以下内容包含一套可编译的高性能后端微服务代码模板（Go 1.22），支持企业内网部署的“文生代码”REST服务与流式SSE响应，并在架构与实现上针对低延迟与高吞吐进行了优化。代码包含请求去重、提示缓存（Prompt Cache）、模型路由与量化参数、并发队列与令牌桶限流、增量生成与片段复用、指令模板压缩与上下文裁剪（Top-K检索）、降级与旁路、本地模板、观测指标与降级回退策略。可直接编译运行，采用内存型依赖以便演示，可替换为企业内网组件（Redis、NATS、vLLM、Triton）实现落地。
目录结构（文件与内容如下所示，逐个保存即可编译）：
- go.mod
- main.go
- internal/config/config.go
- internal/types/types.go
- internal/observability/metrics.go
- internal/ratelimit/limiter.go
- internal/cache/prompt_cache.go
- internal/retrieval/retriever.go
- internal/rules/engine.go
- internal/postcheck/checker.go
- internal/inference/provider.go
- internal/router/model_router.go
- internal/api/handlers.go
- internal/util/stream.go
文件：go.mod
module github.com/acme/codex-service
go 1.22
require (
github.com/prometheus/client_golang v1.19.0
golang.org/x/sync v0.7.0
)
文件：main.go
package main
import (
"context"
"log"
"net/http"
"os"
"os/signal"
"syscall"
"time"
"github.com/acme/codex-service/internal/api"
"github.com/acme/codex-service/internal/config"
"github.com/acme/codex-service/internal/inference"
"github.com/acme/codex-service/internal/observability"
"github.com/acme/codex-service/internal/ratelimit"
"github.com/acme/codex-service/internal/router"
)
func main() {
cfg := config.Load()
metrics := observability.NewMetrics()
limiter := ratelimit.NewLimiter(cfg.RateLimitQPS, cfg.Burst, cfg.MaxConcurrency)
providerRegistry := inference.NewRegistry()
// Register providers (mock + stubs). In prod replace with vLLM/Triton gRPC providers.
providerRegistry.Register(inference.NewMockProvider("fast-small", 20*time.Millisecond, "int4", "cpu"))
providerRegistry.Register(inference.NewMockProvider("balanced", 40*time.Millisecond, "fp8", "gpu"))
providerRegistry.Register(inference.NewMockProvider("quality-large", 70*time.Millisecond, "fp8", "gpu"))
modelRouter := router.NewModelRouter(providerRegistry, metrics)
mux := http.NewServeMux()
api.RegisterRoutes(mux, limiter, metrics, modelRouter)
srv := &http.Server{
Addr: cfg.ListenAddr,
Handler: mux,
ReadTimeout: 3 * time.Second,
ReadHeaderTimeout: 2 * time.Second,
WriteTimeout: 0, // streaming responses
IdleTimeout: 60 * time.Second,
}
go func() {
log.Printf("codex-service listening on %s", cfg.ListenAddr)
if err := srv.ListenAndServe(); err != nil && err != http.ErrServerClosed {
log.Fatalf("listen: %v", err)
}
}()
// Graceful shutdown
stop := make(chan os.Signal, 1)
signal.Notify(stop, syscall.SIGINT, syscall.SIGTERM)
<-stop
log.Println("shutting down...")
ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
defer cancel()
if err := srv.Shutdown(ctx); err != nil {
log.Fatalf("server shutdown: %v", err)
}
}
文件：internal/config/config.go
package config
import (
"log"
"os"
"strconv"
)
type Config struct {
ListenAddr string
RateLimitQPS int
Burst int
MaxConcurrency int
CacheTTLSeconds int
CacheMaxEntries int
}
func Load() *Config {
cfg := &Config{
ListenAddr: getEnv("LISTEN_ADDR", ":8080"),
RateLimitQPS: getEnvInt("RATE_LIMIT_QPS", 200),
Burst: getEnvInt("RATE_LIMIT_BURST", 400),
MaxConcurrency: getEnvInt("MAX_CONCURRENCY", 200),
CacheTTLSeconds: getEnvInt("CACHE_TTL_SECONDS", 300),
CacheMaxEntries: getEnvInt("CACHE_MAX_ENTRIES", 5000),
}
log.Printf("config: %+v", cfg)
return cfg
}
func getEnv(key, def string) string {
if v := os.Getenv(key); v != "" {
return v
}
return def
}
func getEnvInt(key string, def int) int {
if v := os.Getenv(key); v != "" {
if n, err := strconv.Atoi(v); err == nil {
return n
}
}
return def
}
文件：internal/types/types.go
package types
import "time"
type GenerateRequest struct {
Instruction string json:"instruction"
Language string json:"language,omitempty"
Framework string json:"framework,omitempty"
Dependencies []string json:"dependencies,omitempty"
MaxTokens int json:"max_tokens,omitempty"
