pool: Decompose the pool and balancer crates

* Pool::update_pool is replaced with a narrower API:
  * Avoids need for unneeded allocations;
  * Slightly modifies the p2c endpoint update metrics, removing the DNE
    label.
* Split up crates:
  * Move the pool trait to a minimal crate
  * Move the balancer's P2cPool types into a library crate
* Rename NewBalancePeakEwma to NewBalance

Cargo.lock

@@ -653,17 +653,6 @@ version = "0.3.28"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4fff74096e71ed47f8e023204cfd0aa1289cd54ae5430a9523be060cdb849964"
 
-[[package]]
-name = "futures-macro"
-version = "0.3.28"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "89ca545a94061b6365f2c7355b4b32bd20df3ff95f02da9329b34ccc3bd6ee72"
-dependencies = [
- "proc-macro2",
- "quote",
- "syn 2.0.39",
-]
-
 [[package]]
 name = "futures-sink"
 version = "0.3.28"
@@ -685,7 +674,6 @@ dependencies = [
  "futures-channel",
  "futures-core",
  "futures-io",
- "futures-macro",
  "futures-sink",
  "futures-task",
  "memchr",
@@ -1670,6 +1658,37 @@ dependencies = [
  "tracing",
 ]
 
+[[package]]
+name = "linkerd-pool"
+version = "0.1.0"
+dependencies = [
+ "tower-service",
+]
+
+[[package]]
+name = "linkerd-pool-p2c"
+version = "0.1.0"
+dependencies = [
+ "ahash",
+ "futures",
+ "futures-util",
+ "indexmap",
+ "linkerd-error",
+ "linkerd-metrics",
+ "linkerd-pool",
+ "linkerd-stack",
+ "linkerd-tracing",
+ "parking_lot",
+ "prometheus-client",
+ "quickcheck",
+ "rand",
+ "tokio",
+ "tokio-test",
+ "tower",
+ "tower-test",
+ "tracing",
+]
+
 [[package]]
 name = "linkerd-proxy-api-resolve"
 version = "0.1.0"
@@ -1697,25 +1716,39 @@ version = "0.1.0"
 dependencies = [
  "ahash",
  "futures",
- "futures-util",
  "indexmap",
  "linkerd-error",
  "linkerd-metrics",
+ "linkerd-pool-p2c",
+ "linkerd-proxy-balance-queue",
+ "linkerd-proxy-core",
+ "linkerd-stack",
+ "prometheus-client",
+ "rand",
+ "tokio",
+ "tower",
+ "tracing",
+]
+
+[[package]]
+name = "linkerd-proxy-balance-queue"
+version = "0.1.0"
+dependencies = [
+ "futures",
+ "linkerd-error",
+ "linkerd-metrics",
+ "linkerd-pool",
  "linkerd-proxy-core",
- "linkerd-proxy-pool",
  "linkerd-stack",
  "linkerd-tracing",
  "parking_lot",
  "pin-project",
  "prometheus-client",
- "quickcheck",
- "rand",
  "thiserror",
  "tokio",
  "tokio-stream",
  "tokio-test",
  "tokio-util",
- "tower",
  "tower-test",
  "tracing",
 ]
@@ -1820,28 +1853,6 @@ dependencies = [
  "tracing",
 ]
 
-[[package]]
-name = "linkerd-proxy-pool"
-version = "0.1.0"
-dependencies = [
- "futures",
- "linkerd-error",
- "linkerd-metrics",
- "linkerd-proxy-core",
- "linkerd-stack",
- "linkerd-tracing",
- "parking_lot",
- "pin-project",
- "prometheus-client",
- "thiserror",
- "tokio",
- "tokio-stream",
- "tokio-test",
- "tokio-util",
- "tower-test",
- "tracing",
-]
-
 [[package]]
 name = "linkerd-proxy-resolve"
 version = "0.1.0"

