Fixing faulty logic in InstallFunctionAppDependencies and adding unit test (#250)

* Fixing faulty logic in InstallFunctionAppDependencies and refactoring DependencyManager.cs to accommodate for unit test.

* Adding unit test to validate the retry logic in InstallFunctionAppDependencies as well as a successful module download.

* Adding Save-Module number of attempts to error log. Updating unit test to reflect this change.

* Adding logic to dependency manager to fail in the first dependencies installation run if the PSGallery could not be reached, but continue if previous dependencies exist.

* Adding unit test to validate that a function app execution should continue if the PSGallery could not be reached but a previous installation of managed dependencies exists.

Author: Francisco-Gamino

src/DependencyManagement/DependencyManagementUtils.cs

@@ -6,16 +6,11 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
-using System.Net;
-using System.Xml;
 
 namespace Microsoft.Azure.Functions.PowerShellWorker.DependencyManagement
 {
     internal class DependencyManagementUtils
     {
-        // The PowerShellGallery uri to query for the latest module version.
-        private const string PowerShellGalleryFindPackagesByIdUri = "https://www.powershellgallery.com/api/v2/FindPackagesById()?id=";
-
         /// <summary>
         /// Deletes the contents at the given directory.
         /// </summary>
@@ -51,104 +46,5 @@ internal static void EmptyDirectory(string path)
                 throw new InvalidOperationException(errorMsg);
             }
         }
-
-        /// <summary>
-        /// Returns the latest module version from the PSGallery for the given module name and major version.
-        /// </summary>
-        internal static string GetModuleLatestSupportedVersion(string moduleName, string majorVersion)
-        {
-            Uri address = new Uri($"{PowerShellGalleryFindPackagesByIdUri}'{moduleName}'");
-            int configuredRetries = 3;
-            int noOfRetries = 1;
-
-            string latestVersionForMajorVersion = null;
-
-            while (noOfRetries <= configuredRetries)
-            {
-                try
-                {
-                    HttpWebRequest request = WebRequest.Create(address) as HttpWebRequest;
-                    using (HttpWebResponse response = request?.GetResponse() as HttpWebResponse)
-                    {
-                        if (response != null)
-                        {
-                            // Load up the XML response
-                            XmlDocument doc = new XmlDocument();
-                            using (XmlReader reader = XmlReader.Create(response.GetResponseStream()))
-                            {
-                                doc.Load(reader);
-                            }
-
-                            // Add the namespaces for the gallery xml content
-                            XmlNamespaceManager nsmgr = new XmlNamespaceManager(doc.NameTable);
-                            nsmgr.AddNamespace("ps", "http://www.w3.org/2005/Atom");
-                            nsmgr.AddNamespace("d", "http://schemas.microsoft.com/ado/2007/08/dataservices");
-                            nsmgr.AddNamespace("m", "http://schemas.microsoft.com/ado/2007/08/dataservices/metadata");
-
-                            // Find the version information
-                            XmlNode root = doc.DocumentElement;
-                            var props = root.SelectNodes("//m:properties/d:Version", nsmgr);
-                            if (props != null && props.Count > 0)
-                            {
-                                for (int i = 0; i < props.Count; i++)
-                                {
-                                    if (props[i].FirstChild.Value.StartsWith(majorVersion))
-                                    {
-                                        latestVersionForMajorVersion = props[i].FirstChild.Value;
-                                    }
-                                }
-                            }
-                            break;
-                        }
-                    }
-                }
-                catch (Exception ex)
-                {
-                    WebException webEx = ex as WebException;
-                    if (webEx == null || noOfRetries >= configuredRetries)
-                    {
-                        throw;
-                    }
-
-                    // Only retry the web exception
-                    if (ShouldRetry(webEx))
-                    {
-                        noOfRetries++;
-                    }
-                }
-            }
-
-            // If we could not find the latest module version error out.
-            if (string.IsNullOrEmpty(latestVersionForMajorVersion))
-            {
-                var errorMsg = string.Format(PowerShellWorkerStrings.CannotFindModuleVersion, moduleName, majorVersion);
-                var argException = new ArgumentException(errorMsg);
-                throw argException;
-            }
-
-            return latestVersionForMajorVersion;
-        }
-
-        /// <summary>
-        /// Returns true if the given WebException status matches one of the following:
-        /// SendFailure, ConnectFailure, UnknownError or Timeout.
-        /// </summary>
-        private static bool ShouldRetry(WebException webEx)
-        {
-            if (webEx == null)
-            {
-                return false;
-            }
-
-            if (webEx.Status == WebExceptionStatus.SendFailure ||
-                webEx.Status == WebExceptionStatus.ConnectFailure ||
-                webEx.Status == WebExceptionStatus.UnknownError ||
-                webEx.Status == WebExceptionStatus.Timeout)
-            {
-                return true;
-            }
-
-            return false;
-        }
     }
 }