Add support for file event subscribers

Author: ankitkumarr

release_notes.md

@@ -3,5 +3,7 @@
 - My change description (#PR)
 -->
 
+- Add a new host.json property "watchFiles" for restarting the Host when files are modified.
+
 **Release sprint:** Sprint 83
 [ [bugs](https://github.com/Azure/azure-functions-host/issues?q=is%3Aissue+milestone%3A%22Functions+Sprint+83%22+label%3Abug+is%3Aclosed) | [features](https://github.com/Azure/azure-functions-host/issues?q=is%3Aissue+milestone%3A%22Functions+Sprint+83%22+label%3Afeature+is%3Aclosed) ]

src/WebJobs.Script.WebHost/FileMonitoringService.cs

@@ -248,9 +248,7 @@ private void OnFileChanged(FileSystemEventArgs e)
                     Shutdown();
                 }
             }
-            else if (string.Compare(fileName, ScriptConstants.HostMetadataFileName, StringComparison.OrdinalIgnoreCase) == 0 ||
-                string.Compare(fileName, ScriptConstants.FunctionMetadataFileName, StringComparison.OrdinalIgnoreCase) == 0 ||
-                string.Compare(fileName, ScriptConstants.ProxyMetadataFileName, StringComparison.OrdinalIgnoreCase) == 0)
+            else if (_scriptOptions.WatchFiles.Any(f => string.Equals(fileName, f, StringComparison.OrdinalIgnoreCase)))
             {
                 changeDescription = "File";
             }

src/WebJobs.Script/Config/HostJsonFileConfigurationSource.cs

@@ -49,7 +49,7 @@ public class HostJsonFileConfigurationProvider : ConfigurationProvider
         {
             private static readonly string[] WellKnownHostJsonProperties = new[]
             {
-                "version", "functionTimeout", "functions", "http", "watchDirectories", "queues", "serviceBus",
+                "version", "functionTimeout", "functions", "http", "watchDirectories", "watchFiles", "queues", "serviceBus",
                 "eventHub", "singleton", "logging", "aggregator", "healthMonitor", "extensionBundle", "managedDependencies",
                 "customHandler", "httpWorker"
             };

src/WebJobs.Script/Config/ScriptHostOptionsSetup.cs

@@ -30,6 +30,11 @@ public void Configure(ScriptJobHostOptions options)
             // Add the standard built in watched directories set to any the user may have specified
             options.WatchDirectories.Add("node_modules");
 
+            // Add the default files we need to watch
+            options.WatchFiles.Add(ScriptConstants.HostMetadataFileName);
+            options.WatchFiles.Add(ScriptConstants.FunctionMetadataFileName);
+            options.WatchFiles.Add(ScriptConstants.ProxyMetadataFileName);
+
             // Set default logging mode
             options.FileLoggingMode = FileLoggingMode.DebugOnly;
 

src/WebJobs.Script/Config/ScriptJobHostOptions.cs

@@ -19,6 +19,7 @@ public ScriptJobHostOptions()
             FileLoggingMode = FileLoggingMode.Never;
             InstanceId = Guid.NewGuid().ToString();
             WatchDirectories = new Collection<string>();
+            WatchFiles = new Collection<string>();
         }
 
         /// <summary>
@@ -70,6 +71,14 @@ public string RootScriptPath
         /// </summary>
         public ICollection<string> WatchDirectories { get; set; }
 
+        /// <summary>
+        /// Gets or sets the collection of file names that
+        /// should be monitored for changes. If FileWatchingEnabled is true, these files
+        /// will be monitored. When a file from this list is added/modified/deleted,
+        /// the host will restart.
+        /// </summary>
+        public ICollection<string> WatchFiles { get; set; }
+
         /// <summary>
         /// Gets or sets a value governing when logs should be written to disk.
         /// When enabled, logs will be written to the directory specified by

test/WebJobs.Script.Tests/Configuration/ScriptHostOptionsSetupTests.cs

@@ -35,6 +35,11 @@ public void Configure_FileWatching()
             Assert.Equal(1, options.WatchDirectories.Count);
             Assert.Equal("node_modules", options.WatchDirectories.ElementAt(0));
 
+            Assert.Equal(3, options.WatchFiles.Count);
+            Assert.Contains("host.json", options.WatchFiles);
+            Assert.Contains("function.json", options.WatchFiles);
+            Assert.Contains("proxies.json", options.WatchFiles);
+
             // File watching disabled
             settings[ConfigurationPath.Combine(ConfigurationSectionNames.JobHost, "fileWatchingEnabled")] = bool.FalseString;
 
