
+namespace Microsoft.SqlTools.ServiceLayer.Profiler.Contracts
+{
+    /// <summary>
+    /// Class that contains data for a single profile event
+    /// </summary>
+    public class ProfilerEvent
+    {
+        /// <summary>
+        /// Initialize a new ProfilerEvent with required parameters
+        /// </summary>
+        public ProfilerEvent(string name, string timestamp)
+        {
+            this.Name = name;
+            this.Timestamp = timestamp;
+            this.Values = new Dictionary<string, string>();
+        }
+
+        /// <summary>
+        /// Profiler event name
+        /// </summary>
+        public string Name { get; private set; }
+
+        /// <summary>
+        /// Profiler event timestamp
+        /// </summary>
+        public string Timestamp { get; private set; }
+
+        /// <summary>
+        /// Profiler event values collection
+        /// </summary>
+        public Dictionary<string, string> Values { get; private set; }
+
+        /// <summary>
+        /// Equals method
+        /// </summary>
+        public bool Equals(ProfilerEvent p)
+        {
+            // if parameter is null return false:
+            if ((object)p == null)
+            {
+                return false;
+            }
+
+            return this.Name == p.Name
+                && this.Timestamp == p.Timestamp
+                && this.Values.Count == p.Values.Count;
+        }
+
+        /// <summary>
+        /// GetHashCode method
+        /// </summary>
+        public override int GetHashCode()
+        {
+            int hashCode = this.GetType().ToString().GetHashCode();
+
+            if (this.Name != null)
+            {
+                hashCode ^= this.Name.GetHashCode();
+            }
+
+            if (this.Timestamp != null)
+            {
+                hashCode ^= this.Timestamp.GetHashCode();
+            }
+
+            hashCode ^= this.Values.Count.GetHashCode();
+
+            return hashCode;
+        }
+    }
+}

src/Microsoft.SqlTools.ServiceLayer/Profiler/Contracts/ProfilerEventsAvailableNotification.cs

@@ -0,0 +1,27 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using System.Collections.Generic;
+using Microsoft.SqlTools.Hosting.Protocol.Contracts;
+using Microsoft.SqlTools.ServiceLayer.Utility;
+
+namespace Microsoft.SqlTools.ServiceLayer.Profiler.Contracts
+{
+    public class ProfilerEventsAvailableParams
+    {
+        public string SessionId { get; set; }
+
+        public List<ProfilerEvent> Events { get; set; }
+    }
+
+    public class ProfilerEventsAvailableNotification
+    {
+        public static readonly
+            EventType<ProfilerEventsAvailableParams> Type =
+            EventType<ProfilerEventsAvailableParams>.Create("profiler/eventsavailable");
+    }
+}
+
+

src/Microsoft.SqlTools.ServiceLayer/Profiler/Contracts/StartProfilingRequest.cs

@@ -0,0 +1,55 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using Microsoft.SqlTools.Hosting.Protocol.Contracts;
+using Microsoft.SqlTools.ServiceLayer.Utility;
+
+namespace Microsoft.SqlTools.ServiceLayer.Profiler.Contracts
+{
+    /// <summary>
+    /// Start Profiling request parameters
+    /// </summary>
+    public class StartProfilingParams : GeneralRequestDetails
+    {
+        public string OwnerUri { get; set; }
+
+        public string TemplateName 
+        {
+            get
+            {
+                return GetOptionValue<string>("templateName");
+            }
+            set
+            {
+                SetOptionValue("templateName", value);
+            }
+        }
+    }
+
+    public class StartProfilingResult
+    {
+        /// <summary>
+        /// Session ID that was started
+        /// </summary>
+        public string SessionId { get; set; }
+
+        public bool Succeeded { get; set; }
+
+        public string ErrorMessage { get; set; }
+    }
+
+    /// <summary>
+    /// Start Profile request type
+    /// </summary>
+    public class StartProfilingRequest
+    {
+        /// <summary>
+        /// Request definition
+        /// </summary>
+        public static readonly
+            RequestType<StartProfilingParams, StartProfilingResult> Type =
+            RequestType<StartProfilingParams, StartProfilingResult>.Create("profiler/start");
+    }
+}

