From 60e45418654975d27633a683b57c7013b98a23e3 Mon Sep 17 00:00:00 2001 From: Tleiades Hax Date: Thu, 25 Oct 2007 09:26:47 +0000 Subject: [PATCH] Created a generic RESTClient component, which simplifies querying for resources from REST based web-services. Currently it supports a barebones scheme for specifying the path of the resource and querying asynchroneously. POST method is still wacky and a good solid scheme for handling timeout still remain. --- .../RestClient/GenericAsyncResult.cs | 163 +++++++++ .../Communications/RestClient/RestClient.cs | 328 ++++++++++++++++++ prebuild.xml | 1 + 3 files changed, 492 insertions(+) create mode 100644 OpenSim/Framework/Communications/RestClient/GenericAsyncResult.cs create mode 100644 OpenSim/Framework/Communications/RestClient/RestClient.cs diff --git a/OpenSim/Framework/Communications/RestClient/GenericAsyncResult.cs b/OpenSim/Framework/Communications/RestClient/GenericAsyncResult.cs new file mode 100644 index 0000000000..4be459dea7 --- /dev/null +++ b/OpenSim/Framework/Communications/RestClient/GenericAsyncResult.cs @@ -0,0 +1,163 @@ +using System; +using System.Collections.Generic; +using System.Text; +using System.Threading; + +namespace OpenSim.Framework.RestClient +{ + internal class SimpleAsyncResult : IAsyncResult + { + + private readonly AsyncCallback m_callback; + + /// + /// Is process completed? + /// + /// Should really be boolean, but VolatileRead has no boolean method + private byte m_completed; + + /// + /// Did process complete synchroneously? + /// + /// I have a hard time imagining a scenario where this is the case, again, same issue about + /// booleans and VolatileRead as m_completed + /// + private byte m_completedSynchronously; + + private readonly object m_asyncState; + private ManualResetEvent m_waitHandle; + private Exception m_exception; + + internal SimpleAsyncResult(AsyncCallback cb, object state) + { + m_callback = cb; + m_asyncState = state; + m_completed = 0; + m_completedSynchronously = 1; + } + + + #region IAsyncResult Members + + public object AsyncState + { + get { return m_asyncState; } + } + + + + public WaitHandle AsyncWaitHandle + { + get + { + if (m_waitHandle == null) + { + bool done = IsCompleted; + ManualResetEvent mre = new ManualResetEvent(done); + if (Interlocked.CompareExchange(ref m_waitHandle, mre, null) != null) + { + mre.Close(); + } + else + { + if (!done && IsCompleted) + { + m_waitHandle.Set(); + } + } + } + return m_waitHandle; + } + } + + + public bool CompletedSynchronously + { + get { return Thread.VolatileRead(ref m_completedSynchronously) == 1; } + } + + + public bool IsCompleted + { + get { return Thread.VolatileRead(ref m_completed) == 1; } + } + + + #endregion + + + #region class Methods + internal void SetAsCompleted(bool completedSynchronously) + { + m_completed = 1; + if(completedSynchronously) + m_completedSynchronously = 1; + else + m_completedSynchronously = 0; + + SignalCompletion(); + } + + internal void HandleException(Exception e, bool completedSynchronously) + { + m_completed = 1; + if (completedSynchronously) + m_completedSynchronously = 1; + else + m_completedSynchronously = 0; + m_exception = e; + + SignalCompletion(); + } + + private void SignalCompletion() + { + if(m_waitHandle != null) m_waitHandle.Set(); + + if(m_callback != null) m_callback(this); + } + + public void EndInvoke() + { + // This method assumes that only 1 thread calls EndInvoke + if (!IsCompleted) + { + // If the operation isn't done, wait for it + AsyncWaitHandle.WaitOne(); + AsyncWaitHandle.Close(); + m_waitHandle = null; // Allow early GC + } + + // Operation is done: if an exception occured, throw it + if (m_exception != null) throw m_exception; + } + + #endregion + } + + internal class AsyncResult : SimpleAsyncResult + { + private T m_result = default(T); + + public AsyncResult(AsyncCallback asyncCallback, Object state) : + base(asyncCallback, state) { } + + + public void SetAsCompleted(T result, bool completedSynchronously) + { + // Save the asynchronous operation's result + m_result = result; + + // Tell the base class that the operation completed + // sucessfully (no exception) + base.SetAsCompleted(completedSynchronously); + } + + new public T EndInvoke() + { + base.EndInvoke(); + return m_result; + } + + } +} diff --git a/OpenSim/Framework/Communications/RestClient/RestClient.cs b/OpenSim/Framework/Communications/RestClient/RestClient.cs