Temperature float32 json:"temperature,omitempty"
TopK int json:"top_k,omitempty"
Stream bool json:"stream,omitempty"
Precision string json:"precision,omitempty" // "fp8", "int4"
Device string json:"device,omitempty" // "gpu", "cpu"
LatencyBudgetMs int json:"latency_budget_ms,omitempty"
}
type GenerateResponse struct {
Model string json:"model"
Code string json:"code"
Language string json:"language"
GeneratedAt time.Time json:"generated_at"
Cached bool json:"cached"
}
type StreamEvent struct {
Type string json:"type" // "token", "meta", "done", "error"
Data string json:"data" // token or meta info
Model string json:"model"
}
type RetrievalItem struct {
Snippet string
Score float32
Source string
}
文件：internal/observability/metrics.go
package observability
import (
"time"
"github.com/prometheus/client_golang/prometheus"
)
type Metrics struct {
RequestLatency *prometheus.HistogramVec
FirstByteLatency *prometheus.HistogramVec
CacheHit prometheus.Counter
CacheMiss prometheus.Counter
Errors *prometheus.CounterVec
GeneratedTokenCount *prometheus.HistogramVec
ActiveStreams prometheus.Gauge
}
func NewMetrics() *Metrics {
m := &Metrics{
RequestLatency: prometheus.NewHistogramVec(prometheus.HistogramOpts{
Name: "codex_request_latency_ms",
Help: "end-to-end latency in ms",
Buckets: []float64{50, 100, 200, 400, 600, 800, 1200, 2000, 5000},
}, []string{"endpoint", "model", "cached"}),
FirstByteLatency: prometheus.NewHistogramVec(prometheus.HistogramOpts{
Name: "codex_first_byte_latency_ms",
Help: "time to first byte in ms",
Buckets: []float64{10, 20, 50, 100, 200, 300, 500, 800},
}, []string{"endpoint", "model"}),
CacheHit: prometheus.NewCounter(prometheus.CounterOpts{
Name: "codex_cache_hit_total",
Help: "prompt cache hits",
}),
CacheMiss: prometheus.NewCounter(prometheus.CounterOpts{
Name: "codex_cache_miss_total",
Help: "prompt cache misses",
}),
Errors: prometheus.NewCounterVec(prometheus.CounterOpts{
Name: "codex_errors_total",
Help: "errors by type",
}, []string{"type", "endpoint"}),
GeneratedTokenCount: prometheus.NewHistogramVec(prometheus.HistogramOpts{
Name: "codex_generated_tokens",
Help: "number of tokens per generation",
Buckets: []float64{16, 32, 64, 128, 256, 512, 1024},
}, []string{"model"}),
ActiveStreams: prometheus.NewGauge(prometheus.GaugeOpts{
Name: "codex_active_streams",
Help: "active streaming connections",
}),
}
prometheus.MustRegister(
m.RequestLatency, m.FirstByteLatency, m.CacheHit, m.CacheMiss, m.Errors, m.GeneratedTokenCount, m.ActiveStreams,
)
return m
}
func Ms(d time.Duration) float64 { return float64(d.Milliseconds()) }
文件：internal/ratelimit/limiter.go
package ratelimit
import (
"context"
"errors"
"sync"
"time"
)
var ErrRateLimited = errors.New("rate limited")
var ErrQueueFull = errors.New("queue full")
type Limiter struct {
qps int
burst int
tokens int
lastRefill time.Time
mu sync.Mutex
concurrencyCh chan struct{}
}
func NewLimiter(qps, burst, maxConcurrency int) *Limiter {
l := &Limiter{
qps: qps,
burst: burst,
tokens: burst,
lastRefill: time.Now(),
concurrencyCh: make(chan struct{}, maxConcurrency),
}
go l.refillLoop()
return l
}
func (l *Limiter) refillLoop() {
t := time.NewTicker(100 * time.Millisecond)
defer t.Stop()
for range t.C {
l.mu.Lock()
el := time.Since(l.lastRefill)
newTokens := int(el.Seconds() * float64(l.qps))
if newTokens > 0 {
l.tokens = min(l.tokens+newTokens, l.burst)
l.lastRefill = time.Now()
}
l.mu.Unlock()
}
}
func (l *Limiter) Allow() bool {
l.mu.Lock()
defer l.mu.Unlock()
if l.tokens > 0 {
l.tokens--
return true
}
return false
}
func (l *Limiter) Acquire(ctx context.Context) error {
if !l.Allow() {
return ErrRateLimited
}
select {
case l.concurrencyCh <- struct{}{}:
return nil
case <-ctx.Done():
return ctx.Err()
}
}
func (l *Limiter) Release() {
select {
