path: root/core/test/app.go

// Copyright 2018 The dexon-consensus Authors
// This file is part of the dexon-consensus library.
//
// The dexon-consensus 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 dexon-consensus 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 dexon-consensus library. If not, see
// <http://www.gnu.org/licenses/>.

package test

import (
    "fmt"
    "sync"
    "time"

    "github.com/dexon-foundation/dexon-consensus/common"
    "github.com/dexon-foundation/dexon-consensus/core/types"
)

var (
    // ErrEmptyDeliverSequence means there is no delivery event in this App
    // instance.
    ErrEmptyDeliverSequence = fmt.Errorf("empty deliver sequence")
    // ErrMismatchBlockHashSequence means the delivering sequence between two App
    // instances are different.
    ErrMismatchBlockHashSequence = fmt.Errorf("mismatch block hash sequence")
    // ErrMismatchConsensusTime means the consensus timestamp between two blocks
    // with the same hash from two App instances are different.
    ErrMismatchConsensusTime = fmt.Errorf("mismatch consensus time")
    // ErrApplicationIntegrityFailed means the internal datum in a App instance
    // is not integrated.
    ErrApplicationIntegrityFailed = fmt.Errorf("application integrity failed")
    // ErrConsensusTimestampOutOfOrder means the later delivered block has
    // consensus timestamp older than previous block.
    ErrConsensusTimestampOutOfOrder = fmt.Errorf(
        "consensus timestamp out of order")
    // ErrConsensusHeightOutOfOrder means the later delivered block has
    // consensus height not equal to height of previous block plus one.
    ErrConsensusHeightOutOfOrder = fmt.Errorf(
        "consensus height out of order")
    // ErrDeliveredBlockNotConfirmed means some block delivered (confirmed) but
    // not confirmed.
    ErrDeliveredBlockNotConfirmed = fmt.Errorf("delivered block not confirmed")
    // ErrAckingBlockNotDelivered means the delivered sequence not forming a
    // DAG.
    ErrAckingBlockNotDelivered = fmt.Errorf("acking block not delivered")
    // ErrLowerPendingHeight raised when lastPendingHeight is lower than the
    // height to be prepared.
    ErrLowerPendingHeight = fmt.Errorf(
        "last pending height < consensus height")
    // ErrConfirmedHeightNotIncreasing raise when the height of the confirmed
    // block doesn't follow previous confirmed block on the same chain.
    ErrConfirmedHeightNotIncreasing = fmt.Errorf(
        "confirmed height not increasing")
    // ErrParentBlockNotDelivered raised when the parent block is not seen by
    // this app.
    ErrParentBlockNotDelivered = fmt.Errorf("parent block not delivered")
)

// AppDeliveredRecord caches information when this application received
// a block delivered notification.
type AppDeliveredRecord struct {
    Result types.FinalizationResult
    When   time.Time
    Pos    types.Position
}

// App implements Application interface for testing purpose.
type App struct {
    Confirmed             map[common.Hash]*types.Block
    LastConfirmedHeight   uint64
    confirmedLock         sync.RWMutex
    Delivered             map[common.Hash]*AppDeliveredRecord
    DeliverSequence       common.Hashes
    deliveredLock         sync.RWMutex
    state                 *State
    gov                   *Governance
    lastPendingHeightLock sync.RWMutex
    LastPendingHeight     uint64
    roundToNotify         uint64
}

// NewApp constructs a TestApp instance.
func NewApp(initRound uint64, gov *Governance) (app *App) {
    app = &App{
        Confirmed:       make(map[common.Hash]*types.Block),
        Delivered:       make(map[common.Hash]*AppDeliveredRecord),
        DeliverSequence: common.Hashes{},
        gov:             gov,
        roundToNotify:   initRound,
    }
    if gov != nil {
        app.state = gov.State()
    }
    return app
}

// PreparePayload implements Application interface.
func (app *App) PreparePayload(position types.Position) ([]byte, error) {
    if app.state == nil {
        return []byte{}, nil
    }
    return app.state.PackRequests()
}