new file mode 100644 index 0000000000..ccf83761ce --- /dev/null +++ b/OpenSim/Framework/Communications/RestClient/RestClient.cs @@ -0,0 +1,328 @@ +using System; +using System.IO; +using System.Net; +using System.Web; +using System.Text; +using System.Collections.Generic; +using System.Threading; + +namespace OpenSim.Framework.RestClient +{ + /// + /// Implementation of a generic REST client + /// + /// + /// This class is a generic implementation of a REST (Representational State Transfer) web service. This + /// class is designed to execute both synchroneously and asynchroneously. + /// + /// Internally the implementation works as a two stage asynchroneous web-client. + /// When the request is initiated, RestClient will query asynchroneously for for a web-response, + /// sleeping until the initial response is returned by the server. Once the initial response is retrieved + /// the second stage of asynchroneous requests will be triggered, in an attempt to read of the response + /// object into a memorystream as a sequence of asynchroneous reads. + /// + /// The asynchronisity of RestClient is designed to move as much processing into the back-ground, allowing + /// other threads to execute, while it waits for a response from the web-service. RestClient it self, can be + /// invoked by the caller in either synchroneous mode or asynchroneous mode. + /// + public class RestClient + { + /// + /// The base Uri of the web-service e.g. http://www.google.com + /// + private string _url; + + /// + /// Path elements of the query + /// + private List _pathElements = new List(); + + /// + /// Parameter elements of the query, e.g. min=34 + /// + private Dictionary _parameterElements = new Dictionary(); + + /// + /// Request method. E.g. GET, POST, PUT or DELETE + /// + private string _method; + + /// + /// Temporary buffer used to store bytes temporarily as they come in from the server + /// + private byte[] _readbuf; + + /// + /// MemoryStream representing the resultiong resource + /// + MemoryStream _resource; + + /// + /// WebRequest object, held as a member variable + /// + private HttpWebRequest _request; + + /// + /// WebResponse object, held as a member variable, so we can close it + /// + private HttpWebResponse _response; + + /// + /// This flag will help block the main synchroneous method, in case we run in synchroneous mode + /// + public static ManualResetEvent _allDone = new ManualResetEvent(false); + + /// + /// Default time out period + /// + const int DefaultTimeout = 10 * 1000; // 10 seconds timeout + + /// + /// Default Buffer size of a block requested from the web-server + /// + const int BufferSize = 4096; // Read blocks of 4 KB. + + + /// + /// if an exception occours during async processing, we need to save it, so it can be + /// rethrown on the primary thread; + /// + private Exception _asyncException; + + /// + /// Instantiate a new RestClient + /// + /// Web-service to query, e.g. http://osgrid.org:8003 + public RestClient(string url) + { + _url = url; + _readbuf = new byte[BufferSize]; + _resource = new MemoryStream(); + _request = null; + _response = null; + } + + /// + /// Add a path element to the query, e.g. assets + /// + /// path entry + public void AddResourcePath(string element) + { + if(isSlashed(element)) + _pathElements.Add(element.Substring(0, element.Length-1)); + else + _pathElements.Add(element); + } + + /// + /// Add a query parameter to the Url + /// + /// Name of the parameter, e.g. min + /// Value of the parameter, e.g. 42 + public void AddQueryParameter(string name, string value) + { + _parameterElements.Add(HttpUtility.UrlEncode(name), HttpUtility.UrlEncode(value)); + } + + /// + /// Web-Request method, e.g. GET, PUT, POST, DELETE + /// + public string RequestMethod + { + get { return _method; } + set { _method = value; } + } + + /// + /// True if string contains a trailing slash '/' + /// + /// string to be examined + /// true if slash is present + private bool isSlashed(string s) + { + return s.Substring(s.Length - 1, 1) == "/"; + } + + /// + /// return a slash or blank. A slash will be returned if the string does not contain one + /// + /// stromg to be examined + /// slash '/' if not already present + private string slash(string s) + { + return isSlashed(s) ? "" : "/"; + } + + /// + /// Build a Uri based on the intial Url, path elements and parameters + /// + /// fully