Repository: shimingyah/pool
Branch: master
Commit: e796cf9ebea4
Files: 13
Total size: 44.9 KB

Directory structure:
gitextract__zv_kx2m/

├── .gitignore
├── LICENSE
├── README.md
├── conn.go
├── example/
│   ├── client/
│   │   └── main.go
│   ├── pb/
│   │   ├── example.pb.go
│   │   └── example.proto
│   └── server/
│       └── main.go
├── go.mod
├── go.sum
├── options.go
├── pool.go
└── pool_test.go

================================================
FILE CONTENTS
================================================

================================================
FILE: .gitignore
================================================
# Binaries for programs and plugins
*.exe
*.exe~
*.dll
*.so
*.dylib

# Test binary, build with `go test -c`
*.test

# Output of the go coverage tool, specifically when used with LiteIDE
*.out


================================================
FILE: LICENSE
================================================
                                 Apache License
                           Version 2.0, January 2004
                        http://www.apache.org/licenses/

   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION

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      "License" shall mean the terms and conditions for use, reproduction,
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================================================
FILE: README.md
================================================
# Pool
[![GoDoc](https://godoc.org/github.com/shimingyah/pool?status.svg)](https://godoc.org/github.com/shimingyah/pool)
[![Go Report Card](https://goreportcard.com/badge/github.com/shimingyah/pool?style=flat-square)](https://goreportcard.com/report/github.com/shimingyah/pool)
[![LICENSE](https://img.shields.io/badge/licence-Apache%202.0-brightgreen.svg?style=flat-square)](https://github.com/shimingyah/pool/blob/master/LICENSE)

Connection pool for Go's grpc client that supports connection reuse.

Pool provides additional features:

* `Connection reuse` supported by specific MaxConcurrentStreams param.
* `Failure reconnection` supported by grpc's keepalive.

# Getting started

## Install

Import package:

```
import (
    "github.com/shimingyah/pool"
)
```

```
go get github.com/shimingyah/pool
```

# Usage

```
p, err := pool.New("127.0.0.1:8080", pool.DefaultOptions)
if err != nil {
    log.Fatalf("failed to new pool: %v", err)
}
defer p.Close()

conn, err := p.Get()
if err != nil {
    log.Fatalf("failed to get conn: %v", err)
}
defer conn.Close()

// cc := conn.Value()
// client := pb.NewClient(conn.Value())
```
See the complete example: [https://github.com/shimingyah/pool/tree/master/example](https://github.com/shimingyah/pool/tree/master/example)

# Reference
* [https://github.com/fatih/pool](https://github.com/fatih/pool)
* [https://github.com/silenceper/pool](https://github.com/silenceper/pool)

# License

Pool is under the Apache 2.0 license. See the [LICENSE](https://github.com/shimingyah/pool/blob/master/LICENSE) file for details.

================================================
FILE: conn.go
================================================
// Copyright 2019 shimingyah. All rights reserved.
//
// 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.
// ee the License for the specific language governing permissions and
// limitations under the License.

package pool

import (
	"google.golang.org/grpc"
)

// Conn single grpc connection inerface
type Conn interface {
	// Value return the actual grpc connection type *grpc.ClientConn.
	Value() *grpc.ClientConn

	// Close decrease the reference of grpc connection, instead of close it.
	// if the pool is full, just close it.
	Close() error
}

// Conn is wrapped grpc.ClientConn. to provide close and value method.
type conn struct {
	cc   *grpc.ClientConn
	pool *pool
	once bool
}

// Value see Conn interface.
func (c *conn) Value() *grpc.ClientConn {
	return c.cc
}

// Close see Conn interface.
func (c *conn) Close() error {
	c.pool.decrRef()
	if c.once {
		return c.reset()
	}
	return nil
}

func (c *conn) reset() error {
	cc := c.cc
	c.cc = nil
	c.once = false
	if cc != nil {
		return cc.Close()
	}
	return nil
}

func (p *pool) wrapConn(cc *grpc.ClientConn, once bool) *conn {
	return &conn{
		cc:   cc,
		pool: p,
		once: once,
	}
}


================================================
FILE: example/client/main.go
================================================
// Copyright 2019 shimingyah. All rights reserved.
//
// 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.
// ee the License for the specific language governing permissions and
// limitations under the License.

package main

import (
	"context"
	"flag"
	"fmt"
	"log"
	"time"

	"github.com/shimingyah/pool"
	"github.com/shimingyah/pool/example/pb"
)

var addr = flag.String("addr", "127.0.0.1:50000", "the address to connect to")

func main() {
	flag.Parse()

	p, err := pool.New(*addr, pool.DefaultOptions)
	if err != nil {
		log.Fatalf("failed to new pool: %v", err)
	}
	defer p.Close()

	conn, err := p.Get()
	if err != nil {
		log.Fatalf("failed to get conn: %v", err)
	}
	defer conn.Close()

	client := pb.NewEchoClient(conn.Value())
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()

	res, err := client.Say(ctx, &pb.EchoRequest{Message: []byte("hi")})
	if err != nil {
		log.Fatalf("unexpected error from Say: %v", err)
	}
	fmt.Println("rpc response:", res)
}