// PrepareWitness implements Application interface.
func (app *App) PrepareWitness(height uint64) (types.Witness, error) {
    pendingHeight := app.getLastPendingWitnessHeight()
    if pendingHeight < height {
        return types.Witness{}, ErrLowerPendingHeight
    }
    if pendingHeight == 0 {
        return types.Witness{}, nil
    }
    hash := func() common.Hash {
        app.deliveredLock.RLock()
        defer app.deliveredLock.RUnlock()
        // Our witness height starts from 1.
        h := app.DeliverSequence[pendingHeight-1]
        // Double confirm if the delivered record matches the pending height.
        if app.Delivered[h].Result.Height != pendingHeight {
            app.confirmedLock.RLock()
            defer app.confirmedLock.RUnlock()
            panic(fmt.Errorf("unmatched finalization record: %s, %v, %v",
                app.Confirmed[h], pendingHeight,
                app.Delivered[h].Result.Height))
        }
        return h
    }()
    return types.Witness{
        Height: pendingHeight,
        Data:   hash.Bytes(),
    }, nil
}

// VerifyBlock implements Application interface.
func (app *App) VerifyBlock(block *types.Block) types.BlockVerifyStatus {
    // Make sure we can handle the witness carried by this block.
    pendingHeight := app.getLastPendingWitnessHeight()
    if pendingHeight < block.Witness.Height {
        return types.VerifyRetryLater
    }
    // Confirm if the consensus height matches corresponding block hash.
    var h common.Hash
    copy(h[:], block.Witness.Data)
    app.deliveredLock.RLock()
    defer app.deliveredLock.RUnlock()
    // This is the difference between test.App and fullnode, fullnode has the
    // genesis block at height=0, we don't. Thus our reasonable witness starts
    // from 1.
    if block.Witness.Height > 0 {
        if block.Witness.Height != app.Delivered[h].Result.Height {
            return types.VerifyInvalidBlock
        }
    }
    if block.Position.Height != 0 {
        // This check is copied from fullnode, below is quoted from coresponding
        // comment:
        //
        // Check if target block is the next height to be verified, we can only
        // verify the next block in a given chain.
        app.confirmedLock.RLock()
        defer app.confirmedLock.RUnlock()
        if app.LastConfirmedHeight+1 != block.Position.Height {
            return types.VerifyRetryLater
        }
    }
    return types.VerifyOK
}

// BlockConfirmed implements Application interface.
func (app *App) BlockConfirmed(b types.Block) {
    app.confirmedLock.Lock()
    defer app.confirmedLock.Unlock()
    app.Confirmed[b.Hash] = &b
    if b.Position.Height != 0 {
        if app.LastConfirmedHeight+1 != b.Position.Height {
            panic(ErrConfirmedHeightNotIncreasing)
        }
    }
    app.LastConfirmedHeight = b.Position.Height
}

// BlockDelivered implements Application interface.
func (app *App) BlockDelivered(
    blockHash common.Hash, pos types.Position, result types.FinalizationResult) {
    func() {
        app.deliveredLock.Lock()
        defer app.deliveredLock.Unlock()
        app.Delivered[blockHash] = &AppDeliveredRecord{
            Result: result,
            When:   time.Now().UTC(),
            Pos:    pos,
        }
        app.DeliverSequence = append(app.DeliverSequence, blockHash)
        // Make sure parent block also delivered.
        if !result.ParentHash.Equal(common.Hash{}) {
            d, exists := app.Delivered[result.ParentHash]
            if !exists {
                panic(ErrParentBlockNotDelivered)
            }
            if d.Result.Height+1 != result.Height {
                panic(ErrConsensusHeightOutOfOrder)
            }
        }
        app.lastPendingHeightLock.Lock()
        defer app.lastPendingHeightLock.Unlock()
        app.LastPendingHeight = result.Height
    }()
    // Apply packed state change requests in payload.
    func() {
        if app.state == nil {
            return
        }
        app.confirmedLock.RLock()
        defer app.confirmedLock.RUnlock()
        b := app.Confirmed[blockHash]
        if err := app.state.Apply(b.Payload); err != nil {
            if err != ErrDuplicatedChange {
                panic(err)
            }
        }
        if app.roundToNotify == pos.Round {
            if app.gov != nil {
                app.gov.NotifyRound(app.roundToNotify)
                app.roundToNotify++
            }
        }
    }()
}