src/Microsoft.SqlTools.ServiceLayer/Profiler/Contracts/StopProfilingRequest.cs

@@ -0,0 +1,38 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using Microsoft.SqlTools.Hosting.Protocol.Contracts;
+using Microsoft.SqlTools.ServiceLayer.Utility;
+
+namespace Microsoft.SqlTools.ServiceLayer.Profiler.Contracts
+{
+    /// <summary>
+    /// Stop Profiling request parameters
+    /// </summary>
+    public class StopProfilingParams
+    {
+        public string SessionId { get; set; }
+    }
+
+    public class StopProfilingResult
+    {
+        public bool Succeeded { get; set; }
+
+        public string ErrorMessage { get; set; }
+    }
+
+    /// <summary>
+    /// Start Profile request type
+    /// </summary>
+    public class StopProfilingRequest
+    {
+        /// <summary>
+        /// Request definition
+        /// </summary>
+        public static readonly
+            RequestType<StopProfilingParams, StopProfilingResult> Type =
+            RequestType<StopProfilingParams, StopProfilingResult>.Create("profiler/stop");
+    }
+}

src/Microsoft.SqlTools.ServiceLayer/Profiler/IProfilerSessionListener.cs

@@ -0,0 +1,15 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using System.Collections.Generic;
+using Microsoft.SqlTools.ServiceLayer.Profiler.Contracts;
+
+namespace Microsoft.SqlTools.ServiceLayer.Profiler
+{
+    public interface IProfilerSessionListener
+    {
+        void EventsAvailable(string sessionId, List<ProfilerEvent> events);
+    }
+}

src/Microsoft.SqlTools.ServiceLayer/Profiler/IProfilerSessionMonitor.cs

@@ -0,0 +1,32 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using System;
+using System.Collections.Generic;
+using System.Data.SqlClient;
+using System.Linq;
+using System.Xml;
+using Microsoft.SqlTools.ServiceLayer.Connection.Contracts;
+using Microsoft.SqlServer.Management.Sdk.Sfc;
+using Microsoft.SqlServer.Management.XEvent;
+
+namespace Microsoft.SqlTools.ServiceLayer.Profiler
+{
+    /// <summary>
+    /// Profiler session monitor interface
+    /// </summary>
+    public interface IProfilerSessionMonitor
+    {
+        /// <summary>
+        /// Starts monitoring a profiler session
+        /// </summary>
+        bool StartMonitoringSession(ProfilerSession session);
+
+        /// <summary>
+        /// Stops monitoring a profiler session
+        /// </summary>
+        bool StopMonitoringSession(string sessionId);
+    }
+}

src/Microsoft.SqlTools.ServiceLayer/Profiler/IXEventSession.cs

@@ -0,0 +1,18 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+namespace Microsoft.SqlTools.ServiceLayer.Profiler
+{
+    /// <summary>
+    /// Main class for Profiler Service functionality
+    /// </summary>
+    public interface IXEventSession
+    {
+        /// <summary>
+        /// Reads XEvent XML from the default session target
+        /// </summary>
+        string GetTargetXml();
+    }
+}

src/Microsoft.SqlTools.ServiceLayer/Profiler/IXEventSessionFactory.cs

@@ -0,0 +1,23 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+
+using Microsoft.SqlServer.Management.Sdk.Sfc;
+using Microsoft.SqlServer.Management.XEvent;
+using Microsoft.SqlTools.ServiceLayer.Connection;
+
+namespace Microsoft.SqlTools.ServiceLayer.Profiler
+{
+    /// <summary>
+    /// Main class for Profiler Service functionality
+    /// </summary>
+    public interface IXEventSessionFactory
+    {
+        /// <summary>
+        /// Create a new XEvent session
+        /// </summary>
+        IXEventSession CreateXEventSession(ConnectionInfo connInfo);
+    }
+}

