lnd/nursery_store.go

1491 lines
49 KiB
Go
Raw Normal View History

package main
import (
"bytes"
"errors"
"github.com/boltdb/bolt"
"github.com/lightningnetwork/lnd/channeldb"
"github.com/roasbeef/btcd/chaincfg/chainhash"
"github.com/roasbeef/btcd/wire"
)
// NurseryStore abstracts the persistent storage layer for the utxo nursery.
// Concretely, it stores commitment and htlc outputs that until any time-bounded
// constraints have fully matured. The store exposes methods for enumerating
// its contents, and persisting state transitions detected by the utxo nursery.
type NurseryStore interface {
// Incubation Entry Points.
// EnterCrib accepts a new htlc output that the nursery will incubate
// through its two-stage process of sweeping funds back to the user's
// wallet. These outputs are persisted in the nursery store's crib
// bucket, and will be revisited after the output's CLTV has expired.
EnterCrib(*babyOutput) error
// EnterPreschool accepts a new commitment output that the nursery will
// incubate through a single stage before sweeping. Outputs are stored
// in the preschool bucket until the commitment transaction has been
// confirmed, at which point they will be moved to the kindergarten
// bucket.
EnterPreschool(*kidOutput) error
// On-chain Driven State Transtitions.
// CribToKinder atomically moves a babyOutput in the crib bucket to the
// kindergarten bucket. The now mature kidOutput contained in the
// babyOutput will be stored as it waits out the kidOutput's CSV delay.
CribToKinder(*babyOutput) error
// PreschoolToKinder atomically moves a kidOutput from the preschool
// bucket to the kindergarten bucket. This transition should be executed
// after receiving confirmation of the preschool output's commitment
// transaction.
PreschoolToKinder(*kidOutput) error
// AwardDiplomas accepts a variadic number of kidOutputs from the
// kindergarten bucket, and removes their corresponding entries from the
// height and channel indexes. If this method detects that all outputs
// for a particular contract have been incubated, it returns the channel
// points that are ready to be marked as fully closed.
// TODO: make this handle one output at a time?
AwardDiplomas(...kidOutput) ([]wire.OutPoint, error)
IsMatureChannel(*wire.OutPoint) (bool, error)
// TryFinalizeClass accepts a block height as a parameter and purges its
// persistent state for all outputs at that height. During a restart,
// the utxo nursery will begin it's recovery procedure from the next
// height that has yet to be finalized. This block height should lag
// beyond the best height for this chain as a measure of reorg
// protection.
TryFinalizeClass(height uint32) error
// State Bucket Enumeration.
// FetchCribs returns a list of babyOutputs in the crib bucket whose
// CLTV delay expires at the provided block height.
FetchCribs(height uint32) ([]babyOutput, error)
// FetchKindergartens returns a list of kidOutputs in the kindergarten
// bucket whose CSV delay expires at the provided block height.
FetchKindergartens(height uint32) ([]kidOutput, error)
// FetchPreschools returns a list of all outputs currently stored in the
// preschool bucket.
FetchPreschools() ([]kidOutput, error)
// Channel Output Enumeration.
// ForChanOutputs iterates over all outputs being incubated for a
// particular channel point. This method accepts a callback that allows
// the caller to process each key-value pair. The key will be a prefixed
// outpoint, and the value will be the serialized bytes for an output,
// whose type should be inferred from the key's prefix.
ForChanOutputs(*wire.OutPoint, func([]byte, []byte) error) error
RemoveChannel(*wire.OutPoint) error
// The Point of No Return.
// LastFinalizedHeight returns the last block height for which the
// nursery store has purged all persistent state.
LastFinalizedHeight() (uint32, error)
}
// prefixChainKey creates the root level keys for the nursery store. The keys
// are comprised of a nursery-specific prefix and the intended chain hash that
// this nursery store will be used for. This allows multiple nursery stores to
// isolate their state when operating on multiple chains or forks.
func prefixChainKey(sysPrefix []byte, hash *chainhash.Hash) ([]byte, error) {
// Create a buffer to which we will write the system prefix, e.g.
// "utxn", followed by the provided chain hash.
var pfxChainBuffer bytes.Buffer
if _, err := pfxChainBuffer.Write(sysPrefix); err != nil {
return nil, err
}
if _, err := pfxChainBuffer.Write(hash[:]); err != nil {
return nil, err
}
return pfxChainBuffer.Bytes(), nil
}
// prefixOutputKey creates a serialized key that prefixes the serialized
// outpoint with the provided state prefix. The returned bytes will be of the
// form <prefix><outpoint>.
func prefixOutputKey(statePrefix []byte,
outpoint *wire.OutPoint) ([]byte, error) {
// Create a buffer to which we will first write the state prefix,
// followed by the outpoint.
var pfxOutputBuffer bytes.Buffer
if _, err := pfxOutputBuffer.Write(statePrefix); err != nil {
return nil, err
}
err := writeOutpoint(&pfxOutputBuffer, outpoint)
if err != nil {
return nil, err
}
return pfxOutputBuffer.Bytes(), nil
}
var (
// utxnChainPrefix is used to prefix a particular chain hash and create
// the root-level, chain-segmented bucket for each nursery store.
utxnChainPrefix = []byte("utxn")
// lastFinalizedHeightKey is a static key used to locate nursery store's
// last finalized height.
