兄弟连区块链教程policy（背书策略）
兄弟连区块链教程Fabric1.0源代码分析policy（背书策略），2018年下半年，区块链行业正逐渐褪去发展之初的浮躁、回归理性，表面上看相关人才需求与身价似乎正在回落。但事实上，正是初期泡沫的渐退，让人们更多的关注点放在了区块链真正的技术之上。
# Fabric 1.0源代码笔记 之 policy（背书策略）
## 1、policy概述
policy代码分布在core/policy、core/policyprovider、common/policies目录下。目录结构如下：
* core/policy/policy.go，PolicyChecker接口定义及实现、PolicyCheckerFactory接口定义。
* core/policyprovider/provider.go，PolicyChecker工厂默认实现。
* common/policies目录
* policy.go，ChannelPolicyManagerGetter接口及实现。
* implicitmeta_util.go，通道策略工具函数。
## 2、PolicyChecker工厂
### 2.1、PolicyCheckerFactory接口定义
```go
type PolicyCheckerFactory interface {
NewPolicyChecker() PolicyChecker //构造PolicyChecker实例
}
var pcFactory PolicyCheckerFactory //全局变量定义及赋值函数
func RegisterPolicyCheckerFactory(f PolicyCheckerFactory) {
pcFactory = f
}
//代码在core/policy/policy.go
```
### 2.2、PolicyCheckerFactory接口默认实现
```go
type defaultFactory struct{}
//构造policy.PolicyChecker
func (f *defaultFactory) NewPolicyChecker() policy.PolicyChecker {
return policy.NewPolicyChecker(
peer.NewChannelPolicyManagerGetter(), //&channelPolicyManagerGetter{}
mgmt.GetLocalMSP(),
mgmt.NewLocalMSPPrincipalGetter(),
)
}
//获取policy.PolicyChecker，即调用policy.GetPolicyChecker()
func GetPolicyChecker() policy.PolicyChecker
func init() { //初始化全局变量pcFactory
policy.RegisterPolicyCheckerFactory(&defaultFactory{})
}
```
## 3、PolicyChecker接口定义及实现
### 3.1、PolicyChecker接口定义
```go
type PolicyChecker interface {
CheckPolicy(channelID, policyName string, signedProp *pb.SignedProposal) error
CheckPolicyBySignedData(channelID, policyName string, sd []*common.SignedData) error
CheckPolicyNoChannel(policyName string, signedProp *pb.SignedProposal) error
}
//代码在core/policy/policy.go
```
### 3.2、PolicyChecker接口实现
PolicyChecker接口实现，即policyChecker结构体及方法。
```go
type policyChecker struct {
channelPolicyManagerGetter policies.ChannelPolicyManagerGetter //通道策略管理器
localMSP msp.IdentityDeserializer //身份
principalGetter mgmt.MSPPrincipalGetter //委托人
}
//构造policyChecker
func NewPolicyChecker(channelPolicyManagerGetter policies.ChannelPolicyManagerGetter, localMSP msp.IdentityDeserializer, principalGetter mgmt.MSPPrincipalGetter) PolicyChecker
//检查签名提案是否符合通道策略
func (p *policyChecker) CheckPolicy(channelID, policyName string, signedProp *pb.SignedProposal) error
func (p *policyChecker) CheckPolicyNoChannel(policyName string, signedProp *pb.SignedProposal) error
//检查签名数据是否符合通道策略，获取策略并调取policy.Evaluate(sd)
func (p *policyChecker) CheckPolicyBySignedData(channelID, policyName string, sd []*common.SignedData) error
func GetPolicyChecker() PolicyChecker //pcFactory.NewPolicyChecker()
//代码在core/policy/policy.go
```
func (p *policyChecker) CheckPolicy(channelID, policyName string, signedProp *pb.SignedProposal) error代码如下：
```go
func (p *policyChecker) CheckPolicy(channelID, policyName string, signedProp *pb.SignedProposal) error {
if channelID == "" { //channelID为空，调取CheckPolicyNoChannel()
return p.CheckPolicyNoChannel(policyName, signedProp)
}
policyManager, _ := p.channelPolicyManagerGetter.Manager(channelID)
proposal, err := utils.GetProposal(signedProp.ProposalBytes) //获取proposal
header, err := utils.GetHeader(proposal.Header)
shdr, err := utils.GetSignatureHeader(header.SignatureHeader) //SignatureHeader
sd := []*common.SignedData{&common.SignedData{
Data: signedProp.ProposalBytes,
Identity: shdr.Creator,
Signature: signedProp.Signature,
}}
