feat: expose gateway outcome metrics

README.md

@@ -41,6 +41,8 @@ Proxy Pool 用 Controller 协调这些变化，并让 Gateway 数据面只消费
   PostgreSQL 迁移与 Redis 活动池，并支持联动优雅停机。
 - **Checker 指标**：Metrics 启用时暴露 Checker 任务下发与 Observation 接受/拒绝计数；
   标签仅使用固定检查级别和结果，不记录 Proxy、IP、URL 或凭据。
+- **Gateway 指标**：Metrics 启用时暴露代理尝试的固定阶段成功/失败计数，以及本地
+  Outcome 队列满后的丢弃计数；不记录 Proxy、路由、目标、客户端或凭据。
 - **PostgreSQL 管理面**：持久化配置版本、Upstream/Routing 管理状态、Admin
   审计与 Outbox；不保存 Proxy 明细或逐次提取记录。
 - **Gateway 组件**：HTTP 正向代理、HTTPS CONNECT、双向 Tunnel、重试、超时、

docs/configuration/reference.md

@@ -513,8 +513,11 @@ Metrics 启用时 `listen` 必须是合法 `host:port`。该入口固定提供 `
 网络策略限制。当前 `/metrics` 包含 Go/进程基础指标，以及 Checker 的
 `proxy_pool_checker_tasks_dispatched_total{level}` 和
 `proxy_pool_checker_observations_total{level,result}`。`level` 固定为 BASIC、EGRESS、TARGET，
-`result` 固定为 accepted、rejected；绝不包含 Proxy、IP、Checker、Client、URL 或凭据标签。
-Provider、提取和容量等业务指标仍在后续实施范围。Distribution 启用时 `/readyz` 只以 Redis 活动池为
+`result` 固定为 accepted、rejected。Gateway 另暴露
+`proxy_pool_gateway_outcomes_total{stage,result}` 与
+`proxy_pool_gateway_outcome_queue_dropped_total`；`stage` 固定为 DIAL、PROXY_HANDSHAKE、
+RESPONSE_HEADERS、TUNNEL，`result` 固定为 success、failure。绝不包含 Proxy、IP、Checker、
+Client、路由、目标 URL 或凭据标签。Provider、提取和容量等业务指标仍在后续实施范围。Distribution 启用时 `/readyz` 只以 Redis 活动池为
 服务流量门槛，PostgreSQL 故障由 Admin 接口独立报告。Metrics 开关或监听地址
 变更需要重启 Controller。
 

docs/development/implementation-plan.md

@@ -336,8 +336,10 @@ Profile 在启用 Routing 与 Upstream 的组合上才进入调度。
 当前进度（2026-08-02）：已接入 Checker 任务流指标
 `proxy_pool_checker_tasks_dispatched_total{level}` 与
 `proxy_pool_checker_observations_total{level,result}`；标签值仅允许固定的
-`BASIC`、`EGRESS`、`TARGET` 级别及 `accepted`、`rejected` 结果。Provider、提取、
-容量指标与密钥安全的结构化日志仍待补齐。
+`BASIC`、`EGRESS`、`TARGET` 级别及 `accepted`、`rejected` 结果。Gateway 还暴露
+`proxy_pool_gateway_outcomes_total{stage,result}` 和
+`proxy_pool_gateway_outcome_queue_dropped_total`，其中阶段和结果均为固定枚举。Provider、
+提取、容量指标与密钥安全的结构化日志仍待补齐。
 
 ## Task 14: Documentation, Examples, and Diagrams
 

docs/operations/runbook.md

@@ -136,6 +136,14 @@ Checker 指标使用固定标签集：
 `level` 仅为 BASIC、EGRESS、TARGET，`result` 仅为 accepted、rejected。不得将
 Proxy ID、IP、Checker ID、目标 URL、Client ID 或凭据加入指标标签。
 
