Disable optional upgrades in PowerShell function apps (#779)

* Add AutomaticUpgradesAreDisabled message

* Disable optional upgrades

* Update test

Author: Francisco-Gamino

src/DependencyManagement/BackgroundDependencySnapshotMaintainer.cs

@@ -20,6 +20,9 @@ internal class BackgroundDependencySnapshotMaintainer : IBackgroundDependencySna
         private TimeSpan MaxBackgroundUpgradePeriod { get; } =
             PowerShellWorkerConfiguration.GetTimeSpan("MDMaxBackgroundUpgradePeriod") ?? TimeSpan.FromDays(7);
 
+        private bool EnableAutomaticUpgrades { get; } =
+            PowerShellWorkerConfiguration.GetBoolean("MDEnableAutomaticUpgrades") ?? false;
+
         private readonly IDependencyManagerStorage _storage;
         private readonly IDependencySnapshotInstaller _installer;
         private readonly IDependencySnapshotPurger _purger;
@@ -42,6 +45,16 @@ public void Start(string currentSnapshotPath, DependencyManifestEntry[] dependen
 
             _purger.SetCurrentlyUsedSnapshot(currentSnapshotPath, logger);
 
+            if (!EnableAutomaticUpgrades)
+            {
+                logger.Log(
+                    isUserOnlyLog: false,
+                    RpcLog.Types.Level.Warning,
+                    PowerShellWorkerStrings.AutomaticUpgradesAreDisabled);
+
+                return;
+            }
+
             _installAndPurgeTimer = new Timer(
                                             _ => InstallAndPurgeSnapshots(PowerShell.Create, logger),
                                             state: null,

src/DependencyManagement/DependencyManager.cs

@@ -41,6 +41,9 @@ internal class DependencyManager : IDisposable
 
         private Task _dependencyInstallationTask;
 
+        private bool EnableAutomaticUpgrades { get; } =
+            PowerShellWorkerConfiguration.GetBoolean("MDEnableAutomaticUpgrades") ?? false;
+
         #endregion
 
         public DependencyManager(
@@ -198,6 +201,16 @@ internal Exception InstallFunctionAppDependencies(PowerShell firstPwsh, Func<Pow
                     RpcLog.Types.Level.Trace,
                     PowerShellWorkerStrings.AcceptableFunctionAppDependenciesAlreadyInstalled);
 
+                if (!EnableAutomaticUpgrades)
+                {
+                    logger.Log(
+                        isUserOnlyLog: false,
+                        RpcLog.Types.Level.Warning,
+                        PowerShellWorkerStrings.AutomaticUpgradesAreDisabled);
+
+                    return null;
+                }
+
                 // Background installation: can't use the firstPwsh runspace because it belongs
                 // to the pool used to run functions code, so create a new runspace.
                 _nextSnapshotPath = _backgroundSnapshotMaintainer.InstallAndPurgeSnapshots(pwshFactory, logger);

src/resources/PowerShellWorkerStrings.resx

@@ -322,4 +322,7 @@
   <data name="PowerShell6EndOfLifeWarning" xml:space="preserve">
     <value>The Function app uses PowerShell Core 6. Your Function app is still supported, but this version of PowerShell reached end of life, so it is strongly recommended that you migrate the Function app to PowerShell 7. For more details, see https://aka.ms/functions-powershell-6-to-7.</value>
   </data>
+  <data name="AutomaticUpgradesAreDisabled" xml:space="preserve">
+    <value>Automatic upgrades are disabled in PowerShell 6 function apps. To enable this functionality back, please migrate your function app to PowerShell 7. For more details, see https://aka.ms/functions-powershell-6-to-7.</value>
+  </data>
 </root>

test/Unit/DependencyManagement/DependencyManagerTests.cs

@@ -163,40 +163,49 @@ public void StartDependencyInstallationIfNeeded_InstallsSnapshotInForeground_Whe
         [Fact]
         public void StartDependencyInstallationIfNeeded_InvokesBackgroundMaintainer_WhenAcceptableDependenciesAlreadyInstalled()
         {
-            _mockInstalledDependenciesLocator.Setup(_ => _.GetPathWithAcceptableDependencyVersionsInstalled())
-                .Returns("AlreadyInstalled");
-            _mockStorage.Setup(_ => _.GetDependencies()).Returns(GetAnyNonEmptyDependencyManifestEntries());
+            try
+            {
+                Environment.SetEnvironmentVariable("MDEnableAutomaticUpgrades", "true");
 
