以太坊 --- 交易池的特点 与 中断恢复

func NewTxPool(config TxPoolConfig, chainconfig *params.ChainConfig, chain blockChain) *TxPool {
	...
	for _, addr := range config.Locals { // 从配置文件添加 本地地址
		log.Info("Setting new local account", "address", addr)
		// 添加到 locals 变量里面，后面会用它来过滤出一个地址是否是本地地址
		pool.locals.add(addr) 
	}
	...
}

func NewTxPool(config TxPoolConfig, chainconfig *params.ChainConfig, chain blockChain) *TxPool {
	...
	pool.locals = newAccountSet(pool.signer)
	for _, addr := range config.Locals {
		log.Info("Setting new local account", "address", addr)
		pool.locals.add(addr)
	}
	...	
 	// 上面添加完了
	// If local transactions and journaling is enabled, load from disk
	if !config.NoLocals && config.Journal != "" { // 如果配置开启了本地加载的需求
		pool.journal = newTxJournal(config.Journal)
   		// load 是加载函数，pool.AddLocals 是实际添加函数
		if err := pool.journal.load(pool.AddLocals); err != nil {
			log.Warn("Failed to load transaction journal", "err", err)
		}
		if err := pool.journal.rotate(pool.local()); err != nil {
			log.Warn("Failed to rotate transaction journal", "err", err)
		}
	}
	...
    go pool.loop() // 循环处理事件
}

func (journal *txJournal) load(add func([]*types.Transaction) []error) error {
	// Skip the parsing if the journal file doesn't exist at all
	if _, err := os.Stat(journal.path); os.IsNotExist(err) {
		return nil
	}
	// Open the journal for loading any past transactions
	input, err := os.Open(journal.path) // 打开文件，读取流数据
	if err != nil {
		return err
	}
	...
	stream := rlp.NewStream(input, 0) // 使用 rlp 编码算法解码数据
	...
	loadBatch := func(txs types.Transactions) {
		for _, err := range add(txs) { // 调用 add 函数，进行添加
			if err != nil {
				log.Debug("Failed to add journaled transaction", "err", err)
				dropped++
			}
		}
	}
	// loadBatch 在下面会被调用
	...
}

func (pool *TxPool) add(tx *types.Transaction, local bool) (replaced bool, err error) {
	...
 	// 下面的 if，如果已在 pool.pending 里面，那么证明之前已经添加过在 queue 里
	if list := pool.pending[from]; list != nil && list.Overlaps(tx) {
		...
 		pool.journalTx(from, tx) // 内部调用 journal.insert
		return old != nil, nil
	}
	replaced, err = pool.enqueueTx(hash, tx) // 这里，会添加到 pool.enqueue 里面
	if err != nil {
		return false, err
	}
	pool.journalTx(from, tx) // 内部调用 journal.insert
	...
}

func (pool *TxPool) journalTx(from common.Address, tx *types.Transaction) {
	// 本地钱包地址，没指定的话，就跳过
	if pool.journal == nil || !pool.locals.contains(from) {
		return
	}
 	// insert 会在造成重复添加，但是 load 出来的时候会根据 addr 去重
	if err := pool.journal.insert(tx); err != nil {
		log.Warn("Failed to journal local transaction", "err", err)
	}
}

func (pool *TxPool) loop() {
	...
	for {
		select {
		...
		// Handle local transaction journal rotation
 		// journal 定时器，定时执行下面的本地交易数据文件的更新 journal.rotate
		case <-journal.C:
			if pool.journal != nil {
				pool.mu.Lock()
				if err := pool.journal.rotate(pool.local()); err != nil {
					log.Warn("Failed to rotate local tx journal", "err", err)
				}
				pool.mu.Unlock()
			}
		}
	}
}

//输入
func (pool *TxPool) local() map[common.Address]types.Transactions {
	...
	for addr := range pool.locals.accounts {
		if pending := pool.pending[addr]; pending != nil {
 			// 添加 pending 的
			txs[addr] = append(txs[addr], pending.Flatten()...)
		}
		if queued := pool.queue[addr]; queued != nil {
 			// 添加 queue 的
			txs[addr] = append(txs[addr], queued.Flatten()...)
		}
	}
	return txs
}

// all 参数，来源于上面 local()
func (journal *txJournal) rotate(all map[common.Address]types.Transactions) error {
	...
	// journal.path+".new" 后缀 .new
	replacement, err := os.OpenFile(journal.path+".new", os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0755)
	if err != nil {
		return err
	}
	journaled := 0
	for _, txs := range all {
		for _, tx := range txs {
			if err = rlp.Encode(replacement, tx); err != nil {
				replacement.Close()
				return err
			}
		}
		journaled += len(txs)
	}
	replacement.Close()
 	// rename，重命名文件到原始的 path，达到更新，替换目的
	if err = os.Rename(journal.path+".new", journal.path); err != nil {
		return err
	}
	sink, err := os.OpenFile(journal.path, os.O_WRONLY|os.O_APPEND, 0755)
	if err != nil {
		return err
	}
	...
	return nil
}

func New(ctx *node.ServiceContext, config *Config) (*Ethereum, error) {
	...
	if config.TxPool.Journal != "" {
		config.TxPool.Journal = ctx.ResolvePath(config.TxPool.Journal)
	}
 	// 初始化交易池
	eth.txPool = core.NewTxPool(config.TxPool, chainConfig, eth.blockchain)
	...
 	// 使用 交易池指针对象 作为参数初始化 protocolManager
	if eth.protocolManager, err = NewProtocolManager(
    		chainConfig, checkpoint, config.SyncMode, config.NetworkId, 
            	eth.eventMux, `eth.txPool`, eth.engine, 
                eth.blockchain, chainDb, cacheLimit, config.Whitelist); err != nil {
		return nil, err
	}
	...
	return eth, nil
}

func NewProtocolManager(config *params.ChainConfig, checkpoint *params.TrustedCheckpoint, mode downloader.SyncMode, networkID uint64, mux *event.TypeMux, txpool txPool, engine consensus.Engine, blockchain *core.BlockChain, chaindb ethdb.Database, cacheLimit int, whitelist map[uint64]common.Hash) (*ProtocolManager, error) {
	// 下面初始化 tx_fetcher，使用 txpool.AddRemotes 赋值给函数变量 addTxs
	manager.txFetcher = fetcher.NewTxFetcher(txpool.Has, txpool.AddRemotes, fetchTx)
}

func (pm *ProtocolManager) handleMsg(p *peer) error {
	...
    switch {
    ...
    // 接收到其它节点的交易数据
    case msg.Code == TransactionMsg || (msg.Code == PooledTransactionsMsg && p.version >= eth65):
		...
 		// Enqueue 将交易添加到交易池
		pm.txFetcher.Enqueue(p.id, txs, msg.Code == PooledTransactionsMsg)

    }
    ...
}
// tx_fetcher.go 文件
func (f *TxFetcher) Enqueue(peer string, txs []*types.Transaction, direct bool) error {
 	...
	errs := f.addTxs(txs) // 执行添加，这个函数其实就是 tx_pool.go 的 AddRemotes
	...
}

// tx_pool.go
// addTxs 内部就会把交易添加到 Pending 和 Queue 里面
func (pool *TxPool) AddRemotes(txs []*types.Transaction) []error {
	return pool.addTxs(txs, false, false)
}