================================================
FILE: example/pb/example.pb.go
================================================
// Code generated by protoc-gen-go. DO NOT EDIT.
// source: example.proto

package pb

import proto "github.com/golang/protobuf/proto"
import fmt "fmt"
import math "math"

import (
	context "golang.org/x/net/context"
	grpc "google.golang.org/grpc"
)

// Reference imports to suppress errors if they are not otherwise used.
var _ = proto.Marshal
var _ = fmt.Errorf
var _ = math.Inf

// This is a compile-time assertion to ensure that this generated file
// is compatible with the proto package it is being compiled against.
// A compilation error at this line likely means your copy of the
// proto package needs to be updated.
const _ = proto.ProtoPackageIsVersion2 // please upgrade the proto package

// EchoRequest is the request for echo.
type EchoRequest struct {
	Message              []byte   `protobuf:"bytes,1,opt,name=message,proto3" json:"message,omitempty"`
	XXX_NoUnkeyedLiteral struct{} `json:"-"`
	XXX_unrecognized     []byte   `json:"-"`
	XXX_sizecache        int32    `json:"-"`
}

func (m *EchoRequest) Reset()         { *m = EchoRequest{} }
func (m *EchoRequest) String() string { return proto.CompactTextString(m) }
func (*EchoRequest) ProtoMessage()    {}
func (*EchoRequest) Descriptor() ([]byte, []int) {
	return fileDescriptor_example_d72c2831d52b7689, []int{0}
}
func (m *EchoRequest) XXX_Unmarshal(b []byte) error {
	return xxx_messageInfo_EchoRequest.Unmarshal(m, b)
}
func (m *EchoRequest) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
	return xxx_messageInfo_EchoRequest.Marshal(b, m, deterministic)
}
func (dst *EchoRequest) XXX_Merge(src proto.Message) {
	xxx_messageInfo_EchoRequest.Merge(dst, src)
}
func (m *EchoRequest) XXX_Size() int {
	return xxx_messageInfo_EchoRequest.Size(m)
}
func (m *EchoRequest) XXX_DiscardUnknown() {
	xxx_messageInfo_EchoRequest.DiscardUnknown(m)
}

var xxx_messageInfo_EchoRequest proto.InternalMessageInfo

func (m *EchoRequest) GetMessage() []byte {
	if m != nil {
		return m.Message
	}
	return nil
}

// EchoResponse is the response for echo.
type EchoResponse struct {
	Message              []byte   `protobuf:"bytes,1,opt,name=message,proto3" json:"message,omitempty"`
	XXX_NoUnkeyedLiteral struct{} `json:"-"`
	XXX_unrecognized     []byte   `json:"-"`
	XXX_sizecache        int32    `json:"-"`
}

func (m *EchoResponse) Reset()         { *m = EchoResponse{} }
func (m *EchoResponse) String() string { return proto.CompactTextString(m) }
func (*EchoResponse) ProtoMessage()    {}
func (*EchoResponse) Descriptor() ([]byte, []int) {
	return fileDescriptor_example_d72c2831d52b7689, []int{1}
}
func (m *EchoResponse) XXX_Unmarshal(b []byte) error {
	return xxx_messageInfo_EchoResponse.Unmarshal(m, b)
}
func (m *EchoResponse) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
	return xxx_messageInfo_EchoResponse.Marshal(b, m, deterministic)
}
func (dst *EchoResponse) XXX_Merge(src proto.Message) {
	xxx_messageInfo_EchoResponse.Merge(dst, src)
}
func (m *EchoResponse) XXX_Size() int {
	return xxx_messageInfo_EchoResponse.Size(m)
}
func (m *EchoResponse) XXX_DiscardUnknown() {
	xxx_messageInfo_EchoResponse.DiscardUnknown(m)
}

var xxx_messageInfo_EchoResponse proto.InternalMessageInfo

func (m *EchoResponse) GetMessage() []byte {
	if m != nil {
		return m.Message
	}
	return nil
}

func init() {
	proto.RegisterType((*EchoRequest)(nil), "pb.EchoRequest")
	proto.RegisterType((*EchoResponse)(nil), "pb.EchoResponse")
}

// Reference imports to suppress errors if they are not otherwise used.
var _ context.Context
var _ grpc.ClientConn

// This is a compile-time assertion to ensure that this generated file
// is compatible with the grpc package it is being compiled against.
const _ = grpc.SupportPackageIsVersion4

