区块链教程Fabric1.0源代码分析consenter（共识插件）#filter（过滤器），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 consenter（共识插件） #filter（过滤器）

1、filter概述

filter代码分布在orderer/common/filter、orderer/common/configtxfilter、orderer/common/sizefilter、orderer/common/sigfilter、orderer/multichain目录下。

orderer/common/filter/filter.go，Rule接口定义及emptyRejectRule和acceptRule实现，Committer接口定义及noopCommitter实现，RuleSet结构体及方法。
orderer/common/configtxfilter目录，configFilter结构体（实现Rule接口）及configCommitter结构体（实现Committer接口）。
orderer/common/sizefilter目录，maxBytesRule结构体（实现Rule接口）。
orderer/multichain/chainsupport.go，filter工具函数。
orderer/multichain/systemchain.go，systemChainFilter结构体（实现Rule接口）及systemChainCommitter结构体（实现Committer接口）。

2、Rule接口定义及实现

2.1、Rule接口定义

type Action int
const (
    Accept = iota
    Reject
    Forward
)

type Rule interface { //定义一个过滤器函数, 它接受、拒绝或转发 (到下一条规则) 一个信封
    Apply(message *ab.Envelope) (Action, Committer)
}
//代码在orderer/common/filter/filter.go

2.2、emptyRejectRule（校验是否为空过滤器）

type emptyRejectRule struct{}
var EmptyRejectRule = Rule(emptyRejectRule{})

func (a emptyRejectRule) Apply(message *ab.Envelope) (Action, Committer) {
    if message.Payload == nil {
        return Reject, nil
    }
    return Forward, nil
}
//代码在orderer/common/filter/filter.go

2.3、acceptRule（接受过滤器）

type acceptRule struct{}
var AcceptRule = Rule(acceptRule{})

func (a acceptRule) Apply(message *ab.Envelope) (Action, Committer) {
    return Accept, NoopCommitter
}
//代码在orderer/common/filter/filter.go

2.4、configFilter（配置交易合法性过滤器）

type configFilter struct {
    configManager api.Manager
}

func NewFilter(manager api.Manager) filter.Rule //构造configFilter
//配置交易过滤器
func (cf *configFilter) Apply(message *cb.Envelope) (filter.Action, filter.Committer) {
    msgData, err := utils.UnmarshalPayload(message.Payload) //获取Payload
    chdr, err := utils.UnmarshalChannelHeader(msgData.Header.ChannelHeader) //获取ChannelHeader
    if chdr.Type != int32(cb.HeaderType_CONFIG) { //配置交易
        return filter.Forward, nil
    }
    configEnvelope, err := configtx.UnmarshalConfigEnvelope(msgData.Data) //获取configEnvelope
    err = cf.configManager.Validate(configEnvelope) //校验configEnvelope
    return filter.Accept, &configCommitter{
        manager:        cf.configManager,
        configEnvelope: configEnvelope,
    }
}
//代码在orderer/common/configtxfilter/filter.go

2.5、sizefilter（交易大小过滤器）

type maxBytesRule struct {
    support Support
}

func MaxBytesRule(support Support) filter.Rule //构造maxBytesRule
func (r *maxBytesRule) Apply(message *cb.Envelope) (filter.Action, filter.Committer) {
    maxBytes := r.support.BatchSize().AbsoluteMaxBytes
    if size := messageByteSize(message); size > maxBytes {
        return filter.Reject, nil
    }
    return filter.Forward, nil
}
//代码在orderer/common/sizefilter/sizefilter.go

2.6、sigFilter（签名数据校验过滤器）

type sigFilter struct {
    policySource  string
    policyManager policies.Manager
}

func New(policySource string, policyManager policies.Manager) filter.Rule //构造sigFilter
func (sf *sigFilter) Apply(message *cb.Envelope) (filter.Action, filter.Committer) {
    signedData, err := message.AsSignedData() //构造SignedData
    policy, ok := sf.policyManager.GetPolicy(sf.policySource) //获取策略
    err = policy.Evaluate(signedData) //校验策略
    if err == nil {
        return filter.Forward, nil
    }
    return filter.Reject, nil
}
//代码在orderer/common/sigfilter/sigfilter.go