src/Microsoft.SqlTools.ServiceLayer/Profiler/ProfilerService.cs

@@ -0,0 +1,246 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Collections.Specialized;
+using System.Data.SqlClient;
+using System.Diagnostics;
+using System.Linq;
+using System.Text;
+using System.Threading;
+using System.Threading.Tasks;
+using System.Xml;
+using Microsoft.SqlServer.Management.Sdk.Sfc;
+using Microsoft.SqlServer.Management.Smo;
+using Microsoft.SqlServer.Management.XEvent;
+using Microsoft.SqlTools.Hosting.Protocol;
+using Microsoft.SqlTools.Hosting.Protocol.Contracts;
+using Microsoft.SqlTools.ServiceLayer.Connection;
+using Microsoft.SqlTools.ServiceLayer.Connection.Contracts;
+using Microsoft.SqlTools.ServiceLayer.Hosting;
+using Microsoft.SqlTools.ServiceLayer.Profiler.Contracts;
+using Microsoft.SqlTools.Utility;
+
+namespace Microsoft.SqlTools.ServiceLayer.Profiler
+{
+    /// <summary>
+    /// Main class for Profiler Service functionality
+    /// </summary>
+    public sealed class ProfilerService : IDisposable, IXEventSessionFactory, IProfilerSessionListener
+    {
+        private bool disposed;
+
+        private ConnectionService connectionService = null;
+
+        private ProfilerSessionMonitor monitor = new ProfilerSessionMonitor();
+
+        private static readonly Lazy<ProfilerService> instance = new Lazy<ProfilerService>(() => new ProfilerService());
+
+        /// <summary>
+        /// Construct a new ProfilerService instance with default parameters
+        /// </summary>
+        public ProfilerService()
+        {
+            this.XEventSessionFactory = this;
+        }
+
+        /// <summary>
+        /// Gets the singleton instance object
+        /// </summary>
+        public static ProfilerService Instance
+        {
+            get { return instance.Value; }
+        }
+
+        /// <summary>
+        /// Internal for testing purposes only
+        /// </summary>
+        internal ConnectionService ConnectionServiceInstance
+        {
+            get
+            {
+                if (connectionService == null)
+                {
+                    connectionService = ConnectionService.Instance;
+                }
+                return connectionService;
+            }
+
+            set
+            {
+                connectionService = value;
+            }
+        }
+
+        /// <summary>
+        /// XEvent session factory.  Internal to allow mocking in unit tests.
+        /// </summary>
+        internal IXEventSessionFactory XEventSessionFactory { get; set; }
+
+        /// <summary>
+        /// Session monitor instance
+        /// </summary>
+        internal ProfilerSessionMonitor SessionMonitor
+        {
+            get
+            {
+                return this.monitor;
+            }
+        }
+
+        /// <summary>
+        /// Service host object for sending/receiving requests/events.
+        /// Internal for testing purposes.
+        /// </summary>
+        internal IProtocolEndpoint ServiceHost
+        {
+            get;
+            set;
+        }
+
+        /// <summary>
+        /// Initializes the Profiler Service instance
+        /// </summary>
+        public void InitializeService(ServiceHost serviceHost)
+        {
+            this.ServiceHost = serviceHost;
+            this.ServiceHost.SetRequestHandler(StartProfilingRequest.Type, HandleStartProfilingRequest);
+            this.ServiceHost.SetRequestHandler(StopProfilingRequest.Type, HandleStopProfilingRequest);
+
+            this.SessionMonitor.AddSessionListener(this);
+        }
+
+        /// <summary>
+        /// Handle request to start a profiling session
+        /// </summary>
+        internal async Task HandleStartProfilingRequest(StartProfilingParams parameters, RequestContext<StartProfilingResult> requestContext)
+        {
+            try
+            {
+                var result = new StartProfilingResult();
+                ConnectionInfo connInfo;
+                ConnectionServiceInstance.TryFindConnection(
+                    parameters.OwnerUri,
+                    out connInfo);
