Merge pull request #1495 from fatedier/new

support bandwith limit for one proxy

client/proxy/proxy.go

@@ -30,6 +30,7 @@ import (
 	"github.com/fatedier/frp/models/msg"
 	"github.com/fatedier/frp/models/plugin"
 	"github.com/fatedier/frp/models/proto/udp"
+	"github.com/fatedier/frp/utils/limit"
 	frpNet "github.com/fatedier/frp/utils/net"
 	"github.com/fatedier/frp/utils/xlog"
 
@@ -38,6 +39,7 @@ import (
 	"github.com/fatedier/golib/pool"
 	fmux "github.com/hashicorp/yamux"
 	pp "github.com/pires/go-proxyproto"
+	"golang.org/x/time/rate"
 )
 
 // Proxy defines how to handle work connections for different proxy type.
@@ -51,9 +53,16 @@ type Proxy interface {
 }
 
 func NewProxy(ctx context.Context, pxyConf config.ProxyConf, clientCfg config.ClientCommonConf, serverUDPPort int) (pxy Proxy) {
+	var limiter *rate.Limiter
+	limitBytes := pxyConf.GetBaseInfo().BandwithLimit.Bytes()
+	if limitBytes > 0 {
+		limiter = rate.NewLimiter(rate.Limit(float64(limitBytes)), int(limitBytes))
+	}
+
 	baseProxy := BaseProxy{
 		clientCfg:     clientCfg,
 		serverUDPPort: serverUDPPort,
+		limiter:       limiter,
 		xl:            xlog.FromContextSafe(ctx),
 		ctx:           ctx,
 	}
@@ -96,6 +105,7 @@ type BaseProxy struct {
 	closed        bool
 	clientCfg     config.ClientCommonConf
 	serverUDPPort int
+	limiter       *rate.Limiter
 
 	mu  sync.RWMutex
 	xl  *xlog.Logger
@@ -127,8 +137,8 @@ func (pxy *TcpProxy) Close() {
 }
 
 func (pxy *TcpProxy) InWorkConn(conn net.Conn, m *msg.StartWorkConn) {
-	HandleTcpWorkConnection(pxy.ctx, &pxy.cfg.LocalSvrConf, pxy.proxyPlugin, &pxy.cfg.BaseProxyConf, conn,
-		[]byte(pxy.clientCfg.Token), m)
+	HandleTcpWorkConnection(pxy.ctx, &pxy.cfg.LocalSvrConf, pxy.proxyPlugin, &pxy.cfg.BaseProxyConf, pxy.limiter,
+		conn, []byte(pxy.clientCfg.Token), m)
 }
 
 // HTTP
@@ -156,8 +166,8 @@ func (pxy *HttpProxy) Close() {
 }
 
 func (pxy *HttpProxy) InWorkConn(conn net.Conn, m *msg.StartWorkConn) {
-	HandleTcpWorkConnection(pxy.ctx, &pxy.cfg.LocalSvrConf, pxy.proxyPlugin, &pxy.cfg.BaseProxyConf, conn,
-		[]byte(pxy.clientCfg.Token), m)
+	HandleTcpWorkConnection(pxy.ctx, &pxy.cfg.LocalSvrConf, pxy.proxyPlugin, &pxy.cfg.BaseProxyConf, pxy.limiter,
+		conn, []byte(pxy.clientCfg.Token), m)
 }
 
 // HTTPS
@@ -185,8 +195,8 @@ func (pxy *HttpsProxy) Close() {
 }
 
 func (pxy *HttpsProxy) InWorkConn(conn net.Conn, m *msg.StartWorkConn) {
-	HandleTcpWorkConnection(pxy.ctx, &pxy.cfg.LocalSvrConf, pxy.proxyPlugin, &pxy.cfg.BaseProxyConf, conn,
-		[]byte(pxy.clientCfg.Token), m)
+	HandleTcpWorkConnection(pxy.ctx, &pxy.cfg.LocalSvrConf, pxy.proxyPlugin, &pxy.cfg.BaseProxyConf, pxy.limiter,
+		conn, []byte(pxy.clientCfg.Token), m)
 }
 
