Better logging for delivery fenced writer and actual exception safety of PerformIO method

commit_hash:6420854eada61659e5d217fdbe73705d5715e0fa

Author: E1pp

yt/yt/core/net/connection.cpp

@@ -48,6 +48,10 @@ using namespace NConcurrency;
 
 ////////////////////////////////////////////////////////////////////////////////
 
+static constexpr auto& Logger = NetLogger;
+
+////////////////////////////////////////////////////////////////////////////////
+
 namespace {
 
 int GetLastNetworkError()
@@ -93,39 +97,40 @@ ssize_t WriteToFD(TFileDescriptor fd, const char* buffer, size_t length)
 #endif
 }
 
-enum class EPipeReadStatus
-{
-    PipeEmpty,
-    PipeNotEmpty,
-    NotSupportedError,
-};
-
-EPipeReadStatus CheckPipeReadStatus(const TString& pipePath)
+TErrorOr<int> CheckPipeBytesLeftToRead(const TString& pipePath) noexcept
 {
 #ifdef _linux_
     int bytesLeft = 0;
 
+    auto makeSystemError = [&] (TFormatString<> message) {
+        return TError(message)
+            << TError::FromSystem()
+            << TErrorAttribute("pipe_path", pipePath);
+    };
+
     {
         int flags = O_RDONLY | O_CLOEXEC | O_NONBLOCK;
         int fd = HandleEintr(::open, pipePath.c_str(), flags);
 
+        if (fd == -1) {
+            return makeSystemError("Failed to open file descriptor");
+        }
+
         int ret = ::ioctl(fd, FIONREAD, &bytesLeft);
-        if (ret == -1 && errno == EINVAL) {
-            // Some linux platforms do not support
-            // FIONREAD call. In such cases we
-            // expect EINVAL error.
-            return EPipeReadStatus::NotSupportedError;
+
+        if (ret == -1) {
+            return makeSystemError("ioctl failed");
         }
 
-        SafeClose(fd, /*ignoreBadFD*/ false);
+        if (!TryClose(fd, /*ignoreBadFD*/ false)) {
+            return makeSystemError("Failed to close file descriptor");
+        }
     }
 
-    return bytesLeft == 0
-        ? EPipeReadStatus::PipeEmpty
-        : EPipeReadStatus::PipeNotEmpty;
+    return bytesLeft;
 #else
     Y_UNUSED(pipePath);
-    return EPipeReadStatus::NotSupportedError;
+    return TError("Unsupported platform");
 #endif
 }
 
@@ -340,13 +345,19 @@ class TDeliveryFencedWriteOperation
     {
         auto result = TWriteOperation::PerformIO(fd);
         if (IsWriteComplete(result)) {
-            auto pipeReadStatus = CheckPipeReadStatus(PipePath_);
-            if (pipeReadStatus == EPipeReadStatus::NotSupportedError) {
-                return TError("Delivery fenced write failed: FIONDREAD is not supported on your platform")
-                    << TError::FromSystem();
+            auto bytesLeftOrError = CheckPipeBytesLeftToRead(PipePath_);
+
+
+            if (!bytesLeftOrError.IsOK()) {
+                YT_LOG_ERROR(bytesLeftOrError, "Delivery fenced write failed");
+                return std::move(bytesLeftOrError).Wrap();
+            } else {
+                YT_LOG_DEBUG("Delivery fenced write pipe check finished (BytesLeft: %v)", bytesLeftOrError.Value());
             }
 
-            result.Value().Retry = (pipeReadStatus != EPipeReadStatus::PipeEmpty);
+            result.Value().Retry = (bytesLeftOrError.Value() != 0);
+        } else {
+            YT_LOG_DEBUG("Delivery fenced write to pipe step finished (Result: %v)", result);
         }
 
         return result;