lastFinalizedHeightKey = []byte("last-finalized-height")
// channelIndexKey is a static key used to lookup the bucket containing
// all of the nursery's active channels.
channelIndexKey = []byte("channel-index")
// channelIndexKey is a static key used to retrieve a directory
// containing all heights for which the nursery will need to take
// action.
heightIndexKey = []byte("height-index")
// cribPrefix is the state prefix given to htlc outputs waiting for
// their first-stage, absolute locktime to elapse.
cribPrefix = []byte("crib")
// psclPrefix is the state prefix given to commitment outputs awaiting
// the // confirmation of the commitment transaction, as this solidifies
// the absolute height at which they can be spent.
psclPrefix = []byte("pscl")
// kndrPrefix is the state prefix given to all CSV delayed outputs,
// either from the commitment transaction, or a stage-one htlc
// transaction, whose maturity height has solidified. Outputs marked in
// this state are in their final stage of incubation withn the nursery,
// and will be swept into the wallet after waiting out the relative
// timelock.
kndrPrefix = []byte("kndr")
gradPrefix = []byte("grad")
)
// Overview of Nursery Store Storage Hierarchy
//
// CHAIN SEGMENTATION
//
// The root directory of a nursery store is bucketed by the chain hash and
// the 'utxn' prefix. This allows multiple utxo nurseries for distinct chains
// to simultaneously use the same channel.DB instance. This is critical for
// providing replay protection and more to isolate chain-specific data in the
// multichain setting.
//
// utxn<chain-hash>/
// |
// | LAST FINALIZED HEIGHT
// |
// | Each nursery store tracks a "last finalized height", which records the
// | most recent block height for which the nursery store has purged all
// | state. This value lags behind the best block height for reorg safety,
// | and serves as a starting height for rescans after a restart.
// |
// ├── last-finalized-height-key: <last-finalized-height>
// |
// | CHANNEL INDEX
// |
// | The channel index contains a directory for each channel that has a
// | non-zero number of outputs being tracked by the nursery store.
// | Inside each channel directory are files contains serialized spendable
// | outputs that are awaiting some state transition. The name of each file
// | contains the outpoint of the spendable output in the file, and is
// | prefixed with 4-byte state prefix, indicating whether the spendable
// | output is a crib, preschool, or kindergarten output. The nursery store
// | supports the ability to enumerate all outputs for a particular channel,
// | which is useful in constructing nursery reports.
// |
// ├── channel-index-key/
// │   ├── <chain-point-1>/ <- CHANNEL BUCKET
// | |   ├── <state-prefix><outpoint-1>: <spendable-output-1>
// | |   └── <state-prefix><outpoint-2>: <spendable-output-2>
// │   ├── <chain-point-2>/
// | |   └── <state-prefix><outpoint-3>: <spendable-output-3>
// │   └── <chain-point-3>/
// |    ├── <state-prefix><outpoint-4>: <spendable-output-4>
// |    └── <state-prefix><outpoint-5>: <spendable-output-5>
// |
// | HEIGHT INDEX
// |
// | The height index contains a directory for each height at which the
// | nursery still has uncompleted actions. If an output is a crib or
// | kindergarten output,
// | it will have an associated entry in the height index. Inside a
// | particular height directory, the structure is similar to that of the
// | channel index, containing multiple channel directories, each of which
// | contains subdirectories named with a prefixed outpoint belonging to
// | the channel. Enumerating these combinations yields a relative file
// | path:
// | e.g. <chan-point-3>/<prefix><outpoint-2>/
// | that can be queried in the channel index to retrieve the serialized
// | output.
// |
// └── height-index-key/
//    ├── <height-1>/ <- HEIGHT BUCKET
// |   └── <chan-point-3>/ <- HEIGHT-CHANNEL BUCKET
// | |    ├── <state-prefix><outpoint-4>/ <- PREFIXED OUTPOINT
// | |    └── <state-prefix><outpoint-5>/
// |   └── <chan-point-2>/
// |    └── <state-prefix><outpoint-3>/
//    └── <height-2>/
//    └── <chan-point-1>/
//    └── <state-prefix><outpoint-1>/
//    └── <state-prefix><outpoint-2>/
// nurseryStore is a concrete instantiation of a NurseryStore that is backed by
// a channeldb.DB instance.
type nurseryStore struct {
chainHash chainhash.Hash
pfxChainKey []byte
db *channeldb.DB
}
// newNurseryStore accepts a chain hash and a channeldb.DB instance, returning
// an instance of nurseryStore who's database is properly segmented for the
// given chain.
func newNurseryStore(chainHash *chainhash.Hash,
db *channeldb.DB) (*nurseryStore, error) {
// Prefix the provided chain hash with "utxn" to create the key for the
// nursery store's root bucket, ensuring each one has proper chain
// segmentation.
pfxChainKey, err := prefixChainKey(utxnChainPrefix, chainHash)
if err != nil {
return nil, err
}
return &nurseryStore{
chainHash: *chainHash,
pfxChainKey: pfxChainKey,
db: db,
}, nil
}
// Incubation Entry Points.
