Fix check for IsFileSystemReadOnly (#7295)

Update logic to determine if the filesystem is read-only. It's not sufficient to check if SCM_RUN_FROM_PACKAGE is set, the URI also needs to point to an existing blob to deduce it's a zip deployment (therefore read-only).

Author: pgombar

src/WebJobs.Script.WebHost/Configuration/LinuxScriptApplicationHostOptionsSetup.cs

@@ -0,0 +1,92 @@
+// 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.Threading;
+using Microsoft.Azure.Storage.Blob;
+using Microsoft.Extensions.Options;
+using static Microsoft.Azure.WebJobs.Script.EnvironmentSettingNames;
+
+namespace Microsoft.Azure.WebJobs.Script.WebHost.Configuration
+{
+    public class LinuxScriptApplicationHostOptionsSetup : IConfigureOptions<ScriptApplicationHostOptions>
+    {
+        private readonly IEnvironment _environment;
+        private static readonly IConfigureOptions<ScriptApplicationHostOptions> _instance = new NullSetup();
+
+        public LinuxScriptApplicationHostOptionsSetup(IEnvironment environment)
+        {
+            _environment = environment ?? throw new ArgumentNullException(nameof(environment));
+        }
+
+        internal static IConfigureOptions<ScriptApplicationHostOptions> NullInstance => _instance;
+
+        public void Configure(ScriptApplicationHostOptions options)
+        {
+            options.IsFileSystemReadOnly = IsZipDeployment(options);
+        }
+
+        private bool IsZipDeployment(ScriptApplicationHostOptions options)
+        {
+            // If the app is using app settings for run from package, we don't need to check further, it must be a zip deployment.
+            bool runFromPkgConfigured = Utility.IsValidZipSetting(_environment.GetEnvironmentVariable(AzureWebsiteZipDeployment)) ||
+                Utility.IsValidZipSetting(_environment.GetEnvironmentVariable(AzureWebsiteAltZipDeployment)) ||
+                Utility.IsValidZipSetting(_environment.GetEnvironmentVariable(AzureWebsiteRunFromPackage));
+
+            if (runFromPkgConfigured)
+            {
+                return true;
+            }
+
+            // If SCM_RUN_FROM_PACKAGE is set to a valid value and the blob exists, it's a zip deployment.
+            // We need to explicitly check if the blob exists because on Linux Consumption the app setting is always added, regardless if it's used or not.
+            var url = _environment.GetEnvironmentVariable(ScmRunFromPackage);
+            bool scmRunFromPkgConfigured = Utility.IsValidZipSetting(url) && BlobExists(url);
+            options.IsScmRunFromPackage = scmRunFromPkgConfigured;
+
+            return scmRunFromPkgConfigured;
+        }
+
+        public virtual bool BlobExists(string url)
+        {
+            if (string.IsNullOrEmpty(url))
+            {
+                return false;
+            }
+
+            try
+            {
+                CloudBlockBlob blob = new CloudBlockBlob(new Uri(url));
+
+                int attempt = 0;
+                while (true)
+                {
+                    try
+                    {
+                        return blob.Exists();
+                    }
+                    catch (Exception ex) when (!ex.IsFatal())
+                    {
+                        if (++attempt > 2)
+                        {
+                            return false;
+                        }
+                        Thread.Sleep(TimeSpan.FromSeconds(0.3));
+                    }
+                }
+            }
+            catch (Exception)
+            {
+                return false;
+            }
+        }
+
+        private class NullSetup : IConfigureOptions<ScriptApplicationHostOptions>
+        {
+            public void Configure(ScriptApplicationHostOptions options)
+            {
+                // Do nothing.
+            }
+        }
+    }
+}

src/WebJobs.Script.WebHost/Configuration/ScriptApplicationHostOptionsSetup.cs

@@ -6,6 +6,7 @@
 using Microsoft.Azure.WebJobs.Script.Configuration;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.Options;
+using static Microsoft.Azure.WebJobs.Script.EnvironmentSettingNames;
 
 namespace Microsoft.Azure.WebJobs.Script.WebHost.Configuration
 {
@@ -17,16 +18,18 @@ public class ScriptApplicationHostOptionsSetup : IConfigureNamedOptions<ScriptAp
         private readonly IOptionsMonitor<StandbyOptions> _standbyOptions;
         private readonly IDisposable _standbyOptionsOnChangeSubscription;
         private readonly IServiceProvider _serviceProvider;
+        private readonly IEnvironment _environment;
 
         public ScriptApplicationHostOptionsSetup(IConfiguration configuration, IOptionsMonitor<StandbyOptions> standbyOptions,
-            IOptionsMonitorCache<ScriptApplicationHostOptions> cache, IServiceProvider serviceProvider)
+            IOptionsMonitorCache<ScriptApplicationHostOptions> cache, IServiceProvider serviceProvider, IEnvironment environment)
         {
             _cache = cache ?? throw new ArgumentNullException(nameof(cache));
             _configuration = configuration ?? throw new ArgumentNullException(nameof(configuration));
             _standbyOptions = standbyOptions ?? throw new ArgumentNullException(nameof(standbyOptions));
             _serviceProvider = serviceProvider;
             // If standby options change, invalidate this options cache.
             _standbyOptionsOnChangeSubscription = _standbyOptions.OnChange(o => _cache.Clear());
+            _environment = environment ?? throw new ArgumentNullException(nameof(environment));
         }
 