// EchoClient is the client API for Echo service.
//
// For semantics around ctx use and closing/ending streaming RPCs, please refer to https://godoc.org/google.golang.org/grpc#ClientConn.NewStream.
type EchoClient interface {
	// Say is simple request.
	Say(ctx context.Context, in *EchoRequest, opts ...grpc.CallOption) (*EchoResponse, error)
}

type echoClient struct {
	cc *grpc.ClientConn
}

func NewEchoClient(cc *grpc.ClientConn) EchoClient {
	return &echoClient{cc}
}

func (c *echoClient) Say(ctx context.Context, in *EchoRequest, opts ...grpc.CallOption) (*EchoResponse, error) {
	out := new(EchoResponse)
	err := c.cc.Invoke(ctx, "/pb.Echo/Say", in, out, opts...)
	if err != nil {
		return nil, err
	}
	return out, nil
}

// EchoServer is the server API for Echo service.
type EchoServer interface {
	// Say is simple request.
	Say(context.Context, *EchoRequest) (*EchoResponse, error)
}

func RegisterEchoServer(s *grpc.Server, srv EchoServer) {
	s.RegisterService(&_Echo_serviceDesc, srv)
}

func _Echo_Say_Handler(srv interface{}, ctx context.Context, dec func(interface{}) error, interceptor grpc.UnaryServerInterceptor) (interface{}, error) {
	in := new(EchoRequest)
	if err := dec(in); err != nil {
		return nil, err
	}
	if interceptor == nil {
		return srv.(EchoServer).Say(ctx, in)
	}
	info := &grpc.UnaryServerInfo{
		Server:     srv,
		FullMethod: "/pb.Echo/Say",
	}
	handler := func(ctx context.Context, req interface{}) (interface{}, error) {
		return srv.(EchoServer).Say(ctx, req.(*EchoRequest))
	}
	return interceptor(ctx, in, info, handler)
}

var _Echo_serviceDesc = grpc.ServiceDesc{
	ServiceName: "pb.Echo",
	HandlerType: (*EchoServer)(nil),
	Methods: []grpc.MethodDesc{
		{
			MethodName: "Say",
			Handler:    _Echo_Say_Handler,
		},
	},
	Streams:  []grpc.StreamDesc{},
	Metadata: "example.proto",
}

func init() { proto.RegisterFile("example.proto", fileDescriptor_example_d72c2831d52b7689) }

var fileDescriptor_example_d72c2831d52b7689 = []byte{
	// 127 bytes of a gzipped FileDescriptorProto
	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0xe2, 0xe2, 0x4d, 0xad, 0x48, 0xcc,
	0x2d, 0xc8, 0x49, 0xd5, 0x2b, 0x28, 0xca, 0x2f, 0xc9, 0x17, 0x62, 0x2a, 0x48, 0x52, 0x52, 0xe7,
	0xe2, 0x76, 0x4d, 0xce, 0xc8, 0x0f, 0x4a, 0x2d, 0x2c, 0x4d, 0x2d, 0x2e, 0x11, 0x92, 0xe0, 0x62,
	0xcf, 0x4d, 0x2d, 0x2e, 0x4e, 0x4c, 0x4f, 0x95, 0x60, 0x54, 0x60, 0xd4, 0xe0, 0x09, 0x82, 0x71,
	0x95, 0x34, 0xb8, 0x78, 0x20, 0x0a, 0x8b, 0x0b, 0xf2, 0xf3, 0x8a, 0x53, 0x71, 0xab, 0x34, 0x32,
	0xe2, 0x62, 0x01, 0xa9, 0x14, 0xd2, 0xe2, 0x62, 0x0e, 0x4e, 0xac, 0x14, 0xe2, 0xd7, 0x2b, 0x48,
	0xd2, 0x43, 0xb2, 0x43, 0x4a, 0x00, 0x21, 0x00, 0x31, 0x4b, 0x89, 0x21, 0x89, 0x0d, 0xec, 0x22,
	0x63, 0x40, 0x00, 0x00, 0x00, 0xff, 0xff, 0xba, 0x45, 0x75, 0x9d, 0xa2, 0x00, 0x00, 0x00,
}


================================================
FILE: example/pb/example.proto
================================================
// Copyright 2019 shimingyah. All rights reserved.
//
// 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.
// ee the License for the specific language governing permissions and
// limitations under the License.

syntax = "proto3";

package pb;

// EchoRequest is the request for echo.
message EchoRequest {
  bytes message = 1;
}

// EchoResponse is the response for echo.
message EchoResponse {
  bytes message = 1;
}

// Echo is the echo service.
service Echo {
  // Say is simple request.
  rpc Say(EchoRequest) returns (EchoResponse) {}
}

================================================
FILE: example/server/main.go
================================================
// Copyright 2019 shimingyah. All rights reserved.
//
// 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.
// ee the License for the specific language governing permissions and
// limitations under the License.

package main

import (
	"context"
	"flag"
	"fmt"
	"log"
	"net"

	"google.golang.org/grpc"
	"google.golang.org/grpc/keepalive"

