From bef199f8312d624a2d1d1e6c9462ce241d7c4046 Mon Sep 17 00:00:00 2001
From: Nikolay Kim <fafhrd91@gmail.com>
Date: Mon, 11 Mar 2019 22:54:27 -0700
Subject: [PATCH] add blocking mod support

---
 actix-rt/CHANGES.md      |  3 +-
 actix-rt/Cargo.toml      |  7 +++-
 actix-rt/src/blocking.rs | 88 ++++++++++++++++++++++++++++++++++++++++
 actix-rt/src/lib.rs      |  1 +
 4 files changed, 97 insertions(+), 2 deletions(-)
 create mode 100644 actix-rt/src/blocking.rs

diff --git a/actix-rt/CHANGES.md b/actix-rt/CHANGES.md
index 105bbfb8..a0736672 100644
--- a/actix-rt/CHANGES.md
+++ b/actix-rt/CHANGES.md
@@ -4,11 +4,12 @@
 
 ### Added
 
+* Added `blocking` module
+
 * Arbiter::exec_fn - execute fn on the arbiter's thread
 
 * Arbiter::exec - execute fn on the arbiter's thread and wait result
 
-
 ## [0.2.0] - 2019-03-06
 
 * `run` method returns `io::Result<()>`
diff --git a/actix-rt/Cargo.toml b/actix-rt/Cargo.toml
index b60935ef..9ab4db6d 100644
--- a/actix-rt/Cargo.toml
+++ b/actix-rt/Cargo.toml
@@ -18,9 +18,14 @@ name = "actix_rt"
 path = "src/lib.rs"
 
 [dependencies]
-log = "0.4"
 bytes = "0.4"
+derive_more = "0.14"
 futures = "0.1.25"
+parking_lot = "0.7"
+lazy_static = "1.2"
+log = "0.4"
+num_cpus = "1.10"
+threadpool = "1.7"
 tokio-current-thread = "0.1"
 tokio-executor = "0.1.5"
 tokio-reactor = "0.1.7"
diff --git a/actix-rt/src/blocking.rs b/actix-rt/src/blocking.rs
new file mode 100644
index 00000000..e209a3e2
--- /dev/null
+++ b/actix-rt/src/blocking.rs
@@ -0,0 +1,88 @@
+//! Thread pool for blocking operations
+
+use std::fmt;
+
+use derive_more::Display;
+use futures::sync::oneshot;
+use futures::{Async, Future, Poll};
+use parking_lot::Mutex;
+use threadpool::ThreadPool;
+
+/// Env variable for default cpu pool size
+const ENV_CPU_POOL_VAR: &str = "ACTIX_CPU_POOL";
+
+lazy_static::lazy_static! {
+    pub(crate) static ref DEFAULT_POOL: Mutex<ThreadPool> = {
+        let default = match std::env::var(ENV_CPU_POOL_VAR) {
+            Ok(val) => {
+                if let Ok(val) = val.parse() {
+                    val
+                } else {
+                    log::error!("Can not parse ACTIX_CPU_POOL value");
+                    num_cpus::get() * 5
+                }
+            }
+            Err(_) => num_cpus::get() * 5,
+        };
+        Mutex::new(
+            threadpool::Builder::new()
+                .thread_name("actix-web".to_owned())
+                .num_threads(default)
+                .build(),
+        )
+    };
+}
+
+thread_local! {
+    static POOL: ThreadPool = {
+        DEFAULT_POOL.lock().clone()
+    };
+}
+
+/// Blocking operation execution error
+#[derive(Debug, Display)]
+pub enum BlockingError<E: fmt::Debug> {
+    #[display(fmt = "{:?}", _0)]
+    Error(E),
+    #[display(fmt = "Thread pool is gone")]
+    Canceled,
+}
+
+/// Execute blocking function on a thread pool, returns future that resolves
+/// to result of the function execution.
+pub fn run<F, I, E>(f: F) -> CpuFuture<I, E>
+where
+    F: FnOnce() -> Result<I, E> + Send + 'static,
+    I: Send + 'static,
+    E: Send + fmt::Debug + 'static,
+{
+    let (tx, rx) = oneshot::channel();
+    POOL.with(|pool| {
+        pool.execute(move || {
+            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>>,
+}
+
+impl<I, E: fmt::Debug> Future for CpuFuture<I, E> {
+    type Item = I;
+    type Error = BlockingError<E>;
+
+    fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
+        let res = futures::try_ready!(self.rx.poll().map_err(|_| BlockingError::Canceled));
+        match res {
+            Ok(val) => Ok(Async::Ready(val)),
+            Err(err) => Err(BlockingError::Error(err)),
+        }
+    }
+}
diff --git a/actix-rt/src/lib.rs b/actix-rt/src/lib.rs
index 3bfbb7b2..2c585fb5 100644
--- a/actix-rt/src/lib.rs
+++ b/actix-rt/src/lib.rs
@@ -1,6 +1,7 @@
 //! A runtime implementation that runs everything on the current thread.
 
 mod arbiter;
+pub mod blocking;
 mod builder;
 mod runtime;
 mod system;