fix(coalesce): copy the primary response body for waiters

Waiters read the primary response buffer while fasthttp could reuse it for another request. A waiter could then send the wrong body. The primary now gives waiters their own copy.

.gitignore

@@ -5,3 +5,6 @@ dist/
 coverage.out
 CLAUDE.md
 graphql-monitoring-proxy
+
+# Lean proofs: local only, never committed
+theorems/

cache/redis/redis.go

@@ -32,6 +32,9 @@ func escapeGlobPattern(s string) string {
 	return globEscaper.Replace(s)
 }
 
+// scanCountBatch is the SCAN COUNT hint used when counting keys.
+const scanCountBatch = 1000
+
 type RedisConfig struct {
 	ctx         context.Context
 	client      *redis.Client
@@ -163,12 +166,28 @@ func (c *RedisConfig) Clear() error {
 // literally instead of being interpreted as a wildcard, which would
 // otherwise undercount or overcount keys in admin-dashboard stats.
 func (c *RedisConfig) CountQueries() (int64, error) {
-	pattern := escapeGlobPattern(c.prefix) + "*"
-	keys, err := c.client.Keys(c.ctx, pattern).Result()
-	if err != nil {
-		return 0, err
+	return c.scanCount(escapeGlobPattern(c.prefix) + "*")
+}
+
+// scanCount counts keys matching pattern with a cursor SCAN. KEYS builds the
+// whole reply in memory on the server and blocks it, which spiked a shared
+// Dragonfly to its memory limit when the prefix is empty.
+func (c *RedisConfig) scanCount(pattern string) (int64, error) {
+	var (
+		cursor uint64
+		total  int64
+	)
+	for {
+		keys, next, err := c.client.Scan(c.ctx, cursor, pattern, scanCountBatch).Result()
+		if err != nil {
+			return 0, fmt.Errorf("redis: scan at cursor %d: %w", cursor, err)
+		}
+		total += int64(len(keys))
+		cursor = next
+		if cursor == 0 {
+			return total, nil
+		}
 	}
-	return int64(len(keys)), nil
 }
 
 // CountQueriesWithPattern returns the number of keys owned by this cache
@@ -177,12 +196,11 @@ func (c *RedisConfig) CountQueries() (int64, error) {
 // itself is left as given so a caller can still use glob metacharacters
 // intentionally in the suffix it supplies.
 func (c *RedisConfig) CountQueriesWithPattern(pattern string) (int, error) {
-	fullPattern := escapeGlobPattern(c.prefix) + pattern
-	keys, err := c.client.Keys(c.ctx, fullPattern).Result()
+	total, err := c.scanCount(escapeGlobPattern(c.prefix) + pattern)
 	if err != nil {
 		return 0, err
 	}
-	return len(keys), nil
+	return int(total), nil
 }
 
 // GetMemoryUsage returns an approximation of memory usage for Redis.

cache/redis/redis_count_scan_test.go

@@ -0,0 +1,82 @@
+package libpack_cache_redis
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"strings"
+	"sync"
+	"testing"
+
+	"github.com/alicebob/miniredis/v2"
+	redis "github.com/redis/go-redis/v9"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+type commandRecorder struct {
+	mu   sync.Mutex
+	seen []string
+}
+
+func (r *commandRecorder) DialHook(next redis.DialHook) redis.DialHook {
+	return func(ctx context.Context, network, addr string) (net.Conn, error) {
+		return next(ctx, network, addr)
+	}
+}
+
+func (r *commandRecorder) ProcessHook(next redis.ProcessHook) redis.ProcessHook {
+	return func(ctx context.Context, cmd redis.Cmder) error {
+		r.mu.Lock()
+		r.seen = append(r.seen, strings.ToLower(cmd.Name()))
+		r.mu.Unlock()
+		return next(ctx, cmd)
+	}
+}
+
+func (r *commandRecorder) ProcessPipelineHook(next redis.ProcessPipelineHook) redis.ProcessPipelineHook {
+	return next
+}
+
+func (r *commandRecorder) count(name string) int {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	n := 0
+	for _, s := range r.seen {
+		if s == name {
+			n++
+		}
+	}
+	return n
+}
+
+// TestCount_UsesScanNotKeys guards against reintroducing KEYS, which builds
+// the whole key list server-side and spiked a shared Dragonfly to its limit.
+func TestCount_UsesScanNotKeys(t *testing.T) {
+	t.Parallel()
+	s, err := miniredis.Run()
+	require.NoError(t, err)
+	t.Cleanup(s.Close)
+
+	rc, err := New(&RedisClientConfig{RedisServer: s.Addr()})
+	require.NoError(t, err)
+
+	const total = 2500
+	for i := 0; i < total; i++ {
+		require.NoError(t, rc.Set(fmt.Sprintf("k%d", i), []byte("v"), 0))
+	}
+
+	rec := &commandRecorder{}
+	rc.client.AddHook(rec)
+
+	count, err := rc.CountQueries()
+	require.NoError(t, err)
+	assert.Equal(t, int64(total), count)
+
+	patternCount, err := rc.CountQueriesWithPattern("k1*")
+	require.NoError(t, err)
+	assert.Equal(t, 1111, patternCount, "k1, k10-k19, k100-k199, k1000-k1999")
+
+	assert.Zero(t, rec.count("keys"), "counting must not issue KEYS")
+	assert.GreaterOrEqual(t, rec.count("scan"), 2, "counting must issue SCAN")
+}

