test(integration): add GetChangedTargets benchmarks

Makefile

@@ -1,4 +1,4 @@
-.PHONY: build cover test test-integration proto gazelle clean clean-proto run-server run-client-get-graph run-client-changed-targets help
+.PHONY: build cover test test-integration bench proto gazelle clean clean-proto run-server run-client-get-graph run-client-changed-targets help
 
 # Bazel wrapper
 BAZEL = ./tools/bazel
@@ -21,6 +21,20 @@ test-integration:
 	@$(BAZEL) test //integration:integration_test --test_output=errors --test_env=TANGO_REPO_REMOTE=$$(git rev-parse --show-toplevel) --test_env=HOME=$$HOME
 	@echo "Integration tests passed!"
 
+# Run GetChangedTargets benchmarks against fixed, checked-in commit pairs.
+# Measurement only: not part of `make test` / `make test-integration` and not
+# run in CI, so a slow benchmark never fails the build.
+bench:
+	@echo "Running benchmarks..."
+	@$(BAZEL) test //integration:integration_test \
+		--test_output=all \
+		--test_arg=-test.run=^$$ \
+		--test_arg=-test.bench=. \
+		--test_arg=-test.benchtime=15x \
+		--test_env=TANGO_REPO_REMOTE=$$(git rev-parse --show-toplevel) \
+		--test_env=HOME=$$HOME
+	@echo "Benchmarks complete!"
+
 # Generate protobuf files using protoc
 proto:
 	@echo "Generating protobuf files with protoc..."
@@ -97,6 +111,7 @@ help:
 	@echo "  make build            - Build all targets"
 	@echo "  make test             - Run all tests"
 	@echo "  make test-integration - Run integration tests (slow)"
+	@echo "  make bench        - Run GetChangedTargets benchs (measurement only, not in CI)"
 	@echo "  make gazelle          - Update BUILD.bazel files"
 	@echo "  make clean            - Clean generated files and binaries"
 	@echo ""

integration/BUILD.bazel

@@ -4,7 +4,10 @@ go_test(
     name = "integration_test",
     size = "large",
     timeout = "long",
-    srcs = ["integration_test.go"],
+    srcs = [
+        "benchmark_test.go",
+        "integration_test.go",
+    ],
     data = glob(["testdata/**"]),
     tags = [
         "integration",
@@ -23,6 +26,8 @@ go_test(
         "@org_uber_go_yarpc//:yarpc",
         "@org_uber_go_yarpc//api/transport",
         "@org_uber_go_yarpc//transport/grpc",
+        "@org_uber_go_zap//:zap",
+        "@org_uber_go_zap//zapcore",
         "@org_uber_go_zap//zaptest",
     ],
 )

integration/benchmark_test.go

@@ -0,0 +1,79 @@
+// Copyright (c) 2026 Uber Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Benchmarks for GetChangedTargets. Run via `make bench`; not part of
+// `make test` / `make test-integration` and never from CI.
+package integration_test
+
+import (
+	"testing"
+
+	"go.uber.org/zap"
+	"go.uber.org/zap/zapcore"
+)
+
+// coldCommitPairs are distinct consecutive commit pairs from repo history.
+// Each pair produces a unique treehash, guaranteeing a cache miss per call.
+var coldCommitPairs = []struct{ first, second string }{
+	{"57162624a45965a7e783072c56561f91c5d4084d", "74d1cd55155e5f4f43aa92b4e0146a0c528a0d96"},
+	{"74d1cd55155e5f4f43aa92b4e0146a0c528a0d96", "3d54234a3d4c0d940d651e002c5c79d71f01b120"},
+	{"3d54234a3d4c0d940d651e002c5c79d71f01b120", "821c885d304811652fefeeeb2c21e1907bebf7f6"},
+	{"821c885d304811652fefeeeb2c21e1907bebf7f6", "ea874d203f37c58b9ba52cde81309d1e28827eaa"},
+	{"ea874d203f37c58b9ba52cde81309d1e28827eaa", "c0cd90a8c35e2cc981e32f074f9a55657f44d7dd"},
+	{"c0cd90a8c35e2cc981e32f074f9a55657f44d7dd", "8d7e7f93ea68bfb5e37f29df289a54ab8ff79ae1"},
+	{"8d7e7f93ea68bfb5e37f29df289a54ab8ff79ae1", "4d41a6f57d2215db7e78c284f7f8f5e13f6ff07d"},
+	{"4d41a6f57d2215db7e78c284f7f8f5e13f6ff07d", "b4591e33a40135ed5c2fef8ee4f96db8ab231904"},
+	{"b4591e33a40135ed5c2fef8ee4f96db8ab231904", "f2b15a5e058ed0a678f97111080806e26d0239d4"},
+	{"f2b15a5e058ed0a678f97111080806e26d0239d4", "fc7289244106a1a21a146729c6f75eb6d17f2649"},
+	{"3662f8acd9fffb535e56b670beb0de0d811e4181", "381c6585a765e350326520d4e0a588bc604fa656"},
+	{"381c6585a765e350326520d4e0a588bc604fa656", "450d404d4a337ec2809f28c630b126871a88987e"},
+	{"450d404d4a337ec2809f28c630b126871a88987e", "3a07829426dc621d37bdbe2038ac85a20bec5ead"},
+	{"3a07829426dc621d37bdbe2038ac85a20bec5ead", "7876d3870dd0da4ec94cb49362bb85247b373358"},
+	{"7876d3870dd0da4ec94cb49362bb85247b373358", "9cc890fb7a91de8b129a3cc86f362b393655de5b"},
+}
+
+// BenchmarkGetChangedTargets_Cold measures uncached GetChangedTargets calls.
+// Each iteration uses a different commit pair so every call is a cache miss,
+// exercising the full pipeline: git checkout, bazel query, compare, stream.
+func BenchmarkGetChangedTargets_Cold(b *testing.B) {
+	remote := repoRemote(b)
+	logger := zap.New(zapcore.NewNopCore())
+	addr := startServerWithLogger(b, remote, logger)
+	client := newClient(b, addr)
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		pair := coldCommitPairs[i]
+		getChangedTargets(b, client, remote, pair.first, pair.second)
+	}
+}
+
+// BenchmarkGetChangedTargets_Cached measures cached GetChangedTargets calls.
+// The cache is primed with a single call before the timed loop, so every
+// iteration in the loop is a cache hit measuring streaming overhead only.
+func BenchmarkGetChangedTargets_Cached(b *testing.B) {
+	remote := repoRemote(b)
+	logger := zap.New(zapcore.NewNopCore())
+	addr := startServerWithLogger(b, remote, logger)
+	client := newClient(b, addr)
+
+	firstSHA := "57162624a45965a7e783072c56561f91c5d4084d"
+	secondSHA := "74d1cd55155e5f4f43aa92b4e0146a0c528a0d96"
+
+	getChangedTargets(b, client, remote, firstSHA, secondSHA)
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		getChangedTargets(b, client, remote, firstSHA, secondSHA)
+	}
+}