-            var firstPowerShellRunspace = PowerShell.Create();
-            Func<PowerShell> powerShellFactory = PowerShell.Create;
+                _mockInstalledDependenciesLocator.Setup(_ => _.GetPathWithAcceptableDependencyVersionsInstalled())
+                    .Returns("AlreadyInstalled");
+                _mockStorage.Setup(_ => _.GetDependencies()).Returns(GetAnyNonEmptyDependencyManifestEntries());
 
-            _mockStorage.Setup(_ => _.SnapshotExists("AlreadyInstalled")).Returns(true);
+                var firstPowerShellRunspace = PowerShell.Create();
+                Func<PowerShell> powerShellFactory = PowerShell.Create;
 
-            _mockBackgroundDependencySnapshotMaintainer.Setup(
-                _ => _.InstallAndPurgeSnapshots(It.IsAny<Func<PowerShell>>(), It.IsAny<ILogger>()))
-                .Returns("NewSnapshot");
+                _mockStorage.Setup(_ => _.SnapshotExists("AlreadyInstalled")).Returns(true);
 
-            using (var dependencyManager = CreateDependencyManagerWithMocks())
-            {
-                dependencyManager.Initialize(_mockLogger.Object);
-                dependencyManager.StartDependencyInstallationIfNeeded(firstPowerShellRunspace, powerShellFactory, _mockLogger.Object);
-                var hadToWait = dependencyManager.WaitForDependenciesAvailability(() => _mockLogger.Object);
+                _mockBackgroundDependencySnapshotMaintainer.Setup(
+                    _ => _.InstallAndPurgeSnapshots(It.IsAny<Func<PowerShell>>(), It.IsAny<ILogger>()))
+                    .Returns("NewSnapshot");
 
-                Assert.False(hadToWait);
-                Assert.Equal("NewSnapshot", dependencyManager.WaitForBackgroundDependencyInstallationTaskCompletion());
+                using (var dependencyManager = CreateDependencyManagerWithMocks())
+                {
+                    dependencyManager.Initialize(_mockLogger.Object);
+                    dependencyManager.StartDependencyInstallationIfNeeded(firstPowerShellRunspace, powerShellFactory, _mockLogger.Object);
+                    var hadToWait = dependencyManager.WaitForDependenciesAvailability(() => _mockLogger.Object);
 
-                _mockBackgroundDependencySnapshotMaintainer.Verify(
-                    _ => _.InstallAndPurgeSnapshots(powerShellFactory, _mockLogger.Object),
+                    Assert.False(hadToWait);
+                    Assert.Equal("NewSnapshot", dependencyManager.WaitForBackgroundDependencyInstallationTaskCompletion());
+
+                    _mockBackgroundDependencySnapshotMaintainer.Verify(
+                        _ => _.InstallAndPurgeSnapshots(powerShellFactory, _mockLogger.Object),
+                        Times.Once);
+                }
+
+                _mockLogger.Verify(
+                    _ => _.Log(
+                        false,
+                        LogLevel.Trace,
+                        It.Is<string>(message => message.Contains(PowerShellWorkerStrings.AcceptableFunctionAppDependenciesAlreadyInstalled)),
+                        It.IsAny<Exception>()),
                     Times.Once);
             }
-
-            _mockLogger.Verify(
-                _ => _.Log(
-                    false,
-                    LogLevel.Trace,
-                    It.Is<string>(message => message.Contains(PowerShellWorkerStrings.AcceptableFunctionAppDependenciesAlreadyInstalled)),
-                    It.IsAny<Exception>()),
-                Times.Once);
+            finally
+            {
+                Environment.SetEnvironmentVariable("MDEnableAutomaticUpgrades", null);
+            }
         }
 
         [Fact]