coalesced_snapshot_test.go

@@ -0,0 +1,27 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/gofiber/fiber/v3"
+	"github.com/stretchr/testify/assert"
+	"github.com/valyala/fasthttp"
+)
+
+// Pins theorems/Theorems/CoalesceAlias.lean: waiters never alias the primary's response buffer.
+func TestSnapshotCoalescedResponse_OwnsBody(t *testing.T) {
+	app := fiber.New()
+	fctx := &fasthttp.RequestCtx{}
+	c := app.AcquireCtx(fctx)
+	defer app.ReleaseCtx(c)
+
+	c.Response().SetStatusCode(201)
+	c.Response().SetBody([]byte(`{"user":"alice"}`))
+
+	snap := snapshotCoalescedResponse(c)
+
+	c.Response().SetBody([]byte(`{"user":"bobby"}`)) // buffer reused by a later request
+
+	assert.Equal(t, 201, snap.StatusCode)
+	assert.Equal(t, `{"user":"alice"}`, string(snap.Body))
+}

go.mod

@@ -2,23 +2,23 @@ module github.com/lukaszraczylo/graphql-monitoring-proxy
 
 go 1.26.0
 
-toolchain go1.27.2
+toolchain go1.27.3
 
 require (
 	github.com/MicahParks/keyfunc/v3 v3.8.2
 	github.com/VictoriaMetrics/metrics v1.44.1
-	github.com/alicebob/miniredis/v2 v2.39.0
+	github.com/alicebob/miniredis/v2 v2.40.0
 	github.com/avast/retry-go/v5 v5.0.0
-	github.com/goccy/go-json v0.11.2
-	github.com/gofiber/contrib/v3/websocket v1.2.7
-	github.com/gofiber/fiber/v3 v3.5.0
+	github.com/goccy/go-json v0.12.0
+	github.com/gofiber/contrib/v3/websocket v1.2.10
+	github.com/gofiber/fiber/v3 v3.6.1
 	github.com/gofrs/flock v0.13.1
 	github.com/golang-jwt/jwt/v5 v5.3.1
 	github.com/google/uuid v1.6.0
-	github.com/gookit/goutil v0.8.1
+	github.com/gookit/goutil v0.8.6
 	github.com/gorilla/websocket v1.5.3
 	github.com/graphql-go/graphql v0.8.1
-	github.com/jackc/pgx/v5 v5.11.0
+	github.com/jackc/pgx/v5 v5.12.0
 	github.com/lukaszraczylo/ask v0.0.0-20240916204100-6e9ef53a62d9
 	github.com/lukaszraczylo/go-ratecounter v0.1.13
 	github.com/lukaszraczylo/go-simple-graphql v1.2.89
@@ -26,13 +26,13 @@ require (
 	github.com/redis/go-redis/v9 v9.23.0
 	github.com/sony/gobreaker/v2 v2.4.0
 	github.com/stretchr/testify v1.12.1
-	github.com/valyala/fasthttp v1.75.0
+	github.com/valyala/fasthttp v1.77.0
 	go.opentelemetry.io/otel v1.47.0
 	go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc v1.47.0
 	go.opentelemetry.io/otel/sdk v1.47.0
 	go.opentelemetry.io/otel/trace v1.47.0
 	go.uber.org/automaxprocs v1.6.0
-	google.golang.org/grpc v1.84.0
+	google.golang.org/grpc v1.85.0
 )
 
 require (
@@ -43,17 +43,17 @@ require (
 	github.com/fasthttp/websocket v1.5.12 // indirect
 	github.com/go-logr/logr v1.4.4 // indirect
 	github.com/go-logr/stdr v1.2.2 // indirect
-	github.com/gofiber/schema v1.8.8 // indirect
-	github.com/gofiber/utils/v2 v2.6.1 // indirect
-	github.com/grpc-ecosystem/grpc-gateway/v2 v2.31.0 // indirect
+	github.com/gofiber/schema v1.9.2 // indirect
+	github.com/gofiber/utils/v2 v2.6.3 // indirect
+	github.com/grpc-ecosystem/grpc-gateway/v2 v2.33.0 // indirect
 	github.com/jackc/pgpassfile v1.0.0 // indirect
 	github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 // indirect
 	github.com/jackc/puddle/v2 v2.2.3 // indirect
-	github.com/klauspost/compress v1.20.1 // indirect
+	github.com/klauspost/compress v1.20.3 // indirect
 	github.com/mattn/go-colorable v0.1.16 // indirect
 	github.com/mattn/go-isatty v0.0.24 // indirect
-	github.com/molecule-man/go-brrr v1.2.0 // indirect
-	github.com/philhofer/fwd v1.2.0 // indirect
+	github.com/molecule-man/go-brrr v1.3.1 // indirect
+	github.com/philhofer/fwd v1.2.1 // indirect
 	github.com/savsgio/gotils v0.0.0-20250924091648-bce9a52d7761 // indirect
 	github.com/tinylib/msgp v1.6.5 // indirect
 	github.com/valyala/bytebufferpool v1.0.0 // indirect
@@ -67,14 +67,14 @@ require (
 	go.opentelemetry.io/proto/otlp v1.11.1 // indirect
 	go.uber.org/atomic v1.12.0 // indirect
 	go.yaml.in/yaml/v3 v3.0.5 // indirect
-	golang.org/x/crypto v0.57.0 // indirect
-	golang.org/x/net v0.60.0 // indirect
+	golang.org/x/crypto v0.58.0 // indirect
+	golang.org/x/net v0.62.0 // indirect
 	golang.org/x/sync v0.24.0 // indirect
 	golang.org/x/sys v0.49.0 // indirect
-	golang.org/x/term v0.46.0 // indirect
-	golang.org/x/text v0.42.0 // indirect
+	golang.org/x/term v0.47.0 // indirect
+	golang.org/x/text v0.43.0 // indirect
 	golang.org/x/time v0.16.0 // indirect
-	google.golang.org/genproto/googleapis/api v0.0.0-20260928230214-8a89bd6388cc // indirect
-	google.golang.org/genproto/googleapis/rpc v0.0.0-20260928230214-8a89bd6388cc // indirect
+	google.golang.org/genproto/googleapis/api v0.0.0-20261026165753-2ffab32bce7e // indirect
+	google.golang.org/genproto/googleapis/rpc v0.0.0-20261019180522-ce908d29299b // indirect
 	google.golang.org/protobuf v1.36.12 // indirect
 )

