0bf463d7d5
This adds a flushBlockDB function to the UTXO cache. The flushBlockDB function is used to flush the block database to disk prior to flushing the UTXO cache to the UTXO database. This ensures that the block database is always at least as far along as the UTXO database which keeps the UTXO database in a recoverable state in the event of an unclean shutdown.
85 lines
3.1 KiB
Go
85 lines
3.1 KiB
Go
// Copyright (c) 2014-2016 The btcsuite developers
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// Copyright (c) 2015-2021 The Decred developers
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// Use of this source code is governed by an ISC
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// license that can be found in the LICENSE file.
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package blockchain_test
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import (
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"context"
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"fmt"
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"os"
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"path/filepath"
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"github.com/decred/dcrd/blockchain/v4"
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"github.com/decred/dcrd/chaincfg/v3"
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"github.com/decred/dcrd/database/v2"
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_ "github.com/decred/dcrd/database/v2/ffldb"
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"github.com/decred/dcrd/dcrutil/v4"
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)
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// This example demonstrates how to create a new chain instance and use
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// ProcessBlock to attempt to add a block to the chain. As the package
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// overview documentation describes, this includes all of the Decred consensus
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// rules. This example intentionally attempts to insert a duplicate genesis
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// block to illustrate how an invalid block is handled.
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func ExampleBlockChain_ProcessBlock() {
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// Create a new database to store the accepted blocks into. Typically
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// this would be opening an existing database and would not be deleting
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// and creating a new database like this, but it is done here so this is
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// a complete working example and does not leave temporary files laying
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// around.
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mainNetParams := chaincfg.MainNetParams()
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dbPath := filepath.Join(os.TempDir(), "exampleprocessblock")
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_ = os.RemoveAll(dbPath)
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db, err := database.Create("ffldb", dbPath, mainNetParams.Net)
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if err != nil {
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fmt.Printf("Failed to create database: %v\n", err)
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return
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}
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defer os.RemoveAll(dbPath)
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defer db.Close()
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// Create a new BlockChain instance using the underlying database for
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// the main bitcoin network. This example does not demonstrate some
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// of the other available configuration options such as specifying a
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// notification callback and signature cache. Also, the caller would
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// ordinarily keep a reference to the median time source and add time
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// values obtained from other peers on the network so the local time is
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// adjusted to be in agreement with other peers.
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chain, err := blockchain.New(context.Background(),
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&blockchain.Config{
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DB: db,
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ChainParams: mainNetParams,
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TimeSource: blockchain.NewMedianTime(),
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UtxoCache: blockchain.NewUtxoCache(&blockchain.UtxoCacheConfig{
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DB: db,
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FlushBlockDB: func() error {
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return nil
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},
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MaxSize: 100 * 1024 * 1024, // 100 MiB
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}),
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})
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if err != nil {
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fmt.Printf("Failed to create chain instance: %v\n", err)
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return
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}
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// Process a block. For this example, intentionally cause an error by
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// trying to process the genesis block which already exists.
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genesisBlock := dcrutil.NewBlock(mainNetParams.GenesisBlock)
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forkLen, err := chain.ProcessBlock(genesisBlock,
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blockchain.BFNone)
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if err != nil {
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fmt.Printf("Failed to create chain instance: %v\n", err)
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return
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}
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isMainChain := forkLen == 0
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fmt.Printf("Block accepted. Is it on the main chain?: %v", isMainChain)
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// This output is dependent on the genesis block, and needs to be
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// updated if the mainnet genesis block is updated.
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// Output:
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// Failed to process block: already have block 267a53b5ee86c24a48ec37aee4f4e7c0c4004892b7259e695e9f5b321f1ab9d2
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}
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