+
+                if (connInfo != null)
+                {
+                    ProfilerSession session = StartSession(connInfo);
+                    result.SessionId = session.SessionId;
+                    result.Succeeded = true;
+                }
+                else
+                {
+                    result.Succeeded = false;
+                    result.ErrorMessage = SR.ProfilerConnectionNotFound;
+                }
+
+                await requestContext.SendResult(result);
+            }
+            catch (Exception e)
+            {
+                await requestContext.SendError(e);
+            }
+        }
+
+        /// <summary>
+        /// Handle request to stop a profiling session
+        /// </summary>
+        internal async Task HandleStopProfilingRequest(StopProfilingParams parameters, RequestContext<StopProfilingResult> requestContext)
+        {
+            try
+            {
+                monitor.StopMonitoringSession(parameters.SessionId);
+                await requestContext.SendResult(new StopProfilingResult
+                {
+                    Succeeded = true
+                });
+            }
+            catch (Exception e)
+            {
+                await requestContext.SendError(e);
+            } 
+        }
+
+        /// <summary>
+        /// Starts a new profiler session for the provided connection
+        /// </summary>
+        internal ProfilerSession StartSession(ConnectionInfo connInfo)
+        {
+            // create a new XEvent session and Profiler session
+            var xeSession = this.XEventSessionFactory.CreateXEventSession(connInfo);
+            var profilerSession = new ProfilerSession()
+            {
+                SessionId = Guid.NewGuid().ToString(),
+                XEventSession = xeSession
+            };
+
+            // start monitoring the profiler session
+            monitor.StartMonitoringSession(profilerSession);
+
+            return profilerSession;
+        }
+
+        /// <summary>
+        /// Create a new XEvent sessions per the IXEventSessionFactory contract
+        /// </summary>
+        public IXEventSession CreateXEventSession(ConnectionInfo connInfo)
+        {
+            var sqlConnection = ConnectionService.OpenSqlConnection(connInfo);
+            SqlStoreConnection connection = new SqlStoreConnection(sqlConnection);
+            Session session = ProfilerService.GetOrCreateSession(connection, "Profiler");
+
+            // create xevent session wrapper
+            return new XEventSession()
+            {
+                Session = session
+            };
+        }
+
+        /// <summary>
+        /// Gets an existing XEvent session or creates one if no matching session exists.
+        /// Also starts the session if it isn't currently running
+        /// </summary>
+        private static Session GetOrCreateSession(SqlStoreConnection connection, string sessionName)
+        {
+            XEStore store = new XEStore(connection);
+            Session session = store.Sessions["Profiler"];
+            // start the session if it isn't already running
+            if (session != null && !session.IsRunning)
+            {
+                session.Start();
+            }
+            return session;
+        }
+
+        /// <summary>
+        /// Callback when profiler events are available
+        /// </summary>
+        public void EventsAvailable(string sessionId, List<ProfilerEvent> events)
+        {
+            // pass the profiler events on to the client
+            this.ServiceHost.SendEvent(
+                ProfilerEventsAvailableNotification.Type,
+                new ProfilerEventsAvailableParams()
+                {
+                    SessionId = sessionId,
+                    Events = events
+                });
+        }
+
+        /// <summary>
+        /// Disposes the Profiler Service
+        /// </summary>
+        public void Dispose()
+        {
+            if (!disposed)
+            {                
+                disposed = true;
+            }
+        }
+    }
+}