         public void Configure(ScriptApplicationHostOptions options)
@@ -61,6 +64,15 @@ public void Configure(string name, ScriptApplicationHostOptions options)
                 options.IsSelfHost = options.IsSelfHost;
                 options.IsStandbyConfiguration = true;
             }
+
+            options.IsFileSystemReadOnly = IsZipDeployment();
+        }
+
+        private bool IsZipDeployment()
+        {
+            return Utility.IsValidZipSetting(_environment.GetEnvironmentVariable(AzureWebsiteZipDeployment)) ||
+                Utility.IsValidZipSetting(_environment.GetEnvironmentVariable(AzureWebsiteAltZipDeployment)) ||
+                Utility.IsValidZipSetting(_environment.GetEnvironmentVariable(AzureWebsiteRunFromPackage));
         }
 
         public void Dispose()

src/WebJobs.Script.WebHost/Controllers/HostController.cs

@@ -264,7 +264,7 @@ public async Task<IActionResult> SetState([FromBody] string state)
             }
             else if (desiredState == ScriptHostState.Running && currentState == ScriptHostState.Offline)
             {
-                if (_environment.IsFileSystemReadOnly())
+                if (_applicationHostOptions.Value.IsFileSystemReadOnly)
                 {
                     return BadRequest();
                 }
@@ -274,7 +274,7 @@ public async Task<IActionResult> SetState([FromBody] string state)
             }
             else if (desiredState == ScriptHostState.Offline && currentState != ScriptHostState.Offline)
             {
-                if (_environment.IsFileSystemReadOnly())
+                if (_applicationHostOptions.Value.IsFileSystemReadOnly)
                 {
                     return BadRequest();
                 }

src/WebJobs.Script.WebHost/Management/InstanceManager.cs

@@ -302,7 +302,7 @@ private async Task ApplyContext(HostAssignmentContext assignmentContext)
                         $"No {nameof(EnvironmentSettingNames.AzureFilesConnectionString)} or {nameof(EnvironmentSettingNames.AzureFilesContentShare)} configured. Azure FileShare will not be mounted. For PowerShell Functions, Managed Dependencies will not persisted across functions host instances.");
                 }
 
-                if (await pkgContext.IsRunFromPackage(_logger))
+                if (pkgContext.IsRunFromPackage(options, _logger))
                 {
                     if (azureFilesMounted)
                     {
@@ -325,7 +325,7 @@ await _runFromPackageHandler.ApplyBlobPackageContext(pkgContext, options.ScriptP
             }
             else
             {
-                if (await pkgContext.IsRunFromPackage(_logger))
+                if (pkgContext.IsRunFromPackage(options, _logger))
                 {
                     await _runFromPackageHandler.ApplyBlobPackageContext(pkgContext, options.ScriptPath, false);
                 }

src/WebJobs.Script.WebHost/Management/LinuxSpecialization/RunFromPackageCloudBlockBlobService.cs

@@ -2,19 +2,14 @@
 // Licensed under the MIT License. See License.txt in the project root for license information.
 
 using System;
-using System.Threading.Tasks;
-using Microsoft.Azure.WebJobs.Script.WebHost.Management.LinuxSpecialization;
 using Microsoft.Extensions.Logging;
 
 namespace Microsoft.Azure.WebJobs.Script.WebHost.Models
 {
     public class RunFromPackageContext
     {
-        private readonly RunFromPackageCloudBlockBlobService _runFromPackageCloudBlockBlobService;
-
-        public RunFromPackageContext(string envVarName, string url, long? packageContentLength, bool isWarmupRequest, RunFromPackageCloudBlockBlobService runFromPackageCloudBlockBlobService = null)
+        public RunFromPackageContext(string envVarName, string url, long? packageContentLength, bool isWarmupRequest)
         {
-            _runFromPackageCloudBlockBlobService = runFromPackageCloudBlockBlobService ?? new RunFromPackageCloudBlockBlobService();
             EnvironmentVariableName = envVarName;
             Url = url;
             PackageContentLength = packageContentLength;
@@ -31,14 +26,19 @@ public RunFromPackageContext(string envVarName, string url, long? packageContent
 
         public bool IsScmRunFromPackage()
         {
-            return string.Equals(EnvironmentVariableName, EnvironmentSettingNames.ScmRunFromPackage,
-                        StringComparison.OrdinalIgnoreCase);
+            return string.Equals(EnvironmentVariableName, EnvironmentSettingNames.ScmRunFromPackage, StringComparison.OrdinalIgnoreCase);
+        }
+
+        public bool IsRunFromPackage(ScriptApplicationHostOptions options, ILogger logger)
+        {
+            return (IsScmRunFromPackage() && ScmRunFromPackageBlobExists(options, logger)) || (!IsScmRunFromPackage() && !string.IsNullOrEmpty(Url) && Url != "1");
         }
 