 // STCP
@@ -214,8 +224,8 @@ func (pxy *StcpProxy) Close() {
 }
 
 func (pxy *StcpProxy) InWorkConn(conn net.Conn, m *msg.StartWorkConn) {
-	HandleTcpWorkConnection(pxy.ctx, &pxy.cfg.LocalSvrConf, pxy.proxyPlugin, &pxy.cfg.BaseProxyConf, conn,
-		[]byte(pxy.clientCfg.Token), m)
+	HandleTcpWorkConnection(pxy.ctx, &pxy.cfg.LocalSvrConf, pxy.proxyPlugin, &pxy.cfg.BaseProxyConf, pxy.limiter,
+		conn, []byte(pxy.clientCfg.Token), m)
 }
 
 // XTCP
@@ -360,7 +370,7 @@ func (pxy *XtcpProxy) InWorkConn(conn net.Conn, m *msg.StartWorkConn) {
 		return
 	}
 
-	HandleTcpWorkConnection(pxy.ctx, &pxy.cfg.LocalSvrConf, pxy.proxyPlugin, &pxy.cfg.BaseProxyConf,
+	HandleTcpWorkConnection(pxy.ctx, &pxy.cfg.LocalSvrConf, pxy.proxyPlugin, &pxy.cfg.BaseProxyConf, pxy.limiter,
 		muxConn, []byte(pxy.cfg.Sk), m)
 }
 
@@ -429,6 +439,13 @@ func (pxy *UdpProxy) InWorkConn(conn net.Conn, m *msg.StartWorkConn) {
 	// close resources releated with old workConn
 	pxy.Close()
 
+	if pxy.limiter != nil {
+		rwc := frpIo.WrapReadWriteCloser(limit.NewReader(conn, pxy.limiter), limit.NewWriter(conn, pxy.limiter), func() error {
+			return conn.Close()
+		})
+		conn = frpNet.WrapReadWriteCloserToConn(rwc, conn)
+	}
+
 	pxy.mu.Lock()
 	pxy.workConn = conn
 	pxy.readCh = make(chan *msg.UdpPacket, 1024)
@@ -491,13 +508,18 @@ func (pxy *UdpProxy) InWorkConn(conn net.Conn, m *msg.StartWorkConn) {
 
 // Common handler for tcp work connections.
 func HandleTcpWorkConnection(ctx context.Context, localInfo *config.LocalSvrConf, proxyPlugin plugin.Plugin,
-	baseInfo *config.BaseProxyConf, workConn net.Conn, encKey []byte, m *msg.StartWorkConn) {
+	baseInfo *config.BaseProxyConf, limiter *rate.Limiter, workConn net.Conn, encKey []byte, m *msg.StartWorkConn) {
 	xl := xlog.FromContextSafe(ctx)
 	var (
 		remote io.ReadWriteCloser
 		err    error
 	)
 	remote = workConn
+	if limiter != nil {
+		remote = frpIo.WrapReadWriteCloser(limit.NewReader(workConn, limiter), limit.NewWriter(workConn, limiter), func() error {
+			return workConn.Close()
+		})
+	}
 
 	xl.Trace("handle tcp work connection, use_encryption: %t, use_compression: %t",
 		baseInfo.UseEncryption, baseInfo.UseCompression)

conf/frpc_full.ini

@@ -71,6 +71,8 @@ tls_enable = true
 type = tcp
 local_ip = 127.0.0.1
 local_port = 22
+# limit bandwith for this proxy, unit is KB and MB
+bandwith_limit = 1MB
 # true or false, if true, messages between frps and frpc will be encrypted, default is false
 use_encryption = false
 # if true, message will be compressed