src/Microsoft.SqlTools.ServiceLayer/Profiler/ProfilerSession.cs

@@ -0,0 +1,127 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Microsoft.SqlServer.Management.XEvent;
+using Microsoft.SqlTools.ServiceLayer.Connection;
+using Microsoft.SqlTools.ServiceLayer.Profiler.Contracts;
+
+namespace Microsoft.SqlTools.ServiceLayer.Profiler
+{
+    /// <summary>
+    /// Profiler session class
+    /// </summary>
+    public class ProfilerSession
+    {
+        private static readonly TimeSpan DefaultPollingDelay = TimeSpan.FromSeconds(1);
+        private object pollingLock = new object();
+        private bool isPolling = false;
+        private DateTime lastPollTime = DateTime.Now.Subtract(DefaultPollingDelay);
+        private TimeSpan pollingDelay = DefaultPollingDelay;
+        private ProfilerEvent lastSeenEvent = null;
+
+        /// <summary>
+        /// Unique ID for the session
+        /// </summary>
+        public string SessionId { get; set; }
+
+        /// <summary>
+        /// Connection to use for the session
+        /// </summary>
+        public ConnectionInfo ConnectionInfo { get; set; }
+
+        /// <summary>
+        /// Underlying XEvent session wrapper
+        /// </summary>
+        public IXEventSession XEventSession { get; set; }
+
+        /// <summary>
+        /// Try to set the session into polling mode if criteria is meet
+        /// </summary>
+        /// <returns>True if session set to polling mode, False otherwise</returns>
+        public bool TryEnterPolling()
+        {
+            lock (this.pollingLock)
+            {
+                if (!this.isPolling && DateTime.Now.Subtract(this.lastPollTime) >= pollingDelay)
+                {
+                    this.isPolling = true;
+                    this.lastPollTime = DateTime.Now;
+                    return true;
+                }
+                else
+                {
+                    return false;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Is the session currently being polled
+        /// </summary>
+        public bool IsPolling
+        {
+            get
+            {
+                return this.isPolling;
+            }
+            set
+            {
+                lock (this.pollingLock)
+                {
+                    this.isPolling  = value;
+                }
+            }
+        }
+
+        /// <summary>
+        /// The delay between session polls
+        /// </summary>
+        public TimeSpan PollingDelay 
+        {
+            get
+            {
+                return pollingDelay;
+            }
+        }
+
+        /// <summary>
+        /// Filter the event list to not include previously seen events
+        /// </summary>
+        public List<ProfilerEvent> FilterOldEvents(List<ProfilerEvent> events)
+        {
+            if (lastSeenEvent != null)
+            {
+                // find the last event we've previously seen
+                bool foundLastEvent = false;
+                int idx = events.Count;
+                while (--idx >= 0)
+                {
+                    if (events[idx].Equals(lastSeenEvent))
+                    {
+                        foundLastEvent = true;
+                        break;
+                    }
+                }
+
+                // remove all the events we've seen before
+                if (foundLastEvent)
+                {
+                    events.RemoveRange(0, idx + 1);
+                }
+            }
+
+            // save the last event so we know where to clean-up the list from next time
+            if (events.Count > 0)
+            {
+                lastSeenEvent = events.LastOrDefault();
+            }
+
+            return events;
+        }
+    }
+}