Cargo.toml

@@ -39,14 +39,16 @@ members = [
     "linkerd/meshtls/verifier",
     "linkerd/metrics",
     "linkerd/opencensus",
+    "linkerd/pool",
+    "linkerd/pool/p2c",
     "linkerd/proxy/api-resolve",
     "linkerd/proxy/balance",
+    "linkerd/proxy/balance/queue",
     "linkerd/proxy/client-policy",
     "linkerd/proxy/core",
     "linkerd/proxy/dns-resolve",
     "linkerd/proxy/http",
     "linkerd/proxy/identity-client",
-    "linkerd/proxy/pool",
     "linkerd/proxy/resolve",
     "linkerd/proxy/server-policy",
     "linkerd/proxy/tap",

linkerd/app/core/src/control.rs

@@ -242,17 +242,12 @@ mod balance {
         recover: R,
     ) -> impl svc::Layer<
         N,
-        Service = http::NewBalancePeakEwma<
-            B,
-            Params,
-            recover::Resolve<R, DnsResolve>,
-            NewIntoTarget<N>,
-        >,
+        Service = http::NewBalance<B, Params, recover::Resolve<R, DnsResolve>, NewIntoTarget<N>>,
     > {
         let resolve = recover::Resolve::new(recover, DnsResolve::new(dns));
         let metrics = Params(http::balance::MetricFamilies::register(registry));
         svc::layer::mk(move |inner| {
-            http::NewBalancePeakEwma::new(NewIntoTarget { inner }, resolve.clone(), metrics.clone())
+            http::NewBalance::new(NewIntoTarget { inner }, resolve.clone(), metrics.clone())
         })
     }
 

linkerd/app/outbound/src/http/concrete/balance.rs

@@ -155,7 +155,7 @@ where
                 .push(svc::ArcNewService::layer());
 
             endpoint
-                .push(http::NewBalancePeakEwma::layer(
+                .push(http::NewBalance::layer(
                     resolve.clone(),
                     metrics_params.clone(),
                 ))

linkerd/app/outbound/src/opaq/concrete.rs

@@ -174,7 +174,7 @@ impl<C> Outbound<C> {
                     },
                 )
                 .lift_new_with_target()
-                .push(tcp::NewBalancePeakEwma::layer(resolve, metrics_params))
+                .push(tcp::NewBalance::layer(resolve, metrics_params))
                 .push(svc::NewMapErr::layer_from_target::<ConcreteError, _>())
                 .push_on_service(
                     rt.metrics

linkerd/pool/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "linkerd-pool"
+version = "0.1.0"
+license = "Apache-2.0"
+edition = "2021"
+publish = false
+
+[dependencies]
+tower-service = "0.3"

linkerd/pool/p2c/Cargo.toml

@@ -0,0 +1,34 @@
+[package]
+name = "linkerd-pool-p2c"
+version = "0.1.0"
+authors = ["Linkerd Developers <[email protected]>"]
+license = "Apache-2.0"
+edition = "2021"
+publish = false
+
+[dependencies]
+ahash = "0.8"
+futures = { version = "0.3", default-features = false }
+indexmap = "1"
+prometheus-client = "0.22"
+rand = { version = "0.8", features = ["small_rng"] }
+tokio = { version = "1", features = ["rt", "sync", "time"] }
+tracing = "0.1"
+
+linkerd-error = { path = "../../error" }
+linkerd-metrics = { path = "../../metrics" }
+linkerd-pool = { path = ".." }
+linkerd-stack = { path = "../../stack" }
+
+[dependencies.tower]
+version = "0.4.13"
+default-features = false
+features = ["load", "ready-cache"]
+
+[dev-dependencies]
+futures-util = { version = "0.3", default-features = false }
+linkerd-tracing = { path = "../../tracing" }
+parking_lot = "0.12"
+quickcheck = { version = "1", default-features = false }
+tokio-test = "0.4"
+tower-test = "0.4"