内容简介:go-ethereum 中的所有区块数据都存储在源码目录如下,主要就下面 4 个源码文件:我们主要分析下
go-ethereum 中的所有区块数据都存储在 leveldb 中,并且 go-ethereum 又基于 leveldb 进行了一层简单的封装。
leveldb 是一个由 Google 开源(BSD)的 KV(Key/Value Pair)非关系型数据库,是基于 LSM(Log-Structured-Merge tree) 的典型实现。
主要有如下几个 特性 :
源码目录如下,主要就下面 4 个源码文件:
➜ ethdb : . ├── database.go // leveldb 的封装代码 ├── database_test.go // 测试用例 ├── interface.go // 定义了 Database 的一些操作接口 └── memory_database.go // 供测试环境使用的基于内存的数据库
我们主要分析下 database.go 和 interface.go 两个源码文件。
database.go
这里主要封装了 leveldb 的接口,从如下 import 可以看出主要使用了 goleveldb 的封装。
import ( "strconv" "strings" "sync" "time" "github.com/ethereum/go-ethereum/log" "github.com/ethereum/go-ethereum/metrics" "github.com/syndtr/goleveldb/leveldb" "github.com/syndtr/goleveldb/leveldb/errors" "github.com/syndtr/goleveldb/leveldb/filter" "github.com/syndtr/goleveldb/leveldb/iterator" "github.com/syndtr/goleveldb/leveldb/opt" "github.com/syndtr/goleveldb/leveldb/util" )
下面看下在 goleveldb 基础上进一步封装的 LDBDatabase 结构,如下,主要增加了很多维度的 Metrics 用于统计使用情况(几个 metrics 的注释很清晰):
type LDBDatabase struct { fn string // filename for reporting db *leveldb.DB // LevelDB instance compTimeMeter metrics.Meter // Meter for measuring the total time spent in database compaction compReadMeter metrics.Meter // Meter for measuring the data read during compaction compWriteMeter metrics.Meter // Meter for measuring the data written during compaction diskReadMeter metrics.Meter // Meter for measuring the effective amount of data read diskWriteMeter metrics.Meter // Meter for measuring the effective amount of data written quitLock sync.Mutex // Mutex protecting the quit channel access quitChan chan chan error // Quit channel to stop the metrics collection before closing the database log log.Logger // Contextual logger tracking the database path }
通过 NewLDBDatabase 方法来打开(或创建)并返回封装后的 LDBDatabase 实例,如下:
// NewLDBDatabase returns a LevelDB wrapped object. func NewLDBDatabase(file string, cache int, handles int) (*LDBDatabase, error) { // 跟踪对应 leveldb 文件的 logger logger := log.New("database", file) // Ensure we have some minimal caching and file guarantees if cache < 16 { cache = 16 } if handles < 16 { handles = 16 } logger.Info("Allocated cache and file handles", "cache", cache, "handles", handles) // 打开 leveldb 文件,并恢复潜在的冲突 db, err := leveldb.OpenFile(file, &opt.Options{ OpenFilesCacheCapacity: handles, BlockCacheCapacity: cache / 2 * opt.MiB, WriteBuffer: cache / 4 * opt.MiB, // Two of these are used internally Filter: filter.NewBloomFilter(10), }) if _, corrupted := err.(*errors.ErrCorrupted); corrupted { // 如果有冲突,则需要修复文件 db, err = leveldb.RecoverFile(file, nil) } // (Re)check for errors and abort if opening of the db failed if err != nil { return nil, err } // 返回 LDBDatabase 实例 return &LDBDatabase{ fn: file, db: db, log: logger, }, nil }
此外,提供了一些基本操作方法,如 Put,Path,Get,Delete 等等用于操作 leveldb,这些基本操作都是直接调用 leveldb 的封装,如下为 Put 操作:
// Put puts the given key / value to the queue func (db *LDBDatabase) Put(key []byte, value []byte) error { // Generate the data to write to disk, update the meter and write //value = rle.Compress(value) return db.db.Put(key, value, nil) }
创建本地 blockchain 数据库
下面看何时以及如何创建本地区块链DB:
