Handle error conversions properly. (#56)

This adds a type alias, BoxedStdError, for a boxed std::error::Error
trait object, and uses it in the where bounds for the generic service
code.  In the future, we may want to standardize on using
std::error::Error exclusively, but we would then possibly lose out on
backtrace information.

zebra-network/src/lib.rs

@@ -9,6 +9,13 @@ extern crate tracing;
 #[macro_use]
 extern crate bitflags;
 
+/// Type alias to make working with tower traits easier.
+///
+/// Note: the 'static lifetime bound means that the *type* cannot have any
+/// non-'static lifetimes, (e.g., when a type contains a borrow and is
+/// parameterized by 'a), *not* that the object itself has 'static lifetime.
+pub(crate) type BoxedStdError = Box<dyn std::error::Error + Send + Sync + 'static>;
+
 mod network;
 pub use network::Network;
 

zebra-network/src/peer/connector.rs

@@ -18,7 +18,7 @@ use crate::{
     constants,
     protocol::{codec::*, internal::*, message::*, types::*},
     timestamp_collector::{PeerLastSeen, TimestampCollector},
-    Network,
+    BoxedStdError, Network,
 };
 
 use super::{
@@ -37,7 +37,7 @@ impl<S> PeerConnector<S>
 where
     S: Service<Request, Response = Response> + Clone + Send + 'static,
     S::Future: Send,
-    //S::Error: Into<Error>,
+    S::Error: Into<BoxedStdError>,
 {
     /// XXX replace with a builder
     pub fn new(network: Network, internal_service: S, collector: &TimestampCollector) -> Self {
@@ -54,8 +54,7 @@ impl<S> Service<SocketAddr> for PeerConnector<S>
 where
     S: Service<Request, Response = Response> + Clone + Send + 'static,
     S::Future: Send,
-    S::Error: Send,
-    //S::Error: Into<Error>,
+    S::Error: Send + Into<BoxedStdError>,
 {
     type Response = PeerClient;
     type Error = Error;

zebra-network/src/peer/server.rs

@@ -8,9 +8,12 @@ use futures::{
 use tokio::prelude::*;
 use tower::Service;
 
-use crate::protocol::{
-    internal::{Request, Response},
-    message::Message,
+use crate::{
+    protocol::{
+        internal::{Request, Response},
+        message::Message,
+    },
+    BoxedStdError,
 };
 
 use super::{client::ClientRequest, PeerError};
@@ -51,8 +54,7 @@ pub struct PeerServer<S, Tx> {
 impl<S, Tx> PeerServer<S, Tx>
 where
     S: Service<Request, Response = Response>,
-    S::Error: Send,
-    //S::Error: Into<Error>,
+    S::Error: Into<BoxedStdError>,
     Tx: Sink<Message> + Unpin,
     Tx::Error: Into<Error>,
 {
@@ -310,14 +312,21 @@ where
     async fn drive_peer_request(&mut self, req: Request) {
         trace!(?req);
         use tower::ServiceExt;
-        // XXX Drop the errors on the floor for now so that
-        // we can ignore error type alignment
-        match self.svc.ready().await {
-            Err(_) => self.fail_with(format_err!("svc err").into()),
-            Ok(()) => {}
+        if let Err(e) = self
+            .svc
+            .ready()
+            .await
+            .map_err(|e| Error::from_boxed_compat(e.into()))
+        {
+            self.fail_with(e.into());
         }
-        match self.svc.call(req).await {
-            Err(_) => self.fail_with(format_err!("svc err").into()),
+        match self
+            .svc
+            .call(req)
+            .await
+            .map_err(|e| Error::from_boxed_compat(e.into()))
+        {
+            Err(e) => self.fail_with(e.into()),
             Ok(Response::Ok) => { /* generic success, do nothing */ }
             Ok(Response::Peers(addrs)) => {
                 if let Err(e) = self.peer_tx.send(Message::Addr(addrs)).await {