// EnterCrib accepts a new htlc output that the nursery will incubate through
// its two-stage process of sweeping funds back to the user's wallet. These
// outputs are persisted in the nursery store's crib bucket, and will be
// revisited after the output's CLTV has expired.
func (ns *nurseryStore) EnterCrib(bby *babyOutput) error {
return ns.db.Update(func(tx *bolt.Tx) error {
// First, retrieve or create the channel bucket corresponding to
// the baby output's origin channel point.
chanPoint := bby.OriginChanPoint()
chanBucket, err := ns.createChannelBucket(tx, chanPoint)
if err != nil {
return err
}
// Next, retrieve or create the height-channel bucket located in
// the height bucket corresponding to the baby output's CLTV
// expiry height.
hghtChanBucket, err := ns.createHeightChanBucket(tx,
bby.expiry, chanPoint)
if err != nil {
return err
}
// Since we are inserting this output into the crib bucket, we
// create a key that prefixes the baby output's outpoint with
// the crib prefix.
pfxOutputKey, err := prefixOutputKey(cribPrefix, bby.OutPoint())
if err != nil {
return err
}
// Serialize the baby output so that it can be written to the
// underlying key-value store.
var babyBuffer bytes.Buffer
if err := bby.Encode(&babyBuffer); err != nil {
return err
}
babyBytes := babyBuffer.Bytes()
// Now, insert the serialized output into its channel bucket
// under the prefixed key created above.
if err := chanBucket.Put(pfxOutputKey, babyBytes); err != nil {
return err
}
// Finally, create a corresponding bucket in the height-channel
// bucket for this crib output. The existence of this bucket
// indicates that the serialized output can be retrieved from
// the channel bucket using the same prefix key.
_, err = hghtChanBucket.CreateBucketIfNotExists(pfxOutputKey)
return err
})
}
// EnterPreschool accepts a new commitment output that the nursery will
// incubate through a single stage before sweeping. Outputs are stored in the
// preschool bucket until the commitment transaction has been confirmed, at
// which point they will be moved to the kindergarten bucket.
func (ns *nurseryStore) EnterPreschool(kid *kidOutput) error {
return ns.db.Update(func(tx *bolt.Tx) error {
// First, retrieve or create the channel bucket corresponding to
// the baby output's origin channel point.
chanPoint := kid.OriginChanPoint()
chanBucket, err := ns.createChannelBucket(tx, chanPoint)
if err != nil {
return err
}
// Since the babyOutput is being inserted into the preschool
// bucket, we create a key that prefixes its outpoint with the
// preschool prefix.
pfxOutputKey, err := prefixOutputKey(psclPrefix, kid.OutPoint())
if err != nil {
return err
}
// Serialize the kidOutput and insert it into the channel
// bucket.
var kidBuffer bytes.Buffer
if err := kid.Encode(&kidBuffer); err != nil {
return err
}
return chanBucket.Put(pfxOutputKey, kidBuffer.Bytes())
})
}
// On-chain Drive State Transitions.
// CribToKinder atomically moves a babyOutput in the crib bucket to the
// kindergarten bucket. The now mature kidOutput contained in the babyOutput
// will be stored as it waits out the kidOutput's CSV delay.
func (ns *nurseryStore) CribToKinder(bby *babyOutput) error {
return ns.db.Update(func(tx *bolt.Tx) error {
// First, retrieve or create the channel bucket corresponding to
// the baby output's origin channel point.
chanPoint := bby.OriginChanPoint()
chanBucket, err := ns.createChannelBucket(tx, chanPoint)
if err != nil {
return err
}
// The babyOutput should currently be stored in the crib bucket.
// So, we create a key that prefixes the babyOutput's outpoint
// with the crib prefix, allowing us to reference it in the
// store.
pfxOutputKey, err := prefixOutputKey(cribPrefix, bby.OutPoint())
if err != nil {
return err
}
// Since the babyOutput is being moved to the kindergarten
// bucket, we remove the entry from the channel bucket under the
// crib-prefixed outpoint key.
if err := chanBucket.Delete(pfxOutputKey); err != nil {
return err
}
// Next, retrieve the height-channel bucket located in the
// height bucket corresponding to the baby output's CLTV expiry
// height. This bucket should always exist, but if it doesn't
// then we have nothing to clean up.
hghtChanBucketCltv := ns.getHeightChanBucket(tx, bby.expiry,
chanPoint)
if hghtChanBucketCltv != nil {
// We successfully located an existing height chan
// bucket at this babyOutput's expiry height, proceed by
// removing it from the index.
err := hghtChanBucketCltv.DeleteBucket(pfxOutputKey)
if err != nil {
return err
}
}
// Since we are moving this output from the crib bucket to the
// kindergarten bucket, we overwrite the existing prefix of this
// key with the kindergarten prefix.
copy(pfxOutputKey, kndrPrefix)
// Now, serialize babyOutput's encapsulated kidOutput such that
// it can be written to the channel bucket under the new
// kindergarten-prefixed key.
var kidBuffer bytes.Buffer
if err := bby.kidOutput.Encode(&kidBuffer); err != nil {
return err
}
kidBytes := kidBuffer.Bytes()
// Persist the serialized kidOutput under the
// kindergarten-prefixed outpoint key.
if err := chanBucket.Put(pfxOutputKey, kidBytes); err != nil {
return err
}
// Now, compute the height at which this kidOutput's CSV delay
// will expire. This is done by adding the required delay to
// the block height at which the output was confirmed.
maturityHeight := bby.ConfHeight() + bby.BlocksToMaturity()
// Retrive or create a height-channel bucket corresponding to
// the kidOutput's maturity height.
hghtChanBucketCsv, err := ns.createHeightChanBucket(tx,
maturityHeight, chanPoint)
if err != nil {
return err
}
// Register the kindergarten output's prefixed output key in the
// height-channel bucket corresponding to its maturity height.