+Gateway 指标同样使用固定标签集：
+
+- `proxy_pool_gateway_outcomes_total{stage,result}`：每次代理尝试在最远完成阶段的成功/失败数量。
+- `proxy_pool_gateway_outcome_queue_dropped_total`：Outcome 本地有界队列已满后丢弃的观测数量。
+
+`stage` 仅为 DIAL、PROXY_HANDSHAKE、RESPONSE_HEADERS、TUNNEL，`result` 仅为 success、failure。
+前者在写入本地队列前计数，后者用于识别观测背压；二者均不包含 Proxy ID、路由、目标、客户端或凭据。
+
 ### 3.4 发布顺序与兼容性
 
 1. 先做向前兼容数据库迁移。

docs/requirements/completion-audit.md

@@ -104,7 +104,8 @@ Controller/Gateway 入口，完整 mTLS 运行时拓扑仍只有静态验证。
    响应校验场景；`proxy-checker` 的 BASIC 任务进程已经完成，
    `proxy-controller` 已完成
    Admin/Distribution/Metrics 与 PostgreSQL/Redis 启动装配，`proxy-gateway` 已完成
-   HTTP/Metrics 与控制面 Session 装配，但 Provider 和业务指标链未闭环。
+   HTTP/Metrics 与控制面 Session 装配；Checker 与 Gateway Outcome 的低基数业务指标
+   已接入，但 Provider、提取和容量指标链未闭环。
 2. Gateway 的生产连接池调优与代表性流量压测。
 3. Provider 分布式 singleflight/Leader、长期凭据回收和累计额度执行器。
 4. Controller 的 PostgreSQL 连接池、迁移和 pgx Adapter 启动装配已完成；

docs/requirements/traceability.md

@@ -87,5 +87,5 @@
 | OPS-001 | 配置校验后构建不可变快照并原子替换 | 8959-8999 | 100k 索引、版本/epoch 与并发 Apply/Acquire 测试 |
 | OPS-002 | 优雅停机停止新请求/Fetch，等待现有流量后超时关闭 | 8981-9000 | Provider Run 收敛与 `Handler.Shutdown` HTTP 排空、Hijacked CONNECT 超时关闭测试 |
 | OPS-003 | PostgreSQL 只保存管理修订、Upstream/Routing 状态、Admin 审计与 Outbox | 当前会话 | ADR-006、`adminstate` 公用契约和六表 Schema 边界测试；真实 PostgreSQL 契约待完成 |
-| OBS-001 | 指标禁止 Proxy IP、session、Client、完整 URL 高基数标签 | 9001-9029 | Controller Prometheus/探针模块已实现；Checker Collector 仅暴露 `proxy_pool_checker_tasks_dispatched_total{level}` 与 `proxy_pool_checker_observations_total{level,result}`，并以注册表测试固定标签集。Provider、提取和容量业务指标待实现 |
+| OBS-001 | 指标禁止 Proxy IP、session、Client、完整 URL 高基数标签 | 9001-9029 | Controller Prometheus/探针模块已实现；Checker Collector 暴露固定等级和结果，Gateway Collector 暴露 `proxy_pool_gateway_outcomes_total{stage,result}` 与 `proxy_pool_gateway_outcome_queue_dropped_total`，均以注册表测试固定标签集。Provider、提取和容量业务指标待实现 |
 | TEST-001 | 覆盖对话中列出的 11 个关键并发与故障场景 | 9030-9082 | 测试清单；Redis 活动池由 Memory/Redis 公用契约覆盖，跨进程故障场景仍按清单推进 |

internal/domain/outcome/metrics.go

@@ -0,0 +1,9 @@
+package outcome
+
+// MetricsObserver receives aggregate Gateway outcome signals on the local
+// request path. Implementations must only perform bounded in-process work and
+// must never block request forwarding.
+type MetricsObserver interface {
+	Observe(Event)
+	ObserveDropped()
+}

