Fix syncing bugs by recursively attempting to process parents in the … (#429)

* Fix syncing bugs by recursively attempting to process parents in the import queue, change BlockRootsIterator

* Swap from crossbeam channel to tokio mpsc

* Recursion fix

* Remove exess block processing

* Fix network lag, correct attestation topic

* Correct network poll logic

* Overhaul of SimpleSync and modify BlockRootsIterator to return start_slot

* Fix bug in tests relating to StateRootsIterator

* Remove old, commented-out heartbeat code.

* Tidy docs on import queue enum

* Change source logging msg in simple sync

* Rename function parameter in simple sync

* Use `BestBlockRootsIterator` in `reduced_tree`

* Update comments for `BestBlockRootsIterator`

* Fix duplicate dep in cargo.toml

beacon_node/client/src/notifier.rs

@@ -3,39 +3,34 @@ use beacon_chain::BeaconChainTypes;
 use exit_future::Exit;
 use futures::{Future, Stream};
 use slog::{debug, o};
-use std::sync::{Arc, Mutex};
 use std::time::{Duration, Instant};
 use tokio::runtime::TaskExecutor;
 use tokio::timer::Interval;
 
-/// Thread that monitors the client and reports useful statistics to the user.
+/// The interval between heartbeat events.
+pub const HEARTBEAT_INTERVAL_SECONDS: u64 = 5;
 
+/// Spawns a thread that can be used to run code periodically, on `HEARTBEAT_INTERVAL_SECONDS`
+/// durations.
+///
+/// Presently unused, but remains for future use.
 pub fn run<T: BeaconChainTypes + Send + Sync + 'static>(
     client: &Client<T>,
     executor: TaskExecutor,
     exit: Exit,
 ) {
     // notification heartbeat
-    let interval = Interval::new(Instant::now(), Duration::from_secs(5));
+    let interval = Interval::new(
+        Instant::now(),
+        Duration::from_secs(HEARTBEAT_INTERVAL_SECONDS),
+    );
 
     let _log = client.log.new(o!("Service" => "Notifier"));
 
-    // TODO: Debugging only
-    let counter = Arc::new(Mutex::new(0));
-    let network = client.network.clone();
-
-    // build heartbeat logic here
-    let heartbeat = move |_| {
-        //debug!(log, "Temp heartbeat output");
-        //TODO: Remove this logic. Testing only
-        let mut count = counter.lock().unwrap();
-        *count += 1;
-
-        if *count % 5 == 0 {
-            //            debug!(log, "Sending Message");
-            network.send_message();
-        }
-
+    let heartbeat = |_| {
+        // There is not presently any heartbeat logic.
+        //
+        // We leave this function empty for future use.
         Ok(())
     };