return p.CheckPolicyBySignedData(channelID, policyName, sd)
}
//代码在core/policy/policy.go
```
## 4、ChannelPolicyManagerGetter接口及实现
### 4.1、ChannelPolicyManagerGetter接口定义
```go
type ChannelPolicyManagerGetter interface {
Manager(channelID string) (Manager, bool)
}
//代码在common/policies/policy.go
```
### 4.2、ChannelPolicyManagerGetter接口实现
ChannelPolicyManagerGetter接口实现，即ManagerImpl结构体及方法。
```go
type ManagerImpl struct {
parent *ManagerImpl
basePath string
fqPrefix string
providers map[int32]Provider //type Provider interface
config *policyConfig //type policyConfig struct
pendingConfig map[interface{}]*policyConfig //type policyConfig struct
pendingLock sync.RWMutex
SuppressSanityLogMessages bool
}
type Provider interface {
NewPolicy(data []byte) (Policy, proto.Message, error)
}
type policyConfig struct {
policies map[string]Policy //type Policy interface
managers map[string]*ManagerImpl
imps []*implicitMetaPolicy
}
type Policy interface {
//对给定的签名数据，按规则检验确认是否符合约定的条件
Evaluate(signatureSet []*cb.SignedData) error
}
//构造ManagerImpl
func NewManagerImpl(basePath string, providers map[int32]Provider) *ManagerImpl
//获取pm.basePath
func (pm *ManagerImpl) BasePath() string
//获取pm.config.policies，即map[string]Policy中Key列表
func (pm *ManagerImpl) PolicyNames() []string
//获取指-定路径的子管理器
func (pm *ManagerImpl) Manager(path []string) (Manager, bool)
//获取pm.config.policies[relpath]
//获取Policy
func (pm *ManagerImpl) GetPolicy(id string) (Policy, bool)
func (pm *ManagerImpl) BeginPolicyProposals(tx interface{}, groups []string) ([]Proposer, error)
func (pm *ManagerImpl) RollbackProposals(tx interface{})
func (pm *ManagerImpl) PreCommit(tx interface{}) error
func (pm *ManagerImpl) CommitProposals(tx interface{})
func (pm *ManagerImpl) ProposePolicy(tx interface{}, key string, configPolicy *cb.ConfigPolicy) (proto.Message, error)
//代码在common/policies/policy.go
```
```go
type implicitMetaPolicy struct {
conf *cb.ImplicitMetaPolicy
threshold int
subPolicies []Policy
}
//代码在common/policies/implicitmeta.go
```
## 5、通道策略工具函数
```go
type ImplicitMetaPolicy_Rule int32
const (
ImplicitMetaPolicy_ANY ImplicitMetaPolicy_Rule = 0 //任意
ImplicitMetaPolicy_ALL ImplicitMetaPolicy_Rule = 1 //所有
ImplicitMetaPolicy_MAJORITY ImplicitMetaPolicy_Rule = 2 //大多数
)
//代码在protos/common/policies.pb.go
```
```go
//构造cb.Policy
func ImplicitMetaPolicyWithSubPolicy(subPolicyName string, rule cb.ImplicitMetaPolicy_Rule) *cb.ConfigPolicy
func TemplateImplicitMetaPolicyWithSubPolicy(path []string, policyName string, subPolicyName string, rule cb.ImplicitMetaPolicy_Rule) *cb.ConfigGroup
//调取TemplateImplicitMetaPolicyWithSubPolicy(path, policyName, policyName, rule)
func TemplateImplicitMetaPolicy(path []string, policyName string, rule cb.ImplicitMetaPolicy_Rule) *cb.ConfigGroup
//任意，TemplateImplicitMetaPolicy(path, policyName, cb.ImplicitMetaPolicy_ANY)
func TemplateImplicitMetaAnyPolicy(path []string, policyName string) *cb.ConfigGroup
//所有，TemplateImplicitMetaPolicy(path, policyName, cb.ImplicitMetaPolicy_ALL)
func TemplateImplicitMetaAllPolicy(path []string, policyName string) *cb.ConfigGroup
//大多数，TemplateImplicitMetaPolicy(path, policyName, cb.ImplicitMetaPolicy_MAJORITY)
func TemplateImplicitMetaMajorityPolicy(path []string, policyName string) *cb.ConfigGroup
//代码在common/policies/implicitmeta_util.go
```
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