internal/gateway/bootstrap/bootstrap.go

@@ -19,6 +19,7 @@ import (
 	controlplanev1 "proxy-pool/gen/controlplane/v1"
 	"proxy-pool/internal/config"
 	"proxy-pool/internal/controlplane/clienttransport"
+	outcomeDomain "proxy-pool/internal/domain/outcome"
 	proxyDomain "proxy-pool/internal/domain/proxy"
 	"proxy-pool/internal/domain/workerruntime"
 	"proxy-pool/internal/gateway/controlplane"
@@ -146,8 +147,18 @@ func newRuntime(ctx context.Context, configuration *config.Config, options Optio
 		return nil, fmt.Errorf("build gateway target policy: %w", err)
 	}
 	proxyTransport := transport.New(transport.Config{}, snapshotCredentialResolver{store: store})
+	var outcomeMetrics outcomeDomain.MetricsObserver
+	if configuration.Metrics.Enabled {
+		collector, err := platformMetrics.NewGatewayCollector(prometheus.DefaultRegisterer)
+		if err != nil {
+			proxyTransport.CloseIdleConnections()
+			return nil, fmt.Errorf("build gateway outcome metrics: %w", err)
+		}
+		outcomeMetrics = collector
+	}
 	outcomes, err := gatewayOutcome.NewQueue(gatewayOutcome.QueueOptions{
 		Capacity: defaultOutcomeQueueCapacity, MaxBatch: min(defaultOutcomeBatchSize, configuration.ControlPlane.MaxRuntimeCounters),
+		Metrics: outcomeMetrics,
 	})
 	if err != nil {
 		proxyTransport.CloseIdleConnections()

internal/gateway/bootstrap/bootstrap_test.go

@@ -11,6 +11,7 @@ import (
 	"net/url"
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 	"time"
 
@@ -79,6 +80,18 @@ func TestRunServesGatewayOnlyAfterApplyingControlPlaneSnapshot(t *testing.T) {
 			t.Fatalf("gateway did not become ready: %v", err)
 		}
 	}
+	metricsResponse, err := http.Get("http://" + metricsListener.Addr().String() + "/metrics")
+	if err != nil {
+		t.Fatalf("GET gateway metrics: %v", err)
+	}
+	metricsBody, err := io.ReadAll(metricsResponse.Body)
+	_ = metricsResponse.Body.Close()
+	if err != nil {
+		t.Fatalf("ReadAll(gateway metrics) = %v", err)
+	}
+	if metricsResponse.StatusCode != http.StatusOK || !strings.Contains(string(metricsBody), "proxy_pool_gateway_outcome_queue_dropped_total") {
+		t.Fatalf("gateway metrics = (%d, %q), want outcome queue metric", metricsResponse.StatusCode, metricsBody)
+	}
 	proxyURL, err := url.Parse("http://" + proxyListener.Addr().String())
 	if err != nil {
 		t.Fatalf("Parse(proxy URL): %v", err)

internal/gateway/outcome/queue.go

@@ -15,6 +15,7 @@ var ErrInvalidQueueOptions = errors.New("invalid gateway outcome queue options")
 type QueueOptions struct {
 	Capacity int
 	MaxBatch int
+	Metrics  domain.MetricsObserver
 }
 
 // Queue accepts observations from the request path without blocking. Events
@@ -23,6 +24,7 @@ type QueueOptions struct {
 type Queue struct {
 	events   chan domain.Event
 	maxBatch int
+	metrics  domain.MetricsObserver
 	dropped  atomic.Uint64
 }
 
@@ -30,17 +32,27 @@ func NewQueue(options QueueOptions) (*Queue, error) {
 	if options.Capacity <= 0 || options.MaxBatch <= 0 || options.MaxBatch > options.Capacity {
 		return nil, ErrInvalidQueueOptions
 	}
-	return &Queue{events: make(chan domain.Event, options.Capacity), maxBatch: options.MaxBatch}, nil
+	return &Queue{
+		events:   make(chan domain.Event, options.Capacity),
+		maxBatch: options.MaxBatch,
+		metrics:  options.Metrics,
+	}, nil
 }
 
 func (queue *Queue) Record(event domain.Event) {
 	if queue == nil {
 		return
 	}
+	if queue.metrics != nil {
+		queue.metrics.Observe(event)
+	}
 	select {
 	case queue.events <- event:
 	default:
 		queue.dropped.Add(1)
+		if queue.metrics != nil {
+			queue.metrics.ObserveDropped()
+		}
 	}
 }
 

internal/gateway/outcome/queue_test.go

@@ -8,6 +8,19 @@ import (
 	domain "proxy-pool/internal/domain/outcome"
 )
 