go.mod

@@ -29,4 +29,5 @@ require (
 	github.com/xtaci/lossyconn v0.0.0-20190602105132-8df528c0c9ae // indirect
 	golang.org/x/net v0.0.0-20190724013045-ca1201d0de80
 	golang.org/x/text v0.3.2 // indirect
+	golang.org/x/time v0.0.0-20191024005414-555d28b269f0
 )

go.sum

@@ -46,4 +46,6 @@ golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5h
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.2 h1:tW2bmiBqwgJj/UpqtC8EpXEZVYOwU0yG4iWbprSVAcs=
 golang.org/x/text v0.3.2/go.mod h1:bEr9sfX3Q8Zfm5fL9x+3itogRgK3+ptLWKqgva+5dAk=
+golang.org/x/time v0.0.0-20191024005414-555d28b269f0 h1:/5xXl8Y5W96D+TtHSlonuFqGHIWVuyCkGJLwGh9JJFs=
+golang.org/x/time v0.0.0-20191024005414-555d28b269f0/go.mod h1:tRJNPiyCQ0inRvYxbN9jk5I+vvW/OXSQhTDSoE431IQ=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=

models/config/proxy.go

@@ -125,6 +125,11 @@ type BaseProxyConf struct {
 	// values include "v1", "v2", and "". If the value is "", a protocol
 	// version will be automatically selected. By default, this value is "".
 	ProxyProtocolVersion string `json:"proxy_protocol_version"`
+
+	// BandwithLimit limit the proxy bandwith
+	// 0 means no limit
+	BandwithLimit BandwithQuantity `json:"bandwith_limit"`
+
 	LocalSvrConf
 	HealthCheckConf
 }
@@ -140,7 +145,8 @@ func (cfg *BaseProxyConf) compare(cmp *BaseProxyConf) bool {
 		cfg.UseCompression != cmp.UseCompression ||
 		cfg.Group != cmp.Group ||
 		cfg.GroupKey != cmp.GroupKey ||
-		cfg.ProxyProtocolVersion != cmp.ProxyProtocolVersion {
+		cfg.ProxyProtocolVersion != cmp.ProxyProtocolVersion ||
+		cfg.BandwithLimit.Equal(&cmp.BandwithLimit) {
 		return false
 	}
 	if !cfg.LocalSvrConf.compare(&cmp.LocalSvrConf) {
@@ -165,6 +171,7 @@ func (cfg *BaseProxyConf) UnmarshalFromIni(prefix string, name string, section i
 	var (
 		tmpStr string
 		ok     bool
+		err    error
 	)
 	cfg.ProxyName = prefix + name
 	cfg.ProxyType = section["type"]
@@ -183,11 +190,15 @@ func (cfg *BaseProxyConf) UnmarshalFromIni(prefix string, name string, section i
 	cfg.GroupKey = section["group_key"]
 	cfg.ProxyProtocolVersion = section["proxy_protocol_version"]
 
-	if err := cfg.LocalSvrConf.UnmarshalFromIni(prefix, name, section); err != nil {
+	if cfg.BandwithLimit, err = NewBandwithQuantity(section["bandwidth_limit"]); err != nil {
 		return err
 	}
 
-	if err := cfg.HealthCheckConf.UnmarshalFromIni(prefix, name, section); err != nil {
+	if err = cfg.LocalSvrConf.UnmarshalFromIni(prefix, name, section); err != nil {
+		return err
+	}
+
+	if err = cfg.HealthCheckConf.UnmarshalFromIni(prefix, name, section); err != nil {
 		return err
 	}
 

