区块链教程之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 intconst (    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maxBytesRulefunc (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sigFilterfunc (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systemChainFilterfunc (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RuleSetfunc (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