2.7、systemChainFilter（系统链过滤器）

type systemChainFilter struct {
    cc      chainCreator
    support limitedSupport
}

func newSystemChainFilter(ls limitedSupport, cc chainCreator) filter.Rule //构造systemChainFilter
func (scf *systemChainFilter) Apply(env *cb.Envelope) (filter.Action, filter.Committer) {
    msgData := &cb.Payload{}
    err := proto.Unmarshal(env.Payload, msgData) //获取Payload
    chdr, err := utils.UnmarshalChannelHeader(msgData.Header.ChannelHeader)
    if chdr.Type != int32(cb.HeaderType_ORDERER_TRANSACTION) { //ORDERER_TRANSACTION
        return filter.Forward, nil
    }
    maxChannels := scf.support.SharedConfig().MaxChannelsCount()
    if maxChannels > 0 {
        if uint64(scf.cc.channelsCount()) > maxChannels {
            return filter.Reject, nil
        }
    }

    configTx := &cb.Envelope{}
    err = proto.Unmarshal(msgData.Data, configTx)
    err = scf.authorizeAndInspect(configTx)
    return filter.Accept, &systemChainCommitter{
        filter:   scf,
        configTx: configTx,
    }
}
//代码在orderer/multichain/systemchain.go

3、Committer接口定义及实现

3.1、Committer接口定义

type Committer interface {
    Commit() //提交
    Isolated() bool //判断交易是孤立的块，或与其他交易混合的块
}
//代码在orderer/common/filter/filter.go

3.2、noopCommitter

type noopCommitter struct{}
var NoopCommitter = Committer(noopCommitter{})

func (nc noopCommitter) Commit()        {}
func (nc noopCommitter) Isolated() bool { return false }
//代码在orderer/common/filter/filter.go

3.3、configCommitter

type configCommitter struct {
    manager        api.Manager
    configEnvelope *cb.ConfigEnvelope
}

func (cc *configCommitter) Commit() {
    err := cc.manager.Apply(cc.configEnvelope)
}

func (cc *configCommitter) Isolated() bool {
    return true
}
//代码在orderer/common/configtxfilter/filter.go

3.4、systemChainCommitter

type systemChainCommitter struct {
    filter   *systemChainFilter
    configTx *cb.Envelope
}

func (scc *systemChainCommitter) Isolated() bool {
    return true
}

func (scc *systemChainCommitter) Commit() {
    scc.filter.cc.newChain(scc.configTx)
}
//代码在orderer/multichain/systemchain.go

4、RuleSet结构体及方法

type RuleSet struct {
    rules []Rule
}

func NewRuleSet(rules []Rule) *RuleSet //构造RuleSet
func (rs *RuleSet) Apply(message *ab.Envelope) (Committer, error) {
    for _, rule := range rs.rules {
        action, committer := rule.Apply(message)
        switch action {
        case Accept: //接受
            return committer, nil
        case Reject: //拒绝
            return nil, fmt.Errorf("Rejected by rule: %T", rule)
        default:
        }
    }
    return nil, fmt.Errorf("No matching filter found")
}
//代码在orderer/common/filter/filter.go

5、filter工具函数

//为普通 (非系统) 链创建过滤器集
func createStandardFilters(ledgerResources *ledgerResources) *filter.RuleSet {
    return filter.NewRuleSet([]filter.Rule{
        filter.EmptyRejectRule, //EmptyRejectRule
        sizefilter.MaxBytesRule(ledgerResources.SharedConfig()), //sizefilter
        sigfilter.New(policies.ChannelWriters, ledgerResources.PolicyManager()), //sigfilter
        configtxfilter.NewFilter(ledgerResources), //configtxfilter
        filter.AcceptRule, //AcceptRule
    })

}

//为系统链创建过滤器集
func createSystemChainFilters(ml *multiLedger, ledgerResources *ledgerResources) *filter.RuleSet {
    return filter.NewRuleSet([]filter.Rule{
        filter.EmptyRejectRule, //EmptyRejectRule
        sizefilter.MaxBytesRule(ledgerResources.SharedConfig()), //sizefilter
        sigfilter.New(policies.ChannelWriters, ledgerResources.PolicyManager()), //sigfilter
        newSystemChainFilter(ledgerResources, ml),
        configtxfilter.NewFilter(ledgerResources), //configtxfilter
        filter.AcceptRule, //AcceptRule
    })
}
//代码在orderer/multichain/chainsupport.go