	"github.com/shimingyah/pool"
	"github.com/shimingyah/pool/example/pb"
)

var port = flag.Int("port", 50000, "port number")

// server implements EchoServer.
type server struct{}

func (s *server) Say(context.Context, *pb.EchoRequest) (*pb.EchoResponse, error) {
	return &pb.EchoResponse{Message: []byte("hello world")}, nil
}

func main() {
	flag.Parse()

	listen, err := net.Listen("tcp", fmt.Sprintf("127.0.0.1:%v", *port))
	if err != nil {
		log.Fatalf("failed to listen: %v", err)
	}

	s := grpc.NewServer(
		grpc.InitialWindowSize(pool.InitialWindowSize),
		grpc.InitialConnWindowSize(pool.InitialConnWindowSize),
		grpc.MaxSendMsgSize(pool.MaxSendMsgSize),
		grpc.MaxRecvMsgSize(pool.MaxRecvMsgSize),
		grpc.KeepaliveEnforcementPolicy(keepalive.EnforcementPolicy{
			PermitWithoutStream: true,
		}),
		grpc.KeepaliveParams(keepalive.ServerParameters{
			Time:    pool.KeepAliveTime,
			Timeout: pool.KeepAliveTimeout,
		}),
	)
	pb.RegisterEchoServer(s, &server{})

	if err := s.Serve(listen); err != nil {
		log.Fatalf("failed to serve: %v", err)
	}
}


================================================
FILE: go.mod
================================================
module github.com/shimingyah/pool

go 1.12

require (
	github.com/golang/protobuf v1.2.0
	github.com/stretchr/testify v1.3.0
	golang.org/x/net v0.0.0-20190311183353-d8887717615a
	google.golang.org/grpc v1.22.0
)


================================================
FILE: go.sum
================================================
cloud.google.com/go v0.26.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw=
github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
github.com/client9/misspell v0.3.4/go.mod h1:qj6jICC3Q7zFZvVWo7KLAzC3yx5G7kyvSDkc90ppPyw=
github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b h1:VKtxabqXZkF25pY9ekfRL6a582T4P37/31XEstQ5p58=
github.com/golang/glog v0.0.0-20160126235308-23def4e6c14b/go.mod h1:SBH7ygxi8pfUlaOkMMuAQtPIUF8ecWP5IEl/CR7VP2Q=
github.com/golang/mock v1.1.1/go.mod h1:oTYuIxOrZwtPieC+H1uAHpcLFnEyAGVDL/k47Jfbm0A=
github.com/golang/protobuf v1.2.0 h1:P3YflyNX/ehuJFLhxviNdFxQPkGK5cDcApsge1SqnvM=
github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
github.com/google/go-cmp v0.2.0/go.mod h1:oXzfMopK8JAjlY9xF4vHSVASa0yLyX7SntLO5aqRK0M=
github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
github.com/stretchr/testify v1.3.0 h1:TivCn/peBQ7UY8ooIcPgZFpTNSz0Q2U6UrFlUfqbe0Q=
github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
golang.org/x/lint v0.0.0-20190313153728-d0100b6bd8b3/go.mod h1:6SW0HCj/g11FgYtHlgUYUwCkIfeOF89ocIRzGO/8vkc=
golang.org/x/net v0.0.0-20190311183353-d8887717615a h1:oWX7TPOiFAMXLq8o0ikBYfCJVlRHBcsciT5bXOrH628=
golang.org/x/net v0.0.0-20190311183353-d8887717615a/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
golang.org/x/oauth2 v0.0.0-20180821212333-d2e6202438be/go.mod h1:N/0e6XlmueqKjAGxoOufVs8QHGRruUQn6yWY3a++T0U=
golang.org/x/sync v0.0.0-20190423024810-112230192c58 h1:8gQV6CLnAEikrhgkHFbMAEhagSSnXWGV915qUMm9mrU=
golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a h1:1BGLXjeY4akVXGgbC9HugT3Jv3hCI0z56oJR5vAMgBU=
golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
golang.org/x/text v0.3.0 h1:g61tztE5qeGQ89tm6NTjjM9VPIm088od1l6aSorWRWg=
golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
golang.org/x/tools v0.0.0-20190311212946-11955173bddd/go.mod h1:LCzVGOaR6xXOjkQ3onu1FJEFr0SW1gC7cKk1uF8kGRs=
golang.org/x/tools v0.0.0-20190524140312-2c0ae7006135/go.mod h1:RgjU9mgBXZiqYHBnxXauZ1Gv1EHHAz9KjViQ78xBX0Q=
google.golang.org/appengine v1.1.0/go.mod h1:EbEs0AVv82hx2wNQdGPgUI5lhzA/G0D9YwlJXL52JkM=
google.golang.org/genproto v0.0.0-20180817151627-c66870c02cf8 h1:Nw54tB0rB7hY/N0NQvRW8DG4Yk3Q6T9cu9RcFQDu1tc=
google.golang.org/genproto v0.0.0-20180817151627-c66870c02cf8/go.mod h1:JiN7NxoALGmiZfu7CAH4rXhgtRTLTxftemlI0sWmxmc=
google.golang.org/grpc v1.22.0 h1:J0UbZOIrCAl+fpTOf8YLs4dJo8L/owV4LYVtAXQoPkw=
google.golang.org/grpc v1.22.0/go.mod h1:Y5yQAOtifL1yxbo5wqy6BxZv8vAUGQwXBOALyacEbxg=
honnef.co/go/tools v0.0.0-20190523083050-ea95bdfd59fc/go.mod h1:rf3lG4BRIbNafJWhAfAdb/ePZxsR/4RtNHQocxwk9r4=