// This informs the utxo nursery that it should attempt to spend
// this output when the blockchain reaches the maturity height.
_, err = hghtChanBucketCsv.CreateBucketIfNotExists(pfxOutputKey)
if err != nil {
return err
}
// Finally, since we removed a crib output from the height
// index, we opportunistically prune the height bucket
// corresponding to the babyOutput's CLTV delay. This allows us
// to clean up any persistent state as outputs are progressed
// through the incubation process.
err = ns.pruneHeight(tx, bby.expiry)
switch err {
case nil, ErrBucketDoesNotExist:
return nil
case ErrBucketNotEmpty:
return nil
default:
return err
}
})
}
// PreschoolToKinder atomically moves a kidOutput from the preschool bucket to
// the kindergarten bucket. This transition should be executed after receiving
// confirmation of the preschool output's commitment transaction.
func (ns *nurseryStore) PreschoolToKinder(kid *kidOutput) error {
return ns.db.Update(func(tx *bolt.Tx) error {
// Create or retrieve the channel bucket corresponding to the
// kid output's origin channel point.
chanPoint := kid.OriginChanPoint()
chanBucket, err := ns.createChannelBucket(tx, chanPoint)
if err != nil {
return err
}
// First, we will attempt to remove the existing serialized
// output from the channel bucket, where the kid's outpoint will
// be prefixed by a preschool prefix.
// Generate the key of existing serialized kid output by
// prefixing its outpoint with the preschool prefix...
pfxOutputKey, err := prefixOutputKey(psclPrefix, kid.OutPoint())
if err != nil {
return err
}
// And remove the old serialized output from the database.
if err := chanBucket.Delete(pfxOutputKey); err != nil {
return err
}
// Next, we will write the provided kid outpoint to the channel
// bucket, using a key prefixed by the kindergarten prefix.
// Convert the preschool prefix key into a kindergarten key for
// the same outpoint.
copy(pfxOutputKey, kndrPrefix)
// Reserialize the kid here to capture any differences in the
// new and old kid output, such as the confirmation height.
var kidBuffer bytes.Buffer
if err := kid.Encode(&kidBuffer); err != nil {
return err
}
kidBytes := kidBuffer.Bytes()
// And store the kid output in its channel bucket using the
// kindergarten prefixed key.
if err := chanBucket.Put(pfxOutputKey, kidBytes); err != nil {
return err
}
// Since the CSV delay on the kid output has now begun ticking,
// we must insert a record of in the height index to remind us
// to revisit this output once it has fully matured.
// Compute the maturity height, by adding the output's CSV delay
// to its confirmation height.
maturityHeight := kid.ConfHeight() + kid.BlocksToMaturity()
// Create or retrieve the height-channel bucket for this
// channel. This method will first create a height bucket for
// the given maturity height if none exists.
hghtChanBucket, err := ns.createHeightChanBucket(tx,
maturityHeight, chanPoint)
if err != nil {
return err
}
// Finally, we touch a bucket in the height-channel created
// above. The bucket is named using a kindergarten prefixed
// key, signaling that this CSV delayed output will be ready to
// broadcast at the maturity height, after a brief period of
// incubation.
_, err = hghtChanBucket.CreateBucketIfNotExists(pfxOutputKey)
return err
})
}
// AwardDiplomas accepts a list of kidOutputs in the kindergarten bucket,
// removing their corresponding entries from the height and channel indexes.
// If this method detects that all outputs for a particular contract have been
// incubated, it returns the channel points that are ready to be marked as
// fully closed. This method will iterate through the provided kidOutputs and do
// the following:
// 1) Prune the kid height bucket at the kid's confirmation height, if it is
// empty.
// 2) Prune the channel bucket belonging to the kid's origin channel point, if
// it is empty.
func (ns *nurseryStore) AwardDiplomas(
kids ...kidOutput) ([]wire.OutPoint, error) {
// As we iterate over the kids, we will build a list of the channels
// which have been pruned entirely from the nursery store. We will
// return this list to the caller, the utxo nursery, so that it can
// proceed to mark the channels as closed.
// TODO(conner): write list of closed channels to separate bucket so
// that they can be replayed on restart?
var possibleCloseSet = make(map[wire.OutPoint]struct{})
if err := ns.db.Update(func(tx *bolt.Tx) error {
for _, kid := range kids {
confHeight := kid.ConfHeight()
outpoint := kid.OutPoint()
chanPoint := kid.OriginChanPoint()
// Remove output from kindergarten bucket.
pfxOutputKey, err := prefixOutputKey(kndrPrefix, outpoint)
if err != nil {
return err
}
hghtChanBucket := ns.getHeightChanBucket(tx, confHeight, chanPoint)
if hghtChanBucket != nil {
if err := hghtChanBucket.DeleteBucket(pfxOutputKey); err != nil {
return err
}
// Attempt to prune the height bucket matching the kid
// output's confirmation height if it contains no active
// outputs.
err := ns.pruneHeight(tx, confHeight)
switch err {
case ErrBucketNotEmpty:
// Bucket still has active outputs, proceed to
// prune channel bucket.
case ErrBucketDoesNotExist:
// Bucket was previously pruned by another
// graduating output.
