diff --git a/src/configuration.cc b/src/configuration.cc
index 3be46a26..7e2d11f5 100644
--- a/src/configuration.cc
+++ b/src/configuration.cc
@@ -35,105 +35,111 @@
 namespace google {
 
 namespace {
+
 constexpr const char kConfigFileFlag[] = "config-file";
 
-constexpr const char kDefaultProjectId[] = "";
-constexpr const char kDefaultCredentialsFile[] = "";
-constexpr const int kMetadataApiDefaultNumThreads = 3;
-constexpr const int kMetadataApiDefaultPort = 8000;
-constexpr const char kMetadataApiDefaultBindAddress[] = "0.0.0.0";
-constexpr const char kMetadataApiDefaultResourceTypeSeparator[] = ".";
-constexpr const int kMetadataReporterDefaultIntervalSeconds = 60;
-constexpr const int kMetadataReporterDefaultPurgeDeleted = false;
-constexpr const char kMetadataReporterDefaultUserAgent[] =
-    "metadata-agent/" STRINGIFY(AGENT_VERSION);
-constexpr const char kMetadataIngestionDefaultEndpointFormat[] =
-    "https://stackdriver.googleapis.com/v1beta2/projects/{{project_id}}"
-    "/resourceMetadata:batchUpdate";
-constexpr const int kMetadataIngestionDefaultRequestSizeLimitBytes =
-    8*1024*1024;
-constexpr const int kMetadataIngestionDefaultRequestSizeLimitCount = 1000;
-constexpr const char kMetadataIngestionDefaultRawContentVersion[] = "0.1";
-constexpr const int kInstanceUpdaterDefaultIntervalSeconds = 60*60;
-constexpr const char kDefaultInstanceResourceType[] =
-    "";  // A blank value means "unspecified; detect via environment".
-constexpr const int kDockerUpdaterDefaultIntervalSeconds = 0;
-constexpr const char kDockerDefaultEndpointHost[] =
-    "unix://%2Fvar%2Frun%2Fdocker.sock/";
-constexpr const char kDockerDefaultApiVersion[] = "1.23";
-constexpr const char kDockerDefaultContainerFilter[] = "limit=30";
-constexpr const int kKubernetesUpdaterDefaultIntervalSeconds = 0;
-constexpr const int kKubernetesUpdaterDefaultWatchConnectionRetries = 15;
-constexpr const char kKubernetesDefaultEndpointHost[] =
-    "https://kubernetes.default.svc";
-constexpr const char kKubernetesDefaultPodLabelSelector[] = "";
-constexpr const char kKubernetesDefaultClusterName[] = "";
-constexpr const char kKubernetesDefaultClusterLocation[] = "";
-constexpr const char kKubernetesDefaultNodeName[] = "";
-constexpr const bool kKubernetesDefaultUseWatch = false;
-constexpr const bool kKubernetesDefaultClusterLevelMetadata = false;
-constexpr const bool kKubernetesDefaultServiceMetadata = true;
-constexpr const char kDefaultInstanceId[] = "";
-constexpr const char kDefaultInstanceZone[] = "";
-constexpr const char kDefaultHealthCheckFile[] =
-    "/var/run/metadata-agent/health/unhealthy";
-constexpr const int kDefaultHealthCheckMaxDataAgeSeconds = 5*60;
+class Option {
+ public:
+  virtual void Set(const YAML::Node& value) = 0;
+};
 
+template<class T, class D>
+class OptionDef : public Option {
+ public:
+  OptionDef(T& var, const D& default_) : var_(var) {
+    var = default_;
+  }
+  void Set(const YAML::Node& value) { var_ = value.as<T>(var_); }
+ private:
+  T& var_;
+};
+
+template<class T, class D>
+Option* option(T& var, const D& default_) {
+  return new OptionDef<T, D>(var, default_);
 }
 
