Implementing the Warmup module

- Global.asax.cs looks for static pages in ~\App_Data\Warmup
- Orchard.Warmup module contains methods to generate those pages based on
scheduled times, and content publishing

--HG--
branch : dev

src/Orchard.Web/Modules/Orchard.Warmup/Services/WarmupUpdater.cs

@@ -0,0 +1,151 @@
+using System;
+using System.IO;
+using System.Net;
+using System.Web;
+using System.Xml;
+using Orchard.ContentManagement;
+using Orchard.Environment.Warmup;
+using Orchard.FileSystems.AppData;
+using Orchard.FileSystems.LockFile;
+using Orchard.Logging;
+using Orchard.Services;
+using Orchard.Warmup.Models;
+
+namespace Orchard.Warmup.Services {
+    public class WarmupUpdater : IWarmupUpdater {
+        private readonly IOrchardServices _orchardServices;
+        private readonly ILockFileManager _lockFileManager;
+        private readonly IClock _clock;
+        private readonly IAppDataFolder _appDataFolder;
+        private readonly IWebDownloader _webDownloader;
+        private const string BaseFolder = "Warmup";
+        private const string WarmupFilename = "warmup.txt";
+        private readonly string _lockFilename;
+
+        public WarmupUpdater(
+            IOrchardServices orchardServices, 
+            ILockFileManager lockFileManager,
+            IClock clock,
+            IAppDataFolder appDataFolder,
+            IWebDownloader webDownloader) {
+            _orchardServices = orchardServices;
+            _lockFileManager = lockFileManager;
+            _clock = clock;
+            _appDataFolder = appDataFolder;
+            _webDownloader = webDownloader;
+            _lockFilename = _appDataFolder.Combine(BaseFolder, WarmupFilename + ".lock");
+
+            Logger = NullLogger.Instance;
+        }
+
+        public ILogger Logger { get; set; }
+
+        public void EnsureGenerate() {
+            var baseUrl = _orchardServices.WorkContext.CurrentSite.BaseUrl;
+            var part = _orchardServices.WorkContext.CurrentSite.As<WarmupSettingsPart>();
+
+            // do nothing while the base url setting is not defined, or if there is no page defined
+            if (String.IsNullOrWhiteSpace(baseUrl) || String.IsNullOrWhiteSpace(part.Urls)) {
+                return;
+            }
+
+            // prevent multiple appdomains from rebuilding the static page concurrently (e.g., command line)
+            ILockFile lockFile = null;
+            if (!_lockFileManager.TryAcquireLock(_lockFilename, ref lockFile)) {
+                return;
+            }
+
+            using (lockFile) {
+
+                // check if we need to regenerate the pages by reading the last time it has been done
+                // 1- if the warmup file doesn't exists, generate the pages
+                // 2- otherwise, if the scheduled generation option is on, check if the delay is over
+                var warmupPath = _appDataFolder.Combine(BaseFolder, WarmupFilename);
+                if(_appDataFolder.FileExists(warmupPath)) {
+                    try {
+                        var warmupContent = _appDataFolder.ReadFile(warmupPath);
+                        var expired = XmlConvert.ToDateTimeOffset(warmupContent).AddMinutes(part.Delay);
+                        if (expired > _clock.UtcNow) {
+                            return;
+                        }
+                    }
+                    catch {
+                        // invalid file, delete continue processing
+                        _appDataFolder.DeleteFile(warmupPath);
+                    }
+                }
+
+                // delete existing static page files
+                foreach (var filename in _appDataFolder.ListFiles(BaseFolder)) {
+                    var prefix = _appDataFolder.Combine(BaseFolder, "http");
+
+                    // delete only static page files
+                    if (!filename.StartsWith(prefix, StringComparison.OrdinalIgnoreCase)) {
+                        continue;
+                    }
+
+                    try {
+                        _appDataFolder.DeleteFile(filename);
+                    }
+                    catch(Exception e) {
+                        // ignore files which could not be deleted
+                        Logger.Error(e, "Could not delete file {0}", filename);
+                    }
+                }
+
+                // loop over every relative url to generate the contents
+                using (var urlReader = new StringReader(part.Urls)) {
+                    string relativeUrl;
+                    while (null != (relativeUrl = urlReader.ReadLine())) {
+                        string url = null;
+                        relativeUrl = relativeUrl.Trim();
+
+                        try {
+                            url = VirtualPathUtility.RemoveTrailingSlash(baseUrl) + relativeUrl;
+                            var download = _webDownloader.Download(url);
+
+                            if (download != null && download.StatusCode == HttpStatusCode.OK) {
+                                var filename = WarmupUtility.EncodeUrl(url);
+                                var path = _appDataFolder.Combine(BaseFolder, filename);
+                                _appDataFolder.CreateFile(path, download.Content);
+
+                                // if the base url contains http://www, then also render the www-less one
+
+                                if (url.StartsWith("http://www.", StringComparison.OrdinalIgnoreCase)) {
+                                    url = "http://" + url.Substring("http://www.".Length);
+                                    filename = WarmupUtility.EncodeUrl(url);
+                                    path = _appDataFolder.Combine(BaseFolder, filename);
+                                    _appDataFolder.CreateFile(path, download.Content);
+                                }
+
+                            }
+                        }
+                        catch (Exception e) {
+                            Logger.Error(e, "Could not extract warmup page content for: ", url);
+                        }
+                    }
+                }
+
+                // finally write the time the generation has been executed
+                _appDataFolder.CreateFile(warmupPath, XmlConvert.ToString(_clock.UtcNow, XmlDateTimeSerializationMode.Utc));
+            }
+        }
+
+        public void Generate() {
+            // prevent multiple appdomains from rebuilding the static page concurrently (e.g., command line)
+            ILockFile lockFile = null;
+            if (!_lockFileManager.TryAcquireLock(_lockFilename, ref lockFile)) {
+                return;
+            }
+
+            using (lockFile) {
+                var warmupPath = _appDataFolder.Combine(BaseFolder, WarmupFilename);
+                if (_appDataFolder.FileExists(warmupPath)) {
+                    _appDataFolder.DeleteFile(warmupPath);
+                }
+            }
+
+            EnsureGenerate();
+        }
+    }
+}