case <-l.concurrencyCh:
default:
}
}
func min(a, b int) int { if a < b { return a }; return b }
文件：internal/cache/prompt_cache.go
package cache
import (
"sync"
"time"
"github.com/acme/codex-service/internal/types"
)
type CacheEntry struct {
Response types.GenerateResponse
Fragments []string // for streaming replay
Expires time.Time
}
type PromptCache struct {
mu sync.RWMutex
data map[string]*CacheEntry
maxEntries int
ttl time.Duration
}
func NewPromptCache(maxEntries int, ttlSeconds int) *PromptCache {
return &PromptCache{
data: make(map[string]*CacheEntry, maxEntries),
maxEntries: maxEntries,
ttl: time.Duration(ttlSeconds) * time.Second,
}
}
func (pc *PromptCache) Get(key string) (*CacheEntry, bool) {
pc.mu.RLock()
defer pc.mu.RUnlock()
e, ok := pc.data[key]
if !ok || time.Now().After(e.Expires) {
return nil, false
}
return e, true
}
func (pc *PromptCache) Set(key string, resp types.GenerateResponse, fragments []string) {
pc.mu.Lock()
defer pc.mu.Unlock()
if len(pc.data) >= pc.maxEntries {
// naive eviction: random delete one entry
for k := range pc.data {
delete(pc.data, k)
break
}
}
pc.data[key] = &CacheEntry{
Response: resp,
Fragments: fragments,
Expires: time.Now().Add(pc.ttl),
}
}
func NormalizePrompt(s string) string {
// very simple normalization: trim spaces and collapse whitespace
out := make([]rune, 0, len(s))
prevSpace := false
for _, r := range []rune(s) {
if r == '\n' || r == '\t' || r == ' ' {
if !prevSpace {
out = append(out, ' ')
prevSpace = true
}
continue
}
prevSpace = false
out = append(out, r)
}
return string(out)
}
文件：internal/retrieval/retriever.go
package retrieval
import (
"strings"
"github.com/acme/codex-service/internal/types"
)
// Retriever stub; replace with vector DB (FAISS, Milvus) lookup.
type Retriever struct{}
func NewRetriever() *Retriever { return &Retriever{} }
func (r *Retriever) TopK(language, framework string, k int, query string) []types.RetrievalItem {
items := []types.RetrievalItem{}
// Simple heuristic stubs
if strings.Contains(strings.ToLower(language), "go") {
items = append(items, types.RetrievalItem{Snippet: "package main\nfunc main() {}", Score: 0.8, Source: "builtin"})
}
if strings.Contains(strings.ToLower(framework), "spring") {
items = append(items, types.RetrievalItem{Snippet: "@RestController\nclass Demo {}", Score: 0.7, Source: "builtin"})
}
if len(items) > k {
return items[:k]
}
return items
}
func ComposePrompt(instruction string, items []types.RetrievalItem, maxTokens int) string {
// Compress template and trim context under budget (stub).
// In prod estimate tokens (tiktoken) and prune low-score items.
sb := strings.Builder{}
sb.WriteString("You are a code generator. Follow instructions and output only compilable code.\n")
sb.WriteString("Instruction:\n")
sb.WriteString(instruction)
if len(items) > 0 {
sb.WriteString("\nRelevant snippets:\n")
for _, it := range items {
sb.WriteString("// from " + it.Source + "\n")
sb.WriteString(it.Snippet + "\n")
}
}
return sb.String()
}
文件：internal/rules/engine.go
package rules
import "strings"
// Very simple rule engine for local template fallback/degrade.
type Engine struct{}
func NewEngine() *Engine { return &Engine{} }
func (e *Engine) TryLocalTemplate(instruction, language string) (string, bool) {
low := strings.ToLower(instruction)
if strings.Contains(low, "hello world") {
switch strings.ToLower(language) {
case "go":
return "package main\nimport "fmt"\nfunc main(){fmt.Println("hello world")}", true
case "java":
return "public class Main{public static void main(String[] args){System.out.println("hello world");}}", true
}
}
return "", false
}
文件：internal/postcheck/checker.go
package postcheck
import "strings"
// SyntaxChecker stub. In prod: run formatters/parsers per language and fast compile checks.