// GetLatestDeliveredPosition would return the latest position of delivered
// block seen by this application instance.
func (app *App) GetLatestDeliveredPosition() types.Position {
    app.deliveredLock.RLock()
    defer app.deliveredLock.RUnlock()
    app.confirmedLock.RLock()
    defer app.confirmedLock.RUnlock()
    if len(app.DeliverSequence) == 0 {
        return types.Position{}
    }
    return app.Confirmed[app.DeliverSequence[len(app.DeliverSequence)-1]].Position
}

// Compare performs these checks against another App instance
// and return erros if not passed:
// - deliver sequence by comparing block hashes.
// - consensus timestamp of each block are equal.
func (app *App) Compare(other *App) (err error) {
    app.WithLock(func(app *App) {
        other.WithLock(func(other *App) {
            minLength := len(app.DeliverSequence)
            if minLength > len(other.DeliverSequence) {
                minLength = len(other.DeliverSequence)
            }
            if minLength == 0 {
                err = ErrEmptyDeliverSequence
                return
            }
            // Here we assumes both Apps begin from the same height.
            for idx, h := range app.DeliverSequence[:minLength] {
                hOther := other.DeliverSequence[idx]
                if hOther != h {
                    err = ErrMismatchBlockHashSequence
                    return
                }
                if app.Delivered[h].Result.Timestamp !=
                    other.Delivered[h].Result.Timestamp {
                    err = ErrMismatchConsensusTime
                    return
                }
            }
        })
    })
    return
}

// Verify checks the integrity of date received by this App instance.
func (app *App) Verify() error {
    // TODO(mission): verify blocks' position when delivered.
    app.confirmedLock.RLock()
    defer app.confirmedLock.RUnlock()
    app.deliveredLock.RLock()
    defer app.deliveredLock.RUnlock()

    if len(app.DeliverSequence) == 0 {
        return ErrEmptyDeliverSequence
    }
    if len(app.DeliverSequence) != len(app.Delivered) {
        return ErrApplicationIntegrityFailed
    }
    expectHeight := uint64(1)
    prevTime := time.Time{}
    for _, h := range app.DeliverSequence {
        _, exists := app.Confirmed[h]
        if !exists {
            return ErrDeliveredBlockNotConfirmed
        }
        rec, exists := app.Delivered[h]
        if !exists {
            return ErrApplicationIntegrityFailed
        }
        // Make sure the consensus time is incremental.
        ok := prevTime.Before(rec.Result.Timestamp) ||
            prevTime.Equal(rec.Result.Timestamp)
        if !ok {
            return ErrConsensusTimestampOutOfOrder
        }
        prevTime = rec.Result.Timestamp
        // Make sure the consensus height is incremental.
        if expectHeight != rec.Result.Height {
            return ErrConsensusHeightOutOfOrder
        }
        expectHeight++
    }
    return nil
}

// BlockReceived implements interface Debug.
func (app *App) BlockReceived(hash common.Hash) {}

// BlockReady implements interface Debug.
func (app *App) BlockReady(hash common.Hash) {}

// WithLock provides a backdoor to check status of App with reader lock.
func (app *App) WithLock(function func(*App)) {
    app.confirmedLock.RLock()
    defer app.confirmedLock.RUnlock()
    app.deliveredLock.RLock()
    defer app.deliveredLock.RUnlock()
    app.lastPendingHeightLock.RLock()
    defer app.lastPendingHeightLock.RUnlock()

    function(app)
}

func (app *App) getLastPendingWitnessHeight() uint64 {
    app.lastPendingHeightLock.RLock()
    defer app.lastPendingHeightLock.RUnlock()
    return app.LastPendingHeight
}