+type metricsRecorder struct {
+	events  []domain.Event
+	dropped int
+}
+
+func (recorder *metricsRecorder) Observe(event domain.Event) {
+	recorder.events = append(recorder.events, event)
+}
+
+func (recorder *metricsRecorder) ObserveDropped() {
+	recorder.dropped++
+}
+
 func TestQueueBatchesWithoutBlockingAndCountsOverflow(t *testing.T) {
 	queue, err := NewQueue(QueueOptions{Capacity: 2, MaxBatch: 2})
 	if err != nil {
@@ -39,3 +52,22 @@ func TestQueueHonorsCanceledContext(t *testing.T) {
 		t.Fatalf("Next(canceled) = %v, want context canceled", err)
 	}
 }
+
+func TestQueueReportsAttemptedOutcomesAndOverflow(t *testing.T) {
+	metrics := &metricsRecorder{}
+	queue, err := NewQueue(QueueOptions{Capacity: 1, MaxBatch: 1, Metrics: metrics})
+	if err != nil {
+		t.Fatalf("NewQueue() = %v", err)
+	}
+	first := domain.Event{ProxyID: "proxy-a", Stage: domain.StageDial, Success: true}
+	second := domain.Event{ProxyID: "proxy-b", Stage: domain.StageTunnel, Success: false}
+	queue.Record(first)
+	queue.Record(second)
+
+	if len(metrics.events) != 2 || metrics.events[0] != first || metrics.events[1] != second {
+		t.Fatalf("observed events = %+v, want both attempts", metrics.events)
+	}
+	if metrics.dropped != 1 {
+		t.Fatalf("observed dropped = %d, want 1", metrics.dropped)
+	}
+}

internal/platform/metrics/checker.go

@@ -60,11 +60,11 @@ func registerCounterVec(registerer prometheus.Registerer, candidate *prometheus.
 	} else {
 		var registered prometheus.AlreadyRegisteredError
 		if !errors.As(err, &registered) {
-			return nil, fmt.Errorf("register checker metrics: %w", err)
+			return nil, fmt.Errorf("register counter vector: %w", err)
 		}
 		existing, ok := registered.ExistingCollector.(*prometheus.CounterVec)
 		if !ok {
-			return nil, fmt.Errorf("register checker metrics: existing collector has unexpected type")
+			return nil, fmt.Errorf("register counter vector: existing collector has unexpected type")
 		}
 		return existing, nil
 	}