================================================
FILE: options.go
================================================
// Copyright 2019 shimingyah. All rights reserved.
//
// 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.
// ee the License for the specific language governing permissions and
// limitations under the License.

package pool

import (
	"context"
	"time"

	"google.golang.org/grpc"
	"google.golang.org/grpc/keepalive"
)

const (
	// DialTimeout the timeout of create connection
	DialTimeout = 5 * time.Second

	// BackoffMaxDelay provided maximum delay when backing off after failed connection attempts.
	BackoffMaxDelay = 3 * time.Second

	// KeepAliveTime is the duration of time after which if the client doesn't see
	// any activity it pings the server to see if the transport is still alive.
	KeepAliveTime = time.Duration(10) * time.Second

	// KeepAliveTimeout is the duration of time for which the client waits after having
	// pinged for keepalive check and if no activity is seen even after that the connection
	// is closed.
	KeepAliveTimeout = time.Duration(3) * time.Second

	// InitialWindowSize we set it 1GB is to provide system's throughput.
	InitialWindowSize = 1 << 30

	// InitialConnWindowSize we set it 1GB is to provide system's throughput.
	InitialConnWindowSize = 1 << 30

	// MaxSendMsgSize set max gRPC request message size sent to server.
	// If any request message size is larger than current value, an error will be reported from gRPC.
	MaxSendMsgSize = 4 << 30

	// MaxRecvMsgSize set max gRPC receive message size received from server.
	// If any message size is larger than current value, an error will be reported from gRPC.
	MaxRecvMsgSize = 4 << 30
)

// Options are params for creating grpc connect pool.
type Options struct {
	// Dial is an application supplied function for creating and configuring a connection.
	Dial func(address string) (*grpc.ClientConn, error)

	// Maximum number of idle connections in the pool.
	MaxIdle int

	// Maximum number of connections allocated by the pool at a given time.
	// When zero, there is no limit on the number of connections in the pool.
	MaxActive int

	// MaxConcurrentStreams limit on the number of concurrent streams to each single connection
	MaxConcurrentStreams int

	// If Reuse is true and the pool is at the MaxActive limit, then Get() reuse
	// the connection to return, If Reuse is false and the pool is at the MaxActive limit,
	// create a one-time connection to return.
	Reuse bool
}

// DefaultOptions sets a list of recommended options for good performance.
// Feel free to modify these to suit your needs.
var DefaultOptions = Options{
	Dial:                 Dial,
	MaxIdle:              8,
	MaxActive:            64,
	MaxConcurrentStreams: 64,
	Reuse:                true,
}

// Dial return a grpc connection with defined configurations.
func Dial(address string) (*grpc.ClientConn, error) {
	ctx, cancel := context.WithTimeout(context.Background(), DialTimeout)
	defer cancel()
	return grpc.DialContext(ctx, address, grpc.WithInsecure(),
		grpc.WithBackoffMaxDelay(BackoffMaxDelay),
		grpc.WithInitialWindowSize(InitialWindowSize),
		grpc.WithInitialConnWindowSize(InitialConnWindowSize),
		grpc.WithDefaultCallOptions(grpc.MaxCallSendMsgSize(MaxSendMsgSize)),
		grpc.WithDefaultCallOptions(grpc.MaxCallRecvMsgSize(MaxRecvMsgSize)),
		grpc.WithKeepaliveParams(keepalive.ClientParameters{
			Time:                KeepAliveTime,
			Timeout:             KeepAliveTimeout,
			PermitWithoutStream: true,
		}))
}

// DialTest return a simple grpc connection with defined configurations.
func DialTest(address string) (*grpc.ClientConn, error) {
	ctx, cancel := context.WithTimeout(context.Background(), DialTimeout)
	defer cancel()
	return grpc.DialContext(ctx, address, grpc.WithInsecure())
}


================================================
FILE: pool.go
================================================
// Copyright 2019 shimingyah. All rights reserved.
//
// 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.
// ee the License for the specific language governing permissions and
// limitations under the License.

package pool

import (
	"errors"
	"fmt"
	"log"
	"math"
	"sync"
	"sync/atomic"
)

