tonic/xds: wire up lbv2 as a feature

tonic-xds/Cargo.toml

@@ -73,13 +73,20 @@ rcgen = "0.14"
 google-cloud-auth = { version = "1.9", default-features = false }
 
 [features]
+default = []
 testutil = ["dep:tonic-prost"]
 
 # Bundled OpenTelemetry metrics recorder for the gRFC A78 xDS client metrics.
 # The recorder lives in the companion `xds-client-opentelemetry` crate so its
 # OpenTelemetry version is decoupled from the core crates.
 otel = ["dep:opentelemetry", "dep:xds-client-opentelemetry"]
 
+# Load-balancer implementation. The default `tower-lb` stack (tower p2c
+# `Balance` + `Buffer`) is used unless `tonic-xds-lb` is enabled, which switches
+# to the in-crate `loadbalance/` implementation (`LoadBalancer` + pickers +
+# outlier detection).
+tonic-xds-lb = []
+
 # TLS crypto backend — pick exactly one.
 _tls-any = ["dep:rustls", "dep:rustls-pemfile", "dep:x509-parser"]
 tls-ring = ["_tls-any", "tonic/tls-ring", "xds-client/tonic-tls-ring"]

tonic-xds/src/client/loadbalance/channel_state.rs

@@ -18,10 +18,10 @@
 //! manage multiple in-flight state changes and handle cancellation by key.
 //!
 //! The state types hold the raw service `S` directly. In-flight tracking and
-//! load reporting are handled separately by [`LbChannel`] at the pool level.
+//! load reporting are handled separately by [`EndpointChannel`] at the pool level.
 //!
 //! [`KeyedFutures`]: crate::client::loadbalance::keyed_futures::KeyedFutures
-//! [`LbChannel`]: crate::client::loadbalance::channel::LbChannel
+//! [`EndpointChannel`]: crate::client::endpoint::EndpointChannel
 
 use std::future::Future;
 use std::pin::Pin;
@@ -80,6 +80,7 @@ impl EndpointCounters {
 /// can update registry-level counters exactly once per transition.
 #[derive(Debug)]
 pub(crate) struct OutlierChannelState {
+    #[allow(dead_code)]
     addr: EndpointAddress,
     counters: EndpointCounters,
     /// Bumped on each ejection; decremented (saturating) on each
@@ -104,6 +105,7 @@ impl OutlierChannelState {
     }
 
     /// Endpoint address this state belongs to.
+    #[allow(dead_code)]
     pub(crate) fn addr(&self) -> &EndpointAddress {
         &self.addr
     }
@@ -363,6 +365,7 @@ impl<S> ReadyChannel<S> {
     /// Drop the connection and start a fresh connect for the same
     /// address. The outlier state is re-attached from `registry`
     /// when the new connect resolves.
+    #[allow(dead_code)]
     pub(crate) fn reconnect<C: Connector<Service = S>>(
         self,
         connector: Arc<C>,

tonic-xds/src/client/loadbalance/keyed_futures.rs

@@ -90,6 +90,7 @@ where
     }
 
     /// True if a live (non-cancelled) future is tracked for `key`.
+    #[allow(dead_code)]
     pub(crate) fn contains_key(&self, key: &K) -> bool {
         self.cancellations.contains_key(key)
     }

tonic-xds/src/client/loadbalance/mod.rs

@@ -1,7 +1,7 @@
-pub(crate) mod channel;
 pub(crate) mod channel_state;
 pub(crate) mod errors;
 pub(crate) mod keyed_futures;
 pub(crate) mod loadbalancer;
 pub(crate) mod outlier_detection;
 pub(crate) mod pickers;
+pub(crate) mod service;

tonic-xds/src/client/loadbalance/outlier_detection.rs

@@ -117,6 +117,7 @@ impl OutlierStatsRegistry {
     }
 
     /// Number of registered channels.
+    #[allow(dead_code)]
     pub(crate) fn len(&self) -> usize {
         self.channels.len()
     }

tonic-xds/src/client/loadbalance/pickers/mod.rs

@@ -1,4 +1,8 @@
 pub(crate) mod p2c;
+// Ring-hash (gRFC A42) is implemented but not wired into the first-cut LB,
+// which selects P2C.
+// TODO: wire ring-hash into the LB.
+#[allow(dead_code)]
 pub(crate) mod ring_hash;
 
 use indexmap::{IndexMap, IndexSet};