Refactor http client callbacks

Author: cgilmour

src/datadog/datadog_agent.cpp

@@ -159,6 +159,28 @@ DatadogAgent::DatadogAgent(
             send_heartbeat_and_telemetry();
           }
         });
+    // Callback for setting telemetry request headers.
+    telemetry_set_request_headers_ = [](DictWriter& headers) {
+      headers.set("Content-Type", "application/json");
+    };
+    // Callback for successful telemetry HTTP requests, to examine HTTP status.
+    telemetry_on_response_ = [logger = logger_](
+                                 int response_status,
+                                 const DictReader& /*response_headers*/,
+                                 std::string response_body) {
+      if (response_status < 200 || response_status >= 300) {
+        logger->log_error([&](auto& stream) {
+          stream << "Unexpected telemetry response status " << response_status
+                 << " with body (starts on next line):\n"
+                 << response_body;
+        });
+      }
+    };
+    // Callback for unsuccessful telemetry HTTP requests.
+    telemetry_on_error_ = [logger = logger_](Error error) {
+      logger->log_error(error.with_prefix(
+          "Error occurred during HTTP request for telemetry: "));
+    };
   }
 }
 
@@ -310,98 +332,29 @@ void DatadogAgent::flush() {
 
 void DatadogAgent::send_app_started(nlohmann::json&& tracer_config) {
   auto payload = tracer_telemetry_->app_started(std::move(tracer_config));
-  auto set_request_headers = [&](DictWriter& headers) {
-    headers.set("Content-Type", "application/json");
-  };
-
-  // Callback for a successful HTTP request, to examine HTTP status.
-  auto on_response = [logger = logger_](int response_status,
-                                        const DictReader& /*response_headers*/,
-                                        std::string response_body) {
-    if (response_status < 200 || response_status >= 300) {
-      logger->log_error([&](auto& stream) {
-        stream << "Unexpected telemetry response status " << response_status
-               << " with body (starts on next line):\n"
-               << response_body;
-      });
-    }
-  };
-
-  // Callback for unsuccessful HTTP request.
-  auto on_error = [logger = logger_](Error error) {
-    logger->log_error(error.with_prefix(
-        "Error occurred during HTTP request for telemetry: "));
-  };
-
   auto post_result = http_client_->post(
-      telemetry_endpoint_, std::move(set_request_headers), std::move(payload),
-      std::move(on_response), std::move(on_error));
+      telemetry_endpoint_, telemetry_set_request_headers_, std::move(payload),
+      telemetry_on_response_, telemetry_on_error_);
   if (auto* error = post_result.if_error()) {
     logger_->log_error(*error);
   }
 }
 
 void DatadogAgent::send_heartbeat_and_telemetry() {
   auto payload = tracer_telemetry_->heartbeat_and_telemetry();
-  auto set_request_headers = [&](DictWriter& headers) {
-    headers.set("Content-Type", "application/json");
-  };
-
-  // Callback for a successful HTTP request, to examine HTTP status.
-  auto on_response = [logger = logger_](int response_status,
-                                        const DictReader& /*response_headers*/,
-                                        std::string response_body) {
-    if (response_status < 200 || response_status >= 300) {
-      logger->log_error([&](auto& stream) {
-        stream << "Unexpected telemetry response status " << response_status
-               << " with body (starts on next line):\n"
-               << response_body;
-      });
-    }
-  };
-
-  // Callback for unsuccessful HTTP request.
-  auto on_error = [logger = logger_](Error error) {
-    logger->log_error(error.with_prefix(
-        "Error occurred during HTTP request for telemetry: "));
-  };
-
   auto post_result = http_client_->post(
-      telemetry_endpoint_, std::move(set_request_headers), std::move(payload),
-      std::move(on_response), std::move(on_error));
+      telemetry_endpoint_, telemetry_set_request_headers_, std::move(payload),
+      telemetry_on_response_, telemetry_on_error_);
   if (auto* error = post_result.if_error()) {
     logger_->log_error(*error);
   }
 }
 
 void DatadogAgent::send_app_closing() {
   auto payload = tracer_telemetry_->app_closing();
-  auto set_request_headers = [&](DictWriter& headers) {
-    headers.set("Content-Type", "application/json");
-  };
-
-  // Callback for a successful HTTP request, to examine HTTP status.
-  auto on_response = [logger = logger_](int response_status,
-                                        const DictReader& /*response_headers*/,
-                                        std::string response_body) {
-    if (response_status < 200 || response_status >= 300) {
-      logger->log_error([&](auto& stream) {
-        stream << "Unexpected telemetry response status " << response_status
-               << " with body (starts on next line):\n"
-               << response_body;
-      });
-    }
-  };
-
-  // Callback for unsuccessful HTTP request.
-  auto on_error = [logger = logger_](Error error) {
-    logger->log_error(error.with_prefix(
-        "Error occurred during HTTP request for telemetry: "));
-  };
-
   auto post_result = http_client_->post(
-      telemetry_endpoint_, std::move(set_request_headers), std::move(payload),
-      std::move(on_response), std::move(on_error));
+      telemetry_endpoint_, telemetry_set_request_headers_, std::move(payload),
+      telemetry_on_response_, telemetry_on_error_);
   if (auto* error = post_result.if_error()) {
     logger_->log_error(*error);
   }

src/datadog/datadog_agent.h

@@ -45,6 +45,10 @@ class DatadogAgent : public Collector {
   EventScheduler::Cancel cancel_scheduled_flush_;
   EventScheduler::Cancel cancel_telemetry_timer_;
   std::chrono::steady_clock::duration flush_interval_;
+  // Callbacks for submitting telemetry data
+  HTTPClient::HeadersSetter telemetry_set_request_headers_;
+  HTTPClient::ResponseHandler telemetry_on_response_;
+  HTTPClient::ErrorHandler telemetry_on_error_;
 
   void flush();
   void send_heartbeat_and_telemetry();