models/config/types.go

@@ -0,0 +1,100 @@
+// Copyright 2019 fatedier, fatedier@gmail.com
+//
+// 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.
+
+package config
+
+import (
+	"errors"
+	"strconv"
+	"strings"
+)
+
+const (
+	MB = 1024 * 1024
+	KB = 1024
+)
+
+type BandwithQuantity struct {
+	s string // MB or KB
+
+	i int64 // bytes
+}
+
+func NewBandwithQuantity(s string) (BandwithQuantity, error) {
+	q := BandwithQuantity{}
+	err := q.UnmarshalString(s)
+	if err != nil {
+		return q, err
+	}
+	return q, nil
+}
+
+func (q *BandwithQuantity) Equal(u *BandwithQuantity) bool {
+	if q == nil && u == nil {
+		return true
+	}
+	if q != nil && u != nil {
+		return q.i == u.i
+	}
+	return false
+}
+
+func (q *BandwithQuantity) String() string {
+	return q.s
+}
+
+func (q *BandwithQuantity) UnmarshalString(s string) error {
+	q.s = strings.TrimSpace(s)
+	if q.s == "" {
+		return nil
+	}
+
+	var (
+		base int64
+		f    float64
+		err  error
+	)
+	if strings.HasSuffix(s, "MB") {
+		base = MB
+		s = strings.TrimSuffix(s, "MB")
+		f, err = strconv.ParseFloat(s, 64)
+		if err != nil {
+			return err
+		}
+	} else if strings.HasSuffix(s, "KB") {
+		base = KB
+		s = strings.TrimSuffix(s, "KB")
+		f, err = strconv.ParseFloat(s, 64)
+		if err != nil {
+			return err
+		}
+	} else {
+		return errors.New("unit not support")
+	}
+
+	q.i = int64(f * float64(base))
+	return nil
+}
+
+func (q *BandwithQuantity) UnmarshalJSON(b []byte) error {
+	return q.UnmarshalString(string(b))
+}
+
+func (q *BandwithQuantity) MarshalJSON() ([]byte, error) {
+	return []byte(q.s), nil
+}
+
+func (q *BandwithQuantity) Bytes() int64 {
+	return q.i
+}

utils/limit/reader.go

@@ -0,0 +1,51 @@
+// Copyright 2019 fatedier, fatedier@gmail.com
+//
+// 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.
+
+package limit
+
+import (
+	"context"
+	"io"
+
+	"golang.org/x/time/rate"
+)
+
+type Reader struct {
+	r       io.Reader
+	limiter *rate.Limiter
+}
+
+func NewReader(r io.Reader, limiter *rate.Limiter) *Reader {
+	return &Reader{
+		r:       r,
+		limiter: limiter,
+	}
+}
+
+func (r *Reader) Read(p []byte) (n int, err error) {
+	b := r.limiter.Burst()
+	if b < len(p) {
+		p = p[:b]
+	}
+	n, err = r.r.Read(p)
+	if err != nil {
+		return
+	}
+
+	err = r.limiter.WaitN(context.Background(), n)
+	if err != nil {
+		return
+	}
+	return
+}

utils/limit/writer.go

@@ -0,0 +1,60 @@
+// Copyright 2019 fatedier, fatedier@gmail.com
+//
+// 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.
+
+package limit
+
+import (
+	"context"
+	"io"
+
+	"golang.org/x/time/rate"
+)
+
+type Writer struct {
+	w       io.Writer
+	limiter *rate.Limiter
+}
+
+func NewWriter(w io.Writer, limiter *rate.Limiter) *Writer {
+	return &Writer{
+		w:       w,
+		limiter: limiter,
+	}
+}
+
+func (w *Writer) Write(p []byte) (n int, err error) {
+	var nn int
+	b := w.limiter.Burst()
+	for {
+		end := len(p)
+		if end == 0 {
+			break
+		}
+		if b < len(p) {
+			end = b
+		}
+		err = w.limiter.WaitN(context.Background(), end)
+		if err != nil {
+			return
+		}
+
+		nn, err = w.w.Write(p[:end])
+		n += nn
+		if err != nil {
+			return
+		}
+		p = p[end:]
+	}
+	return
+}

vendor/golang.org/x/time/AUTHORS

@@ -0,0 +1,3 @@
+# This source code refers to The Go Authors for copyright purposes.
+# The master list of authors is in the main Go distribution,
+# visible at http://tip.golang.org/AUTHORS.

