path: root/miner/unconfirmed.go

// Copyright 2016 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package miner

import (
    "container/ring"
    "fmt"
    "sync"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/core/types"
    "github.com/ethereum/go-ethereum/log"
)

// headerRetriever is used by the unconfirmed block set to verify whether a previously
// mined block is part of the canonical chain or not.
type headerRetriever interface {
    // GetHeaderByNumber retrieves the canonical header associated with a block number.
    GetHeaderByNumber(number uint64) *types.Header
}

// unconfirmedBlock is a small collection of metadata about a locally mined block
// that is placed into a unconfirmed set for canonical chain inclusion tracking.
type unconfirmedBlock struct {
    index uint64
    hash  common.Hash
}

// unconfirmedBlocks implements a data structure to maintain locally mined blocks
// have have not yet reached enough maturity to guarantee chain inclusion. It is
// used by the miner to provide logs to the user when a previously mined block
// has a high enough guarantee to not be reorged out of te canonical chain.
type unconfirmedBlocks struct {
    chain  headerRetriever // Blockchain to verify canonical status through
    depth  uint            // Depth after which to discard previous blocks
    blocks *ring.Ring      // Block infos to allow canonical chain cross checks
    lock   sync.RWMutex    // Protects the fields from concurrent access
}

// newUnconfirmedBlocks returns new data structure to track currently unconfirmed blocks.
func newUnconfirmedBlocks(chain headerRetriever, depth uint) *unconfirmedBlocks {
    return &unconfirmedBlocks{
        chain: chain,
        depth: depth,
    }
}

// Insert adds a new block to the set of unconfirmed ones.
func (set *unconfirmedBlocks) Insert(index uint64, hash common.Hash) {
    // If a new block was mined locally, shift out any old enough blocks
    set.Shift(index)

    // Create the new item as its own ring
    item := ring.New(1)
    item.Value = &unconfirmedBlock{
        index: index,
        hash:  hash,
    }
    // Set as the initial ring or append to the end
    set.lock.Lock()
    defer set.lock.Unlock()

    if set.blocks == nil {
        set.blocks = item
    } else {
        set.blocks.Move(-1).Link(item)
    }
    // Display a log for the user to notify of a new mined block unconfirmed
    log.Info(fmt.Sprintf("🔨  mined potential block #%d [%x…], waiting for %d blocks to confirm", index, hash.Bytes()[:4], set.depth))
}

// Shift drops all unconfirmed blocks from the set which exceed the unconfirmed sets depth
// allowance, checking them against the canonical chain for inclusion or staleness
// report.
func (set *unconfirmedBlocks) Shift(height uint64) {
    set.lock.Lock()
    defer set.lock.Unlock()

    for set.blocks != nil {
        // Retrieve the next unconfirmed block and abort if too fresh
        next := set.blocks.Value.(*unconfirmedBlock)
        if next.index+uint64(set.depth) > height {
            break
        }
        // Block seems to exceed depth allowance, check for canonical status
        header := set.chain.GetHeaderByNumber(next.index)
        switch {
        case header == nil:
            log.Warn(fmt.Sprintf("failed to retrieve header of mined block #%d [%x…]", next.index, next.hash.Bytes()[:4]))
        case header.Hash() == next.hash:
            log.Info(fmt.Sprintf("🔗  mined block #%d [%x…] reached canonical chain", next.index, next.hash.Bytes()[:4]))
        default:
            log.Info(fmt.Sprintf("⑂ mined block #%d [%x…] became a side fork", next.index, next.hash.Bytes()[:4]))
        }
        // Drop the block out of the ring
        if set.blocks.Value == set.blocks.Next().Value {
            set.blocks = nil
        } else {
            set.blocks = set.blocks.Move(-1)
            set.blocks.Unlink(1)
            set.blocks = set.blocks.Move(1)
        }
    }
}