From 2f6df111832112ad012687557f66b112ef0d1ed1 Mon Sep 17 00:00:00 2001
From: Nikolay Kim <fafhrd91@gmail.com>
Date: Thu, 7 Mar 2019 19:31:17 -0800
Subject: [PATCH] do not execute blocking fn if result is not required

---
 src/blocking.rs | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/blocking.rs b/src/blocking.rs
index 01be30dd2..fc9cec299 100644
--- a/src/blocking.rs
+++ b/src/blocking.rs
@@ -41,6 +41,7 @@ thread_local! {
     };
 }
 
+/// Blocking operation execution error
 #[derive(Debug, Display)]
 pub enum BlockingError<E: fmt::Debug> {
     #[display(fmt = "{:?}", _0)]
@@ -62,13 +63,17 @@ where
     let (tx, rx) = oneshot::channel();
     POOL.with(|pool| {
         pool.execute(move || {
-            let _ = tx.send(f());
+            if !tx.is_canceled() {
+                let _ = tx.send(f());
+            }
         })
     });
 
     CpuFuture { rx }
 }
 
+/// Blocking operation completion future. It resolves with results
+/// of blocking function execution.
 pub struct CpuFuture<I, E> {
     rx: oneshot::Receiver<Result<I, E>>,
 }