vendor/golang.org/x/time/CONTRIBUTORS

@@ -0,0 +1,3 @@
+# This source code was written by the Go contributors.
+# The master list of contributors is in the main Go distribution,
+# visible at http://tip.golang.org/CONTRIBUTORS.

vendor/golang.org/x/time/LICENSE

@@ -0,0 +1,27 @@
+Copyright (c) 2009 The Go Authors. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+   * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+   * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+   * Neither the name of Google Inc. nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

vendor/golang.org/x/time/PATENTS

@@ -0,0 +1,22 @@
+Additional IP Rights Grant (Patents)
+
+"This implementation" means the copyrightable works distributed by
+Google as part of the Go project.
+
+Google hereby grants to You a perpetual, worldwide, non-exclusive,
+no-charge, royalty-free, irrevocable (except as stated in this section)
+patent license to make, have made, use, offer to sell, sell, import,
+transfer and otherwise run, modify and propagate the contents of this
+implementation of Go, where such license applies only to those patent
+claims, both currently owned or controlled by Google and acquired in
+the future, licensable by Google that are necessarily infringed by this
+implementation of Go.  This grant does not include claims that would be
+infringed only as a consequence of further modification of this
+implementation.  If you or your agent or exclusive licensee institute or
+order or agree to the institution of patent litigation against any
+entity (including a cross-claim or counterclaim in a lawsuit) alleging
+that this implementation of Go or any code incorporated within this
+implementation of Go constitutes direct or contributory patent
+infringement, or inducement of patent infringement, then any patent
+rights granted to you under this License for this implementation of Go
+shall terminate as of the date such litigation is filed.