// ErrClosed is the error resulting if the pool is closed via pool.Close().
var ErrClosed = errors.New("pool is closed")

// Pool interface describes a pool implementation.
// An ideal pool is threadsafe and easy to use.
type Pool interface {
	// Get returns a new connection from the pool. Closing the connections puts
	// it back to the Pool. Closing it when the pool is destroyed or full will
	// be counted as an error. we guarantee the conn.Value() isn't nil when conn isn't nil.
	Get() (Conn, error)

	// Close closes the pool and all its connections. After Close() the pool is
	// no longer usable. You can't make concurrent calls Close and Get method.
	// It will be cause panic.
	Close() error

	// Status returns the current status of the pool.
	Status() string
}

type pool struct {
	// atomic, used to get connection random
	index uint32

	// atomic, the current physical connection of pool
	current int32

	// atomic, the using logic connection of pool
	// logic connection = physical connection * MaxConcurrentStreams
	ref int32

	// pool options
	opt Options

	// all of created physical connections
	conns []*conn

	// the server address is to create connection.
	address string

	// closed set true when Close is called.
	closed int32

	// control the atomic var current's concurrent read write.
	sync.RWMutex
}

// New return a connection pool.
func New(address string, option Options) (Pool, error) {
	if address == "" {
		return nil, errors.New("invalid address settings")
	}
	if option.Dial == nil {
		return nil, errors.New("invalid dial settings")
	}
	if option.MaxIdle <= 0 || option.MaxActive <= 0 || option.MaxIdle > option.MaxActive {
		return nil, errors.New("invalid maximum settings")
	}
	if option.MaxConcurrentStreams <= 0 {
		return nil, errors.New("invalid maximun settings")
	}

	p := &pool{
		index:   0,
		current: int32(option.MaxIdle),
		ref:     0,
		opt:     option,
		conns:   make([]*conn, option.MaxActive),
		address: address,
		closed:  0,
	}

	for i := 0; i < p.opt.MaxIdle; i++ {
		c, err := p.opt.Dial(address)
		if err != nil {
			p.Close()
			return nil, fmt.Errorf("dial is not able to fill the pool: %s", err)
		}
		p.conns[i] = p.wrapConn(c, false)
	}
	log.Printf("new pool success: %v\n", p.Status())

	return p, nil
}

func (p *pool) incrRef() int32 {
	newRef := atomic.AddInt32(&p.ref, 1)
	if newRef == math.MaxInt32 {
		panic(fmt.Sprintf("overflow ref: %d", newRef))
	}
	return newRef
}

func (p *pool) decrRef() {
	newRef := atomic.AddInt32(&p.ref, -1)
	if newRef < 0 && atomic.LoadInt32(&p.closed) == 0 {
		panic(fmt.Sprintf("negative ref: %d", newRef))
	}
	if newRef == 0 && atomic.LoadInt32(&p.current) > int32(p.opt.MaxIdle) {
		p.Lock()
		if atomic.LoadInt32(&p.ref) == 0 {
			log.Printf("shrink pool: %d ---> %d, decrement: %d, maxActive: %d\n",
				p.current, p.opt.MaxIdle, p.current-int32(p.opt.MaxIdle), p.opt.MaxActive)
			atomic.StoreInt32(&p.current, int32(p.opt.MaxIdle))
			p.deleteFrom(p.opt.MaxIdle)
		}
		p.Unlock()
	}
}

func (p *pool) reset(index int) {
	conn := p.conns[index]
	if conn == nil {
		return
	}
	conn.reset()
	p.conns[index] = nil
}

func (p *pool) deleteFrom(begin int) {
	for i := begin; i < p.opt.MaxActive; i++ {
		p.reset(i)
	}
}

// Get see Pool interface.
func (p *pool) Get() (Conn, error) {
	// the first selected from the created connections
	nextRef := p.incrRef()
	p.RLock()
	current := atomic.LoadInt32(&p.current)
	p.RUnlock()
	if current == 0 {
		return nil, ErrClosed
	}
	if nextRef <= current*int32(p.opt.MaxConcurrentStreams) {
		next := atomic.AddUint32(&p.index, 1) % uint32(current)
		return p.conns[next], nil
	}

	// the number connection of pool is reach to max active
	if current == int32(p.opt.MaxActive) {
		// the second if reuse is true, select from pool's connections
		if p.opt.Reuse {
			next := atomic.AddUint32(&p.index, 1) % uint32(current)
			return p.conns[next], nil
		}
		// the third create one-time connection
		c, err := p.opt.Dial(p.address)
		return p.wrapConn(c, true), err
	}

