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|
package limithandler
import (
"context"
grpcmwtags "github.com/grpc-ecosystem/go-grpc-middleware/tags"
"github.com/prometheus/client_golang/prometheus"
"gitlab.com/gitlab-org/gitaly/v14/internal/gitaly/config"
"google.golang.org/grpc"
)
// GetLockKey function defines the lock key of an RPC invocation based on its context
type GetLockKey func(context.Context) string
// LimitConcurrencyByRepo implements GetLockKey by using the repository path as lock.
func LimitConcurrencyByRepo(ctx context.Context) string {
tags := grpcmwtags.Extract(ctx)
ctxValue := tags.Values()["grpc.request.repoPath"]
if ctxValue == nil {
return ""
}
s, ok := ctxValue.(string)
if ok {
return s
}
return ""
}
// Limiter limits incoming requests
type Limiter interface {
Limit(ctx context.Context, lockKey string, f LimitedFunc) (interface{}, error)
}
// LimitedFunc represents a function that will be limited
type LimitedFunc func() (resp interface{}, err error)
// LimiterMiddleware contains rate limiter state
type LimiterMiddleware struct {
methodLimiters map[string]Limiter
getLockKey GetLockKey
requestsDroppedMetric *prometheus.CounterVec
collect func(metrics chan<- prometheus.Metric)
}
// New creates a new middleware that limits requests. SetupFunc sets up the
// middlware with a specific kind of limiter.
func New(cfg config.Cfg, getLockKey GetLockKey, setupMiddleware SetupFunc) *LimiterMiddleware {
middleware := &LimiterMiddleware{
getLockKey: getLockKey,
requestsDroppedMetric: prometheus.NewCounterVec(
prometheus.CounterOpts{
Name: "gitaly_requests_dropped_total",
Help: "Number of requests dropped from the queue",
},
[]string{
"system",
"grpc_service",
"grpc_method",
"reason",
},
),
}
setupMiddleware(cfg, middleware)
return middleware
}
// Describe is used to describe Prometheus metrics.
func (c *LimiterMiddleware) Describe(descs chan<- *prometheus.Desc) {
prometheus.DescribeByCollect(c, descs)
}
// Collect is used to collect Prometheus metrics.
func (c *LimiterMiddleware) Collect(metrics chan<- prometheus.Metric) {
c.requestsDroppedMetric.Collect(metrics)
if c.collect != nil {
c.collect(metrics)
}
}
// UnaryInterceptor returns a Unary Interceptor
func (c *LimiterMiddleware) UnaryInterceptor() grpc.UnaryServerInterceptor {
return func(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
lockKey := c.getLockKey(ctx)
if lockKey == "" {
return handler(ctx, req)
}
limiter := c.methodLimiters[info.FullMethod]
if limiter == nil {
// No concurrency limiting
return handler(ctx, req)
}
return limiter.Limit(ctx, lockKey, func() (interface{}, error) {
return handler(ctx, req)
})
}
}
// StreamInterceptor returns a Stream Interceptor
func (c *LimiterMiddleware) StreamInterceptor() grpc.StreamServerInterceptor {
return func(srv interface{}, stream grpc.ServerStream, info *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
wrapper := &wrappedStream{stream, info, c, true}
return handler(srv, wrapper)
}
}
// SetupFunc set up a middleware to limiting requests
type SetupFunc func(cfg config.Cfg, middleware *LimiterMiddleware)
type wrappedStream struct {
grpc.ServerStream
info *grpc.StreamServerInfo
limiterMiddleware *LimiterMiddleware
initial bool
}
func (w *wrappedStream) RecvMsg(m interface{}) error {
if err := w.ServerStream.RecvMsg(m); err != nil {
return err
}
// Only perform limiting on the first request of a stream
if !w.initial {
return nil
}
w.initial = false
ctx := w.Context()
lockKey := w.limiterMiddleware.getLockKey(ctx)
if lockKey == "" {
return nil
}
limiter := w.limiterMiddleware.methodLimiters[w.info.FullMethod]
if limiter == nil {
// No concurrency limiting
return nil
}
ready := make(chan struct{})
errs := make(chan error)
go func() {
if _, err := limiter.Limit(ctx, lockKey, func() (interface{}, error) {
close(ready)
<-ctx.Done()
return nil, nil
}); err != nil {
errs <- err
}
}()
select {
case <-ctx.Done():
return ctx.Err()
case <-ready:
// It's our turn!
return nil
case err := <-errs:
return err
}
}
|
