Asink sink (#3309)

Replace async logger with async sink

tests/test_sink.h

@@ -8,10 +8,10 @@
 #include <chrono>
 #include <mutex>
 #include <thread>
+#include <exception>
 
 #include "spdlog/details/null_mutex.h"
 #include "spdlog/details/os.h"
-#include "spdlog/fmt/fmt.h"
 #include "spdlog/sinks/base_sink.h"
 
 namespace spdlog {
@@ -37,6 +37,14 @@ public:
         delay_ = delay;
     }
 
+    void set_exception(const std::runtime_error& ex) {
+        exception_ptr_ = std::make_exception_ptr(ex);
+    }
+
+    void clear_exception() {
+        exception_ptr_ = nullptr;
+    }
+
     // return last output without the eol
     std::vector<std::string> lines() {
         std::lock_guard<Mutex> lock(base_sink<Mutex>::mutex_);
@@ -45,6 +53,9 @@ public:
 
 protected:
     void sink_it_(const details::log_msg &msg) override {
+        if (exception_ptr_) {
+            std::rethrow_exception(exception_ptr_);
+        }
         memory_buf_t formatted;
         base_sink<Mutex>::formatter_->format(msg, formatted);
         // save the line without the eol
@@ -56,12 +67,18 @@ protected:
         std::this_thread::sleep_for(delay_);
     }
 
-    void flush_() override { flush_counter_++; }
+    void flush_() override {
+        if (exception_ptr_) {
+            std::rethrow_exception(exception_ptr_);
+        }
+        flush_counter_++;
+    }
 
     size_t msg_counter_{0};
     size_t flush_counter_{0};
     std::chrono::milliseconds delay_{std::chrono::milliseconds::zero()};
     std::vector<std::string> lines_;
+    std::exception_ptr exception_ptr_; // will be thrown on next log or flush if not null
 };
 
 using test_sink_mt = test_sink<std::mutex>;