	// the fourth create new connections given back to pool
	p.Lock()
	current = atomic.LoadInt32(&p.current)
	if current < int32(p.opt.MaxActive) && nextRef > current*int32(p.opt.MaxConcurrentStreams) {
		// 2 times the incremental or the remain incremental
		increment := current
		if current+increment > int32(p.opt.MaxActive) {
			increment = int32(p.opt.MaxActive) - current
		}
		var i int32
		var err error
		for i = 0; i < increment; i++ {
			c, er := p.opt.Dial(p.address)
			if er != nil {
				err = er
				break
			}
			p.reset(int(current + i))
			p.conns[current+i] = p.wrapConn(c, false)
		}
		current += i
		log.Printf("grow pool: %d ---> %d, increment: %d, maxActive: %d\n",
			p.current, current, increment, p.opt.MaxActive)
		atomic.StoreInt32(&p.current, current)
		if err != nil {
			p.Unlock()
			return nil, err
		}
	}
	p.Unlock()
	next := atomic.AddUint32(&p.index, 1) % uint32(current)
	return p.conns[next], nil
}

// Close see Pool interface.
func (p *pool) Close() error {
	atomic.StoreInt32(&p.closed, 1)
	atomic.StoreUint32(&p.index, 0)
	atomic.StoreInt32(&p.current, 0)
	atomic.StoreInt32(&p.ref, 0)
	p.deleteFrom(0)
	log.Printf("close pool success: %v\n", p.Status())
	return nil
}

// Status see Pool interface.
func (p *pool) Status() string {
	return fmt.Sprintf("address:%s, index:%d, current:%d, ref:%d. option:%v",
		p.address, p.index, p.current, p.ref, p.opt)
}


================================================
FILE: pool_test.go
================================================
// Copyright 2019 shimingyah. All rights reserved.
//
// 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.
// ee the License for the specific language governing permissions and
// limitations under the License.

package pool

import (
	"context"
	"flag"
	"sync"
	"sync/atomic"
	"testing"
	"time"

	"github.com/shimingyah/pool/example/pb"
	"github.com/stretchr/testify/require"
)

var endpoint = flag.String("endpoint", "127.0.0.1:50000", "grpc server endpoint")

func newPool(op *Options) (Pool, *pool, Options, error) {
	opt := DefaultOptions
	opt.Dial = DialTest
	if op != nil {
		opt = *op
	}
	p, err := New(*endpoint, opt)
	return p, p.(*pool), opt, err
}

func TestNew(t *testing.T) {
	p, nativePool, opt, err := newPool(nil)
	require.NoError(t, err)
	defer p.Close()

	require.EqualValues(t, 0, nativePool.index)
	require.EqualValues(t, 0, nativePool.ref)
	require.EqualValues(t, opt.MaxIdle, nativePool.current)
	require.EqualValues(t, opt.MaxActive, len(nativePool.conns))
}

func TestNew2(t *testing.T) {
	opt := DefaultOptions

	_, err := New("", opt)
	require.Error(t, err)

	opt.Dial = nil
	_, err = New("127.0.0.1:8080", opt)
	require.Error(t, err)

	opt = DefaultOptions
	opt.MaxConcurrentStreams = 0
	_, err = New("127.0.0.1:8080", opt)
	require.Error(t, err)

	opt = DefaultOptions
	opt.MaxIdle = 0
	_, err = New("127.0.0.1:8080", opt)
	require.Error(t, err)

	opt = DefaultOptions
	opt.MaxActive = 0
	_, err = New("127.0.0.1:8080", opt)
	require.Error(t, err)

	opt = DefaultOptions
	opt.MaxIdle = 2
	opt.MaxActive = 1
	_, err = New("127.0.0.1:8080", opt)
	require.Error(t, err)
}

func TestClose(t *testing.T) {
	p, nativePool, opt, err := newPool(nil)
	require.NoError(t, err)
	p.Close()

	require.EqualValues(t, 0, nativePool.index)
	require.EqualValues(t, 0, nativePool.ref)
	require.EqualValues(t, 0, nativePool.current)
	require.EqualValues(t, true, nativePool.conns[0] == nil)
	require.EqualValues(t, true, nativePool.conns[opt.MaxIdle-1] == nil)
}

func TestReset(t *testing.T) {
	p, nativePool, opt, err := newPool(nil)
	require.NoError(t, err)
	defer p.Close()

	nativePool.reset(0)
	require.EqualValues(t, true, nativePool.conns[0] == nil)
	nativePool.reset(opt.MaxIdle + 1)
	require.EqualValues(t, true, nativePool.conns[opt.MaxIdle+1] == nil)
}

func TestBasicGet(t *testing.T) {
	p, nativePool, _, err := newPool(nil)
	require.NoError(t, err)
	defer p.Close()

	conn, err := p.Get()
	require.NoError(t, err)
	require.EqualValues(t, true, conn.Value() != nil)

	require.EqualValues(t, 1, nativePool.index)
	require.EqualValues(t, 1, nativePool.ref)

	conn.Close()

	require.EqualValues(t, 1, nativePool.index)
	require.EqualValues(t, 0, nativePool.ref)
}

func TestGetAfterClose(t *testing.T) {
	p, _, _, err := newPool(nil)
	require.NoError(t, err)
	p.Close()