vendor/golang.org/x/time/rate/rate.go

@@ -0,0 +1,400 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package rate provides a rate limiter.
+package rate
+
+import (
+	"context"
+	"fmt"
+	"math"
+	"sync"
+	"time"
+)
+
+// Limit defines the maximum frequency of some events.
+// Limit is represented as number of events per second.
+// A zero Limit allows no events.
+type Limit float64
+
+// Inf is the infinite rate limit; it allows all events (even if burst is zero).
+const Inf = Limit(math.MaxFloat64)
+
+// Every converts a minimum time interval between events to a Limit.
+func Every(interval time.Duration) Limit {
+	if interval <= 0 {
+		return Inf
+	}
+	return 1 / Limit(interval.Seconds())
+}
+
+// A Limiter controls how frequently events are allowed to happen.
+// It implements a "token bucket" of size b, initially full and refilled
+// at rate r tokens per second.
+// Informally, in any large enough time interval, the Limiter limits the
+// rate to r tokens per second, with a maximum burst size of b events.
+// As a special case, if r == Inf (the infinite rate), b is ignored.
+// See https://en.wikipedia.org/wiki/Token_bucket for more about token buckets.
+//
+// The zero value is a valid Limiter, but it will reject all events.
+// Use NewLimiter to create non-zero Limiters.
+//
+// Limiter has three main methods, Allow, Reserve, and Wait.
+// Most callers should use Wait.
+//
+// Each of the three methods consumes a single token.
+// They differ in their behavior when no token is available.
+// If no token is available, Allow returns false.
+// If no token is available, Reserve returns a reservation for a future token
+// and the amount of time the caller must wait before using it.
+// If no token is available, Wait blocks until one can be obtained
+// or its associated context.Context is canceled.
+//
+// The methods AllowN, ReserveN, and WaitN consume n tokens.
+type Limiter struct {
+	limit Limit
+	burst int
+
+	mu     sync.Mutex
+	tokens float64
+	// last is the last time the limiter's tokens field was updated
+	last time.Time
+	// lastEvent is the latest time of a rate-limited event (past or future)
+	lastEvent time.Time
+}
+
+// Limit returns the maximum overall event rate.
+func (lim *Limiter) Limit() Limit {
+	lim.mu.Lock()
+	defer lim.mu.Unlock()
+	return lim.limit
+}
+
+// Burst returns the maximum burst size. Burst is the maximum number of tokens
+// that can be consumed in a single call to Allow, Reserve, or Wait, so higher
+// Burst values allow more events to happen at once.
+// A zero Burst allows no events, unless limit == Inf.
+func (lim *Limiter) Burst() int {
+	return lim.burst
+}
+
+// NewLimiter returns a new Limiter that allows events up to rate r and permits
+// bursts of at most b tokens.
+func NewLimiter(r Limit, b int) *Limiter {
+	return &Limiter{
+		limit: r,
+		burst: b,
+	}
+}
+
+// Allow is shorthand for AllowN(time.Now(), 1).
+func (lim *Limiter) Allow() bool {
+	return lim.AllowN(time.Now(), 1)
+}
+
+// AllowN reports whether n events may happen at time now.
+// Use this method if you intend to drop / skip events that exceed the rate limit.
+// Otherwise use Reserve or Wait.
+func (lim *Limiter) AllowN(now time.Time, n int) bool {
+	return lim.reserveN(now, n, 0).ok
+}
+
+// A Reservation holds information about events that are permitted by a Limiter to happen after a delay.
+// A Reservation may be canceled, which may enable the Limiter to permit additional events.
+type Reservation struct {
+	ok        bool
+	lim       *Limiter
+	tokens    int
+	timeToAct time.Time
+	// This is the Limit at reservation time, it can change later.
+	limit Limit
+}
+
+// OK returns whether the limiter can provide the requested number of tokens
+// within the maximum wait time.  If OK is false, Delay returns InfDuration, and
+// Cancel does nothing.
+func (r *Reservation) OK() bool {
+	return r.ok
+}
+
+// Delay is shorthand for DelayFrom(time.Now()).
+func (r *Reservation) Delay() time.Duration {
+	return r.DelayFrom(time.Now())
+}
+
+// InfDuration is the duration returned by Delay when a Reservation is not OK.
+const InfDuration = time.Duration(1<<63 - 1)
+
