Linux - Support for container restart trigger (projectkudu#2529)

Linux - Support for container restart trigger

Linux App Service now supports a generic file-based communication mechanism
for requesting a restart of the app container. This was previously implemented
in a limited fashion only for the "Docker CI" webhook. This generalizes the
implementation and also requests a restart after a git deployment by default,
in addition to receipt of a Docker webhook request.

.gitattributes

@@ -1,3 +1,5 @@
+.gitattributes text=auto
+
 *.doc  diff=astextplain
 *.DOC	diff=astextplain
 *.docx	diff=astextplain
@@ -47,4 +49,5 @@
 *.fsproj text=auto
 *.dbproj text=auto
 *.sln text=auto eol=crlf
-*.sh text eol=lf
+*.sh text eol=lf
+*.resx text=auto

Kudu.Contracts/Settings/DeploymentSettingsExtension.cs

@@ -218,5 +218,19 @@ public static bool TouchWebConfigAfterDeployment(this IDeploymentSettingsManager
         {
             return settings.GetValue(SettingsKeys.TouchWebConfigAfterDeployment) != "0";
         }
+
+        public static bool IsDockerCiEnabled(this IDeploymentSettingsManager settings)
+        {
+            string value = settings.GetValue(SettingsKeys.DockerCiEnabled);
+            return StringUtils.IsTrueLike(value);
+        }
+
+        public static bool RestartAppContainerOnGitDeploy(this IDeploymentSettingsManager settings)
+        {
+            string value = settings.GetValue(SettingsKeys.LinuxRestartAppContainerAfterDeployment);
+
+            // Default is true
+            return value == null || StringUtils.IsTrueLike(value);
+        }
     }
 }

Kudu.Contracts/Settings/SettingsKeys.cs

@@ -39,5 +39,7 @@ public static class SettingsKeys
         public const string DisableDeploymentOnPush = "SCM_DISABLE_DEPLOY_ON_PUSH";
         public const string TouchWebConfigAfterDeployment = "SCM_TOUCH_WEBCONFIG_AFTER_DEPLOYMENT";
         public const string MaxRandomDelayInSec = "SCM_MAX_RANDOM_START_DELAY";
+        public const string DockerCiEnabled = "DOCKER_ENABLE_CI";
+        public const string LinuxRestartAppContainerAfterDeployment = "SCM_RESTART_APP_CONTAINER_AFTER_DEPLOYMENT";
     }
 }

Kudu.Core/Deployment/DeploymentManager.cs

@@ -34,6 +34,7 @@ public class DeploymentManager : IDeploymentManager
         private readonly IDeploymentStatusManager _status;
         private readonly IWebHooksManager _hooksManager;
 
+        private const string RestartTriggerReason = "App deployment";
         private const string XmlLogFile = "log.xml";
         public const string TextLogFile = "log.log";
         private const string TemporaryDeploymentIdPrefix = "temp-";
@@ -225,6 +226,12 @@ public async Task DeployAsync(IRepository repository, ChangeSet changeSet, strin
 
                     // Perform the build deployment of this changeset
                     await Build(changeSet, tracer, deployStep, repository, deploymentAnalytics);
+
+                    if (!OSDetector.IsOnWindows() && _settings.RestartAppContainerOnGitDeploy())
+                    {
+                        logger.Log(Resources.Log_TriggeringContainerRestart);
+                        LinuxContainerRestartTrigger.RequestContainerRestart(_environment, RestartTriggerReason);
+                    }
                 }
                 catch (Exception ex)
                 {