case nil:
// Bucket was pruned successfully and no errors
// were encounter.
utxnLog.Infof("Height bucket %d pruned", confHeight)
default:
// Unexpected database error.
return err
}
}
chanBucket, err := ns.createChannelBucket(tx, chanPoint)
if err != nil {
return err
}
if err := chanBucket.Delete(pfxOutputKey); err != nil {
return err
}
// Convert kindergarten key to graduate key.
copy(pfxOutputKey, gradPrefix)
var gradBuffer bytes.Buffer
if err := kid.Encode(&gradBuffer); err != nil {
return err
}
err = chanBucket.Put(pfxOutputKey, gradBuffer.Bytes())
if err != nil {
return err
}
// If we've arrived here, we have encountered no
// database errors and a bucket was either successfully
// pruned or already has been. Thus it is safe to add it
// to our set of closed channels to be closed, since
// these may need to be replayed to ensure the channel
// database is aware that incubation has completed.
possibleCloseSet[*chanPoint] = struct{}{}
}
return nil
}); err != nil {
return nil, err
}
// Convert our set of channels to be closed into a list.
possibleCloses := make([]wire.OutPoint, 0, len(possibleCloseSet))
for chanPoint := range possibleCloseSet {
possibleCloses = append(possibleCloses, chanPoint)
}
utxnLog.Infof("Possible channels to be marked fully closed: %v",
possibleCloses)
return possibleCloses, nil
}
// TryFinalizeClass accepts a block height as a parameter and purges its
// persistent state for all outputs at that height. During a restart, the utxo
// nursery will begin it's recovery procedure from the next height that has
// yet to be finalized.
func (ns *nurseryStore) TryFinalizeClass(height uint32) error {
return ns.db.Update(func(tx *bolt.Tx) error {
utxnLog.Infof("Attempting to finalize class at height %v", height)
lastHeight, err := ns.getNextLastFinalizedHeight(tx, height)
if err != nil {
return err
}
utxnLog.Infof("Finalizing class at height %v", lastHeight)
return ns.putLastFinalizedHeight(tx, lastHeight)
})
}
// State Bucket Enumeration.
// FetchCribs returns a list of babyOutputs in the crib bucket whose CLTV
// delay expires at the provided block height.
func (ns *nurseryStore) FetchCribs(height uint32) ([]babyOutput, error) {
// Construct a list of all babyOutputs that need TLC at the provided
// block height.
var babies []babyOutput
if err := ns.forEachHeightPrefix(cribPrefix, height,
func(buf []byte) error {
// We will attempt to deserialize all outputs stored
// with the crib prefix into babyOutputs, since this is
// the expected type that would have been serialized
// previously.
var bby babyOutput
if err := bby.Decode(bytes.NewReader(buf)); err != nil {
return err
}
// Append the deserialized object to our list of
// babyOutputs.
babies = append(babies, bby)
return nil
}); err != nil {
return nil, err
}
return babies, nil
}
// FetchKindergartens returns a list of kidOutputs in the kindergarten bucket
// whose CSV delay expires at the provided block height.
func (ns *nurseryStore) FetchKindergartens(height uint32) ([]kidOutput, error) {
// Construct a list of all kidOutputs that mature at the provided block
// height.
utxnLog.Infof("Fetching kinders")
var kids []kidOutput
if err := ns.forEachHeightPrefix(kndrPrefix, height,
func(buf []byte) error {
utxnLog.Infof("Inside kinder")
// We will attempt to deserialize all outputs stored
// with the kindergarten prefix into kidOutputs, since
// this is the expected type that would have been
// serialized previously.
var kid kidOutput
if err := kid.Decode(bytes.NewReader(buf)); err != nil {
return err
}
// Append the deserialized object to our list of
// kidOutputs.
kids = append(kids, kid)
return nil
}); err != nil {
return nil, err
}
utxnLog.Infof("Returning kinders")
return kids, nil
}
// FetchPreschools returns a list of all outputs currently stored in the
// preschool bucket.
func (ns *nurseryStore) FetchPreschools() ([]kidOutput, error) {
var kids []kidOutput
if err := ns.db.View(func(tx *bolt.Tx) error {
// Retrieve the existing chain bucket for this nursery store.
chainBucket := tx.Bucket(ns.pfxChainKey)
if chainBucket == nil {
return nil
}
// Load the existing channel index from the chain bucket.
chanIndex := chainBucket.Bucket(channelIndexKey)
if chanIndex == nil {
return nil
}
// Construct a list of all channels in the channel index that
// are currently being tracked by the nursery store.
var activeChannels [][]byte
if err := chanIndex.ForEach(func(chanBytes, _ []byte) error {
activeChannels = append(activeChannels, chanBytes)
return nil
}); err != nil {
return err
}
// Iterate over all of the accumulated channels, and do a prefix
// scan inside of each channel bucket. Each output found that
// has a preschool prefix will be deserialized into a kidOutput,
// and added to our list of preschool outputs to return to the
// caller.
for _, chanBytes := range activeChannels {
// Retrieve the channel bucket associated with this
// channel.
chanBucket := chanIndex.Bucket(chanBytes)
if chanBucket == nil {
continue
}
// All of the outputs of interest will start with the
// "pscl" prefix. So, we will perform a prefix scan of
// the channel bucket to efficiently enumerate all the
// desired outputs.
c := chanBucket.Cursor()
// Seek and iterate over all outputs starting with the
// prefix "pscl".
pfxOutputKey, kidBytes := c.Seek(psclPrefix)
for bytes.HasPrefix(pfxOutputKey, psclPrefix) {
// Deserialize each output as a kidOutput, since
// this should have been the type that was
// serialized when it was written to disk.
var psclOutput kidOutput
psclReader := bytes.NewReader(kidBytes)
err := psclOutput.Decode(psclReader)
if err != nil {
return err
}
// Add the deserialized output to our list of
// preschool outputs.
kids = append(kids, psclOutput)
// Advance to the subsequent key-value pair of
// the prefix scan.
pfxOutputKey, kidBytes = c.Next()
}
}
return nil
}); err != nil {
return nil, err
}
return kids, nil
}
// Channel Output Enumberation.