+// DelayFrom returns the duration for which the reservation holder must wait
+// before taking the reserved action.  Zero duration means act immediately.
+// InfDuration means the limiter cannot grant the tokens requested in this
+// Reservation within the maximum wait time.
+func (r *Reservation) DelayFrom(now time.Time) time.Duration {
+	if !r.ok {
+		return InfDuration
+	}
+	delay := r.timeToAct.Sub(now)
+	if delay < 0 {
+		return 0
+	}
+	return delay
+}
+
+// Cancel is shorthand for CancelAt(time.Now()).
+func (r *Reservation) Cancel() {
+	r.CancelAt(time.Now())
+	return
+}
+
+// CancelAt indicates that the reservation holder will not perform the reserved action
+// and reverses the effects of this Reservation on the rate limit as much as possible,
+// considering that other reservations may have already been made.
+func (r *Reservation) CancelAt(now time.Time) {
+	if !r.ok {
+		return
+	}
+
+	r.lim.mu.Lock()
+	defer r.lim.mu.Unlock()
+
+	if r.lim.limit == Inf || r.tokens == 0 || r.timeToAct.Before(now) {
+		return
+	}
+
+	// calculate tokens to restore
+	// The duration between lim.lastEvent and r.timeToAct tells us how many tokens were reserved
+	// after r was obtained. These tokens should not be restored.
+	restoreTokens := float64(r.tokens) - r.limit.tokensFromDuration(r.lim.lastEvent.Sub(r.timeToAct))
+	if restoreTokens <= 0 {
+		return
+	}
+	// advance time to now
+	now, _, tokens := r.lim.advance(now)
+	// calculate new number of tokens
+	tokens += restoreTokens
+	if burst := float64(r.lim.burst); tokens > burst {
+		tokens = burst
+	}
+	// update state
+	r.lim.last = now
+	r.lim.tokens = tokens
+	if r.timeToAct == r.lim.lastEvent {
+		prevEvent := r.timeToAct.Add(r.limit.durationFromTokens(float64(-r.tokens)))
+		if !prevEvent.Before(now) {
+			r.lim.lastEvent = prevEvent
+		}
+	}
+
+	return
+}
+
+// Reserve is shorthand for ReserveN(time.Now(), 1).
+func (lim *Limiter) Reserve() *Reservation {
+	return lim.ReserveN(time.Now(), 1)
+}
+
+// ReserveN returns a Reservation that indicates how long the caller must wait before n events happen.
+// The Limiter takes this Reservation into account when allowing future events.
+// ReserveN returns false if n exceeds the Limiter's burst size.
+// Usage example:
+//   r := lim.ReserveN(time.Now(), 1)
+//   if !r.OK() {
+//     // Not allowed to act! Did you remember to set lim.burst to be > 0 ?
+//     return
+//   }
+//   time.Sleep(r.Delay())
+//   Act()
+// Use this method if you wish to wait and slow down in accordance with the rate limit without dropping events.
+// If you need to respect a deadline or cancel the delay, use Wait instead.
+// To drop or skip events exceeding rate limit, use Allow instead.
+func (lim *Limiter) ReserveN(now time.Time, n int) *Reservation {
+	r := lim.reserveN(now, n, InfDuration)
+	return &r
+}
+
+// Wait is shorthand for WaitN(ctx, 1).
+func (lim *Limiter) Wait(ctx context.Context) (err error) {
+	return lim.WaitN(ctx, 1)
+}
+
+// WaitN blocks until lim permits n events to happen.
+// It returns an error if n exceeds the Limiter's burst size, the Context is
+// canceled, or the expected wait time exceeds the Context's Deadline.
+// The burst limit is ignored if the rate limit is Inf.
+func (lim *Limiter) WaitN(ctx context.Context, n int) (err error) {
+	lim.mu.Lock()
+	burst := lim.burst
+	limit := lim.limit
+	lim.mu.Unlock()
+
+	if n > burst && limit != Inf {
+		return fmt.Errorf("rate: Wait(n=%d) exceeds limiter's burst %d", n, lim.burst)
+	}
+	// Check if ctx is already cancelled
+	select {
+	case <-ctx.Done():
+		return ctx.Err()
+	default:
+	}
+	// Determine wait limit
+	now := time.Now()
+	waitLimit := InfDuration
+	if deadline, ok := ctx.Deadline(); ok {
+		waitLimit = deadline.Sub(now)
+	}
+	// Reserve
+	r := lim.reserveN(now, n, waitLimit)
+	if !r.ok {
+		return fmt.Errorf("rate: Wait(n=%d) would exceed context deadline", n)
+	}
+	// Wait if necessary
+	delay := r.DelayFrom(now)
+	if delay == 0 {
+		return nil
+	}
+	t := time.NewTimer(delay)
+	defer t.Stop()
+	select {
+	case <-t.C:
+		// We can proceed.
+		return nil
+	case <-ctx.Done():
+		// Context was canceled before we could proceed.  Cancel the