type SyntaxChecker struct{}
func NewSyntaxChecker() *SyntaxChecker { return &SyntaxChecker{} }
func (c *SyntaxChecker) QuickCheck(language, code string) bool {
// trivial heuristics
if strings.TrimSpace(code) == "" {
return false
}
// ensure begins with known markers
if strings.Contains(strings.ToLower(language), "go") && !strings.Contains(code, "package") {
return false
}
return true
}
文件：internal/inference/provider.go
package inference
import (
"context"
"strings"
"time"
)
type GenOptions struct {
MaxTokens int
Temperature float32
TopK int
Precision string // "fp8", "int4"
Device string // "gpu", "cpu"
}
type GenEvent struct {
Token string
Done bool
}
type InferenceProvider interface {
Name() string
Stream(ctx context.Context, prompt string, opts GenOptions) (<-chan GenEvent, <-chan error)
Generate(ctx context.Context, prompt string, opts GenOptions) (string, error)
SupportsPrecision(p string) bool
DeviceType() string
}
type Registry struct {
providers []InferenceProvider
}
func NewRegistry() *Registry { return &Registry{providers: []InferenceProvider{}} }
func (r *Registry) Register(p InferenceProvider) { r.providers = append(r.providers, p) }
func (r *Registry) Providers() []InferenceProvider { return r.providers }
// Mock provider simulates streaming generation with configurable latency.
type MockProvider struct {
name string
delay time.Duration
precision string
device string
}
func NewMockProvider(name string, tokenDelay time.Duration, precision, device string) *MockProvider {
return &MockProvider{name: name, delay: tokenDelay, precision: precision, device: device}
}
func (m *MockProvider) Name() string { return m.name }
func (m *MockProvider) SupportsPrecision(p string) bool { return m.precision == "" || strings.EqualFold(p, m.precision) }
func (m *MockProvider) DeviceType() string { return m.device }
func (m *MockProvider) Stream(ctx context.Context, prompt string, opts GenOptions) (<-chan GenEvent, <-chan error) {
out := make(chan GenEvent, 64)
errCh := make(chan error, 1)
go func() {
defer close(out)
defer close(errCh)
// Very naive: produce small scaffold based on prompt language markers
code := scaffoldFromPrompt(prompt)
tokens := chunk(code, 16) // chunk into pseudo-tokens
for i, t := range tokens {
select {
case <-ctx.Done():
errCh <- ctx.Err()
return
default:
}
time.Sleep(m.delay)
out <- GenEvent{Token: t, Done: i == len(tokens)-1}
}
}()
return out, errCh
}
func (m MockProvider) Generate(ctx context.Context, prompt string, opts GenOptions) (string, error) {
// Non-streaming full output
code := scaffoldFromPrompt(prompt)
// Simulate latency proportional to length
time.Sleep(minDuration(m.delay10, 400*time.Millisecond))
return code, nil
}
func scaffoldFromPrompt(prompt string) string {
pl := strings.ToLower(prompt)
if strings.Contains(pl, "java") || strings.Contains(pl, "spring") {
return "import org.springframework.web.bind.annotation.*;\n@RestController\npublic class HelloController {\n @GetMapping("/hello")\n public String hello(){return "hello";}\n}"
}
if strings.Contains(pl, "go") {
return "package main\nimport "net/http"\nfunc main(){http.ListenAndServe(":8080", nil)}"
}
return "def main():\n print('hello')\nif name=='main':\n main()"
}
func chunk(s string, size int) []string {
var res []string
for i := 0; i < len(s); i += size {
end := i + size
if end > len(s) {
end = len(s)
}
res = append(res, s[i:end])
}
return res
}
func minDuration(a, b time.Duration) time.Duration {
if a < b {
return a
}
return b
}
文件：internal/router/model_router.go
package router
import (
"strings"
"time"
"github.com/acme/codex-service/internal/inference"
"github.com/acme/codex-service/internal/observability"
"github.com/acme/codex-service/internal/types"
)
type ModelRouter struct {
reg *inference.Registry
metrics *observability.Metrics
}
func NewModelRouter(reg *inference.Registry, m *observability.Metrics) *ModelRouter {
return &ModelRouter{reg: reg, metrics: m}
}
func (mr *ModelRouter) SelectProvider(req types.GenerateRequest) inference.InferenceProvider {
// Route by latency budget and complexity markers; prefer GPU for longer generations.
var selected inference.InferenceProvider
low := strings.ToLower(req.Instruction)
if req.Precision != "" || req.Device != "" {
// Respect explicit hints if available.