// source: eth/backend.go // // New creates a new Ethereum object (including the // initialisation of the common Ethereum object) func New(ctx *node.ServiceContext, config *Config) (*Ethereum, error) { if config.SyncMode == downloader.LightSync { return nil, errors.New("can't run eth.Ethereum in light sync mode, use les.LightEthereum") } if !config.SyncMode.IsValid() { return nil, fmt.Errorf("invalid sync mode %d", config.SyncMode) } // 创建本地 blockchain 数据库 // 返回的 chainDb chainDb, err := CreateDB(ctx, config, "chaindata") if err != nil { return nil, err } stopDbUpgrade := upgradeDeduplicateData(chainDb) // 设置创世区块,并写入 chainDb 中 chainConfig, genesisHash, genesisErr := core.SetupGenesisBlock(chainDb, config.Genesis) if _, ok := genesisErr.(*params.ConfigCompatError); genesisErr != nil && !ok { return nil, genesisErr } log.Info("Initialised chain configuration", "config", chainConfig) eth := &Ethereum{ config: config, chainDb: chainDb, chainConfig: chainConfig, eventMux: ctx.EventMux, accountManager: ctx.AccountManager, engine: CreateConsensusEngine(ctx, &config.Ethash, chainConfig, chainDb), shutdownChan: make(chan bool), stopDbUpgrade: stopDbUpgrade, networkId: config.NetworkId, gasPrice: config.GasPrice, etherbase: config.Etherbase, bloomRequests: make(chan chan *bloombits.Retrieval), bloomIndexer: NewBloomIndexer(chainDb, params.BloomBitsBlocks), } // ... }
可以看到在创建和初始化 Ethereum 对象的时候会同时通过调用 CreateDB 方法来创建本地区块链数据库,并将 ethdb.LDBDatabase 实例 chainDb 作为 eth 实例的成员,在后续区块数据写入本地库时,都是通过该 chainDb 实例来操作写入的,如下代码:
// source: eth/backend.go // // CreateDB creates the chain database. func CreateDB(ctx *node.ServiceContext, config *Config, name string) (ethdb.Database, error) { // 打开 name 数据库 db, err := ctx.OpenDatabase(name, config.DatabaseCache, config.DatabaseHandles) if err != nil { return nil, err } if db, ok := db.(*ethdb.LDBDatabase); ok { db.Meter("eth/db/chaindata/") } return db, nil }
这里打开 “chaindata” 数据库,并且启动 Metric(见下面),在 ctx.OpenDatabase 中创建 LDBDatabase,如下:
// source: node/node.go // // OpenDatabase opens an existing database with the given name (or creates one if no // previous can be found) from within the node's instance directory. If the node is // ephemeral, a memory database is returned. func (n *Node) OpenDatabase(name string, cache, handles int) (ethdb.Database, error) { if n.config.DataDir == "" { // 没有指定 DataDir,则启动为内存数据库 return ethdb.NewMemDatabase() } return ethdb.NewLDBDatabase(n.config.resolvePath(name), cache, handles) }
将 block 写入到 leveldb
在 core/database_util.go 中,封装了 WriteHeader, WriteBody, WriteBlock 等方法用于将区块 header, body, block 写入 leveldb 中。
// source: core/database_util.go // // WriteHeader serializes a block header into the database. func WriteHeader(db ethdb.Putter, header *types.Header) error { data, err := rlp.EncodeToBytes(header) if err != nil { return err } hash := header.Hash().Bytes() num := header.Number.Uint64() encNum := encodeBlockNumber(num) key := append(blockHashPrefix, hash...) if err := db.Put(key, encNum); err != nil { log.Crit("Failed to store hash to number mapping", "err", err) } key = append(append(headerPrefix, encNum...), hash...) if err := db.Put(key, data); err != nil { log.Crit("Failed to store header", "err", err) } return nil } // WriteBody serializes the body of a block into the database. func WriteBody(db ethdb.Putter, hash common.Hash, number uint64, body *types.Body) error { data, err := rlp.EncodeToBytes(body) if err != nil { return err } return WriteBodyRLP(db, hash, number, data) } // WriteBodyRLP writes a serialized body of a block into the database. func