go.sum

@@ -4,8 +4,8 @@ github.com/MicahParks/keyfunc/v3 v3.8.2 h1:eydEwk/pBAVrDIpmFfB/gkCcrp++xQ7YYXirr
 github.com/MicahParks/keyfunc/v3 v3.8.2/go.mod h1:T4snFPe26GwMg45bBAdM5P6qWQyLxZHLwBhxR/9PnCs=
 github.com/VictoriaMetrics/metrics v1.44.1 h1:OMyGrMkhI3hnq+IpJ1gZK9VhXcsOjUX1CoOFv//bJ0I=
 github.com/VictoriaMetrics/metrics v1.44.1/go.mod h1:xDM82ULLYCYdFRgQ2JBxi8Uf1+8En1So9YUwlGTOqTc=
-github.com/alicebob/miniredis/v2 v2.39.0 h1:M7WbmV5BmV56L8KTG0rw6vEQ+woTOghpDgin2xv4A0g=
-github.com/alicebob/miniredis/v2 v2.39.0/go.mod h1:TcL7YfarKPGDAthEtl5NBeHZfeUQj6OXMm/+iu5cLMM=
+github.com/alicebob/miniredis/v2 v2.40.0 h1:6IgTQbvm2JiMYZ8yur/acNJzVjtSOWCelxXbk/LUBXc=
+github.com/alicebob/miniredis/v2 v2.40.0/go.mod h1:TcL7YfarKPGDAthEtl5NBeHZfeUQj6OXMm/+iu5cLMM=
 github.com/avast/retry-go/v4 v4.7.0 h1:yjDs35SlGvKwRNSykujfjdMxMhMQQM0TnIjJaHB+Zio=
 github.com/avast/retry-go/v4 v4.7.0/go.mod h1:ZMPDa3sY2bKgpLtap9JRUgk2yTAba7cgiFhqxY2Sg6Q=
 github.com/avast/retry-go/v5 v5.0.0 h1:kf1Qc2UsTZ4qq8elDymqfbISvkyMuhgRxuJqX2NHP7k=
@@ -21,25 +21,25 @@ github.com/cespare/xxhash/v2 v2.3.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XL
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/fasthttp/websocket v1.5.12 h1:e4RGPpWW2HTbL3zV0Y/t7g0ub294LkiuXXUuTOUInlE=
 github.com/fasthttp/websocket v1.5.12/go.mod h1:I+liyL7/4moHojiOgUOIKEWm9EIxHqxZChS+aMFltyg=
-github.com/fxamacker/cbor/v2 v2.9.4 h1:xwjVlxEMR3S605oUlgBjKLTTeGFciYPGYCtF/35LKGo=
-github.com/fxamacker/cbor/v2 v2.9.4/go.mod h1:vM4b+DJCtHn+zz7h3FFp/hDAI9WNWCsZj23V5ytsSxQ=
+github.com/fxamacker/cbor/v2 v2.9.6 h1:NHZPxuUjJXQjX9itA785y/5NKSlI4HQ+S7noZsmI7hs=
+github.com/fxamacker/cbor/v2 v2.9.6/go.mod h1:4EaZp6ClVunETjQ4GHmGNzysDK91Lr+r6Yz6tJqzVCw=
 github.com/go-logr/logr v1.2.2/go.mod h1:jdQByPbusPIv2/zmleS9BjJVeZ6kBagPoEUsqbVz/1A=
 github.com/go-logr/logr v1.4.4 h1:tG4xh9yMsRCAiodLVTxyrkzSZ9+o0L1Kg/+cPVcbP/8=
 github.com/go-logr/logr v1.4.4/go.mod h1:9T104GzyrTigFIr8wt5mBrctHMim0Nb2HLGrmQ40KvY=
 github.com/go-logr/stdr v1.2.2 h1:hSWxHoqTgW2S2qGc0LTAI563KZ5YKYRhT3MFKZMbjag=
 github.com/go-logr/stdr v1.2.2/go.mod h1:mMo/vtBO5dYbehREoey6XUKy/eSumjCCveDpRre4VKE=
-github.com/goccy/go-json v0.11.2 h1:jdZv93Tt4ioR8yW1CoNsvSxrcZlCXAUU1aZXN7gpXUA=
-github.com/goccy/go-json v0.11.2/go.mod h1:3NdmfEkZlB7YI5UFw/qdFKq8XN1aiWR0YyRPWZNQltY=
+github.com/goccy/go-json v0.12.0 h1:pD+oWouAiz4yruwXIt/iT+lOMeyhr1aTtxzaMP/RgVI=
+github.com/goccy/go-json v0.12.0/go.mod h1:3NdmfEkZlB7YI5UFw/qdFKq8XN1aiWR0YyRPWZNQltY=
 github.com/goccy/go-reflect v1.2.0 h1:O0T8rZCuNmGXewnATuKYnkL0xm6o8UNOJZd/gOkb9ms=
 github.com/goccy/go-reflect v1.2.0/go.mod h1:n0oYZn8VcV2CkWTxi8B9QjkCoq6GTtCEdfmR66YhFtE=
-github.com/gofiber/contrib/v3/websocket v1.2.7 h1:Na87WdkBkMl5wcf1MyD0q8neEmd1We57xSoJfIypmrk=
-github.com/gofiber/contrib/v3/websocket v1.2.7/go.mod h1:L1ELWKh/Tn3sGEjQdLCmnb6HbroXsD83dcRCEwNXwOg=
-github.com/gofiber/fiber/v3 v3.5.0 h1:dk7TOUH6DXJGtOLsN2XEG+0ZML7cznzHILTVozbNEK8=
-github.com/gofiber/fiber/v3 v3.5.0/go.mod h1:GOVDTW+gjJvfe0iJyVujbQ1Lnx+JUjFySJRI/9/xX/w=
-github.com/gofiber/schema v1.8.8 h1:md5t65+Z9LttOuj7FdMcQ63D2+6GniT2ganLXwvTJM4=
-github.com/gofiber/schema v1.8.8/go.mod h1:Hzf0L/fTPP1IwOAwKipKflm9C2722aebnSKJCMOgb1I=
-github.com/gofiber/utils/v2 v2.6.1 h1:x3zsS/oUQz0ia2Zx8XXtG/7naR5a+/95FRO8mwQ5QQ4=
-github.com/gofiber/utils/v2 v2.6.1/go.mod h1:tc9KqdRAQZRD/u0mN2d1ZHROGheSZv+0FcC9cg5OEdw=
+github.com/gofiber/contrib/v3/websocket v1.2.10 h1:tUyRcHSH9GUsh6WO03Xn+Kjvt3850W6raF6WPngdJLE=
+github.com/gofiber/contrib/v3/websocket v1.2.10/go.mod h1:O6MOrNHCVdCrrstdLrYmRIL0eJy2N87Wa/y2dszuxvQ=
+github.com/gofiber/fiber/v3 v3.6.1 h1:wYjbgqpJm6VErIVLSGzGpX7lLZyTNgElsj8nQ1i+iFo=