internal/platform/metrics/gateway.go

@@ -0,0 +1,99 @@
+package metrics
+
+import (
+	"errors"
+	"fmt"
+
+	"github.com/prometheus/client_golang/prometheus"
+
+	outcomeDomain "proxy-pool/internal/domain/outcome"
+)
+
+// GatewayCollector exposes fixed-cardinality request-path outcome metrics.
+// Proxy, route, destination, client and credential values are never labels.
+type GatewayCollector struct {
+	outcomes *prometheus.CounterVec
+	dropped  prometheus.Counter
+}
+
+var _ outcomeDomain.MetricsObserver = (*GatewayCollector)(nil)
+
+func NewGatewayCollector(registerer prometheus.Registerer) (*GatewayCollector, error) {
+	if registerer == nil {
+		return nil, ErrInvalidDependencies
+	}
+	outcomes, err := registerCounterVec(registerer, prometheus.NewCounterVec(prometheus.CounterOpts{
+		Namespace: "proxy_pool", Subsystem: "gateway", Name: "outcomes_total",
+		Help: "Number of Gateway proxy attempts by furthest completed stage and result.",
+	}, []string{"stage", "result"}))
+	if err != nil {
+		return nil, err
+	}
+	dropped, err := registerCounter(registerer, prometheus.NewCounter(prometheus.CounterOpts{
+		Namespace: "proxy_pool", Subsystem: "gateway", Name: "outcome_queue_dropped_total",
+		Help: "Number of Gateway outcome observations dropped after the local queue was full.",
+	}))
+	if err != nil {
+		return nil, err
+	}
+	return &GatewayCollector{outcomes: outcomes, dropped: dropped}, nil
+}
+
+func (collector *GatewayCollector) Observe(event outcomeDomain.Event) {
+	if collector == nil || collector.outcomes == nil || !validGatewayStage(event.Stage) {
+		return
+	}
+	result := "failure"
+	if event.Success {
+		result = "success"
+	}
+	collector.outcomes.WithLabelValues(gatewayStageLabel(event.Stage), result).Inc()
+}
+
+func (collector *GatewayCollector) ObserveDropped() {
+	if collector == nil || collector.dropped == nil {
+		return
+	}
+	collector.dropped.Inc()
+}
+
+func registerCounter(registerer prometheus.Registerer, candidate prometheus.Counter) (prometheus.Counter, error) {
+	if err := registerer.Register(candidate); err == nil {
+		return candidate, nil
+	} else {
+		var registered prometheus.AlreadyRegisteredError
+		if !errors.As(err, &registered) {
+			return nil, fmt.Errorf("register counter: %w", err)
+		}
+		existing, ok := registered.ExistingCollector.(prometheus.Counter)
+		if !ok {
+			return nil, fmt.Errorf("register counter: existing collector has unexpected type")
+		}
+		return existing, nil
+	}
+}
+
+func validGatewayStage(stage outcomeDomain.Stage) bool {
+	switch stage {
+	case outcomeDomain.StageDial, outcomeDomain.StageProxyHandshake,
+		outcomeDomain.StageResponseHeaders, outcomeDomain.StageTunnel:
+		return true
+	default:
+		return false
+	}
+}
+
+func gatewayStageLabel(stage outcomeDomain.Stage) string {
+	switch stage {
+	case outcomeDomain.StageDial:
+		return "DIAL"
+	case outcomeDomain.StageProxyHandshake:
+		return "PROXY_HANDSHAKE"
+	case outcomeDomain.StageResponseHeaders:
+		return "RESPONSE_HEADERS"
+	case outcomeDomain.StageTunnel:
+		return "TUNNEL"
+	default:
+		return ""
+	}
+}

internal/platform/metrics/gateway_test.go

@@ -0,0 +1,44 @@
+package metrics
+
+import (
+	"testing"
+
+	"github.com/prometheus/client_golang/prometheus"
+
+	outcomeDomain "proxy-pool/internal/domain/outcome"
+)
+
+func TestGatewayCollectorRecordsOnlyFixedDimensions(t *testing.T) {
+	registry := prometheus.NewRegistry()
+	collector, err := NewGatewayCollector(registry)
+	if err != nil {
+		t.Fatalf("NewGatewayCollector() = %v", err)
+	}
+	collector.Observe(outcomeDomain.Event{Stage: outcomeDomain.StageDial, Success: true})
+	collector.Observe(outcomeDomain.Event{Stage: outcomeDomain.StageTunnel, Success: false})
+	collector.Observe(outcomeDomain.Event{Stage: outcomeDomain.StageUnspecified, Success: true})
+	collector.ObserveDropped()
+
+	assertMetricValue(t, registry, "proxy_pool_gateway_outcomes_total", map[string]string{
+		"stage": "DIAL", "result": "success",
+	}, 1)
+	assertMetricValue(t, registry, "proxy_pool_gateway_outcomes_total", map[string]string{
+		"stage": "TUNNEL", "result": "failure",
+	}, 1)
+	assertMetricValue(t, registry, "proxy_pool_gateway_outcome_queue_dropped_total", nil, 1)
+}
+
+func TestNewGatewayCollectorReusesRegisteredCollectors(t *testing.T) {
+	registry := prometheus.NewRegistry()
+	first, err := NewGatewayCollector(registry)
+	if err != nil {
+		t.Fatalf("first NewGatewayCollector() = %v", err)
+	}
+	second, err := NewGatewayCollector(registry)
+	if err != nil {
+		t.Fatalf("second NewGatewayCollector() = %v", err)
+	}
+	first.ObserveDropped()
+	second.ObserveDropped()
+	assertMetricValue(t, registry, "proxy_pool_gateway_outcome_queue_dropped_total", nil, 2)
+}