WriteBodyRLP(db ethdb.Putter, hash common.Hash, number uint64, rlp rlp.RawValue) error { key := append(append(bodyPrefix, encodeBlockNumber(number)...), hash.Bytes()...) if err := db.Put(key, rlp); err != nil { log.Crit("Failed to store block body", "err", err) } return nil } // WriteTd serializes the total difficulty of a block into the database. func WriteTd(db ethdb.Putter, hash common.Hash, number uint64, td *big.Int) error { data, err := rlp.EncodeToBytes(td) if err != nil { return err } key := append(append(append(headerPrefix, encodeBlockNumber(number)...), hash.Bytes()...), tdSuffix...) if err := db.Put(key, data); err != nil { log.Crit("Failed to store block total difficulty", "err", err) } return nil } // WriteBlock serializes a block into the database, header and body separately. func WriteBlock(db ethdb.Putter, block *types.Block) error { // Store the body first to retain database consistency if err := WriteBody(db, block.Hash(), block.NumberU64(), block.Body()); err != nil { return err } // Store the header too, signaling full block ownership if err := WriteHeader(db, block.Header()); err != nil { return err } return nil }
其中都通过 db.Put 方法将区块信息写入 leveldb 中。
Metrics
在 Meter 方法中创建了各种 Metrics 采集器,然后创建了 quitChan,最后启动一个协程调用了 db.meter 方法每隔 3 秒收集一次。
// Meter configures the database metrics collectors and func (db *LDBDatabase) Meter(prefix string) { // Short circuit metering if the metrics system is disabled if !metrics.Enabled { return } // Initialize all the metrics collector at the requested prefix db.compTimeMeter = metrics.NewRegisteredMeter(prefix+"compact/time", nil) db.compReadMeter = metrics.NewRegisteredMeter(prefix+"compact/input", nil) db.compWriteMeter = metrics.NewRegisteredMeter(prefix+"compact/output", nil) db.diskReadMeter = metrics.NewRegisteredMeter(prefix+"disk/read", nil) db.diskWriteMeter = metrics.NewRegisteredMeter(prefix+"disk/write", nil) // Create a quit channel for the periodic collector and run it db.quitLock.Lock() db.quitChan = make(chan chan error) db.quitLock.Unlock() go db.meter(3 * time.Second) }
metrics.Enabled开关默认为关闭(false),通过命令行选项参数 metrics 来设置。
// go-ethereum/metrics.go // Enabled is checked by the constructor functions for all of the // standard metrics. If it is true, the metric returned is a stub. // // This global kill-switch helps quantify the observer effect and makes // for less cluttered pprof profiles. var Enabled bool = false // MetricsEnabledFlag is the CLI flag name to use to enable metrics collections. const MetricsEnabledFlag = "metrics" const DashboardEnabledFlag = "dashboard" // Init enables or disables the metrics system. Since we need this to run before // any other code gets to create meters and timers, we'll actually do an ugly hack // and peek into the command line args for the metrics flag. func init() { for _, arg := range os.Args { if flag := strings.TrimLeft(arg, "-"); flag == MetricsEnabledFlag || flag == DashboardEnabledFlag { log.Info("Enabling metrics collection") Enabled = true } } }
在启动 metrics 开关后,每隔 3 秒会从 leveldb 内部获取计数器,然后公布到 metrics 子系统,这里是一个无限循环,直到 quitChan 收到一个退出信号。
