[release/1.1] Prevent EdgeHub from starting without a valid configura…

…tion (Azure#5515)

Currently, EdgeHub 1.1 can start without a valid configuration. This PR backports logic introduced in later releases to check that a configuration was pulled successfully, and modifies the configuration pulling task to fail when appropriate.

Fixes Azure#5398.

edge-hub/src/Microsoft.Azure.Devices.Edge.Hub.Core/config/ConfigUpdater.cs

@@ -56,6 +56,13 @@ await this.currentConfig.Match(
                     {
                         Events.GettingConfig();
                         await pullTask;
+
+                        this.currentConfig.Expect<InvalidOperationException>(() => throw new InvalidOperationException(
+                                        "Could not obtain twin neither from local store nor from cloud. " +
+                                        "This happens when there is no upstream connection and this is the first EdgeHub startup, " +
+                                        "or there is no persistent store to save a previous twin configuration. " +
+                                        "EdgeHub cannot start without basic configuration stored in twin. Stopping now."));
+
                         return this.currentConfig;
                     });
 

edge-hub/src/Microsoft.Azure.Devices.Edge.Hub.Service/Program.cs

@@ -92,7 +92,8 @@ static async Task<int> MainAsync(IConfigurationRoot configuration)
             logger.LogInformation("Initializing configuration");
             IConfigSource configSource = await container.Resolve<Task<IConfigSource>>();
             ConfigUpdater configUpdater = await container.Resolve<Task<ConfigUpdater>>();
-            await configUpdater.Init(configSource);
+
+            var configDownloadTask = configUpdater.Init(configSource);
 
             if (!Enum.TryParse(configuration.GetValue("AuthenticationMode", string.Empty), true, out AuthenticationMode authenticationMode)
                 || authenticationMode != AuthenticationMode.Cloud)
@@ -107,8 +108,17 @@ static async Task<int> MainAsync(IConfigurationRoot configuration)
             using (IProtocolHead protocolHead = await GetEdgeHubProtocolHeadAsync(logger, configuration, container, hosting))
             using (var renewal = new CertificateRenewal(certificates, logger))
             {
-                await protocolHead.StartAsync();
-                await Task.WhenAny(cts.Token.WhenCanceled(), renewal.Token.WhenCanceled());
+                try
+                {
+                    await configDownloadTask;
+                    await protocolHead.StartAsync();
+                    await Task.WhenAny(cts.Token.WhenCanceled(), renewal.Token.WhenCanceled());
+                }
+                catch (Exception ex)
+                {
+                    logger.LogError($"Error starting protocol heads: {ex.Message}");
+                }
+
                 logger.LogInformation("Stopping the protocol heads...");
                 await protocolHead.CloseAsync(CancellationToken.None);
                 logger.LogInformation("Protocol heads stopped.");