for _, p := range mr.reg.Providers() {
if (req.Precision == "" || p.SupportsPrecision(req.Precision)) &&
(req.Device == "" || strings.EqualFold(p.DeviceType(), req.Device)) {
selected = p
break
}
}
}
if selected == nil {
for _, p := range mr.reg.Providers() {
if req.LatencyBudgetMs > 0 && req.LatencyBudgetMs <= 300 {
// use fastest small
if strings.Contains(strings.ToLower(p.Name()), "fast") {
selected = p; break
}
} else if strings.Contains(low, "enterprise") || req.MaxTokens > 512 {
if strings.Contains(strings.ToLower(p.Name()), "quality-large") {
selected = p; break
}
} else {
if strings.Contains(strings.ToLower(p.Name()), "balanced") {
selected = p; break
}
}
}
}
// fallback to first provider
if selected == nil && len(mr.reg.Providers()) > 0 {
selected = mr.reg.Providers()[0]
}
return selected
}
func (mr *ModelRouter) RecordFirstByte(endpoint, model string, d time.Duration) {
mr.metrics.FirstByteLatency.WithLabelValues(endpoint, model).Observe(observability.Ms(d))
}
文件：internal/api/handlers.go
package api
import (
"context"
"encoding/json"
"log"
"net/http"
"strings"
"time"
"golang.org/x/sync/singleflight"
"github.com/acme/codex-service/internal/cache"
"github.com/acme/codex-service/internal/inference"
"github.com/acme/codex-service/internal/observability"
"github.com/acme/codex-service/internal/postcheck"
"github.com/acme/codex-service/internal/ratelimit"
"github.com/acme/codex-service/internal/retrieval"
"github.com/acme/codex-service/internal/router"
"github.com/acme/codex-service/internal/types"
"github.com/acme/codex-service/internal/util"
"github.com/prometheus/client_golang/prometheus/promhttp"
)
var sfGroup singleflight.Group
type serviceDeps struct {
limiter *ratelimit.Limiter
metrics *observability.Metrics
modelRouter *router.ModelRouter
cache *cache.PromptCache
retriever *retrieval.Retriever
checker *postcheck.SyntaxChecker
}
func RegisterRoutes(mux *http.ServeMux, limiter *ratelimit.Limiter, metrics *observability.Metrics, mr *router.ModelRouter) {
deps := &serviceDeps{
limiter: limiter,
metrics: metrics,
modelRouter: mr,
cache: cache.NewPromptCache(5000, 300),
retriever: retrieval.NewRetriever(),
checker: postcheck.NewSyntaxChecker(),
}
mux.HandleFunc("/healthz", func(w http.ResponseWriter, r *http.Request) { w.WriteHeader(http.StatusOK); _, _ = w.Write([]byte("ok")) })
mux.Handle("/metrics", promhttp.Handler())
mux.HandleFunc("/v1/code/generate", deps.handleGenerate)
// Non-stream JSON (explicit sync path)
mux.HandleFunc("/v1/code/generate/sync", deps.handleGenerateSync)
}
func (d *serviceDeps) handleGenerate(w http.ResponseWriter, r *http.Request) {
start := time.Now()
ctx := r.Context()
if err := d.limiter.Acquire(ctx); err != nil {
http.Error(w, "rate limited", http.StatusTooManyRequests)
d.metrics.Errors.WithLabelValues("rate_limit", "generate").Inc()
return
}
defer d.limiter.Release()
var req types.GenerateRequest
if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
http.Error(w, "bad request", http.StatusBadRequest)
d.metrics.Errors.WithLabelValues("bad_request", "generate").Inc()
return
}
// default values
if req.MaxTokens == 0 { req.MaxTokens = 512 }
if req.TopK == 0 { req.TopK = 4 }
req.Stream = true // streaming endpoint
norm := cache.NormalizePrompt(req.Instruction)
// Local rule-based bypass for very common scaffolds
if tpl, ok := rulesQuick(norm, req.Language); ok {
d.metrics.CacheHit.Inc() // treat as hot path
d.streamFromFragments(w, r, req, "local-template", strings.Split(tpl, ""), start)
return
}
// Prompt cache
if entry, ok := d.cache.Get(norm); ok {
d.metrics.CacheHit.Inc()
d.streamFromFragments(w, r, req, entry.Response.Model, entry.Fragments, start)
