兄弟连区块链教程Fabric1.0源代码分析Orderer multichain，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 Orderer multichain（多链支持包）
## 1、multichain概述
multichain代码集中在orderer/multichain目录下，目录结构如下：
* manager.go，Manager接口定义及实现。
* chainsupport.go，ChainSupport接口定义及实现。
* systemchain.go，system chain。
## 2、Manager接口定义及实现
### 2.1、Manager接口定义
用于链的创建和访问。
```go
type Manager interface {
//获取ChainSupport，以及判断链是否存在
GetChain(chainID string) (ChainSupport, bool)
//获取系统通道的通道ID
SystemChannelID() string
//支持通道创建请求
NewChannelConfig(envConfigUpdate *cb.Envelope) (configtxapi.Manager, error)
}
//代码在orderer/multichain/manager.go
```
### 2.2、Manager接口实现
Manager接口实现，即multiLedger结构体及方法。
```go
type multiLedger struct {
chains map[string]*chainSupport
consenters map[string]Consenter
ledgerFactory ledger.Factory
signer crypto.LocalSigner
systemChannelID string
systemChannel *chainSupport
}
type configResources struct {
configtxapi.Manager
}
type ledgerResources struct {
*configResources
ledger ledger.ReadWriter
}
//代码在orderer/multichain/manager.go
```
涉及方法如下：
```go
func (cr *configResources) SharedConfig() config.Orderer
//获取配置交-易Envelope
func getConfigTx(reader ledger.Reader) *cb.Envelope
//构造multiLedger
func NewManagerImpl(ledgerFactory ledger.Factory, consenters map[string]Consenter, signer crypto.LocalSigner) Manager
//获取系统链ID
func (ml *multiLedger) SystemChannelID() string
//按chainID获取ChainSupport
func (ml *multiLedger) GetChain(chainID string) (ChainSupport, bool)
//构造ledgerResources
func (ml *multiLedger) newLedgerResources(configTx *cb.Envelope) *ledgerResources
//创建新链
func (ml *multiLedger) newChain(configtx *cb.Envelope)
//通道或链的个数
func (ml *multiLedger) channelsCount() int
//支持创建新的通道
func (ml *multiLedger) NewChannelConfig(envConfigUpdate *cb.Envelope) (configtxapi.Manager, error)
//代码在orderer/multichain/manager.go
```
func NewManagerImpl(ledgerFactory ledger.Factory, consenters map[string]Consenter, signer crypto.LocalSigner) Manager代码如下：
```go
func NewManagerImpl(ledgerFactory ledger.Factory, consenters map[string]Consenter, signer crypto.LocalSigner) Manager {
ml := &multiLedger{
chains: make(map[string]*chainSupport),
ledgerFactory: ledgerFactory,
consenters: consenters,
signer: signer,
}
existingChains := ledgerFactory.ChainIDs()
for _, chainID := range existingChains {
rl, err := ledgerFactory.GetOrCreate(chainID)
configTx := getConfigTx(rl)
ledgerResources := ml.newLedgerResources(configTx)
chainID := ledgerResources.ChainID()
if _, ok := ledgerResources.ConsortiumsConfig(); ok { //系统链
chain := newChainSupport(createSystemChainFilters(ml, ledgerResources), ledgerResources, consenters, signer)
ml.chains[chainID] = chain
ml.systemChannelID = chainID
ml.systemChannel = chain
defer chain.start()
} else { //普通链
chain := newChainSupport(createStandardFilters(ledgerResources), ledgerResources, consenters, signer)
ml.chains[chainID] = chain
chain.start()
}
}
return ml
}
//代码在orderer/multichain/manager.go
```
## 3、ChainSupport接口定义及实现
### 3.1、ChainSupport接口定义
```go
type ChainSupport interface {
PolicyManager() policies.Manager //策略管理
Reader() ledger.Reader
Errored() <-chan struct{}
broadcast.Support
ConsenterSupport //嵌入ConsenterSupport接口
Sequence() uint64
//支持通道更新
ProposeConfigUpdate(env *cb.Envelope) (*cb.ConfigEnvelope, error)
}
type ConsenterSupport interface {
crypto.LocalSigner
BlockCutter() blockcutter.Receiver
SharedConfig() config.Orderer
CreateNextBlock(messages []*cb.Envelope) *cb.Block
WriteBlock(block *cb.Block, committers []filter.Committer, encodedMetadataValue []byte) *cb.Block
ChainID() string
Height() uint64
}
type Consenter interface { //定义支持排序机制
HandleChain(support ConsenterSupport, metadata *cb.Metadata) (Chain, error)
}
type Chain interface {
//接受消息
Enqueue(env *cb.Envelope) bool
Errored() <-chan struct{}
Start() //开始
Halt() //挂起
}
//代码在orderer/multichain/chainsupport.go
```
### 3.2、ChainSupport和ConsenterSupport接口实现
ChainSupport接口实现，即chainSupport结构体及方法。
```go
type chainSupport struct {
*ledgerResources
chain Chain
cutter blockcutter.Receiver
filters *filter.RuleSet
signer crypto.LocalSigner
lastConfig uint64
lastConfigSeq uint64
}
//代码在orderer/multichain/chainsupport.go
```
涉及方法如下：
```go
//构造chainSupport
func newChainSupport(filters *filter.RuleSet,ledgerResources *ledgerResources,consenters map[string]Consenter,signer crypto.LocalSigner,) *chainSupport
func createStandardFilters(ledgerResources *ledgerResources) *filter.RuleSet
func createSystemChainFilters(ml *multiLedger, ledgerResources *ledgerResources) *filter.RuleSet
func (cs *chainSupport) start()
func (cs *chainSupport) NewSignatureHeader() (*cb.SignatureHeader, error)
func (cs *chainSupport) Sign(message []byte) ([]byte, error)
func (cs *chainSupport) Filters() *filter.RuleSet
func (cs *chainSupport) BlockCutter() blockcutter.Receiver
func (cs *chainSupport) Reader() ledger.Reader
func (cs *chainSupport) Enqueue(env *cb.Envelope) bool
func (cs *chainSupport) Errored() <-chan struct{}
//创建块，调取ledger.CreateNextBlock(cs.ledger, messages)
func (cs *chainSupport) CreateNextBlock(messages []*cb.Envelope) *cb.Block
func (cs *chainSupport) addBlockSignature(block *cb.Block)
func (cs *chainSupport) addLastConfigSignature(block *cb.Block)
//写入块
func (cs *chainSupport) WriteBlock(block *cb.Block, committers []filter.Committer, encodedMetadataValue []byte) *cb.Block
func (cs *chainSupport) Height() uint64
//代码在orderer/multichain/chainsupport.go
```
func (cs *chainSupport) WriteBlock(block *cb.Block, committers []filter.Committer, encodedMetadataValue []byte) *cb.Block 代码如下：
```go
func (cs *chainSupport) WriteBlock(block *cb.Block, committers []filter.Committer, encodedMetadataValue []byte) *cb.Block {
for _, committer := range committers {
committer.Commit()
}
cs.addBlockSignature(block)
cs.addLastConfigSignature(block)
err := cs.ledger.Append(block)//账本追加块
return block
}
//代码在orderer/multichain/chainsupport.go
```
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