constructed Uri + Uri buildUri() + { + StringBuilder sb = new StringBuilder(); + sb.Append(_url); + + foreach (string e in _pathElements) + { + sb.Append("/"); + sb.Append(e); + } + + bool firstElement = true; + foreach (KeyValuePair kv in _parameterElements) + { + if (firstElement) + { + sb.Append("?"); + firstElement = false; + } else + sb.Append("&"); + + sb.Append(kv.Key); + if (kv.Value != null && kv.Value.Length != 0) + { + sb.Append("="); + sb.Append(kv.Value); + } + } + return new Uri(sb.ToString()); + } + + /// + /// Async method, invoked when a block of data has been received from the service + /// + /// + private void StreamIsReadyDelegate(IAsyncResult ar) + { + try + { + Stream s = (Stream)ar.AsyncState; + int read = s.EndRead(ar); + + // Read the HTML page and then print it to the console. + if (read > 0) + { + _resource.Write(_readbuf, 0, read); + IAsyncResult asynchronousResult = s.BeginRead(_readbuf, 0, BufferSize, new AsyncCallback(StreamIsReadyDelegate), s); + + // TODO! Implement timeout, without killing the server + //ThreadPool.RegisterWaitForSingleObject(asynchronousResult.AsyncWaitHandle, new WaitOrTimerCallback(TimeoutCallback), _request, DefaultTimeout, true); + return; + } + else + { + s.Close(); + _allDone.Set(); + } + } + catch (Exception e) + { + _allDone.Set(); + _asyncException = e; + } + } + + /// + /// Async method, invoked when the intial response if received from the server + /// + /// + private void ResponseIsReadyDelegate(IAsyncResult ar) + { + try + { + // grab response + WebRequest wr = (WebRequest)ar.AsyncState; + _response = (HttpWebResponse)wr.EndGetResponse(ar); + + // get response stream, and setup async reading + Stream s = _response.GetResponseStream(); + IAsyncResult asynchronousResult = s.BeginRead(_readbuf, 0, BufferSize, new AsyncCallback(StreamIsReadyDelegate), s); + + // TODO! Implement timeout, without killing the server + // wait until completed, or we timed out + // ThreadPool.RegisterWaitForSingleObject(asynchronousResult.AsyncWaitHandle, new WaitOrTimerCallback(TimeoutCallback), _request, DefaultTimeout, true); + } + catch (Exception e) + { + _allDone.Set(); + _asyncException = e; + } + } + + // Abort the request if the timer fires. + private static void TimeoutCallback(object state, bool timedOut) + { + if (timedOut) + { + HttpWebRequest request = state as HttpWebRequest; + if (request != null) + { + request.Abort(); + } + } + } + + /// + /// Perform synchroneous request + /// + public Stream Request() + { + _request = (HttpWebRequest)WebRequest.Create(buildUri()); + _request.KeepAlive = false; + _request.ContentType = "text/html"; + _request.Timeout = 200; + _asyncException = null; + + IAsyncResult responseAsyncResult = _request.BeginGetResponse(new AsyncCallback(ResponseIsReadyDelegate), _request); + + // TODO! Implement timeout, without killing the server + // this line implements the timeout, if there is a timeout, the callback fires and the request becomes aborted + //ThreadPool.RegisterWaitForSingleObject(responseAsyncResult.AsyncWaitHandle, new WaitOrTimerCallback(TimeoutCallback), _request, DefaultTimeout, true); + + _allDone.WaitOne(); + if(_response != null) + _response.Close(); + if (_asyncException != null) + throw _asyncException; + return _resource; + } + + #region Async Invocation + public IAsyncResult BeginRequest(AsyncCallback callback, object state) + { + /// + /// In case, we are invoked asynchroneously this object will keep track of the state + /// + AsyncResult ar = new AsyncResult(callback, state); + ThreadPool.QueueUserWorkItem(RequestHelper, ar); + return ar; + } + + public Stream EndRequest(IAsyncResult asyncResult) + { + AsyncResult ar = (AsyncResult)asyncResult; + + // Wait for operation to complete, then return result or + // throw exception + return ar.EndInvoke(); + } + + private void RequestHelper(Object asyncResult) + { + // We know that it's really an AsyncResult object + AsyncResult ar = (AsyncResult)asyncResult; + try + { + // Perform the operation; if sucessful set the result + Stream s = Request(); + ar.SetAsCompleted(s, false); + } + catch (Exception e) + { + // If operation fails, set the exception + ar.HandleException(e, false); + } + } + #endregion Async Invocation + } +} diff --git a/prebuild.xml b/prebuild.xml index 536d650a12..57ace78a69 100644 --- a/prebuild.xml +++ b/prebuild.xml @@ -376,6 +376,7 @@ ../../../bin/ +