Thumbnail file hits. Based on a patch from D Bera

[beagle.git] / beagled / Server.cs

//
// Server.cs
//
// Copyright (C) 2005 Novell, Inc.
//

//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//

using System;
using System.Collections;
using System.IO;
using System.Net.Sockets;
using System.Reflection;
using System.Threading;
using System.Xml.Serialization;

using Beagle.Util;

namespace Beagle.Daemon {

        class ConnectionHandler {

                private static int connection_count = 0;
                private static XmlSerializer serializer = new XmlSerializer (typeof (ResponseWrapper), ResponseMessage.Types);

                private object client_lock = new object ();
                private object blocking_read_lock = new object ();

                private UnixClient client;
                private RequestMessageExecutor executor = null; // Only set in the keepalive case
                private Thread thread;
                private bool in_blocking_read;

                public ConnectionHandler (UnixClient client)
                {
                        this.client = client;
                }

                public bool SendResponse (ResponseMessage response)
                {
                        lock (this.client_lock) {
                                if (this.client == null)
                                        return false;

                                try { 
                                        serializer.Serialize (this.client.GetStream (), new ResponseWrapper (response));
                                        // Send an end of message marker
                                        this.client.GetStream ().WriteByte (0xff);
                                        this.client.GetStream ().Flush ();
                                } catch (Exception e) {
                                        Logger.Log.Debug ("Caught an exception sending response; socket shut down: {0}", e.Message);
                                        return false;
                                }

                                return true;
                        }
                }

                public void CancelIfBlocking ()
                {
                        // Work around some crappy .net behavior.  We can't
                        // close a socket and have it exit out of a blocking
                        // read, so we have to abort the thread it's blocking
                        // in.
                        lock (this.blocking_read_lock) {
                                if (this.in_blocking_read) {
                                        this.thread.Abort ();
                                }
                        }
                }
                
                public void Close ()
                {
                        CancelIfBlocking ();

                        // It's important that we abort the thread before we
                        // grab the lock here and close the underlying
                        // UnixClient, or else we'd deadlock between here and
                        // the Read() in HandleConnection()
                        lock (this.client_lock) {
                                if (this.client != null) {
                                        this.client.Close ();
                                        this.client = null;
                                }
                        }

                        if (this.executor != null) {
                                this.executor.Cleanup ();
                                this.executor.AsyncResponseEvent -= OnAsyncResponse;
                        }
                }

                public void WatchCallback (IAsyncResult ar)
                {
                        int bytes_read = 0;

                        try {
                                bytes_read = this.client.GetStream ().EndRead (ar);
                        } catch (SocketException) {
                        } catch (IOException) { }

                        if (bytes_read == 0)
                                Close ();
                        else
                                SetupWatch ();
                }

                private void SetupWatch ()
                {
                        if (this.client == null) {
                                this.Close ();
                                return;
                        }

                        this.client.GetStream ().BeginRead (new byte[1024], 0, 1024,
                                                            new AsyncCallback (WatchCallback), null);
                }

                private void OnAsyncResponse (ResponseMessage response)
                {
                        if (!SendResponse (response))
                                Close ();
                }

                static XmlSerializer req_serializer = new XmlSerializer (typeof (RequestWrapper), RequestMessage.Types);

                public void HandleConnection ()
                {
                        this.thread = Thread.CurrentThread;

                        RequestMessage req = null;
                        ResponseMessage resp = null;

                        bool force_close_connection = false;
                        
                        // Read the data off the socket and store it in a
                        // temporary memory buffer.  Once the end-of-message
                        // character has been read, discard remaining data
                        // and deserialize the request.
                        byte[] network_data = new byte [4096];
                        MemoryStream buffer_stream = new MemoryStream ();
                        int bytes_read, total_bytes = 0, end_index = -1;

                        // We use the network_data array as an object to represent this worker.
                        Shutdown.WorkerStart (network_data, String.Format ("HandleConnection ({0})", ++connection_count));

                        do {
                                bytes_read = 0;

                                try {
                                        lock (this.blocking_read_lock)
                                                this.in_blocking_read = true;

                                        lock (this.client_lock) {
                                                // The connection may have been closed within this loop.
                                                if (this.client != null)
                                                        bytes_read = this.client.GetStream ().Read (network_data, 0, 4096);
                                        }