// meter periodically retrieves internal leveldb counters and reports them to // the metrics subsystem. // // This is how a stats table look like (currently): // Compactions // Level | Tables | Size(MB) | Time(sec) | Read(MB) | Write(MB) // -------+------------+---------------+---------------+---------------+--------------- // 0 | 0 | 0.00000 | 1.27969 | 0.00000 | 12.31098 // 1 | 85 | 109.27913 | 28.09293 | 213.92493 | 214.26294 // 2 | 523 | 1000.37159 | 7.26059 | 66.86342 | 66.77884 // 3 | 570 | 1113.18458 | 0.00000 | 0.00000 | 0.00000 // // This is how the iostats look like (currently): // Read(MB):3895.04860 Write(MB):3654.64712 func (db *LDBDatabase) meter(refresh time.Duration) { // Create the counters to store current and previous compaction values // 创建一个计数器,用于存储当前和上一次的压缩值 // 一个二维数组,第 1 维表示 当前 和 上一次,第 2 维表示统计值 compactions := make([][]float64, 2) for i := 0; i < 2; i++ { compactions[i] = make([]float64, 3) } // Create storage for iostats. var iostats [2]float64 // Iterate ad infinitum and collect the stats for i := 1; ; i++ { // Retrieve the database stats stats, err := db.db.GetProperty("leveldb.stats") if err != nil { db.log.Error("Failed to read database stats", "err", err) return } // Find the compaction table, skip the header lines := strings.Split(stats, "\n") for len(lines) > 0 && strings.TrimSpace(lines[0]) != "Compactions" { lines = lines[1:] } if len(lines) <= 3 { db.log.Error("Compaction table not found") return } lines = lines[3:] // Iterate over all the table rows, and accumulate the entries for j := 0; j < len(compactions[i%2]); j++ { compactions[i%2][j] = 0 } for _, line := range lines { parts := strings.Split(line, "|") if len(parts) != 6 { break } for idx, counter := range parts[3:] { value, err := strconv.ParseFloat(strings.TrimSpace(counter), 64) if err != nil { db.log.Error("Compaction entry parsing failed", "err", err) return } compactions[i%2][idx] += value } } // Update all the requested meters if db.compTimeMeter != nil { db.compTimeMeter.Mark(int64((compactions[i%2][0] - compactions[(i-1)%2][0]) * 1000 * 1000 * 1000)) } if db.compReadMeter != nil { db.compReadMeter.Mark(int64((compactions[i%2][1] - compactions[(i-1)%2][1]) * 1024 * 1024)) } if db.compWriteMeter != nil { db.compWriteMeter.Mark(int64((compactions[i%2][2] - compactions[(i-1)%2][2]) * 1024 * 1024)) } // Retrieve the database iostats. ioStats, err := db.db.GetProperty("leveldb.iostats") if err != nil { db.log.Error("Failed to read database iostats", "err", err) return } parts := strings.Split(ioStats, " ") if len(parts) < 2 { db.log.Error("Bad syntax of ioStats", "ioStats", ioStats) return } r := strings.Split(parts[0], ":") if len(r) < 2 { db.log.Error("Bad syntax of read entry", "entry", parts[0]) return } read, err := strconv.ParseFloat(r[1], 64) if err != nil { db.log.Error("Read entry parsing failed", "err", err) return } w := strings.Split(parts[1], ":") if len(w) < 2 { db.log.Error("Bad syntax of write entry", "entry", parts[1]) return } write, err := strconv.ParseFloat(w[1], 64) if err != nil { db.log.Error("Write entry parsing failed", "err", err) return } if db.diskReadMeter != nil { db.diskReadMeter.Mark(int64((read - iostats[0]) * 1024 * 1024)) } if db.diskWriteMeter != nil { db.diskWriteMeter.Mark(int64((write - iostats[1]) * 1024 * 1024)) } iostats[0] = read iostats[1] = write // Sleep a bit, then repeat the stats collection select { case errc := <-db.quitChan: // Quit requesting, stop hammering the database errc <- nil return case <-time.After(refresh): // Timeout, gather a new set of stats } } }
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