+github.com/gofiber/fiber/v3 v3.6.1/go.mod h1:+nxjBal3gw0EPf3gqK5EmtxaxTL01+zbSTagFletlDI=
+github.com/gofiber/schema v1.9.2 h1:Gzw2PF1K5DpWgG2L51/9t9dkmxw4kqK6auKMvgD9mIU=
+github.com/gofiber/schema v1.9.2/go.mod h1:219nYAgzIEBWl/aHCyhQtFoXBvfLjsC6+FI3DUN1+Ck=
+github.com/gofiber/utils/v2 v2.6.3 h1:VlnOB89rFnonlXoYOkESOkXtIkAw4CBBwpBHu+/a/YQ=
+github.com/gofiber/utils/v2 v2.6.3/go.mod h1:Mq3OXwyBPxORb3jPafy6Swki4/TJJW9TDPHeerXkXpg=
 github.com/gofrs/flock v0.13.1 h1:jjREztyBeSKBZYAC+mgc1laB+xsgy4kYMf3FbKF2UBo=
 github.com/gofrs/flock v0.13.1/go.mod h1:sf4BFiHwnvgxa25DlQoDqXQnwRMEOwqxRq37P6MzzmE=
 github.com/golang-jwt/jwt/v5 v5.3.1 h1:kYf81DTWFe7t+1VvL7eS+jKFVWaUnK9cB1qbwn63YCY=
@@ -50,24 +50,24 @@ github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
 github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
 github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
 github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
-github.com/gookit/goutil v0.8.1 h1:kmNpOdJ/76KbNk8Xb7yTKfbQhUWY8T1nV1MrWI7dmZo=
-github.com/gookit/goutil v0.8.1/go.mod h1:vJS9HXctYTCLtCsZot5L5xF+O1oR17cDYO9R0HxBmnU=
+github.com/gookit/goutil v0.8.6 h1:8LfEg9xVDdlQ1yWzk0seLslJCUPt8YnZQo5v0ycGs3E=
+github.com/gookit/goutil v0.8.6/go.mod h1:vJS9HXctYTCLtCsZot5L5xF+O1oR17cDYO9R0HxBmnU=
 github.com/gorilla/websocket v1.5.3 h1:saDtZ6Pbx/0u+bgYQ3q96pZgCzfhKXGPqt7kZ72aNNg=
 github.com/gorilla/websocket v1.5.3/go.mod h1:YR8l580nyteQvAITg2hZ9XVh4b55+EU/adAjf1fMHhE=
 github.com/graphql-go/graphql v0.8.1 h1:p7/Ou/WpmulocJeEx7wjQy611rtXGQaAcXGqanuMMgc=
 github.com/graphql-go/graphql v0.8.1/go.mod h1:nKiHzRM0qopJEwCITUuIsxk9PlVlwIiiI8pnJEhordQ=
-github.com/grpc-ecosystem/grpc-gateway/v2 v2.31.0 h1:Bd7KaOxzULLxtZ/K5s1aLbWhR0+5RToO65TXHsf3bqQ=
-github.com/grpc-ecosystem/grpc-gateway/v2 v2.31.0/go.mod h1:nN7ts3dFXKtCZWc//yfkpcQNKJABg16/uDVAZpLDalo=
+github.com/grpc-ecosystem/grpc-gateway/v2 v2.33.0 h1:5T5Ns3kMpWr+z3s5ZA0e7ljVyWNVNxK76sHPAxi5D1k=
+github.com/grpc-ecosystem/grpc-gateway/v2 v2.33.0/go.mod h1:oWNYw09cH8wl8fFgC5hKlBLxR4XfKy2KQpP8MJjeCcc=
 github.com/jackc/pgpassfile v1.0.0 h1:/6Hmqy13Ss2zCq62VdNG8tM1wchn8zjSGOBJ6icpsIM=
 github.com/jackc/pgpassfile v1.0.0/go.mod h1:CEx0iS5ambNFdcRtxPj5JhEz+xB6uRky5eyVu/W2HEg=
 github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 h1:iCEnooe7UlwOQYpKFhBabPMi4aNAfoODPEFNiAnClxo=
 github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761/go.mod h1:5TJZWKEWniPve33vlWYSoGYefn3gLQRzjfDlhSJ9ZKM=
-github.com/jackc/pgx/v5 v5.11.0 h1:IzBBtyK9AHqf98cctWFifYSci2hgQR/cd56wB4p+ogg=
-github.com/jackc/pgx/v5 v5.11.0/go.mod h1:mal1tBGAFfLHvZzaYh77YS/eC6IX9OWbRV1QIIM0Jn4=
+github.com/jackc/pgx/v5 v5.12.0 h1:hWwax8YiGT0YiN50U1oIDn5kgR7KC2tG3rmavwpPkxY=
+github.com/jackc/pgx/v5 v5.12.0/go.mod h1:u2Fi6no03HCSBYE+ZVdLxbwdu3xyi2vU+K/YNJioSds=
 github.com/jackc/puddle/v2 v2.2.3 h1:f8HoREISb3l5eO9coPgK7U3hKLhWGokOFVcThl5jrao=
 github.com/jackc/puddle/v2 v2.2.3/go.mod h1:vriiEXHvEE654aYKXXjOvZM39qJ0q+azkZFrfEOc3H4=
-github.com/klauspost/compress v1.20.1 h1:T7kKElXUMXrUJ2E9QhQhxFtcK5rPyLdsGZvdbLMPdiQ=
-github.com/klauspost/compress v1.20.1/go.mod h1:LUdAzn7YLVvxLpc7y3V1m40wESHTgc1422pwwBSKYuI=
+github.com/klauspost/compress v1.20.3 h1:zWNoFqq/lSuYQRim3dUXlXeA0IqwuZGicdG5ZTfY5j4=
+github.com/klauspost/compress v1.20.3/go.mod h1:LUdAzn7YLVvxLpc7y3V1m40wESHTgc1422pwwBSKYuI=
 github.com/klauspost/cpuid/v2 v2.4.0 h1:S6Hrbc7+ywsr0r+RLapfGBHfyefhCTwEh3A0tV913Dw=
 github.com/klauspost/cpuid/v2 v2.4.0/go.mod h1:19jmZ9mjzoF//ddRSUsv0zfBTJWh3QJh9FNxZTMrGxU=
 github.com/lukaszraczylo/ask v0.0.0-20240916204100-6e9ef53a62d9 h1:pL8B9mjv6RPUfKYYGm/uJ7QL6Ndf+z+OEl0qJE6KmEc=
@@ -82,10 +82,10 @@ github.com/mattn/go-colorable v0.1.16 h1:+2YjeAe7xP1OQbZW1jERPWWCDLlNqFNCvjiqGiA