+}
+
+class Configuration::OptionMap
+    : public std::map<std::string, std::unique_ptr<Option>> {
+ public:
+  OptionMap(std::vector<std::pair<const char*, Option*>>&& v) {
+    for (const auto& p : v) {
+      emplace(p.first, std::unique_ptr<Option>(p.second));
+    }
+  }
+};
+
 Configuration::Configuration()
-    : project_id_(kDefaultProjectId),
-      credentials_file_(kDefaultCredentialsFile),
-      verbose_logging_(false),
-      metadata_api_num_threads_(kMetadataApiDefaultNumThreads),
-      metadata_api_port_(kMetadataApiDefaultPort),
-      metadata_api_bind_address_(kMetadataApiDefaultBindAddress),
-      metadata_api_resource_type_separator_(
-          kMetadataApiDefaultResourceTypeSeparator),
-      metadata_reporter_interval_seconds_(
-          kMetadataReporterDefaultIntervalSeconds),
-      metadata_reporter_purge_deleted_(
-          kMetadataReporterDefaultPurgeDeleted),
-      metadata_reporter_user_agent_(
-          kMetadataReporterDefaultUserAgent),
-      metadata_ingestion_endpoint_format_(
-          kMetadataIngestionDefaultEndpointFormat),
-      metadata_ingestion_request_size_limit_bytes_(
-          kMetadataIngestionDefaultRequestSizeLimitBytes),
-      metadata_ingestion_request_size_limit_count_(
-          kMetadataIngestionDefaultRequestSizeLimitCount),
-      metadata_ingestion_raw_content_version_(
-          kMetadataIngestionDefaultRawContentVersion),
-      instance_updater_interval_seconds_(
-          kInstanceUpdaterDefaultIntervalSeconds),
-      instance_resource_type_(kDefaultInstanceResourceType),
-      docker_updater_interval_seconds_(kDockerUpdaterDefaultIntervalSeconds),
-      docker_endpoint_host_(kDockerDefaultEndpointHost),
-      docker_api_version_(kDockerDefaultApiVersion),
-      docker_container_filter_(kDockerDefaultContainerFilter),
-      kubernetes_updater_interval_seconds_(
-          kKubernetesUpdaterDefaultIntervalSeconds),
-      kubernetes_updater_watch_connection_retries_(
-          kKubernetesUpdaterDefaultWatchConnectionRetries),
-      kubernetes_endpoint_host_(kKubernetesDefaultEndpointHost),
-      kubernetes_pod_label_selector_(kKubernetesDefaultPodLabelSelector),
-      kubernetes_cluster_name_(kKubernetesDefaultClusterName),
-      kubernetes_cluster_location_(kKubernetesDefaultClusterLocation),
-      kubernetes_node_name_(kKubernetesDefaultNodeName),
-      kubernetes_use_watch_(kKubernetesDefaultUseWatch),
-      kubernetes_cluster_level_metadata_(
-          kKubernetesDefaultClusterLevelMetadata),
-      kubernetes_service_metadata_(kKubernetesDefaultServiceMetadata),
-      instance_id_(kDefaultInstanceId),
-      instance_zone_(kDefaultInstanceZone),
-      health_check_file_(kDefaultHealthCheckFile),
-      health_check_max_data_age_seconds_(
-          kDefaultHealthCheckMaxDataAgeSeconds) {}
+    : verbose_logging_(false),
+      options_(new OptionMap({
+        {"ProjectId", option(project_id_, "")},
+        {"CredentialsFile", option(credentials_file_, "")},
+        {"MetadataApiNumThreads", option(metadata_api_num_threads_, 3)},
+        {"MetadataApiPort", option(metadata_api_port_, 8000)},
+        {"MetadataApiBindAddress",
+         option(metadata_api_bind_address_, "0.0.0.0")},
+        {"MetadataApiResourceTypeSeparator",
+         option(metadata_api_resource_type_separator_, ".")},
+        {"MetadataReporterIntervalSeconds",
+         option(metadata_reporter_interval_seconds_, 60)},
+        {"MetadataReporterPurgeDeleted",
+         option(metadata_reporter_purge_deleted_, false)},
+        {"MetadataReporterUserAgent",
+         option(metadata_reporter_user_agent_,
+                "metadata-agent/" STRINGIFY(AGENT_VERSION))},
+        {"MetadataIngestionEndpointFormat",
+         option(metadata_ingestion_endpoint_format_,
+                "https://stackdriver.googleapis.com/v1beta2/projects/"
+                "{{project_id}}/resourceMetadata:batchUpdate")},
+        {"MetadataIngestionRequestSizeLimitBytes",
+         option(metadata_ingestion_request_size_limit_bytes_, 8*1024*1024)},
+        {"MetadataIngestionRequestSizeLimitCount",
+         option(metadata_ingestion_request_size_limit_count_, 1000)},
+        {"MetadataIngestionRawContentVersion",
+         option(metadata_ingestion_raw_content_version_, "0.1")},
+        {"InstanceUpdaterIntervalSeconds",
+         option(instance_updater_interval_seconds_, 60*60)},
+        // A blank value means "unspecified; detect via environment".
+        {"InstanceResourceType", option(instance_resource_type_, "")},
+        {"DockerUpdaterIntervalSeconds",
+         option(docker_updater_interval_seconds_, 0)},
+        {"DockerEndpointHost",
+         option(docker_endpoint_host_, "unix://%2Fvar%2Frun%2Fdocker.sock/")},
+        {"DockerApiVersion", option(docker_api_version_, "1.23")},
+        {"DockerContainerFilter", option(docker_container_filter_, "limit=30")},
+        {"KubernetesUpdaterIntervalSeconds",
+         option(kubernetes_updater_interval_seconds_, 0)},
+        {"KubernetesUpdaterWatchConnectionRetries",
+         option(kubernetes_updater_watch_connection_retries_, 15)},
+        {"KubernetesEndpointHost",
+         option(kubernetes_endpoint_host_, "https://kubernetes.default.svc")},
+        {"KubernetesPodLabelSelector",
+         option(kubernetes_pod_label_selector_, "")},
+        {"KubernetesClusterName", option(kubernetes_cluster_name_, "")},
+        {"KubernetesClusterLocation", option(kubernetes_cluster_location_, "")},
+        {"KubernetesNodeName", option(kubernetes_node_name_, "")},
+        {"KubernetesUseWatch", option(kubernetes_use_watch_, false)},
+        {"KubernetesClusterLevelMetadata",
+         option(kubernetes_cluster_level_metadata_, false)},
+        {"KubernetesServiceMetadata",
+         option(kubernetes_service_metadata_, true)},
+        {"InstanceId", option(instance_id_, "")},
+        {"InstanceZone", option(instance_zone_, "")},
+        {"HealthCheckFile",
+         option(health_check_file_,
+                "/var/run/metadata-agent/health/unhealthy")},
+        {"HealthCheckMaxDataAgeSeconds",
+         option(health_check_max_data_age_seconds_, 5*60)},
+      })) {}
 
