Pipeline: Use a custom tokio threadpool

This reverts commit e64883eecb
and 40dd2d6923

Seems like core.run() returns once its done even if there
are still tasks in the Runtime underneath. A way to solve that
would be to call the shutdown_on_idle method.

We need ownership of the threadpool in order to invoke
`shutdown_on_idle` method but core.runtime only returns a
referrence so we need to create our own threadpool.

Cargo.lock

@@ -1504,8 +1504,9 @@ dependencies = [
  "rfc822_sanitizer 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "rss 1.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "tempdir 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)",
- "tokio 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "tokio-core 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
+ "tokio-executor 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "tokio-threadpool 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "url 1.7.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "xdg 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "xml-rs 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",

podcasts-data/Cargo.toml

@@ -18,8 +18,9 @@ xdg = "2.1.0"
 xml-rs = "0.8.0"
 futures = "0.1.23"
 hyper = "0.11.27"
-tokio = "0.1.8"
 tokio-core = "0.1.17"
+tokio-threadpool = "0.1.6"
+tokio-executor = "0.1"
 hyper-tls = "0.1.3"
 native-tls = "0.1.5"
 num_cpus = "1.8.0"

podcasts-data/src/errors.rs

@@ -4,6 +4,7 @@ use diesel_migrations::RunMigrationsError;
 use hyper;
 use native_tls;
 use rss;
+use tokio_executor;
 use url;
 use xml;
 
@@ -46,6 +47,8 @@ pub enum DataError {
     R2D2PoolError(#[cause] r2d2::PoolError),
     #[fail(display = "Hyper Error: {}", _0)]
     HyperError(#[cause] hyper::Error),
+    #[fail(display = "Tokio Spawn Error: {}", _0)]
+    SpawnError(#[cause] tokio_executor::SpawnError),
     #[fail(display = "Failed to parse a url: {}", _0)]
     UrlError(#[cause] url::ParseError),
     #[fail(display = "TLS Error: {}", _0)]
@@ -101,6 +104,12 @@ impl From<hyper::Error> for DataError {
     }
 }
 
+impl From<tokio_executor::SpawnError> for DataError {
+    fn from(err: tokio_executor::SpawnError) -> Self {
+        DataError::SpawnError(err)
+    }
+}
+
 impl From<url::ParseError> for DataError {
     fn from(err: url::ParseError) -> Self {
         DataError::UrlError(err)

podcasts-data/src/lib.rs

@@ -82,8 +82,9 @@ extern crate num_cpus;
 extern crate rayon;
 extern crate rfc822_sanitizer;
 extern crate rss;
-extern crate tokio;
 extern crate tokio_core;
+extern crate tokio_executor;
+extern crate tokio_threadpool;
 extern crate url;
 extern crate xdg;
 extern crate xml;

podcasts-data/src/pipeline.rs

@@ -1,14 +1,15 @@
 // FIXME:
 //! Docs.
 
+use futures::future::*;
 use futures::prelude::*;
-use futures::{future::ok, lazy, stream::iter_ok};
+use futures::stream::*;
 
 use hyper::client::HttpConnector;
 use hyper::Client;
 use hyper_tls::HttpsConnector;
-use tokio::runtime::TaskExecutor;
 use tokio_core::reactor::Core;
+use tokio_threadpool::{self, ThreadPool};
 
 use num_cpus;
 
@@ -26,7 +27,7 @@ type HttpsClient = Client<HttpsConnector<HttpConnector>>;
 pub fn pipeline<'a, S>(
     sources: S,
     client: HttpsClient,
-    executor: TaskExecutor,
+    pool: tokio_threadpool::Sender,
 ) -> impl Future<Item = Vec<()>, Error = DataError> + 'a
 where
     S: Stream<Item = Source, Error = DataError> + 'a,
@@ -34,9 +35,9 @@ where
     sources
         .and_then(move |s| s.into_feed(client.clone()))
         .and_then(move |feed| {
-            let fut = lazy(|| feed.index().map_err(|err| error!("Error: {}", err)));
-            executor.spawn(fut);
-            Ok(())
+            pool.spawn(lazy(|| {
+                feed.index().map_err(|err| error!("Error: {}", err))
+            })).map_err(From::from)
         })
         // the stream will stop at the first error so
         // we ensure that everything will succeded regardless.
@@ -51,16 +52,20 @@ pub fn run<S>(sources: S) -> Result<(), DataError>
 where
     S: IntoIterator<Item = Source>,
 {
+    let pool = ThreadPool::new();
+    let sender = pool.sender().clone();
     let mut core = Core::new()?;
-    let executor = core.runtime().executor();
     let handle = core.handle();
     let client = Client::configure()
         .connector(HttpsConnector::new(num_cpus::get(), &handle)?)
         .build(&handle);
 
     let stream = iter_ok::<_, DataError>(sources);
-    let p = pipeline(stream, client, executor);
-    core.run(p).map(|_| ())
+    let p = pipeline(stream, client, sender);
+    core.run(p)?;
+
+    pool.shutdown_on_idle().wait().unwrap();
+    Ok(())
 }
 
 #[cfg(test)]