 github.com/mattn/go-colorable v0.1.16/go.mod h1:6LmQG8QLFO4G5z1gPvYEzlUgJ2wF+stgPZH1UqBm1s8=
 github.com/mattn/go-isatty v0.0.24 h1:tGZZoVgT/KiqK1c8ocVLeDS8BSWMRd47J3Lbz7vsReI=
 github.com/mattn/go-isatty v0.0.24/go.mod h1:nMCL3Zebbrt45jsMDgnfIwz6ydEQApk5oEI3HqDio6A=
-github.com/molecule-man/go-brrr v1.2.0 h1:dOJU45BC3Gc2WXoxAW0rgCAgVuu2gruAOGncfieA0Jw=
-github.com/molecule-man/go-brrr v1.2.0/go.mod h1:7ybW6/7gA3oKY45jOfVNjSJDtrr6ea4tzbsTkjmQDC4=
-github.com/philhofer/fwd v1.2.0 h1:e6DnBTl7vGY+Gz322/ASL4Gyp1FspeMvx1RNDoToZuM=
-github.com/philhofer/fwd v1.2.0/go.mod h1:RqIHx9QI14HlwKwm98g9Re5prTQ6LdeRQn+gXJFxsJM=
+github.com/molecule-man/go-brrr v1.3.1 h1:EwaJUzRIlp/dFmIpzq4J17CA5Zi5OHo2vOGmu09hF1w=
+github.com/molecule-man/go-brrr v1.3.1/go.mod h1:7ybW6/7gA3oKY45jOfVNjSJDtrr6ea4tzbsTkjmQDC4=
+github.com/philhofer/fwd v1.2.1 h1:UtpS73q8bFgy/yH3gCq8LSNvj5gv/FowNOiWZa7uKwQ=
+github.com/philhofer/fwd v1.2.1/go.mod h1:RqIHx9QI14HlwKwm98g9Re5prTQ6LdeRQn+gXJFxsJM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/prashantv/gostub v1.1.0 h1:BTyx3RfQjRHnUWaGF9oQos79AlQ5k8WNktv7VGvVH4g=
 github.com/prashantv/gostub v1.1.0/go.mod h1:A5zLQHz7ieHGG7is6LLXLz7I8+3LZzsrV0P1IAHhP5U=
@@ -93,8 +93,8 @@ github.com/redis/go-redis/v9 v9.23.0 h1:/TTVdJa8BRNsybwwGGnmiYktHNlUXtbOQxlWpHBP
 github.com/redis/go-redis/v9 v9.23.0/go.mod h1:EWP2UUk+XDaI1s5nQB5mablZN6vccXlmBQTyfnF87D0=
 github.com/savsgio/gotils v0.0.0-20250924091648-bce9a52d7761 h1:McifyVxygw1d67y6vxUqls2D46J8W9nrki9c8c0eVvE=
 github.com/savsgio/gotils v0.0.0-20250924091648-bce9a52d7761/go.mod h1:Vi9gvHvTw4yCUHIznFl5TPULS7aXwgaTByGeBY75Wko=
-github.com/shamaton/msgpack/v3 v3.2.3 h1:0r0aZtrXDFOPpwWJTEOpFq+Ih/JmMLm0pqLN5mSilrw=
-github.com/shamaton/msgpack/v3 v3.2.3/go.mod h1:sgBYvEiyz8JR1NC3yGRoPVME9xXovpnh3l/plW1nfRo=
+github.com/shamaton/msgpack/v3 v3.2.6 h1:i8I++0ehiIO8yK4+ZU6j5MIWFz5e8J6EeJvdM/qeyTw=
+github.com/shamaton/msgpack/v3 v3.2.6/go.mod h1:sgBYvEiyz8JR1NC3yGRoPVME9xXovpnh3l/plW1nfRo=
 github.com/sony/gobreaker/v2 v2.4.0 h1:g2KJRW1Ubty3+ZOcSEUN7K+REQJdN6yo6XvaML+jptg=
 github.com/sony/gobreaker/v2 v2.4.0/go.mod h1:pTyFJgcZ3h2tdQVLZZruK2C0eoFL1fb/G83wK1ZQl+s=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
@@ -106,8 +106,8 @@ github.com/tinylib/msgp v1.6.5 h1:iAH6XTP7BpzErjBZlujJQXxA+GmRi2YWs6M4KdLtNbE=
 github.com/tinylib/msgp v1.6.5/go.mod h1:RSp0LW9oSxFut3KzESt5Voq4GVWyS+PSulT77roAqEA=
 github.com/valyala/bytebufferpool v1.0.0 h1:GqA5TC/0021Y/b9FG4Oi9Mr3q7XYx6KllzawFIhcdPw=
 github.com/valyala/bytebufferpool v1.0.0/go.mod h1:6bBcMArwyJ5K/AmCkWv1jt77kVWyCJ6HpOuEn7z0Csc=
-github.com/valyala/fasthttp v1.75.0 h1:W3xrvNJHG60j2ZCjxpP8kkB+oPG8kh9/g1n4+3xUwNA=
-github.com/valyala/fasthttp v1.75.0/go.mod h1:JiVkPRZU124PuPsreV/s9dZRgG2lRK7wNEikdQ0Rk4s=
+github.com/valyala/fasthttp v1.77.0 h1:6mxBJdHabRmU4Cmw79Uqhgvjzsp6pjOaQk2t8COflzo=
+github.com/valyala/fasthttp v1.77.0/go.mod h1:m8oTPC8riDDky07invpl+Gz3RixnAN5BbwyUuVB5H2o=
 github.com/valyala/fastrand v1.1.0 h1:f+5HkLW4rsgzdNoleUOB69hyT9IlD2ZQh9GyDMfb5G8=
 github.com/valyala/fastrand v1.1.0/go.mod h1:HWqCzkrkg6QXT8V2EXWvXCoow7vLwOFN002oeRzjapQ=
 github.com/valyala/histogram v1.2.0 h1:wyYGAZZt3CpwUiIb9AU/Zbllg1llXyrtApRS815OLoQ=
@@ -146,30 +146,30 @@ go.uber.org/goleak v1.3.0 h1:2K3zAYmnTNqV73imy9J1T3WC+gmCePx2hEGkimedGto=
 go.uber.org/goleak v1.3.0/go.mod h1:CoHD4mav9JJNrW/WLlf7HGZPjdw8EucARQHekz1X6bE=
 go.yaml.in/yaml/v3 v3.0.5 h1:N6y/pJk8buWs9NY5ERU2HSMfm+IuD/OtfdAnq6kESPw=
 go.yaml.in/yaml/v3 v3.0.5/go.mod h1:HVTZu1O7/Vkt2N+BFy8Zza+lnLsABggaTM2ZpNIGuKg=
-golang.org/x/crypto v0.57.0 h1:3ZVCjf8Ggz7zneR/EHRVx68Ctf+2pmIMP2UFhh9cC6M=
-golang.org/x/crypto v0.57.0/go.mod h1:Fdz0i5U6CoizGwLda9DttjSk6qlZo25zYNtR+ycvuZA=