	_, err = p.Get()
	require.EqualError(t, err, "pool is closed")
}

func TestBasicGet2(t *testing.T) {
	opt := DefaultOptions
	opt.Dial = DialTest
	opt.MaxIdle = 1
	opt.MaxActive = 2
	opt.MaxConcurrentStreams = 2
	opt.Reuse = true

	p, nativePool, _, err := newPool(&opt)
	require.NoError(t, err)
	defer p.Close()

	conn1, err := p.Get()
	require.NoError(t, err)
	defer conn1.Close()

	conn2, err := p.Get()
	require.NoError(t, err)
	defer conn2.Close()

	require.EqualValues(t, 2, nativePool.index)
	require.EqualValues(t, 2, nativePool.ref)
	require.EqualValues(t, 1, nativePool.current)

	// create new connections push back to pool
	conn3, err := p.Get()
	require.NoError(t, err)
	defer conn3.Close()

	require.EqualValues(t, 3, nativePool.index)
	require.EqualValues(t, 3, nativePool.ref)
	require.EqualValues(t, 2, nativePool.current)

	conn4, err := p.Get()
	require.NoError(t, err)
	defer conn4.Close()

	// reuse exists connections
	conn5, err := p.Get()
	require.NoError(t, err)
	defer conn5.Close()

	nativeConn := conn5.(*conn)
	require.EqualValues(t, false, nativeConn.once)
}

func TestBasicGet3(t *testing.T) {
	opt := DefaultOptions
	opt.Dial = DialTest
	opt.MaxIdle = 1
	opt.MaxActive = 1
	opt.MaxConcurrentStreams = 1
	opt.Reuse = false

	p, _, _, err := newPool(&opt)
	require.NoError(t, err)
	defer p.Close()

	conn1, err := p.Get()
	require.NoError(t, err)
	defer conn1.Close()

	// create new connections doesn't push back to pool
	conn2, err := p.Get()
	require.NoError(t, err)
	defer conn2.Close()

	nativeConn := conn2.(*conn)
	require.EqualValues(t, true, nativeConn.once)
}

func TestConcurrentGet(t *testing.T) {
	opt := DefaultOptions
	opt.Dial = DialTest
	opt.MaxIdle = 8
	opt.MaxActive = 64
	opt.MaxConcurrentStreams = 2
	opt.Reuse = false

	p, nativePool, _, err := newPool(&opt)
	require.NoError(t, err)
	defer p.Close()

	var wg sync.WaitGroup
	wg.Add(500)

	for i := 0; i < 500; i++ {
		go func(i int) {
			conn, err := p.Get()
			require.NoError(t, err)
			require.EqualValues(t, true, conn != nil)
			conn.Close()
			wg.Done()
			t.Logf("goroutine: %v, index: %v, ref: %v, current: %v", i,
				atomic.LoadUint32(&nativePool.index),
				atomic.LoadInt32(&nativePool.ref),
				atomic.LoadInt32(&nativePool.current))
		}(i)
	}
	wg.Wait()

	require.EqualValues(t, 0, nativePool.ref)
	require.EqualValues(t, opt.MaxIdle, nativePool.current)
	require.EqualValues(t, true, nativePool.conns[0] != nil)
	require.EqualValues(t, true, nativePool.conns[opt.MaxIdle] == nil)
}

var size = 4 * 1024 * 1024

func BenchmarkPoolRPC(b *testing.B) {
	opt := DefaultOptions
	p, err := New(*endpoint, opt)
	if err != nil {
		b.Fatalf("failed to new pool: %v", err)
	}
	defer p.Close()

	testFunc := func() {
		conn, err := p.Get()
		if err != nil {
			b.Fatalf("failed to get conn: %v", err)
		}
		defer conn.Close()

		client := pb.NewEchoClient(conn.Value())
		ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
		defer cancel()

		data := make([]byte, size)
		_, err = client.Say(ctx, &pb.EchoRequest{Message: data})
		if err != nil {
			b.Fatalf("unexpected error from Say: %v", err)
		}
	}

	b.ResetTimer()
	b.RunParallel(func(tpb *testing.PB) {
		for tpb.Next() {
			testFunc()
		}
	})
}

func BenchmarkSingleRPC(b *testing.B) {
	testFunc := func() {
		cc, err := Dial(*endpoint)
		if err != nil {
			b.Fatalf("failed to create grpc conn: %v", err)
		}

		client := pb.NewEchoClient(cc)
		ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
		defer cancel()

		data := make([]byte, size)
		_, err = client.Say(ctx, &pb.EchoRequest{Message: data})
		if err != nil {
			b.Fatalf("unexpected error from Say: %v", err)
		}
	}

	b.RunParallel(func(tpb *testing.PB) {
		for tpb.Next() {
			testFunc()
		}
	})
}