Kudu.Core/Infrastructure/LinuxContainerRestartTrigger.cs

@@ -0,0 +1,42 @@
+using System;
+using System.Globalization;
+using System.IO;
+using Kudu.Core.Helpers;
+
+namespace Kudu.Core.Infrastructure
+{
+    // Utility for touching the restart trigger file on Linux, which will restart the
+    // site container.
+    // Contents of the trigger file are irrelevant but this leaves a small explanation for
+    // users who stumble on it.
+    public static class LinuxContainerRestartTrigger
+    {
+        private const string CONFIG_DIR_NAME = "config";
+        private const string TRIGGER_FILENAME = "restartTrigger.txt";
+
+        private static readonly string FILE_CONTENTS_FORMAT = String.Concat(
+            "Modifying this file will trigger a restart of the app container.",
+            System.Environment.NewLine, System.Environment.NewLine,
+            "The last modification Kudu made to this file was at {0}, for the following reason: {1}.",
+            System.Environment.NewLine);
+
+        public static void RequestContainerRestart(IEnvironment environment, string reason)
+        {
+            if (OSDetector.IsOnWindows())
+            {
+                throw new NotSupportedException("RequestContainerRestart not supported on Windows");
+            }
+
+            var restartTriggerPath = Path.Combine(environment.SiteRootPath, CONFIG_DIR_NAME, TRIGGER_FILENAME);
+
+            FileSystemHelpers.CreateDirectory(Path.GetDirectoryName(restartTriggerPath));
+
+            var fileContents = String.Format(
+                FILE_CONTENTS_FORMAT,
+                DateTimeOffset.UtcNow.ToString("o", CultureInfo.InvariantCulture),
+                reason);
+
+            FileSystemHelpers.WriteAllText(restartTriggerPath, fileContents);
+        }
+    }
+}

Kudu.Core/Kudu.Core.csproj

@@ -254,6 +254,7 @@
     <Compile Include="Infrastructure\IFileSystemWatcher.cs" />
     <Compile Include="Infrastructure\InstanceIdUtility.cs" />
     <Compile Include="Infrastructure\IServerConfiguration.cs" />
+    <Compile Include="Infrastructure\LinuxContainerRestartTrigger.cs" />
     <Compile Include="Infrastructure\NaiveFileSystemWatcher.cs" />
     <Compile Include="Infrastructure\SecurityUtility.cs" />
     <Compile Include="Infrastructure\PathUtils\PathLinuxUtility.cs" />

Kudu.Core/Resources.resx

@@ -225,4 +225,7 @@
   <data name="Error_FailedToLocateBash" xml:space="preserve">
     <value>Unable to locate 'bash.exe'. Make sure it is installed.</value>
   </data>
+  <data name="Log_TriggeringContainerRestart" xml:space="preserve">
+    <value>App container will begin restart within 10 seconds.</value>
+  </data>
 </root>

Kudu.Services/Docker/DockerController.cs

@@ -1,21 +1,27 @@
-using Kudu.Core.Helpers;
-using Kudu.Core.Tracing;
-using System;
-using System.IO;
+using System;
 using System.Net;
 using System.Net.Http;
 using System.Web.Http;
+using Kudu.Core.Helpers;
+using Kudu.Core.Tracing;
+using Kudu.Contracts.Settings;
+using Kudu.Core.Infrastructure;
+using Kudu.Core;
 
 namespace Kudu.Services.Docker
 {
     public class DockerController : ApiController
     {
-        const string TimestampDirectory = "/home/site/config";
-        ITraceFactory _traceFactory;
+        private const string RESTART_REASON = "Docker CI webhook";
+        private readonly ITraceFactory _traceFactory;
+        private readonly IDeploymentSettingsManager _settings;
+        private readonly IEnvironment _environment;
 
-        public DockerController(ITraceFactory traceFactory)
+        public DockerController(ITraceFactory traceFactory, IDeploymentSettingsManager settings, IEnvironment environment)
         {
             _traceFactory = traceFactory;
+            _settings = settings;
+            _environment = environment;
         }
 
         [HttpPost]
@@ -27,21 +33,22 @@ public HttpResponseMessage ReceiveHook()
             }
 
             var tracer = _traceFactory.GetTracer();
-            using (tracer.Step("Docker.SetDockerTimestamp"))
+            using (tracer.Step("Docker.ReceiveWebhook"))
             {
-                string timestampPath = Path.Combine(TimestampDirectory, "dockerTimestamp.txt");
                 try
                 {
-                    Directory.CreateDirectory(Path.GetDirectoryName((timestampPath)));
-                    File.WriteAllText(timestampPath, DateTime.UtcNow.ToString());
+                    if (_settings.IsDockerCiEnabled())
+                    {
+                        LinuxContainerRestartTrigger.RequestContainerRestart(_environment, RESTART_REASON);
+                    }
                 }
                 catch (Exception e)
                 {
-                    return Request.CreateResponse(HttpStatusCode.InternalServerError, e.Message);
+                    return Request.CreateResponse(HttpStatusCode.InternalServerError, e.Message); 
                 }
-
-                return Request.CreateResponse(HttpStatusCode.OK);
             }
+
+            return Request.CreateResponse(HttpStatusCode.OK);
         }
     }
 }