@@ -49,6 +54,8 @@ public void Configure_FileWatching()
             settings[ConfigurationPath.Combine(ConfigurationSectionNames.JobHost, "fileWatchingEnabled")] = bool.TrueString;
             settings[ConfigurationPath.Combine(ConfigurationSectionNames.JobHost, "watchDirectories", "0")] = "Shared";
             settings[ConfigurationPath.Combine(ConfigurationSectionNames.JobHost, "watchDirectories", "1")] = "Tools";
+            settings[ConfigurationPath.Combine(ConfigurationSectionNames.JobHost, "watchFiles", "0")] = "myFirstFile.ext";
+            settings[ConfigurationPath.Combine(ConfigurationSectionNames.JobHost, "watchFiles", "1")] = "mySecondFile.ext";
 
             setup = CreateSetupWithConfiguration(settings);
 
@@ -60,6 +67,13 @@ public void Configure_FileWatching()
             Assert.Equal("node_modules", options.WatchDirectories.ElementAt(0));
             Assert.Equal("Shared", options.WatchDirectories.ElementAt(1));
             Assert.Equal("Tools", options.WatchDirectories.ElementAt(2));
+
+            Assert.Equal(5, options.WatchFiles.Count);
+            Assert.Contains("host.json", options.WatchFiles);
+            Assert.Contains("function.json", options.WatchFiles);
+            Assert.Contains("proxies.json", options.WatchFiles);
+            Assert.Contains("myFirstFile.ext", options.WatchFiles);
+            Assert.Contains("mySecondFile.ext", options.WatchFiles);
         }
 
         [Fact(Skip = "ApplyConfiguration no longer exists. Validate logic (moved to HostJsonFileConfigurationSource)")]

test/WebJobs.Script.Tests/FileMonitoringServiceTests.cs

@@ -1,6 +1,7 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the MIT License. See License.txt in the project root for license information.
 
+using System;
 using System.IO;
 using System.Threading;
 using System.Threading.Tasks;
@@ -56,6 +57,53 @@ public void InitializesGetDirectorySnapshot()
             }
         }
 
+        [Fact]
+        public static async Task HostRestarts_OnWatchFilesChange()
+        {
+            using (var directory = new TempDirectory())
+            {
+                // Setup
+                string tempDir = directory.Path;
+                Directory.CreateDirectory(Path.Combine(tempDir, "Host"));
+                File.Create(Path.Combine(tempDir, "my_watched_file.txt"));
+                File.Create(Path.Combine(tempDir, "my_ignored_file.txt"));
+
+                var jobHostOptions = new ScriptJobHostOptions
+                {
+                    RootLogPath = tempDir,
+                    RootScriptPath = tempDir,
+                    FileWatchingEnabled = true,
+                    WatchFiles = { "my_watched_file.txt" }
+                };
+
+                var loggerFactory = new LoggerFactory();
+                var mockApplicationLifetime = new Mock<IApplicationLifetime>();
+                var mockScriptHostManager = new Mock<IScriptHostManager>();
+                var mockEventManager = new ScriptEventManager();
+                var environment = new TestEnvironment();
+
+                // Act
+                FileMonitoringService fileMonitoringService = new FileMonitoringService(new OptionsWrapper<ScriptJobHostOptions>(jobHostOptions),
+                    loggerFactory, mockEventManager, mockApplicationLifetime.Object, mockScriptHostManager.Object, environment);
+                await fileMonitoringService.StartAsync(new CancellationToken(canceled: false));
+
+                var ignoredFileEventArgs = new FileSystemEventArgs(WatcherChangeTypes.Created, tempDir, "my_ignored_file.txt");
+                FileEvent ignoredFileEvent = new FileEvent("ScriptFiles", ignoredFileEventArgs);
+
+                var watchedFileEventArgs = new FileSystemEventArgs(WatcherChangeTypes.Created, tempDir, "my_watched_file.txt");
+                FileEvent watchedFileEvent = new FileEvent("ScriptFiles", watchedFileEventArgs);
+
+                // Test
+                mockEventManager.Publish(ignoredFileEvent);
+                await Task.Delay(TimeSpan.FromSeconds(3));
+                mockScriptHostManager.Verify(m => m.RestartHostAsync(default), Times.Never);
+
+                mockEventManager.Publish(watchedFileEvent);
+                await Task.Delay(TimeSpan.FromSeconds(3));
+                mockScriptHostManager.Verify(m => m.RestartHostAsync(default));
+            }
+        }
+
         [Theory]
         [InlineData("app_offline.htm", 150, true, false)]
         [InlineData("app_offline.htm", 10, true, false)]
@@ -75,7 +123,8 @@ public static async Task TestAppOfflineDebounceTime(string fileName, int delayIn
                 {
                     RootLogPath = tempDir,
                     RootScriptPath = tempDir,
-                    FileWatchingEnabled = true
+                    FileWatchingEnabled = true,
+                    WatchFiles = { "host.json" }
                 };
                 var loggerFactory = new LoggerFactory();
                 var mockApplicationLifetime = new Mock<IApplicationLifetime>();