Pipeline: reuse the prexisting runtime executor

Instead of creating our own threadpool, we should reuse the executor
of the tokio::runtime::Runtime that backs the tokio::reactor::Core.

Cargo.lock

@@ -1504,6 +1504,7 @@ 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)",

podcasts-data/Cargo.toml

@@ -18,6 +18,7 @@ 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"

podcasts-data/src/lib.rs

@@ -82,6 +82,7 @@ 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;

podcasts-data/src/pipeline.rs

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