// ForChanOutputs iterates over all outputs being incubated for a particular
// channel point. This method accepts a callback that allows the caller to
// process each key-value pair. The key will be a prefixed outpoint, and the
// value will be the serialized bytes for an output, whose type should be
// inferred from the key's prefix.
// NOTE: The callback should be not modify the provided byte slices and is
// preferably non-blocking.
func (ns *nurseryStore) ForChanOutputs(chanPoint *wire.OutPoint,
callback func([]byte, []byte) error) error {
return ns.db.View(func(tx *bolt.Tx) error {
return ns.forChanOutputs(tx, chanPoint, callback)
})
}
func (ns *nurseryStore) forChanOutputs(tx *bolt.Tx, chanPoint *wire.OutPoint,
callback func([]byte, []byte) error) error {
chanBucket := ns.getChannelBucket(tx, chanPoint)
if chanBucket == nil {
return ErrContractNotFound
}
return chanBucket.ForEach(callback)
}
func (ns *nurseryStore) IsMatureChannel(chanPoint *wire.OutPoint) (bool, error) {
var isMature bool
if err := ns.db.View(func(tx *bolt.Tx) error {
var nOutputs, nGrads int
if err := ns.forChanOutputs(tx, chanPoint, func(pfxKey, _ []byte) error {
// Count total and number of grad outputs
if string(pfxKey[:4]) == string(gradPrefix) {
nGrads++
}
nOutputs++
return nil
}); err != nil {
return err
}
utxnLog.Infof("Found %d graduated outputs out of %d", nGrads, nOutputs)
// Channel is mature if all outputs are graduated.
if nGrads == nOutputs {
isMature = true
}
return nil
}); err != nil {
return false, err
}
return isMature, nil
}
// The Point of No Return.
// LastFinalizedHeight returns the last block height for which the nursery
// store has purged all persistent state. This occurs after a fixed interval
// for reorg safety.
func (ns *nurseryStore) LastFinalizedHeight() (uint32, error) {
var lastFinalizedHeight uint32
err := ns.db.View(func(tx *bolt.Tx) error {
lastHeight, err := ns.getLastFinalizedHeight(tx)
if err != nil {
return err
}
lastFinalizedHeight = lastHeight
return nil
})
return lastFinalizedHeight, err
}
// getLastFinalizedHeight is a helper method that retrieves the last height for
// which the database finalized its persistent state.
func (ns *nurseryStore) getLastFinalizedHeight(tx *bolt.Tx) (uint32, error) {
// Retrieve the chain bucket associated with the given nursery store.
chainBucket := tx.Bucket(ns.pfxChainKey)
if chainBucket == nil {
return 0, nil
}
// Lookup the last finalized height in the top-level chain bucket.
heightBytes := chainBucket.Get(lastFinalizedHeightKey)
// If the resulting bytes are not sized like a uint32, then we have
// never finalized, so we return 0.
if len(heightBytes) != 4 {
return 0, nil
}
// Otherwise, parse the bytes and return the last finalized height.
return byteOrder.Uint32(heightBytes), nil
}
func (ns *nurseryStore) getNextLastFinalizedHeight(tx *bolt.Tx, height uint32) (uint32, error) {
// Retrieve the previous last finalized height.
lastHeight, err := ns.getLastFinalizedHeight(tx)
if err != nil {
return 0, err
}
// TODO(conner): add lower bound after which all state is purged.
// Retrieve the existing chain bucket for this nursery store.
chainBucket := tx.Bucket(ns.pfxChainKey)
if chainBucket == nil {
return lastHeight, nil
}
// Retrieve the existing height index.
hghtIndex := chainBucket.Bucket(heightIndexKey)
if hghtIndex == nil {
return lastHeight, nil
}
for curHeight := lastHeight + 1; curHeight <= height; curHeight++ {
var curHeightBytes [4]byte
byteOrder.PutUint32(curHeightBytes[:], curHeight)
hghtBucket := hghtIndex.Bucket(curHeightBytes[:])
if hghtBucket == nil {
continue
}
nChildren, err := ns.numChildrenInBucket(hghtBucket)
if err != nil {
return 0, err
}
if nChildren > 0 {
return curHeight - 1, nil
}
}
return height, nil
}
// pubLastFinalizedHeight is a helper method that writes the provided height
// under the last finalized height key.
func (ns *nurseryStore) putLastFinalizedHeight(tx *bolt.Tx,
height uint32) error {
// Ensure that the chain bucket for this nursery store exists.
chainBucket, err := tx.CreateBucketIfNotExists(ns.pfxChainKey)
if err != nil {
return err
}
// Serialize the provided last-finalized height, and store it in the
// top-level chain bucket for this nursery store.
