feat: Graceful shutdown (#1801)

Fixes #442.

src/etl/impl/SubscriptionSource.hpp

@@ -24,6 +24,7 @@
 #include "feed/SubscriptionManagerInterface.hpp"
 #include "util/Mutex.hpp"
 #include "util/Retry.hpp"
+#include "util/StopHelper.hpp"
 #include "util/log/Logger.hpp"
 #include "util/prometheus/Gauge.hpp"
 #include "util/requests/Types.hpp"
@@ -39,7 +40,6 @@
 #include <chrono>
 #include <cstdint>
 #include <functional>
-#include <future>
 #include <memory>
 #include <optional>
 #include <string>
@@ -50,6 +50,7 @@ namespace etl::impl {
 
 /**
  * @brief This class is used to subscribe to a source of ledger data and forward it to the subscription manager.
+ * @note This class is safe to delete only if io_context is stopped.
  */
 class SubscriptionSource {
 public:
@@ -89,7 +90,7 @@ private:
 
     std::reference_wrapper<util::prometheus::GaugeInt> lastMessageTimeSecondsSinceEpoch_;
 
-    std::future<void> runFuture_;
+    util::StopHelper stopHelper_;
 
     static constexpr std::chrono::seconds kWS_TIMEOUT{30};
     static constexpr std::chrono::seconds kRETRY_MAX_DELAY{30};
@@ -124,13 +125,6 @@ public:
         std::chrono::steady_clock::duration const retryDelay = SubscriptionSource::kRETRY_DELAY
     );
 
-    /**
-     * @brief Destroy the Subscription Source object
-     *
-     * @note This will block to wait for all the async operations to complete. io_context must be still running
-     */
-    ~SubscriptionSource();
-
     /**
      * @brief Run the source
      */
@@ -192,7 +186,7 @@ public:
      * @brief Stop the source. The source will complete already scheduled operations but will not schedule new ones
      */
     void
-    stop();
+    stop(boost::asio::yield_context yield);
 
 private:
     void