Logging Settings for host split (#9747)

* changes

* updating unit test

* comments

* updating test back

* logging change

* addressing comments

* changing current directory name

* debug log

Author: aishwaryabh

src/WebJobs.Script.WebHost/Diagnostics/Extensions/ScriptHostServiceLoggerExtension.cs

@@ -182,6 +182,12 @@ public static class ScriptHostServiceLoggerExtension
                 new EventId(529, nameof(HostStateChanged)),
                 "Host state changed from {previousState} to {newState}.");
 
+        private static readonly Action<ILogger, string, Exception> _logHostInitializationSettings =
+            LoggerMessage.Define<string>(
+                LogLevel.Debug,
+                new EventId(530, nameof(LogHostInitializationSettings)),
+                "{hostInitializationSettings}");
+
         public static void HostStateChanged(this ILogger logger, ScriptHostState previousHostState, ScriptHostState newHostState)
         {
             var newState = newHostState.ToString();
@@ -323,5 +329,18 @@ public static void ScriptHostServiceRestartCanceledByRuntime(this ILogger logger
         {
             _scriptHostServiceRestartCanceledByRuntime(logger, null);
         }
+
+        public static void LogHostInitializationSettings(this ILogger logger, string functionWorkerRuntime, string functionExtensionVersion, string siteExtensionDirectory, bool inStandbyMode)
+        {
+            var hostInitializationSettings = $@"{{
+    ""HostInitializationSettings"": {{
+        ""functionsWorkerRuntime"": ""{functionWorkerRuntime}"",
+        ""functionsExtensionVersion"": ""{functionExtensionVersion}"",
+        ""siteExtensionDirectory"": ""{siteExtensionDirectory}"",
+        ""inStandbyMode"": {inStandbyMode}
+    }}
+}}";
+            _logHostInitializationSettings(logger, hostInitializationSettings, null);
+        }
     }
 }

src/WebJobs.Script.WebHost/WebJobsScriptHostService.cs

@@ -685,6 +685,14 @@ private void LogInitialization(IHost host, bool isOffline, int attemptCount, int
                 // Reading the string from resources to make sure resource loading code path is warmed up during placeholder as well.
                 logger.InStandByMode(operationId);
             }
+
+            // Log settings
+            var functionWorkerRuntime = _environment.GetEnvironmentVariable(FunctionWorkerRuntime);
+            var functionExtensionVersion = _environment.GetEnvironmentVariable(FunctionsExtensionVersion);
+            var currentDirectory = Directory.GetCurrentDirectory();
+            var inStandbyMode = _scriptWebHostEnvironment.InStandbyMode;
+
+            logger.LogHostInitializationSettings(functionWorkerRuntime, functionExtensionVersion, currentDirectory, inStandbyMode);
         }
 
         private void OnHostHealthCheckTimer(object state)