revert: 290cc27 (#229)

Commit `290cc278` introduced a concurrency issue when cleaning requests
in-flight.

Author: dmehala

src/datadog/curl.cpp

@@ -11,14 +11,14 @@
 #include <chrono>
 #include <condition_variable>
 #include <cstddef>
-#include <iterator>
 #include <list>
 #include <memory>
 #include <mutex>
 #include <system_error>
 #include <unordered_map>
 #include <unordered_set>
 
+#include "json.hpp"
 #include "string_util.h"
 
 namespace datadog {
@@ -428,7 +428,6 @@ void CurlImpl::drain(std::chrono::steady_clock::time_point deadline) {
   });
 
   log_on_error(curl_.multi_wakeup(multi_handle_));
-  clear_requests();
 }
 
 std::size_t CurlImpl::on_read_header(char *data, std::size_t,

src/datadog/curl.h

@@ -19,8 +19,6 @@
 #include <string>
 #include <thread>
 
-#include "json.hpp"
-
 namespace datadog {
 namespace tracing {
 

test/test_curl.cpp

@@ -156,31 +156,6 @@ const auto ignore = [](auto &&...) {};
 
 using namespace std::chrono_literals;
 
-CURL_TEST("API") {
-  const auto clock = default_clock;
-  const auto logger = std::make_shared<MockLogger>();
-  SingleRequestMockCurlLibrary library;
-  const auto client = std::make_shared<Curl>(logger, clock, library);
-
-  SECTION("drain remove requests in-flight") {
-    /// Prevent to process the request.
-    library.on_multi_perform = [] { return CURLM_OK; };
-
-    const HTTPClient::URL url = {"http", "whatever", ""};
-
-    const auto result = client->post(url, ignore, "whatever", ignore, ignore,
-                                     clock().tick + 60min);
-
-    REQUIRE(result);
-    REQUIRE(library.created_handles_.size() == 1);
-    REQUIRE(library.destroyed_handles_.size() == 0);
-
-    client->drain(clock().tick + 1s);
-    CHECK(library.created_handles_.size() == 1);
-    CHECK(library.destroyed_handles_.size() == 1);
-  }
-}
-
 CURL_TEST("parse response headers and body") {
   const auto clock = default_clock;
   const auto logger = std::make_shared<MockLogger>();