src/Microsoft.SqlTools.ServiceLayer/Profiler/ProfilerSessionMonitor.cs

@@ -0,0 +1,201 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Data.SqlClient;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using System.Xml;
+using Microsoft.SqlServer.Management.Sdk.Sfc;
+using Microsoft.SqlServer.Management.XEvent;
+using Microsoft.SqlTools.ServiceLayer.Connection.Contracts;
+using Microsoft.SqlTools.ServiceLayer.Profiler.Contracts;
+
+namespace Microsoft.SqlTools.ServiceLayer.Profiler
+{
+    /// <summary>
+    /// Classs to monitor active profiler sessions
+    /// </summary>
+    public class ProfilerSessionMonitor : IProfilerSessionMonitor
+    {
+        private const int PollingLoopDelay = 1000;
+
+        private object sessionsLock = new object();
+
+        private object listenersLock = new object();
+
+        private Task processorThread = null;
+
+        private Dictionary<string, ProfilerSession> monitoredSessions = new Dictionary<string, ProfilerSession>();
+
+        private List<IProfilerSessionListener> listeners = new List<IProfilerSessionListener>();
+
+        /// <summary>
+        /// Registers a session event listener to receive a callback when events arrive
+        /// </summary>
+        public void AddSessionListener(IProfilerSessionListener listener)
+        {   
+            lock (this.listenersLock) 
+            {
+                this.listeners.Add(listener);
+            }
+        }
+
+        /// <summary>
+        /// Start monitoring the provided sessions
+        /// </summary>
+        public bool StartMonitoringSession(ProfilerSession session)
+        {
+            lock (this.sessionsLock)
+            {
+                // start the monitoring thread 
+                if (this.processorThread == null)
+                {
+                    this.processorThread = Task.Factory.StartNew(ProcessSessions);;
+                }
+
+                if (!this.monitoredSessions.ContainsKey(session.SessionId))
+                {
+                    this.monitoredSessions.Add(session.SessionId, session);
+                }
+            }
+
+            return true;
+        }
+
+        /// <summary>
+        /// Stop monitoring the session specified by the sessionId
+        /// </summary>
+        public bool StopMonitoringSession(string sessionId)
+        {
+            lock (this.sessionsLock)
+            {
+                if (this.monitoredSessions.ContainsKey(sessionId))
+                {
+                    ProfilerSession session;
+                    return this.monitoredSessions.Remove(sessionId, out session);
+                }
+                else
+                {
+                    return false;
+                }
+            }
+        }
+
+        /// <summary>
+        /// The core queue processing method
+        /// </summary>
+        /// <param name="state"></param>
+        private void ProcessSessions()
+        {    
+            while (true)
+            {
+                lock (this.sessionsLock)
+                {
+                    foreach (var session in this.monitoredSessions.Values)
+                    {
+                        ProcessSession(session);
+                    }
+                }
+
+                Thread.Sleep(PollingLoopDelay);
+            }
+        }
+
+        /// <summary>
+        /// Process a session for new XEvents if it meets the polling criteria
+        /// </summary>
+        private void ProcessSession(ProfilerSession session)
+        {
+            if (session.TryEnterPolling())
+            {
+                Task.Factory.StartNew(() => 
+                {
+                    var events = PollSession(session);
+                    if (events.Count > 0)
+                    {
+                        SendEventsToListeners(session.SessionId, events);
+                    }
+                });
+            }
+        }
+
+        private List<ProfilerEvent> PollSession(ProfilerSession session)
+        {
+            var events = new List<ProfilerEvent>();
+            try
+            {
+                if (session == null || session.XEventSession == null)
+                {
+                    return events;
+                }
+
+                var targetXml = session.XEventSession.GetTargetXml();
+
+                XmlDocument xmlDoc = new XmlDocument();
+                xmlDoc.LoadXml(targetXml);
+
+                var nodes = xmlDoc.DocumentElement.GetElementsByTagName("event");
+                foreach (XmlNode node in nodes)
+                {
+                    var profilerEvent = ParseProfilerEvent(node);
+                    if (profilerEvent != null)
+                    {
+                        events.Add(profilerEvent);
+                    }
+                }
+            }
+            finally
+            {
+                session.IsPolling = false;
+            }
+
+            return session.FilterOldEvents(events);
+        }
+
+        /// <summary>
+        /// Notify listeners when new profiler events are available
+        /// </summary>
+        private void SendEventsToListeners(string sessionId, List<ProfilerEvent> events)
+        {
+            lock (listenersLock)
+            {
+                foreach (var listener in this.listeners)
+                {
+                    listener.EventsAvailable(sessionId, events);
+                }
+            }
+        }
+
+        /// <summary>
+        /// Parse a single event node from XEvent XML
+        /// </summary>
+        private ProfilerEvent ParseProfilerEvent(XmlNode node)
+        {
+            var name = node.Attributes["name"];
+            var timestamp = node.Attributes["timestamp"];
+
+            var profilerEvent = new ProfilerEvent(name.InnerText, timestamp.InnerText);
+    
+            foreach (XmlNode childNode in node.ChildNodes)
+            {
+                var childName = childNode.Attributes["name"];
+                XmlNode typeNode = childNode.SelectSingleNode("type");
+                var typeName = typeNode.Attributes["name"];
+                XmlNode valueNode = childNode.SelectSingleNode("value");
+
+                if (!profilerEvent.Values.ContainsKey(childName.InnerText))
+                {
+                    profilerEvent.Values.Add(childName.InnerText, valueNode.InnerText);
+                }
+            }
+
+            return profilerEvent;
+        }
+    }
+}

src/Microsoft.SqlTools.ServiceLayer/Profiler/XEventSession.cs

@@ -0,0 +1,29 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using System.Linq;
+using Microsoft.SqlServer.Management.XEvent;
+using Microsoft.SqlTools.ServiceLayer.Connection;
+using Microsoft.SqlTools.ServiceLayer.Profiler.Contracts;
+
+namespace Microsoft.SqlTools.ServiceLayer.Profiler
+{
+    public class XEventSession : IXEventSession
+    {
+        public Session Session { get; set; }
+
+        public string GetTargetXml()
+        {
+            if (this.Session == null)
+            {
+                return string.Empty;
+            }
+
+            // try to read events from the first target
+            Target defaultTarget = this.Session.Targets.FirstOrDefault();
+            return defaultTarget != null ? defaultTarget.GetTargetData() : string.Empty;
+        }
+    }
+}