-        public async Task<bool> IsRunFromPackage(ILogger logger)
+        private bool ScmRunFromPackageBlobExists(ScriptApplicationHostOptions options, ILogger logger)
         {
-            return (IsScmRunFromPackage() && await _runFromPackageCloudBlockBlobService.BlobExists(Url, EnvironmentVariableName, logger)) ||
-                   (!IsScmRunFromPackage() && !string.IsNullOrEmpty(Url) && Url != "1");
+            var blobExists = options.IsScmRunFromPackage;
+            logger.LogDebug($"{EnvironmentSettingNames.ScmRunFromPackage} points to an existing blob: {blobExists}");
+            return blobExists;
         }
     }
 }

src/WebJobs.Script.WebHost/Models/RunFromPackageContext.cs

@@ -91,7 +91,7 @@ public static void AddWebJobsScriptHost(this IServiceCollection services, IConfi
             services.AddLinuxContainerServices();
 
             // ScriptSettingsManager should be replaced. We're setting this here as a temporary step until
-            // broader configuaration changes are made:
+            // broader configuration changes are made:
             services.AddSingleton<ScriptSettingsManager>();
             services.AddSingleton<IEventGenerator>(p =>
             {
@@ -163,6 +163,15 @@ public static void AddWebJobsScriptHost(this IServiceCollection services, IConfi
 
             // Configuration
             services.ConfigureOptions<ScriptApplicationHostOptionsSetup>();
+            services.AddSingleton<IConfigureOptions<ScriptApplicationHostOptions>>(p =>
+            {
+                var environment = p.GetService<IEnvironment>();
+                if (environment.IsLinuxConsumption())
+                {
+                    return new LinuxScriptApplicationHostOptionsSetup(environment);
+                }
+                return LinuxScriptApplicationHostOptionsSetup.NullInstance;
+            });
             services.ConfigureOptions<StandbyOptionsSetup>();
             services.ConfigureOptions<LanguageWorkerOptionsSetup>();
             services.ConfigureOptionsWithChangeTokenSource<AppServiceOptions, AppServiceOptionsSetup, SpecializationChangeTokenSource<AppServiceOptions>>();

src/WebJobs.Script.WebHost/WebHostServiceCollectionExtensions.cs

@@ -169,7 +169,7 @@ public async Task StartAsync(CancellationToken cancellationToken)
         private void CheckFileSystem()
         {
             // Shutdown if RunFromZipFailed
-            if (_environment.IsZipDeployment(validate: false))
+            if (_environment.ZipDeploymentAppSettingsExist())
             {
                 string path = Path.Combine(_applicationHostOptions.CurrentValue.ScriptPath, ScriptConstants.RunFromPackageFailedFileName);
                 if (File.Exists(path))

src/WebJobs.Script.WebHost/WebJobsScriptHostService.cs

@@ -228,7 +228,7 @@ private JObject GetDefaultHostConfigObject()
             {
                 var hostJsonJObj = JObject.Parse("{'version': '2.0'}");
                 if (string.Equals(_configurationSource.Environment.GetEnvironmentVariable(RpcWorkerConstants.FunctionWorkerRuntimeSettingName), "powershell", StringComparison.InvariantCultureIgnoreCase)
-                    && !_configurationSource.Environment.IsFileSystemReadOnly())
+                    && !_configurationSource.HostOptions.IsFileSystemReadOnly)
                 {
                     hostJsonJObj.Add("managedDependency", JToken.Parse("{'Enabled': true}"));
                 }
@@ -238,7 +238,7 @@ private JObject GetDefaultHostConfigObject()
 
             private void TryWriteHostJson(string filePath, JObject content)
             {
-                if (!_configurationSource.Environment.IsFileSystemReadOnly())
+                if (!_configurationSource.HostOptions.IsFileSystemReadOnly)
                 {
                     try
                     {
@@ -257,7 +257,7 @@ private void TryWriteHostJson(string filePath, JObject content)
 
             private JObject TryAddBundleConfiguration(JObject content, string bundleId)
             {
-                if (!_configurationSource.Environment.IsFileSystemReadOnly())
+                if (!_configurationSource.HostOptions.IsFileSystemReadOnly)
                 {
                     string bundleConfiguration = "{ 'id': '" + bundleId + "', 'version': '[2.*, 3.0.0)'}";
                     content.Add("extensionBundle", JToken.Parse(bundleConfiguration));

src/WebJobs.Script/Config/HostJsonFileConfigurationSource.cs

@@ -31,5 +31,9 @@ public class ScriptApplicationHostOptions
         public IServiceProvider RootServiceProvider { get; set; }
 
         public bool IsStandbyConfiguration { get; internal set; }
+
+        public bool IsFileSystemReadOnly { get; set; }
+
+        public bool IsScmRunFromPackage { get; set; }
     }
 }