 Configuration::Configuration(std::istream& input) : Configuration() {
   ParseConfiguration(input);
 }
 
+Configuration::~Configuration() = default;
+
 int Configuration::ParseArguments(int ac, char** av) {
   std::string config_file;
   boost::program_options::options_description flags_desc;
@@ -219,93 +225,15 @@ void Configuration::ParseConfigFile(const std::string& filename) {
 void Configuration::ParseConfiguration(std::istream& input) {
   YAML::Node config = YAML::Load(input);
   std::lock_guard<std::mutex> lock(mutex_);
-  project_id_ =
-      config["ProjectId"].as<std::string>(project_id_);
-  credentials_file_ =
-      config["CredentialsFile"].as<std::string>(credentials_file_);
-  metadata_api_num_threads_ =
-      config["MetadataApiNumThreads"].as<int>(metadata_api_num_threads_);
-  metadata_api_port_ =
-      config["MetadataApiPort"].as<int>(metadata_api_port_);
-  metadata_api_bind_address_ =
-      config["MetadataApiBindAddress"].as<std::string>(
-          metadata_api_bind_address_);
-  metadata_api_resource_type_separator_ =
-      config["MetadataApiResourceTypeSeparator"].as<std::string>(
-          metadata_api_resource_type_separator_);
-  metadata_reporter_interval_seconds_ =
-      config["MetadataReporterIntervalSeconds"].as<int>(
-          metadata_reporter_interval_seconds_);
-  metadata_reporter_purge_deleted_ =
-      config["MetadataReporterPurgeDeleted"].as<bool>(
-          metadata_reporter_purge_deleted_);
-  metadata_reporter_user_agent_ =
-      config["MetadataReporterUserAgent"].as<std::string>(
-          metadata_reporter_user_agent_);
-  metadata_ingestion_endpoint_format_ =
-      config["MetadataIngestionEndpointFormat"].as<std::string>(
-          metadata_ingestion_endpoint_format_);
-  metadata_ingestion_request_size_limit_bytes_ =
-      config["MetadataIngestionRequestSizeLimitBytes"].as<int>(
-          metadata_ingestion_request_size_limit_bytes_);
-  metadata_ingestion_request_size_limit_count_ =
-      config["MetadataIngestionRequestSizeLimitCount"].as<int>(
-          metadata_ingestion_request_size_limit_count_);
-  metadata_ingestion_raw_content_version_ =
-      config["MetadataIngestionRawContentVersion"].as<std::string>(
-          metadata_ingestion_raw_content_version_);
-  instance_updater_interval_seconds_ =
-      config["InstanceUpdaterIntervalSeconds"].as<int>(
-          instance_updater_interval_seconds_);
-  instance_resource_type_ =
-      config["InstanceResourceType"].as<std::string>(instance_resource_type_);
-  docker_updater_interval_seconds_ =
-      config["DockerUpdaterIntervalSeconds"].as<int>(
-          docker_updater_interval_seconds_);
-  docker_endpoint_host_ =
-      config["DockerEndpointHost"].as<std::string>(docker_endpoint_host_);
-  docker_api_version_ =
-      config["DockerApiVersion"].as<std::string>(docker_api_version_);
-  docker_container_filter_ =
-      config["DockerContainerFilter"].as<std::string>(
-          docker_container_filter_);
-  kubernetes_updater_interval_seconds_ =
-      config["KubernetesUpdaterIntervalSeconds"].as<int>(
-          kubernetes_updater_interval_seconds_);
-  kubernetes_updater_watch_connection_retries_ =
-      config["KubernetesUpdaterWatchConnectionRetries"].as<int>(
-          kubernetes_updater_watch_connection_retries_);
-  kubernetes_endpoint_host_ =
-      config["KubernetesEndpointHost"].as<std::string>(
-          kubernetes_endpoint_host_);
-  kubernetes_pod_label_selector_ =
-      config["KubernetesPodLabelSelector"].as<std::string>(
-          kubernetes_pod_label_selector_);
-  kubernetes_cluster_name_ =
-      config["KubernetesClusterName"].as<std::string>(
-          kubernetes_cluster_name_);
-  kubernetes_cluster_location_ =
-      config["KubernetesClusterLocation"].as<std::string>(
-          kubernetes_cluster_location_);
-  kubernetes_node_name_ =
-      config["KubernetesNodeName"].as<std::string>(kubernetes_node_name_);
-  kubernetes_use_watch_ =
-      config["KubernetesUseWatch"].as<bool>(kubernetes_use_watch_);
-  kubernetes_cluster_level_metadata_ =
-      config["KubernetesClusterLevelMetadata"].as<bool>(
-          kubernetes_cluster_level_metadata_);
-  kubernetes_service_metadata_ =
-      config["KubernetesServiceMetadata"].as<bool>(
-          kubernetes_service_metadata_);
-  instance_id_ =
-      config["InstanceId"].as<std::string>(instance_id_);
-  instance_zone_ =
-      config["InstanceZone"].as<std::string>(instance_zone_);
-  health_check_file_ =
-      config["HealthCheckFile"].as<std::string>(health_check_file_);
-  health_check_max_data_age_seconds_ =
-      config["HealthCheckMaxDataAgeSeconds"].as<int>(
-          health_check_max_data_age_seconds_);
+  for (const auto& kv : config) {
+    const std::string key = kv.first.as<std::string>();
+    auto option_it = options_->find(key);
+    if (option_it != options_->end()) {
+      option_it->second->Set(kv.second);
+    } else {
+      std::cerr << "Invalid option " << key << std::endl;
+    }
+  }
 }
 