var lastHeightBytes [4]byte
byteOrder.PutUint32(lastHeightBytes[:], height)
return chainBucket.Put(lastFinalizedHeightKey, lastHeightBytes[:])
}
// createChannelBucket creates or retrieves a channel bucket for the provided
// channel point.
func (ns *nurseryStore) createChannelBucket(tx *bolt.Tx,
chanPoint *wire.OutPoint) (*bolt.Bucket, error) {
// Ensure that the chain bucket for this nursery store exists.
chainBucket, err := tx.CreateBucketIfNotExists(ns.pfxChainKey)
if err != nil {
return nil, err
}
// Ensure that the channel index has been properly initialized for this
// chain.
chanIndex, err := chainBucket.CreateBucketIfNotExists(channelIndexKey)
if err != nil {
return nil, err
}
// Serialize the provided channel point, as this provides the name of
// the channel bucket of interest.
var chanBuffer bytes.Buffer
if err := writeOutpoint(&chanBuffer, chanPoint); err != nil {
return nil, err
}
// Finally, create or retrieve the channel bucket using the serialized
// key.
return chanIndex.CreateBucketIfNotExists(chanBuffer.Bytes())
}
// getChannelBucket retrieves an existing channel bucket from the nursery store,
// using the given channel point. If the bucket does not exist, or any bucket
// along its path does not exist, a nil value is returned.
func (ns *nurseryStore) getChannelBucket(tx *bolt.Tx,
chanPoint *wire.OutPoint) *bolt.Bucket {
// Retrieve the existing chain bucket for this nursery store.
chainBucket := tx.Bucket(ns.pfxChainKey)
if chainBucket == nil {
return nil
}
// Retrieve the existing channel index.
chanIndex := chainBucket.Bucket(channelIndexKey)
if chanIndex == nil {
return nil
}
// Serialize the provided channel point and return the bucket matching
// the serialized key.
var chanBuffer bytes.Buffer
if err := writeOutpoint(&chanBuffer, chanPoint); err != nil {
return nil
}
return chanIndex.Bucket(chanBuffer.Bytes())
}
// createHeightBucket creates or retrieves an existing bucket from the height
// index, corresponding to the provided height.
func (ns *nurseryStore) createHeightBucket(tx *bolt.Tx,
height uint32) (*bolt.Bucket, error) {
// Ensure that the chain bucket for this nursery store exists.
chainBucket, err := tx.CreateBucketIfNotExists(ns.pfxChainKey)
if err != nil {
return nil, err
}
// Ensure that the height index has been properly initialized for this
// chain.
hghtIndex, err := chainBucket.CreateBucketIfNotExists(heightIndexKey)
if err != nil {
return nil, err
}
// Serialize the provided height, as this will form the name of the
// bucket.
var heightBytes [4]byte
byteOrder.PutUint32(heightBytes[:], height)
// Finally, create or retrieve the bucket in question.
return hghtIndex.CreateBucketIfNotExists(heightBytes[:])
}
// getHeightBucket retrieves an existing height bucket from the nursery store,
// using the provided block height. If the bucket does not exist, or any bucket
// along its path does not exist, a nil value is returned.
func (ns *nurseryStore) getHeightBucket(tx *bolt.Tx,
height uint32) *bolt.Bucket {
// Retrieve the existing chain bucket for this nursery store.
chainBucket := tx.Bucket(ns.pfxChainKey)
if chainBucket == nil {
return nil
}
// Retrieve the existing channel index.
hghtIndex := chainBucket.Bucket(heightIndexKey)
if hghtIndex == nil {
return nil
}
// Serialize the provided block height and return the bucket matching
// the serialized key.
var heightBytes [4]byte
byteOrder.PutUint32(heightBytes[:], height)
return hghtIndex.Bucket(heightBytes[:])
}
// createHeightChanBucket creates or retrieves an existing height-channel bucket
// for the provided block height and channel point. This method will attempt to
// instantiate all buckets along the path if required.
func (ns *nurseryStore) createHeightChanBucket(tx *bolt.Tx,
height uint32, chanPoint *wire.OutPoint) (*bolt.Bucket, error) {
// Ensure that the height bucket for this nursery store exists.
hghtBucket, err := ns.createHeightBucket(tx, height)
if err != nil {
return nil, err
}
// Serialize the provided channel point, as this generates the name of
// the subdirectory corresponding to the channel of interest.
var chanBuffer bytes.Buffer
if err := writeOutpoint(&chanBuffer, chanPoint); err != nil {
return nil, err
}
chanBytes := chanBuffer.Bytes()
// Finally, create or retrieve an existing height-channel bucket for
// this channel point.
return hghtBucket.CreateBucketIfNotExists(chanBytes)
}
// getHeightChanBucket retrieves an existing height-channel bucket from the
// nursery store, using the provided block height and channel point. if the
// bucket does not exist, or any bucket along its path does not exist, a nil
// value is returned.
func (ns *nurseryStore) getHeightChanBucket(tx *bolt.Tx,
height uint32, chanPoint *wire.OutPoint) *bolt.Bucket {
// Retrieve the existing height bucket from this nursery store.
hghtBucket := ns.getHeightBucket(tx, height)
if hghtBucket == nil {
return nil
}
// Serialize the provided channel point, which generates the key for
// looking up the proper height-channel bucket inside the height bucket.