-golang.org/x/net v0.60.0 h1:79p50tfZlm0J9YfoDsSi639qSXNGVwEzOPLCxM2FsYU=
-golang.org/x/net v0.60.0/go.mod h1:2DA/G1UfVbCpQPeWTmMPGY7Cs2PkBkwu743bVX5PIVg=
+golang.org/x/crypto v0.58.0 h1:COkYLr4k7nDI4r6QtMML2AfzeIswWHAJthLS6K/M/54=
+golang.org/x/crypto v0.58.0/go.mod h1:Xh+kl5A+M0gMiWDytH2Hhr5Z7WbNCpv/eB/EFgfSk+w=
+golang.org/x/net v0.62.0 h1:18ELalfM5+XNRwzM2nYqXsZQ9ByS1uhj2O/U7+5jqRY=
+golang.org/x/net v0.62.0/go.mod h1:WgDCOTH8iwtB66T4/GfI94AHo/hhdb7Hah9NDseQfiI=
 golang.org/x/sync v0.24.0 h1:iqiDrGoDgyuvAKrhLQthUEzU/R378N78gXbBjxed7oA=
 golang.org/x/sync v0.24.0/go.mod h1:sUUOizhqBxiL6pEWpqNLUiaJn1ShEbZ6BBqskPbjZm0=
 golang.org/x/sys v0.49.0 h1:XbzkgYJHdqh/8m2Uu0W/dQv8nktxx4BFHp1M0gROTXA=
 golang.org/x/sys v0.49.0/go.mod h1:hNLxWAXmnKAxqDtdwIYC4bM9oQPEecfsnNMuSxOs3og=
-golang.org/x/term v0.46.0 h1:3+OXuTbaKDgwk8jTi3aSLHRlmWqHEUDUtxnbFigO4YE=
-golang.org/x/term v0.46.0/go.mod h1:+K02xbkittuwc0Am4abfA3Fc+XRGXkvBXNO88NCXPoc=
-golang.org/x/text v0.42.0 h1:JbOZXgfeCPU9gacVtYliJqOhD+zhrEqK4LfdpmlUZqI=
-golang.org/x/text v0.42.0/go.mod h1:ojzP1Z+2QtioaF8DTtO8K5q7JWVVYwZKenzujK0Zd0E=
+golang.org/x/term v0.47.0 h1:cpyOwQkr2Nzxe2p6KnrTG7Ei2wtzjsuSjhpXXepZ/BM=
+golang.org/x/term v0.47.0/go.mod h1:efAfAuG6RKABvg1ArGebRkvX6LXul14SM67o2e4mUCY=
+golang.org/x/text v0.43.0 h1:1QivrlhwAsnMOcqgOdl9my7s9OyZl8O5/UGUTJVXoWc=
+golang.org/x/text v0.43.0/go.mod h1:hbSIYA/amXcRXTFSZqh8tWHEoqRvvbKPJ2uz/KU+a+s=
 golang.org/x/time v0.16.0 h1:vMb6ptszcQMkcwiRTAuNNU50gom6++Q/6gY2hDM6VDE=
 golang.org/x/time v0.16.0/go.mod h1:rVKOqvZeKvrDKTQiAHJ7wmwP0RzleSphoEA9RcdLA0s=
-golang.org/x/tools v0.50.0 h1:c2ifzfcuY7L90lZ2aKd8S4K2NpASF08SZx9ZuJkHmSU=
-golang.org/x/tools v0.50.0/go.mod h1:7ulVMw3831Mwi5EZD6RomGyffr4VFjuNYXf2BbCEAV0=
+golang.org/x/tools v0.52.0 h1:ryxg4U63oaUYk7uOLTF37n43f4qgtGvqV4Ioit1BaEs=
+golang.org/x/tools v0.52.0/go.mod h1:ItcP5UNaVGG+Yc4eIYmaFLNJ4soEopkx5Y2d4lcEurs=
 gonum.org/v1/gonum v0.17.0 h1:VbpOemQlsSMrYmn7T2OUvQ4dqxQXU+ouZFQsZOx50z4=
 gonum.org/v1/gonum v0.17.0/go.mod h1:El3tOrEuMpv2UdMrbNlKEh9vd86bmQ6vqIcDwxEOc1E=
-google.golang.org/genproto/googleapis/api v0.0.0-20260928230214-8a89bd6388cc h1:rZHRz0ogq4Pid1IKtA/ivHi8XONVF5tqUQXA2TtgpkE=
-google.golang.org/genproto/googleapis/api v0.0.0-20260928230214-8a89bd6388cc/go.mod h1:K/n0XLazCJHjD73YuMyNJsN38BPPy1kfFnKxUXaThFU=
-google.golang.org/genproto/googleapis/rpc v0.0.0-20260928230214-8a89bd6388cc h1:4bNTbnb44EqGVy9HaQxSY2jnafSUdgV3qHtedvNpDKg=
-google.golang.org/genproto/googleapis/rpc v0.0.0-20260928230214-8a89bd6388cc/go.mod h1:OaIUM3+LpYcK2GXM4FTmhWoIq371Owdr+Cc7/BsYHHc=
-google.golang.org/grpc v1.84.0 h1:soMyaPJ8pAak5PIQ0DGBUir0XRo2fRoMqhNWMLlLxO0=
-google.golang.org/grpc v1.84.0/go.mod h1:ljCht0DrxQrXBDRTZp52Qxh3Ffk8CdYm2sj4O2QN2C0=
+google.golang.org/genproto/googleapis/api v0.0.0-20261026165753-2ffab32bce7e h1:e789sLZjeTdc02ZCQGTSzHOu0fR73+dwPQVKUp67Z88=
+google.golang.org/genproto/googleapis/api v0.0.0-20261026165753-2ffab32bce7e/go.mod h1:vHV3wJM9WZyfV7GyB+OQGq5dWVrFwCDxapPK4WlRD88=
+google.golang.org/genproto/googleapis/rpc v0.0.0-20261019180522-ce908d29299b h1:6WNWHZk91dp4gZ25642OALkuG1UVNZbwENJD19DnB8k=
+google.golang.org/genproto/googleapis/rpc v0.0.0-20261019180522-ce908d29299b/go.mod h1:OaIUM3+LpYcK2GXM4FTmhWoIq371Owdr+Cc7/BsYHHc=
+google.golang.org/grpc v1.85.0 h1:BPBCfuVRQ1qvBhKDOq9uvQllMvO59rKsYhXpp7Dd8vw=
+google.golang.org/grpc v1.85.0/go.mod h1:0rQrOD58yjal/0EaVbGBANindixsCZNQPDV3VKtaKuQ=
 google.golang.org/protobuf v1.36.12 h1:pJOKDDOyeXErUroCihFAd5LQuwXBSpVnKGrj5o/fwxc=
 google.golang.org/protobuf v1.36.12/go.mod h1:HTf+CrKn2C3g5S8VImy6tdcUvCska2kB7j23XfzDpco=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=

