more information in TEpollPoller::SetImpl error messages

- don't hide epoll_ctl add errors;
 - print "fd" and "what" args.

1 files changed, 7 insertions, 0 deletions

diff --git a/util/network/poller_ut.cpp b/util/network/poller_ut.cpp
index 6df0dda8ec..e5914b7df3 100644
--- a/util/network/poller_ut.cpp
+++ b/util/network/poller_ut.cpp
@@ -232,5 +232,12 @@ Y_UNIT_TEST_SUITE(TSocketPollerTest) {
         UNIT_ASSERT_EQUAL(TPoller::ExtractFilter(&e), CONT_POLL_RDHUP);
         UNIT_ASSERT_EQUAL(TPoller::ExtractEvent(&e), (void*)17);
     }
+
+    Y_UNIT_TEST(TestSetSocketErrors) {
+        TGenericPoller<TEpollPoller<TWithoutLocking>> poller;
+
+        UNIT_ASSERT_EXCEPTION_CONTAINS(poller.Set(nullptr, Max<int>(), CONT_POLL_READ), TSystemError, "epoll add failed");
+        UNIT_ASSERT_EXCEPTION_CONTAINS(poller.Set(nullptr, Max<int>(), CONT_POLL_READ | CONT_POLL_MODIFY), TSystemError, "epoll modify failed");
+    }
 #endif
 }