Improve tokio task execution (#1181)

* Add logging on shutdown

* Replace tokio::spawn with handle.spawn

* Upgrade tokio

* Add a task executor

* Beacon chain tasks use task executor

* Validator client tasks use task executor

* Rename runtime_handle to executor

* Add duration histograms; minor fixes

* Cleanup

* Fix logs

* Fix tests

* Remove random file

* Get enr dependency instead of libp2p

* Address some review comments

* Libp2p takes a TaskExecutor

* Ugly fix libp2p tests

* Move TaskExecutor to own file

* Upgrade Dockerfile rust version

* Minor fixes

* Revert "Ugly fix libp2p tests"

This reverts commit 58d4bb690f52de28d893943b7504d2d0c6621429.

* Pretty fix libp2p tests

* Add spawn_without_exit; change Counter to Gauge

* Tidy

* Move log from RuntimeContext to TaskExecutor

* Fix errors

* Replace histogram with int_gauge for async tasks

* Fix todo

* Fix memory leak in test by exiting all spawned tasks at the end

beacon_node/network/src/sync/manager.rs

@@ -48,7 +48,7 @@ use smallvec::SmallVec;
 use std::boxed::Box;
 use std::ops::Sub;
 use std::sync::Arc;
-use tokio::sync::{mpsc, oneshot};
+use tokio::sync::mpsc;
 use types::{EthSpec, Hash256, SignedBeaconBlock, Slot};
 
 /// The number of slots ahead of us that is allowed before requesting a long-range (batch)  Sync
@@ -181,17 +181,12 @@ impl SingleBlockRequest {
 /// chain. This allows the chain to be
 /// dropped during the syncing process which will gracefully end the `SyncManager`.
 pub fn spawn<T: BeaconChainTypes>(
-    runtime_handle: &tokio::runtime::Handle,
+    executor: environment::TaskExecutor,
     beacon_chain: Arc<BeaconChain<T>>,
     network_globals: Arc<NetworkGlobals<T::EthSpec>>,
     network_send: mpsc::UnboundedSender<NetworkMessage<T::EthSpec>>,
     log: slog::Logger,
-) -> (
-    mpsc::UnboundedSender<SyncMessage<T::EthSpec>>,
-    oneshot::Sender<()>,
-) {
-    // generate the exit channel
-    let (sync_exit, exit_rx) = tokio::sync::oneshot::channel();
+) -> mpsc::UnboundedSender<SyncMessage<T::EthSpec>> {
     // generate the message channel
     let (sync_send, sync_recv) = mpsc::unbounded_channel::<SyncMessage<T::EthSpec>>();
 
@@ -215,11 +210,8 @@ pub fn spawn<T: BeaconChainTypes>(
 
     // spawn the sync manager thread
     debug!(log, "Sync Manager started");
-    runtime_handle.spawn(async move {
-        futures::future::select(Box::pin(sync_manager.main()), exit_rx).await;
-        info!(log.clone(), "Sync Manager shutdown");
-    });
-    (sync_send, sync_exit)
+    executor.spawn(async move { Box::pin(sync_manager.main()).await }, "sync");
+    sync_send
 }
 
 impl<T: BeaconChainTypes> SyncManager<T> {