proxy.go

@@ -740,11 +740,7 @@ func performProxyRequest(c fiber.Ctx, proxyURL string) error {
 				}, proxyErr
 			}
 
-			return &CoalescedResponse{
-				Body:       c.Response().Body(),
-				StatusCode: c.Response().StatusCode(),
-				// Headers intentionally left nil; not populated or read anywhere.
-			}, nil
+			return snapshotCoalescedResponse(c), nil
 		})
 
 		// Check for error from rc.Do (though it typically returns nil)
@@ -773,6 +769,17 @@ func performProxyRequest(c fiber.Ctx, proxyURL string) error {
 	return performProxyRequestCore(c, proxyURL, cacheKey)
 }
 
+// snapshotCoalescedResponse captures the primary's response for waiters. It
+// copies the body because fasthttp reuses the buffer once the primary handler
+// returns, while waiters can still be reading.
+func snapshotCoalescedResponse(c fiber.Ctx) *CoalescedResponse {
+	return &CoalescedResponse{
+		Body:       bytes.Clone(c.Response().Body()),
+		StatusCode: c.Response().StatusCode(),
+		// Headers intentionally left nil; not populated or read anywhere.
+	}
+}
+
 // performProxyRequestCore executes the proxy request with retries and circuit breaker
 // This is the core implementation used by both direct calls and coalesced requests
 func performProxyRequestCore(c fiber.Ctx, proxyURL string, cacheKey string) error {

retry_budget.go

@@ -148,31 +148,39 @@ func (rb *RetryBudget) refill() {
 	now := time.Now().UnixNano()
 	last := rb.lastRefill.Load()
 