                                        lock (this.blocking_read_lock)
                                                this.in_blocking_read = false;
                                } catch (Exception e) {
                                        // Aborting the thread mid-read will
                                        // cause an IOException to be thorwn,
                                        // which sets the ThreadAbortException
                                        // as its InnerException.
                                        if (!(e is IOException || e is ThreadAbortException))
                                                throw;

                                        Logger.Log.Debug ("Bailing out of HandleConnection -- shutdown requested");
                                        Server.MarkHandlerAsKilled (this);
                                        Shutdown.WorkerFinished (network_data);
                                        return;
                                }

                                total_bytes += bytes_read;

                                if (bytes_read > 0) {
                                        // 0xff signifies end of message
                                        end_index = ArrayFu.IndexOfByte (network_data, (byte) 0xff);

                                        buffer_stream.Write (network_data, 0,
                                                             end_index == -1 ? bytes_read : end_index);
                                }
                        } while (bytes_read > 0 && end_index == -1);

                        // Something just connected to our socket and then
                        // hung up.  The IndexHelper (among other things) does
                        // this to check that a server is still running.  It's
                        // no big deal, so just clean up and close without
                        // running any handlers.
                        if (total_bytes == 0) {
                                force_close_connection = true;
                                goto cleanup;
                        }

                        buffer_stream.Seek (0, SeekOrigin.Begin);

                        try {
                                RequestWrapper wrapper = (RequestWrapper) req_serializer.Deserialize (buffer_stream);
                                
                                req = wrapper.Message;
                        } catch (Exception e) {
                                resp = new ErrorResponse (e);
                                force_close_connection = true;
                        }

                        // If XmlSerializer can't deserialize the payload, we
                        // may get a null payload and not an exception.  Or
                        // maybe the client just didn't send one.
                        if (req == null && resp == null) {
                                resp = new ErrorResponse ("Missing payload");
                                force_close_connection = true;
                        }

                        // And if there are no errors, execute the command
                        if (resp == null) {

                                RequestMessageExecutor exec;
                                exec = Server.GetExecutor (req);

                                if (exec == null) {
                                        resp = new ErrorResponse (String.Format ("No handler available for {0}", req.GetType ()));
                                        force_close_connection = true;
                                } else if (req.Keepalive) {
                                        this.executor = exec;
                                        exec.AsyncResponseEvent += OnAsyncResponse;
                                }

                                resp = exec.Execute (req);
                        }

                        // It's okay if the response is null; this means
                        // that keepalive is set and that we'll be sending
                        // back responses asynchronously.  First, enforce
                        // that the response is not null if keepalive isn't
                        // set.
                        if (resp == null && !req.Keepalive)
                                resp = new ErrorResponse ("No response available, but keepalive is not set");

                        if (resp != null) {
                                //Logger.Log.Debug ("Sending response of type {0}", resp.GetType ());
                                if (!this.SendResponse (resp))
                                        force_close_connection = true;
                        }

                cleanup:
                        buffer_stream.Close ();

                        if (force_close_connection || !req.Keepalive)
                                Close ();
                        else
                                SetupWatch ();

                        Server.MarkHandlerAsKilled (this);
                        Shutdown.WorkerFinished (network_data);
                }
        }

        public class Server {

                private string socket_path;
                private UnixListener listener;
                private static Hashtable live_handlers = new Hashtable ();
                private bool running = false;

                public Server (string name)
                {
                        ScanAssemblyForExecutors (Assembly.GetCallingAssembly ());

                        // Use the default name when passed null
                        if (name == null)
                                name = "socket";

                        this.socket_path = Path.Combine (PathFinder.GetRemoteStorageDir (true), name);
                        this.listener = new UnixListener (this.socket_path);
                }

                public Server () : this (null)
                {

                }

                static Server ()
                {
                        ScanAssemblyForExecutors (Assembly.GetExecutingAssembly ());

                        Shutdown.ShutdownEvent += OnShutdown;
                }

                static internal void MarkHandlerAsKilled (ConnectionHandler handler)
                {
                        lock (live_handlers) {
                                live_handlers.Remove (handler);
                        }
                }

                private static void OnShutdown ()
                {
                        lock (live_handlers) {
                                foreach (ConnectionHandler handler in live_handlers.Values) {
                                        Logger.Log.Debug ("CancelIfBlocking {0}", handler);
                                        handler.CancelIfBlocking ();
                                }
                        }
                }

                private void Run ()
                {
                        this.listener.Start ();
                        this.running = true;