 }  // google
diff --git a/src/configuration.h b/src/configuration.h
index d7f1f5ca..eb10da26 100644
--- a/src/configuration.h
+++ b/src/configuration.h
@@ -16,6 +16,7 @@
 #ifndef AGENT_CONFIG_H_
 #define AGENT_CONFIG_H_
 
+#include <memory>
 #include <mutex>
 #include <string>
 
@@ -29,8 +30,13 @@ class Configuration {
   Configuration(std::istream& input);
   // Used to accept inline construction of streams.
   Configuration(std::istream&& input) : Configuration(input) {}
+  ~Configuration();
 
   // Shared configuration.
+  bool VerboseLogging() const {
+    std::lock_guard<std::mutex> lock(mutex_);
+    return verbose_logging_;
+  }
   const std::string& ProjectId() const {
     std::lock_guard<std::mutex> lock(mutex_);
     return project_id_;
@@ -39,10 +45,6 @@ class Configuration {
     std::lock_guard<std::mutex> lock(mutex_);
     return credentials_file_;
   }
-  bool VerboseLogging() const {
-    std::lock_guard<std::mutex> lock(mutex_);
-    return verbose_logging_;
-  }
   // Metadata API server configuration options.
   int MetadataApiNumThreads() const {
     std::lock_guard<std::mutex> lock(mutex_);
@@ -179,6 +181,8 @@ class Configuration {
   friend class ConfigurationArgumentParserTest;
   friend int ::main(int, char**);  // Calls ParseArguments.
 
+  class OptionMap;  // Internal helper class.
+
   void ParseConfigFile(const std::string& filename);
   void ParseConfiguration(std::istream& input);
   // Parse the command line.
@@ -189,9 +193,9 @@ class Configuration {
   int ParseArguments(int ac, char** av);
 
   mutable std::mutex mutex_;
+  bool verbose_logging_;
   std::string project_id_;
   std::string credentials_file_;
-  bool verbose_logging_;
   int metadata_api_num_threads_;
   int metadata_api_port_;
   std::string metadata_api_bind_address_;
@@ -223,6 +227,8 @@ class Configuration {
   std::string instance_zone_;
   std::string health_check_file_;
   int health_check_max_data_age_seconds_;
+
+  std::unique_ptr<const OptionMap> options_;
 };
 
 }