chore(tonic): Move ConnectError type from transport (#1828)

* chore(tonic): Move TimeoutExpired out of transport

By moving the TimeoutExpired type from the transport module
to the the tonic engine proper, the type is made available to
other transport implementations and tonic can be built without
the "server" feature while still returning a Status indicating
the timeout.

Alternative transport implementations can use the type, now that it is
moved, when they want the tonic Status error handling to recognize the
error as having been triggered by a timeout in the transport logic. The
tonic Status error will have a code of Cancelled with a message of
"Timeout expired".

There is already a test for this:

    cargo test picks_server_timeout_if_thats_sorter

which worked the original way and contines to work; but now a new
transport implementation can get the same behavior.

Addresses #1825.

* chore(tonic): Move ConnectError out of transport

Author: FrankReh

tonic/src/lib.rs

@@ -120,7 +120,7 @@ pub use extensions::GrpcMethod;
 pub use http::Extensions;
 pub use request::{IntoRequest, IntoStreamingRequest, Request};
 pub use response::Response;
-pub use status::{Code, Status, TimeoutExpired};
+pub use status::{Code, ConnectError, Status, TimeoutExpired};
 
 pub(crate) type Error = Box<dyn std::error::Error + Send + Sync>;
 

tonic/src/status.rs

@@ -615,10 +615,7 @@ fn find_status_in_source_chain(err: &(dyn Error + 'static)) -> Option<Status> {
         // matches the spec of:
         // > The service is currently unavailable. This is most likely a transient condition that
         // > can be corrected if retried with a backoff.
-        #[cfg(feature = "channel")]
-        if let Some(connect) =
-            err.downcast_ref::<crate::transport::channel::service::ConnectError>()
-        {
+        if let Some(connect) = err.downcast_ref::<ConnectError>() {
             return Some(Status::unavailable(connect.to_string()));
         }
 
@@ -1032,3 +1029,20 @@ impl fmt::Display for TimeoutExpired {
 
 // std::error::Error only requires a type to impl Debug and Display
 impl std::error::Error for TimeoutExpired {}
+
+/// Wrapper type to indicate that an error occurs during the connection
+/// process, so that the appropriate gRPC Status can be inferred.
+#[derive(Debug)]
+pub struct ConnectError(pub Box<dyn std::error::Error + Send + Sync>);
+
+impl fmt::Display for ConnectError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Display::fmt(&self.0, f)
+    }
+}
+
+impl std::error::Error for ConnectError {
+    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
+        Some(self.0.as_ref())
+    }
+}

tonic/src/transport/channel/service/connector.rs

@@ -2,7 +2,9 @@ use super::BoxedIo;
 #[cfg(feature = "tls")]
 use super::TlsConnector;
 use crate::transport::channel::BoxFuture;
+use crate::ConnectError;
 use http::Uri;
+#[cfg(feature = "tls")]
 use std::fmt;
 use std::task::{Context, Poll};
 
@@ -12,23 +14,6 @@ use hyper::rt;
 use hyper_util::rt::TokioIo;
 use tower_service::Service;
 
-/// Wrapper type to indicate that an error occurs during the connection
-/// process, so that the appropriate gRPC Status can be inferred.
-#[derive(Debug)]
-pub(crate) struct ConnectError(pub(crate) crate::Error);
-
-impl fmt::Display for ConnectError {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        fmt::Display::fmt(&self.0, f)
-    }
-}
-
-impl std::error::Error for ConnectError {
-    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
-        Some(self.0.as_ref())
-    }
-}
-
 pub(crate) struct Connector<C> {
     inner: C,
     #[cfg(feature = "tls")]

tonic/src/transport/channel/service/mod.rs

@@ -17,7 +17,7 @@ mod io;
 use self::io::BoxedIo;
 
 mod connector;
-pub(crate) use self::connector::{ConnectError, Connector};
+pub(crate) use self::connector::Connector;
 
 mod executor;
 pub(super) use self::executor::{Executor, SharedExec};