                        Shutdown.WorkerStart (this, String.Format ("server '{0}'", socket_path));

                        while (this.running) {
                                UnixClient client;
                                try {
                                        // This will block for an incoming connection.
                                        // FIXME: But not really, it'll only wait a second.
                                        // see the FIXME in UnixListener for more info.
                                        client = this.listener.AcceptUnixClient ();
                                } catch (SocketException) {
                                        // If the listener is stopped while we
                                        // wait for a connection, a
                                        // SocketException is thrown.
                                        break;
                                }

                                // FIXME: This is a hack to work around a mono
                                // bug.  See the FIXMEs in UnixListener.cs for
                                // more info, but client should never be null,
                                // because AcceptUnixClient() should be
                                // throwing a SocketException when the
                                // listener is shut down.  So when that is
                                // fixed, remove the if conditional.

                                // If client is null, the socket timed out.
                                if (client != null) {
                                        ConnectionHandler handler = new ConnectionHandler (client);
                                        lock (live_handlers)
                                                live_handlers [handler] = handler;
                                        ExceptionHandlingThread.Start (new ThreadStart (handler.HandleConnection));
                                }
                        }
                        
                        Shutdown.WorkerFinished (this);

                        Logger.Log.Debug ("Server '{0}' shut down", this.socket_path);
                }

                public void Start ()
                {
                        ExceptionHandlingThread.Start (new ThreadStart (this.Run));
                }

                public void Stop ()
                {
                        this.running = false;
                        this.listener.Stop ();
                        File.Delete (this.socket_path);
                }

                //////////////////////////////////////////////////////////////////////////////

                //
                // Code to dispatch requests to the correct RequestMessageExecutor.
                //
                
                public delegate ResponseMessage RequestMessageHandler (RequestMessage msg);

                // A simple wrapper class to turn a RequestMessageHandler delegate into
                // a RequestMessageExecutor.
                private class SimpleRequestMessageExecutor : RequestMessageExecutor {

                        RequestMessageHandler handler;
                        
                        public SimpleRequestMessageExecutor (RequestMessageHandler handler)
                        {
                                this.handler = handler;
                        }

                        public override ResponseMessage Execute (RequestMessage req)
                        {
                                return this.handler (req);
                        }
                }

                static private Hashtable scanned_assemblies = new Hashtable ();
                static private Hashtable request_type_to_handler = new Hashtable ();
                static private Hashtable request_type_to_executor_type = new Hashtable ();

                static public void RegisterRequestMessageHandler (Type request_type, RequestMessageHandler handler)
                {
                        request_type_to_handler [request_type] = handler;
                }

                static public void ScanAssemblyForExecutors (Assembly assembly)
                {
                        if (scanned_assemblies.Contains (assembly))
                                return;
                        scanned_assemblies [assembly] = assembly;

                        foreach (Type t in assembly.GetTypes ()) {

                                if (!t.IsSubclassOf (typeof (RequestMessageExecutor)))
                                        continue;

                                // Yes, we know it doesn't have a RequestMessageAttribute
                                if (t == typeof (SimpleRequestMessageExecutor))
                                        continue;

                                Attribute attr = Attribute.GetCustomAttribute (t, typeof (RequestMessageAttribute));

                                if (attr == null) {
                                        Logger.Log.Warn ("No handler attribute for executor {0}", t);
                                        continue;
                                }

                                RequestMessageAttribute pra = (RequestMessageAttribute) attr;

                                request_type_to_executor_type [pra.MessageType] = t;
                        }
                }

                static internal RequestMessageExecutor GetExecutor (RequestMessage req)
                {
                        Type req_type = req.GetType ();

                        RequestMessageExecutor exec = null;

                        RequestMessageHandler handler;
                        handler = request_type_to_handler [req_type] as RequestMessageHandler;

                        if (handler != null) {
                                exec = new SimpleRequestMessageExecutor (handler);
                        } else {
                                Type t = request_type_to_executor_type [req_type] as Type;
                                if (t != null)
                                        exec = (RequestMessageExecutor) Activator.CreateInstance (t);
                        }

                        return exec;
                }
                
                
        }
}