integration/integration_test.go

@@ -40,6 +40,7 @@ import (
 	"go.uber.org/yarpc"
 	"go.uber.org/yarpc/api/transport"
 	yarpcgrpc "go.uber.org/yarpc/transport/grpc"
+	"go.uber.org/zap"
 	"go.uber.org/zap/zaptest"
 )
 
@@ -48,14 +49,14 @@ const (
 	configTemplateFile = "testdata/tango-config.yaml.tmpl"
 )
 
-func repoRemote(t *testing.T) string {
+func repoRemote(t testing.TB) string {
 	t.Helper()
 	remote := os.Getenv("TANGO_REPO_REMOTE")
 	require.NotEmpty(t, remote, "TANGO_REPO_REMOTE must be set (pass --test_env=TANGO_REPO_REMOTE=... to bazel test)")
 	return remote
 }
 
-func writeConfig(t *testing.T, dir, remote, clonePath, workerPath string) string {
+func writeConfig(t testing.TB, dir, remote, clonePath, workerPath string) string {
 	t.Helper()
 
 	tmpl, err := template.ParseFiles(configTemplateFile)
@@ -82,7 +83,12 @@ func writeConfig(t *testing.T, dir, remote, clonePath, workerPath string) string
 	return configPath
 }
 
-func startServer(t *testing.T, remote string) string {
+func startServer(t testing.TB, remote string) string {
+	t.Helper()
+	return startServerWithLogger(t, remote, zaptest.NewLogger(t))
+}
+
+func startServerWithLogger(t testing.TB, remote string, zl *zap.Logger) string {
 	t.Helper()
 
 	configDir := t.TempDir()
@@ -91,7 +97,6 @@ func startServer(t *testing.T, remote string) string {
 
 	configPath := writeConfig(t, configDir, remote, clonePath, workerPath)
 
-	zl := zaptest.NewLogger(t)
 	logger := zl.Sugar()
 
 	appCtx, cancel := context.WithCancel(context.Background())
@@ -142,7 +147,7 @@ func startServer(t *testing.T, remote string) string {
 	return listener.Addr().String()
 }
 
-func newClient(t *testing.T, addr string) pb.TangoYARPCClient {
+func newClient(t testing.TB, addr string) pb.TangoYARPCClient {
 	t.Helper()
 
 	grpcTransport := yarpcgrpc.NewTransport()
@@ -251,7 +256,7 @@ type parsedChangedTargets struct {
 	Distances map[string]int32
 }
 
-func getChangedTargets(t *testing.T, client pb.TangoYARPCClient, remote, firstSHA, secondSHA string) parsedChangedTargets {
+func getChangedTargets(t testing.TB, client pb.TangoYARPCClient, remote, firstSHA, secondSHA string) parsedChangedTargets {
 	t.Helper()
 
 	ctx, cancel := context.WithTimeout(context.Background(), requestTimeout)