return
}
d.metrics.CacheMiss.Inc()
// Singleflight dedupe for identical prompts
v, err, shared := sfGroup.Do(norm, func() (any, error) {
// Compose prompt with retrieval Top-K
items := d.retriever.TopK(req.Language, req.Framework, req.TopK, req.Instruction)
prompt := retrieval.ComposePrompt(req.Instruction, items, req.MaxTokens)
provider := d.modelRouter.SelectProvider(req)
// Stream generation
opts := inference.GenOptions{MaxTokens: req.MaxTokens, Temperature: req.Temperature, TopK: req.TopK, Precision: req.Precision, Device: req.Device}
return d.doStream(ctx, w, r, req, prompt, provider, opts, start)
})
if err != nil {
// If streaming writer already started, it handled error. Otherwise:
if !util.WroteHeader(w) {
http.Error(w, "generation error", http.StatusInternalServerError)
}
d.metrics.Errors.WithLabelValues("generate_failed", "generate").Inc()
return
}
if shared {
log.Printf("singleflight shared for prompt")
}
_ = v // result already streamed
}
func (d *serviceDeps) doStream(ctx context.Context, w http.ResponseWriter, r *http.Request, req types.GenerateRequest, prompt string, provider inference.InferenceProvider, opts inference.GenOptions, start time.Time) (any, error) {
// SSE setup
util.PrepareSSE(w)
flusher := util.GetFlusher(w)
if flusher == nil {
http.Error(w, "stream not supported", http.StatusInternalServerError)
return nil, http.ErrNotSupported
}
d.metrics.ActiveStreams.Inc()
defer d.metrics.ActiveStreams.Dec()
model := provider.Name()
firstWrite := time.Now()
// Send meta event quickly
util.WriteSSE(w, types.StreamEvent{Type: "meta", Data: "model=" + model, Model: model})
flusher.Flush()
d.modelRouter.RecordFirstByte("generate", model, time.Since(firstWrite))
// Stream tokens
evCh, errCh := provider.Stream(ctx, prompt, opts)
fragments := make([]string, 0, 256)
sentFirstByte := false
for {
select {
case ev, ok := <-evCh:
if !ok {
if !sentFirstByte {
d.metrics.FirstByteLatency.WithLabelValues("generate", model).Observe(observability.Ms(time.Since(start)))
}
d.metrics.RequestLatency.WithLabelValues("generate", model, "false").Observe(observability.Ms(time.Since(start)))
// done event
util.WriteSSE(w, types.StreamEvent{Type: "done", Data: "", Model: model})
flusher.Flush()
// Cache completed response
code := strings.Join(fragments, "")
resp := types.GenerateResponse{Model: model, Code: code, Language: req.Language, GeneratedAt: time.Now(), Cached: false}
d.cache.Set(cache.NormalizePrompt(req.Instruction), resp, fragments)
// Post-check and possible repair fallback
if !d.checker.QuickCheck(req.Language, code) {
d.metrics.Errors.WithLabelValues("syntax_check_fail", "generate").Inc()
// try fallback to smaller/faster provider
fallbackReq := req
fallbackReq.Precision = "int4"
fallbackReq.Device = "cpu"
fallbackProv := d.modelRouter.SelectProvider(fallbackReq)
util.WriteSSE(w, types.StreamEvent{Type: "meta", Data: "fallback="+fallbackProv.Name(), Model: fallbackProv.Name()})
flusher.Flush()
repairOut, repairErr := fallbackProv.Generate(ctx, prompt+" Repair syntax and output only code.", opts)
if repairErr == nil && repairOut != "" {
// emit repaired code as tokens
for _, tk := range inferenceChunk(repairOut) {
util.WriteSSE(w, types.StreamEvent{Type: "token", Data: tk, Model: fallbackProv.Name()})
flusher.Flush()
}
util.WriteSSE(w, types.StreamEvent{Type: "done", Data: "", Model: fallbackProv.Name()})
flusher.Flush()
}
}
return nil, nil
}
if !sentFirstByte {
d.metrics.FirstByteLatency.WithLabelValues("generate", model).Observe(observability.Ms(time.Since(start)))
sentFirstByte = true
}
fragments = append(fragments, ev.Token)
util.WriteSSE(w, types.StreamEvent{Type: "token", Data: ev.Token, Model: model})
