threadpool: add panic_handler (#1052)

tokio-threadpool/src/builder.rs

@@ -6,6 +6,7 @@ use shutdown::ShutdownTrigger;
 use thread_pool::ThreadPool;
 use worker::{self, Worker, WorkerId};
 
+use std::any::Any;
 use std::cmp::max;
 use std::error::Error;
 use std::fmt;
@@ -106,6 +107,7 @@ impl Builder {
                 around_worker: None,
                 after_start: None,
                 before_stop: None,
+                panic_handler: None,
             },
             new_park,
         }
@@ -199,6 +201,34 @@ impl Builder {
         self
     }
 
+    /// Sets a callback to be triggered when a panic during a future bubbles up
+    /// to Tokio. By default Tokio catches these panics, and they will be
+    /// ignored. The parameter passed to this callback is the same error value
+    /// returned from std::panic::catch_unwind(). To abort the process on
+    /// panics, use std::panic::resume_unwind() in this callback as shown
+    /// below.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # extern crate tokio_threadpool;
+    /// # extern crate futures;
+    /// # use tokio_threadpool::Builder;
+    ///
+    /// # pub fn main() {
+    /// let thread_pool = Builder::new()
+    ///     .panic_handler(|err| std::panic::resume_unwind(err))
+    ///     .build();
+    /// # }
+    /// ```
+    pub fn panic_handler<F>(&mut self, f: F) -> &mut Self
+    where
+        F: Fn(Box<Any + Send>) + Send + Sync + 'static,
+    {
+        self.config.panic_handler = Some(Arc::new(f));
+        self
+    }
+
     /// Set name prefix of threads spawned by the scheduler
     ///
     /// Thread name prefix is used for generating thread names. For example, if