+		// reservation, which may permit other events to proceed sooner.
+		r.Cancel()
+		return ctx.Err()
+	}
+}
+
+// SetLimit is shorthand for SetLimitAt(time.Now(), newLimit).
+func (lim *Limiter) SetLimit(newLimit Limit) {
+	lim.SetLimitAt(time.Now(), newLimit)
+}
+
+// SetLimitAt sets a new Limit for the limiter. The new Limit, and Burst, may be violated
+// or underutilized by those which reserved (using Reserve or Wait) but did not yet act
+// before SetLimitAt was called.
+func (lim *Limiter) SetLimitAt(now time.Time, newLimit Limit) {
+	lim.mu.Lock()
+	defer lim.mu.Unlock()
+
+	now, _, tokens := lim.advance(now)
+
+	lim.last = now
+	lim.tokens = tokens
+	lim.limit = newLimit
+}
+
+// SetBurst is shorthand for SetBurstAt(time.Now(), newBurst).
+func (lim *Limiter) SetBurst(newBurst int) {
+	lim.SetBurstAt(time.Now(), newBurst)
+}
+
+// SetBurstAt sets a new burst size for the limiter.
+func (lim *Limiter) SetBurstAt(now time.Time, newBurst int) {
+	lim.mu.Lock()
+	defer lim.mu.Unlock()
+
+	now, _, tokens := lim.advance(now)
+
+	lim.last = now
+	lim.tokens = tokens
+	lim.burst = newBurst
+}
+
+// reserveN is a helper method for AllowN, ReserveN, and WaitN.
+// maxFutureReserve specifies the maximum reservation wait duration allowed.
+// reserveN returns Reservation, not *Reservation, to avoid allocation in AllowN and WaitN.
+func (lim *Limiter) reserveN(now time.Time, n int, maxFutureReserve time.Duration) Reservation {
+	lim.mu.Lock()
+
+	if lim.limit == Inf {
+		lim.mu.Unlock()
+		return Reservation{
+			ok:        true,
+			lim:       lim,
+			tokens:    n,
+			timeToAct: now,
+		}
+	}
+
+	now, last, tokens := lim.advance(now)
+
+	// Calculate the remaining number of tokens resulting from the request.
+	tokens -= float64(n)
+
+	// Calculate the wait duration
+	var waitDuration time.Duration
+	if tokens < 0 {
+		waitDuration = lim.limit.durationFromTokens(-tokens)
+	}
+
+	// Decide result
+	ok := n <= lim.burst && waitDuration <= maxFutureReserve
+
+	// Prepare reservation
+	r := Reservation{
+		ok:    ok,
+		lim:   lim,
+		limit: lim.limit,
+	}
+	if ok {
+		r.tokens = n
+		r.timeToAct = now.Add(waitDuration)
+	}
+
+	// Update state
+	if ok {
+		lim.last = now
+		lim.tokens = tokens
+		lim.lastEvent = r.timeToAct
+	} else {
+		lim.last = last
+	}
+
+	lim.mu.Unlock()
+	return r
+}
+
+// advance calculates and returns an updated state for lim resulting from the passage of time.
+// lim is not changed.
+func (lim *Limiter) advance(now time.Time) (newNow time.Time, newLast time.Time, newTokens float64) {
+	last := lim.last
+	if now.Before(last) {
+		last = now
+	}
+
+	// Avoid making delta overflow below when last is very old.
+	maxElapsed := lim.limit.durationFromTokens(float64(lim.burst) - lim.tokens)
+	elapsed := now.Sub(last)
+	if elapsed > maxElapsed {
+		elapsed = maxElapsed
+	}
+
+	// Calculate the new number of tokens, due to time that passed.
+	delta := lim.limit.tokensFromDuration(elapsed)
+	tokens := lim.tokens + delta
+	if burst := float64(lim.burst); tokens > burst {
+		tokens = burst
+	}
+
+	return now, last, tokens
+}
+
+// durationFromTokens is a unit conversion function from the number of tokens to the duration
+// of time it takes to accumulate them at a rate of limit tokens per second.
+func (limit Limit) durationFromTokens(tokens float64) time.Duration {
+	seconds := tokens / float64(limit)
+	return time.Nanosecond * time.Duration(1e9*seconds)
+}
+
+// tokensFromDuration is a unit conversion function from a time duration to the number of tokens
+// which could be accumulated during that duration at a rate of limit tokens per second.
+func (limit Limit) tokensFromDuration(d time.Duration) float64 {
+	// Split the integer and fractional parts ourself to minimize rounding errors.
+	// See golang.org/issues/34861.
+	sec := float64(d/time.Second) * float64(limit)
+	nsec := float64(d%time.Second) * float64(limit)
+	return sec + nsec/1e9
+}

vendor/modules.txt

@@ -83,3 +83,5 @@ golang.org/x/text/secure/bidirule
 golang.org/x/text/transform
 golang.org/x/text/unicode/bidi
 golang.org/x/text/unicode/norm
+# golang.org/x/time v0.0.0-20191024005414-555d28b269f0
+golang.org/x/time/rate