flusher.Flush()
if ev.Done {
// end handled when channel closes
}
case e := <-errCh:
if e != nil {
util.WriteSSE(w, types.StreamEvent{Type: "error", Data: e.Error(), Model: model})
flusher.Flush()
d.metrics.Errors.WithLabelValues("stream_error", "generate").Inc()
return nil, e
}
case <-ctx.Done():
util.WriteSSE(w, types.StreamEvent{Type: "error", Data: "client_cancelled", Model: model})
flusher.Flush()
return nil, ctx.Err()
}
}
}
func (d *serviceDeps) streamFromFragments(w http.ResponseWriter, r *http.Request, req types.GenerateRequest, model string, fragments []string, start time.Time) {
util.PrepareSSE(w)
flusher := util.GetFlusher(w)
d.metrics.ActiveStreams.Inc()
defer d.metrics.ActiveStreams.Dec()
util.WriteSSE(w, types.StreamEvent{Type: "meta", Data: "model=" + model + ";cached=true", Model: model})
flusher.Flush()
for _, tk := range fragments {
util.WriteSSE(w, types.StreamEvent{Type: "token", Data: tk, Model: model})
flusher.Flush()
}
util.WriteSSE(w, types.StreamEvent{Type: "done", Data: "", Model: model})
flusher.Flush()
d.metrics.FirstByteLatency.WithLabelValues("generate", model).Observe(observability.Ms(time.Since(start)))
d.metrics.RequestLatency.WithLabelValues("generate", model, "true").Observe(observability.Ms(time.Since(start)))
}
func (d *serviceDeps) handleGenerateSync(w http.ResponseWriter, r *http.Request) {
start := time.Now()
ctx := r.Context()
if err := d.limiter.Acquire(ctx); err != nil {
http.Error(w, "rate limited", http.StatusTooManyRequests)
d.metrics.Errors.WithLabelValues("rate_limit", "generateSync").Inc()
return
}
defer d.limiter.Release()
var req types.GenerateRequest
if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
http.Error(w, "bad request", http.StatusBadRequest)
d.metrics.Errors.WithLabelValues("bad_request", "generateSync").Inc()
return
}
if req.MaxTokens == 0 { req.MaxTokens = 512 }
if req.TopK == 0 { req.TopK = 4 }
norm := cache.NormalizePrompt(req.Instruction)
if tpl, ok := rulesQuick(norm, req.Language); ok {
resp := types.GenerateResponse{
Model: "local-template",
Code: tpl,
Language: req.Language,
GeneratedAt: time.Now(),
Cached: true,
}
_ = json.NewEncoder(w).Encode(resp)
d.metrics.CacheHit.Inc()
d.metrics.RequestLatency.WithLabelValues("generateSync", "local-template", "true").Observe(observability.Ms(time.Since(start)))
return
}
if entry, ok := d.cache.Get(norm); ok {
_ = json.NewEncoder(w).Encode(entry.Response)
d.metrics.CacheHit.Inc()
d.metrics.RequestLatency.WithLabelValues("generateSync", entry.Response.Model, "true").Observe(observability.Ms(time.Since(start)))
return
}
d.metrics.CacheMiss.Inc()
items := d.retriever.TopK(req.Language, req.Framework, req.TopK, req.Instruction)
prompt := retrieval.ComposePrompt(req.Instruction, items, req.MaxTokens)
prov := d.modelRouter.SelectProvider(req)
out, err := prov.Generate(ctx, prompt, inference.GenOptions{
MaxTokens: req.MaxTokens, Temperature: req.Temperature, TopK: req.TopK, Precision: req.Precision, Device: req.Device,
})
if err != nil {
http.Error(w, "generation error", http.StatusInternalServerError)
d.metrics.Errors.WithLabelValues("generate_failed", "generateSync").Inc()
return
}
resp := types.GenerateResponse{
Model: prov.Name(),
Code: out,
Language: req.Language,
GeneratedAt: time.Now(),
Cached: false,
}
d.cache.Set(norm, resp, strings.Split(out, "")) // cache for future streaming replay
_ = json.NewEncoder(w).Encode(resp)
d.metrics.RequestLatency.WithLabelValues("generateSync", prov.Name(), "false").Observe(observability.Ms(time.Since(start)))
}
func rulesQuick(instruction, language string) (string, bool) {
// inline small rule shortcuts for hot path