-	// Calculate elapsed time in seconds
-	elapsed := float64(now-last) / float64(time.Second)
+	tokensToAdd, newLast := refillStep(tokensPerSecond, last, now)
+	if tokensToAdd <= 0 {
+		return
+	}
+	if rb.lastRefill.CompareAndSwap(last, newLast) {
+		for {
+			current := rb.currentTokens.Load()
+			newValue := current + tokensToAdd
+			if newValue > maxTokens {
+				newValue = maxTokens
+			}
 
-	// Calculate tokens to add
-	tokensToAdd := int64(elapsed * tokensPerSecond)
-
-	if tokensToAdd > 0 {
-		// Update last refill time
-		if rb.lastRefill.CompareAndSwap(last, now) {
-			// Add tokens, capped at maxTokens
-			for {
-				current := rb.currentTokens.Load()
-				newValue := current + tokensToAdd
-				if newValue > maxTokens {
-					newValue = maxTokens
-				}
-
-				if rb.currentTokens.CompareAndSwap(current, newValue) {
-					break
-				}
+			if rb.currentTokens.CompareAndSwap(current, newValue) {
+				break
 			}
 		}
 	}
 }
 
+// refillStep returns the whole tokens earned between last and now (ns) and the
+// clock to store. The clock advances only by the time those tokens pay for, so
+// the fractional remainder carries into the next tick.
+func refillStep(tokensPerSecond float64, last, now int64) (int64, int64) {
+	if tokensPerSecond <= 0 || now <= last {
+		return 0, last
+	}
+	tokens := int64(float64(now-last) / float64(time.Second) * tokensPerSecond)
+	if tokens <= 0 {
+		return 0, last
+	}
+	return tokens, last + int64(float64(tokens)/tokensPerSecond*float64(time.Second))
+}
+
 // GetStats returns current statistics
 func (rb *RetryBudget) GetStats() map[string]any {
 	totalAttempts := rb.totalAttempts.Load()

retry_budget_refill_test.go

@@ -0,0 +1,47 @@
+package main
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
+
+// Pins theorems/Theorems/RetryRefill.lean: total_added(15 tps, 100ms ticks, 10s) = 150.
+func TestRefillStep_KeepsFractionalTokens(t *testing.T) {
+	tests := []struct {
+		name string
+		tps  float64
+		want int64
+	}{
+		{"15 tps", 15, 150},
+		{"25 tps", 25, 250},
+		{"5 tps (sub-token per tick)", 5, 50},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			tick := 100 * time.Millisecond
+			var last, total int64
+			now := int64(tick)
+			for i := 0; i < 100; i++ {
+				added, newLast := refillStep(tt.tps, last, now)
+				total += added
+				last = newLast
+				now += int64(tick)
+			}
+			assert.Equal(t, tt.want, total)
+		})
+	}
+}
+
+func TestRefillStep_NoElapsedNoChange(t *testing.T) {
+	added, last := refillStep(10, 1000, 1000)
+	assert.Zero(t, added)
+	assert.Equal(t, int64(1000), last)
+}
+
+func TestRefillStep_ZeroRateNeverAdds(t *testing.T) {
+	added, last := refillStep(0, 0, int64(time.Hour))
+	assert.Zero(t, added)
+	assert.Zero(t, last)
+}

rps_tracker.go

@@ -57,17 +57,23 @@ func (r *RPSTracker) Shutdown() {
 
 // sample calculates RPS since last sample
 func (r *RPSTracker) sample() {
-	now := time.Now()
-	nowNano := now.UnixNano()
+	r.sampleCount()
+}
+
+// sampleCount performs one sample and returns the requests it consumed.
+func (r *RPSTracker) sampleCount() int64 {
+	nowNano := time.Now().UnixNano()
 
-	currentCount := r.lastCount.Load()
 	lastSampleNano := r.lastSampleTime.Load()
 
 	if lastSampleNano == 0 {
 		r.lastSampleTime.Store(nowNano)
-		return
+		return 0
 	}
 
+	// Swap, not Load+Store(0): requests recorded between the two would be lost.
+	currentCount := r.lastCount.Swap(0)
+
 	elapsed := float64(nowNano-lastSampleNano) / float64(time.Second)
 	if elapsed > 0 {
 		rps := float64(currentCount) / elapsed
@@ -75,9 +81,8 @@ func (r *RPSTracker) sample() {
 		r.currentRPS.Store(uint64(rps * 100))
 	}
 
-	// Reset for next sample
-	r.lastCount.Store(0)
 	r.lastSampleTime.Store(nowNano)
+	return currentCount
 }
 
 // GetCurrentRPS returns the current requests per second

rps_tracker_sample_test.go

@@ -0,0 +1,43 @@
+package main
+
+import (
+	"context"
+	"sync"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+// Pins theorems/Theorems/RpsSample.lean: no recorded request is dropped by sample().
+func TestRPSTracker_SampleKeepsConcurrentRequests(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	tr := NewRPSTracker(ctx)
+	tr.Shutdown() // stop the background sampler; sample() is driven by the test
+
+	const writers, perWriter = 8, 20000
+	var wg sync.WaitGroup
+	for i := 0; i < writers; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			for j := 0; j < perWriter; j++ {
+				tr.RecordRequest()
+			}
+		}()
+	}
+	var sampled int64
+	done := make(chan struct{})
+	go func() { wg.Wait(); close(done) }()
+loop:
+	for {
+		select {
+		case <-done:
+			break loop
+		default:
+			sampled += tr.sampleCount()
+		}
+	}
+	sampled += tr.sampleCount()
+	assert.Equal(t, int64(writers*perWriter), sampled)
+}