Retry installing Visual Studio Build Tools on failure

.github/workflows/scripts/windows/install-vsb.ps1

@@ -9,13 +9,20 @@
 ## See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
 ##
 ##===----------------------------------------------------------------------===##
+
+Import-Module $PSScriptRoot\web-request-utils.psm1
+
 $VSB='https://download.visualstudio.microsoft.com/download/pr/5536698c-711c-4834-876f-2817d31a2ef2/c792bdb0fd46155de19955269cac85d52c4c63c23db2cf43d96b9390146f9390/vs_BuildTools.exe'
 $VSB_SHA256='C792BDB0FD46155DE19955269CAC85D52C4C63C23DB2CF43D96B9390146F9390'
 Set-Variable ErrorActionPreference Stop
 Set-Variable ProgressPreference SilentlyContinue
 Write-Host -NoNewLine ('Downloading {0} ... ' -f ${VSB})
-Invoke-WebRequest -Uri $VSB -OutFile $env:TEMP\vs_buildtools.exe
-Write-Host 'SUCCESS'
+try {
+    Invoke-WebRequestWithRetry -Uri $VSB -OutFile $env:TEMP\vs_buildtools.exe
+}
+catch {
+    exit 1
+}
 Write-Host -NoNewLine ('Verifying SHA256 ({0}) ... ' -f $VSB_SHA256)
 $Hash = Get-FileHash $env:TEMP\vs_buildtools.exe -Algorithm sha256
 if ($Hash.Hash -eq $VSB_SHA256) {

.github/workflows/scripts/windows/swift/install-swift.ps1

@@ -9,6 +9,9 @@
 ## See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
 ##
 ##===----------------------------------------------------------------------===##
+
+Import-Module $PSScriptRoot\..\web-request-utils.psm1
+
 function Install-Swift {
     param (
         [string]$Url,
@@ -17,8 +20,12 @@ function Install-Swift {
     Set-Variable ErrorActionPreference Stop
     Set-Variable ProgressPreference SilentlyContinue
     Write-Host -NoNewLine ('Downloading {0} ... ' -f $url)
-    Invoke-WebRequest -Uri $url -OutFile installer.exe
-    Write-Host 'SUCCESS'
+    try {
+        Invoke-WebRequestWithRetry -Uri $url -OutFile installer.exe
+    }
+    catch {
+        exit 1
+    }
     Write-Host -NoNewLine ('Verifying SHA256 ({0}) ... ' -f $Sha256)
     $Hash = Get-FileHash installer.exe -Algorithm sha256
     if ($Hash.Hash -eq $Sha256 -or $Sha256 -eq "") {

.github/workflows/scripts/windows/web-request-utils.psm1

@@ -0,0 +1,75 @@
+##===----------------------------------------------------------------------===##
+##
+## This source file is part of the Swift.org open source project
+##
+## Copyright (c) 2024 Apple Inc. and the Swift project authors
+## Licensed under Apache License v2.0 with Runtime Library Exception
+##
+## See https://swift.org/LICENSE.txt for license information
+## See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+##
+##===----------------------------------------------------------------------===##
+
+# Shared utilities for web requests with retry logic
+
+<#
+.SYNOPSIS
+Invokes a web request with retry logic and exponential backoff.
+
+.DESCRIPTION
+Attempts to download a file from a URL with automatic retry on failure.
+Uses exponential backoff to handle transient network failures.
+
+.PARAMETER Uri
+The URL to download from.
+
+.PARAMETER OutFile
+The destination file path for the download.
+
+.PARAMETER MaxRetries
+Maximum number of retry attempts (default: 10).
+
+.PARAMETER BaseDelay
+Base delay in seconds for exponential backoff (default: 1).
+
+.EXAMPLE
+Invoke-WebRequestWithRetry -Uri "https://example.com/file.exe" -OutFile "file.exe"
+
+.EXAMPLE
+Invoke-WebRequestWithRetry -Uri "https://example.com/file.exe" -OutFile "file.exe" -MaxRetries 5 -BaseDelay 2
+#>
+function Invoke-WebRequestWithRetry {
+    param(
+        [Parameter(Mandatory=$true)]
+        [string]$Uri,
+        [Parameter(Mandatory=$true)]
+        [string]$OutFile,
+        [int]$MaxRetries = 10,
+        [int]$BaseDelay = 1
+    )
+
+    $Attempt = 0
+    $Success = $false
+
+    while (-not $Success -and $Attempt -lt $MaxRetries) {
+        $Attempt++
+        try {
+            Invoke-WebRequest -Uri $Uri -OutFile $OutFile
+            $Success = $true
+            Write-Host 'SUCCESS'
+        }
+        catch {
+            if ($Attempt -eq $MaxRetries) {
+                Write-Host "FAILED after $MaxRetries attempts: $($_.Exception.Message)"
+                throw
+            }
+
+            # Calculate exponential backoff delay (2^attempt * base delay)
+            $Delay = $BaseDelay * [Math]::Pow(2, $Attempt - 1)
+            Write-Host "Attempt $Attempt failed, retrying in $Delay seconds..."
+            Start-Sleep -Seconds $Delay
+        }
+    }
+}
+
+Export-ModuleMember -Function Invoke-WebRequestWithRetry