low := strings.ToLower(instruction)
if strings.Contains(low, "hello world") {
if strings.Contains(strings.ToLower(language), "go") {
return "package main\nimport "fmt"\nfunc main(){fmt.Println("hello world")}", true
}
if strings.Contains(strings.ToLower(language), "java") {
return "public class Main{public static void main(String[] args){System.out.println("hello world");}}", true
}
}
return "", false
}
func inferenceChunk(s string) []string {
chunks := make([]string, 0, len(s))
for _, r := range s {
chunks = append(chunks, string(r))
}
return chunks
}
文件：internal/util/stream.go
package util
import (
"encoding/json"
"net/http"
"sync/atomic"
"github.com/acme/codex-service/internal/types"
)
var wroteHeaderFlag uint32
func PrepareSSE(w http.ResponseWriter) {
w.Header().Set("Content-Type", "text/event-stream")
w.Header().Set("Cache-Control", "no-cache")
w.Header().Set("Connection", "keep-alive")
w.Header().Set("X-Accel-Buffering", "no") // disable buffering in nginx
atomic.StoreUint32(&wroteHeaderFlag, 1)
}
func WriteSSE(w http.ResponseWriter, ev types.StreamEvent) {
// SSE format: "data: \n\n"
b, _ := json.Marshal(ev)
w.Write([]byte("data: "))
w.Write(b)
w.Write([]byte("\n\n"))
}
func GetFlusher(w http.ResponseWriter) http.Flusher {
if f, ok := w.(http.Flusher); ok {
return f
}
return nil
}
func WroteHeader(w http.ResponseWriter) bool {
return atomic.LoadUint32(&wroteHeaderFlag) == 1
}
——
运行方式：
- 安装 Go 1.22
- 保存上述文件到项目目录
- go mod tidy
- go run main.go
- 测试：
- 同步：curl -X POST localhost:8080/v1/code/generate/sync -d '{"instruction":"用Go创建HTTP服务","language":"go"}' -H 'Content-Type: application/json'
- 流式SSE：curl -N -X POST localhost:8080/v1/code/generate -d '{"instruction":"用Spring Boot创建Hello接口","language":"java","framework":"spring","stream":true}' -H 'Content-Type: application/json'
关键设计选择与性能策略：
- 流式响应缩短首字节时间：SSE即时发送meta与首个token，目标TTFB<100–200ms（在GPU/量化模型下真实可达）。
- 请求去重与提示缓存：
- singleflight对相同指令并发进行合并，避免热路径重复算。
- Prompt Cache缓存完整结果与逐字符片段；流式路径可重放缓存碎片，实现秒级首字节。
- 模型路由与量化：
- ModelRouter依据延迟预算、指令复杂度、MaxTokens及显式Precision/Device选择不同提供者。
- 支持FP8/INT4参数透传；在GPU较忙或预算紧时优先INT4+CPU或更小模型。
- 限流与并发队列：
- 令牌桶QPS+Burst限制入站请求，bounded channel控制并发，防止过载与尾部膨胀。
- 业务级可扩展至租户维度令牌桶与公平调度。
- 上下文裁剪与Top-K检索：
- 基于检索器将高相关片段拼入提示；在生产中根据token预算、相似度阈值与去重策略进行裁剪，保证上下文性同时控制提示长度。
- 增量生成与片段复用：
- 缓存碎片（字符/小块）用于重放与节省重复生成成本；生产可在提示中加入“补齐策略”，仅生成差异片段。
- 降级与旁路：
- 规则引擎对常见脚手架（Hello World、基础Controller）直接走本地模板，极大降低尾延迟。
- 失败或预算超时时回退到更小模型进行“repair”，保障可用性。
- 生成后快速语法检查与编译预检查：
- 快速检查不通过时触发repair；生产可集成语言级parser/formatter与沙箱编译（如Go vet/build、javac dry-run）以在p95内完成。
- 观测指标：
- 延迟分布（请求与首字节）、缓存命中率、生成长度（token数/片段数量）、错误率、活动流数。
- /metrics 暴露Prometheus，结合Grafana做SLO看板与告警。
- GPU/CPU混部与弹性扩缩：
- Provider注册可区分device=GPU/CPU，Router基于负载/预算选择。
- 落地建议：推理服务（vLLM/Triton）用HPA（CPU/GPU利用率）与KEDA（队列长度/请求速率）弹性扩缩；前置网关服务也可按QPS与并发自适应扩容。
- 首字节与吞吐优化细节：
- 网络：启用HTTP keep-alive、禁用Nginx缓冲（X-Accel-Buffering），Chunked传输。
- 请求整形：入站限流+队列避免排队超时；SSE头与首个meta事件作为早期字节。
- 模型：低温度与限制max_tokens减少采样延迟；量化（INT4/FP8）提高吞吐与降低成本，结合KV cache在推理端提升热路径速度。
- 热路径优化与Prompt压缩：
- 指令模板压缩，避免冗长system prompt；结构化few-shot仅保留高权重例子。
- 对相似指令复用模板ID，缓存路由结果与上下文片段。
- 可扩展集成点（生产化落地）：
- 替换MockProvider为vLLM或Triton客户端（gRPC/HTTP），启用Prefill+Streaming。
- Redis/Memcached实现分布式Prompt Cache与Singleflight（基于分布式锁/去重键）。
- Vector DB（Milvus/FAISS）实现Top-K检索；tiktoken计算token预算进行裁剪。
- 规则引擎（Open Policy/自研）实现旁路策略管理；常用脚手架版本化与DI模板库。
- OpenTelemetry tracing接入（HTTP handler、路由、推理调用）观测端到端链路。
默认SLO目标与验证建议：
- 目标：P95延迟<800ms（含TTFB<200ms，长文本除外），错误率<1%，缓存命中率>40%于常见指令。
- 压测：用vegeta/fortio进行SSE与同步路径压测，分别模拟缓存命中/未命中场景；在GPU供给充足时验证吞吐稳定性。
注意：
- 本模板重点展示结构与关键路径优化策略，推理侧的真正低延迟需要使用高性能推理服务（如vLLM开启PagedAttention与KV Cache、Triton加速）以及正确的量化模型与GPU资源管理。将provider替换为真实客户端后，即可在企业内网实现端到端的低延迟与高吞吐。
