Split polkadot-service (#310)

* Substrate service

* Splitting polkadot service

* Specialised components

* Specialised components

* Docs and style

* Docs and style

* Final touches

* Added db key assertion

substrate/substrate/extrinsic-pool/src/api.rs

@@ -17,6 +17,7 @@
 //! External API for extrinsic pool.
 
 use txpool;
+use futures::sync::mpsc;
 
 /// Extrinsic pool error.
 pub trait Error: ::std::error::Error + Send + Sized {
@@ -32,6 +33,9 @@ impl Error for txpool::Error {
 	fn into_pool_error(self) -> Result<txpool::Error, Self> { Ok(self) }
 }
 
+/// Modification notification event stream type;
+pub type EventStream = mpsc::UnboundedReceiver<()>;
+
 /// Extrinsic pool.
 pub trait ExtrinsicPool<Ex, BlockId, Hash>: Send + Sync + 'static {
 	/// Error type
@@ -39,4 +43,10 @@ pub trait ExtrinsicPool<Ex, BlockId, Hash>: Send + Sync + 'static {
 
 	/// Submit a collection of extrinsics to the pool.
 	fn submit(&self, block: BlockId, xt: Vec<Ex>) -> Result<Vec<Hash>, Self::Error>;
+
+	/// Returns light status of the pool.
+	fn light_status(&self) -> txpool::LightStatus;
+
+	/// Return an event stream of transactions imported to the pool.
+	fn import_notification_stream(&self) -> EventStream;
 }

substrate/substrate/extrinsic-pool/src/pool.rs

@@ -18,7 +18,7 @@ use std::{
 	collections::HashMap,
 	fmt,
 	marker::PhantomData,
-	sync::{Arc, Weak},
+	sync::Arc,
 };
 
 use futures::sync::mpsc;
@@ -40,7 +40,7 @@ pub struct Pool<Hash, VEx, S, E> where
 		S,
 		Listener<Hash>,
 	>>,
-	import_notification_sinks: Mutex<Vec<mpsc::UnboundedSender<Weak<VEx>>>>,
+	import_notification_sinks: Mutex<Vec<mpsc::UnboundedSender<()>>>,
 }
 
 impl<Hash, VEx, S, E> Pool<Hash, VEx, S, E> where
@@ -62,15 +62,14 @@ impl<Hash, VEx, S, E> Pool<Hash, VEx, S, E> where
 	pub fn import(&self, xt: VEx) -> Result<Arc<VEx>, E> {
 		let result = self.pool.write().import(xt)?;
 
-		let weak = Arc::downgrade(&result);
 		self.import_notification_sinks.lock()
-			.retain(|sink| sink.unbounded_send(weak.clone()).is_ok());
+			.retain(|sink| sink.unbounded_send(()).is_ok());
 
 		Ok(result)
 	}
 
 	/// Return an event stream of transactions imported to the pool.
-	pub fn import_notification_stream(&self) -> mpsc::UnboundedReceiver<Weak<VEx>> {
+	pub fn import_notification_stream(&self) -> mpsc::UnboundedReceiver<()> {
 		let (sink, stream) = mpsc::unbounded();
 		self.import_notification_sinks.lock().push(sink);
 		stream