var chanBuffer bytes.Buffer
if err := writeOutpoint(&chanBuffer, chanPoint); err != nil {
return nil
}
chanBytes := chanBuffer.Bytes()
// Finally, return the height bucket specified by the serialized channel
// point.
return hghtBucket.Bucket(chanBytes)
}
// forEachHeightPrefix enumerates all outputs at the given height whose state
// prefix matches that which is provided. This is used as a subroutine to help
// enumerate crib and kindergarten outputs at a particular height. The callback
// is invoked with serialized bytes retrieved for each output of interest,
// allowing the caller to deserialize them into the appropriate type.
func (ns *nurseryStore) forEachHeightPrefix(prefix []byte, height uint32,
callback func([]byte) error) error {
return ns.db.View(func(tx *bolt.Tx) error {
// Start by retrieving the height bucket corresponding to the
// provided block height.
hghtBucket := ns.getHeightBucket(tx, height)
if hghtBucket == nil {
return nil
}
// Using the height bucket as a starting point, we will traverse
// its entire two-tier directory structure, and filter for
// outputs that have the provided prefix. The first layer of the
// height bucket contains buckets identified by a channel point,
// thus we first create list of channels contained in this
// height bucket.
var channelsAtHeight [][]byte
if err := hghtBucket.ForEach(func(chanBytes, _ []byte) error {
channelsAtHeight = append(channelsAtHeight, chanBytes)
return nil
}); err != nil {
return err
}
// As we enumerate the outputs referenced in this height bucket,
// we will need to load the serialized value of each output,
// which is ultimately stored its respective channel bucket. To
// do so, we first load the top-level chain bucket, which should
// already be created if we are at this point.
chainBucket := tx.Bucket(ns.pfxChainKey)
if chainBucket == nil {
return nil
}
// Additionally, grab the chain index, which we will facilitate
// queries for each of the channel buckets of each of the
// channels in the list we assembled above.
chanIndex := chainBucket.Bucket(channelIndexKey)
if chanIndex == nil {
return nil
}
// Now, we are ready to enumerate all outputs with the desired
// prefix t this block height. We do so by iterating over our
// list of channels at this height, filtering for outputs in
// each height-channel bucket that begin with the given prefix,
// and then retrieving the serialized outputs from the
// appropriate channel bucket.
for _, chanBytes := range channelsAtHeight {
// Retrieve the height-channel bucket for this channel,
// which holds a sub-bucket for all outputs maturing at
// this height.
hghtChanBucket := hghtBucket.Bucket(chanBytes)
if hghtChanBucket == nil {
continue
}
// Load the appropriate channel bucket from the channel
// index, this will allow us to retrieve the individual
// serialized outputs.
chanBucket := chanIndex.Bucket(chanBytes)
if chanBucket == nil {
continue
}
// Since all of the outputs of interest will start with
// the same prefix, we will perform a prefix scan of the
// buckets contained in the height-channel bucket,
// efficiently enumerating the desired outputs.
c := hghtChanBucket.Cursor()
// Seek to and iterate over all entries starting with
// the given prefix.
var pfxOutputKey, _ = c.Seek(prefix)
for bytes.HasPrefix(pfxOutputKey, prefix) {
// Use the prefix output key emitted from our
// scan to load the serialized babyOutput from
// the appropriate channel bucket.
outputBytes := chanBucket.Get(pfxOutputKey)
if outputBytes == nil {
pfxOutputKey, _ = c.Next()
continue
}
// Present the serialized bytes to our call back
// function, which is responsible for
// deserializing the bytes into the appropriate
// type.
if err := callback(outputBytes); err != nil {
return err
}
// Lastly, advance our prefix output key for the
// next iteration.
pfxOutputKey, _ = c.Next()
}
}
return nil
})
}
var (
// ErrBucketDoesNotExist signals that a bucket has already been removed,
// or was never created.
ErrBucketDoesNotExist = errors.New("bucket does not exist")
// ErrBucketNotEmpty signals that an attempt to prune a particular
// bucket failed because it still has active outputs.
ErrBucketNotEmpty = errors.New("bucket is not empty, cannot be pruned")
)
// deleteAndPruneHeight removes an output from a channel bucket matching the
// provided channel point. The output is assumed top be in the kindergarten
// bucket, since pruning should never occur for any other type of output. If
// after deletion, the channel bucket is empty, this method will attempt to
// delete the bucket as well.
// NOTE: This method returns two concrete errors apart from those returned by
// the underlying database: ErrBucketDoesNotExist and ErrBucketNotEmpty. These
// should be handled in the context of the caller so as they may be benign
// depending on context. Errors returned other than these two should be
// interpreted as database errors.
func (ns *nurseryStore) deleteAndPruneChannel(tx *bolt.Tx,
chanPoint, outpoint *wire.OutPoint) error {
// Retrieve the existing chain bucket for this nursery store.
chainBucket := tx.Bucket(ns.pfxChainKey)
if chainBucket == nil {
return nil
}
// Retrieve the channel index stored in the chain bucket.
chanIndex := chainBucket.Bucket(channelIndexKey)
if chanIndex == nil {
return nil
}
// Serialize the provided channel point, such that we can retrieve the
// desired channel bucket.
var chanBuffer bytes.Buffer
if err := writeOutpoint(&chanBuffer, chanPoint); err != nil {
return err
}
chanBytes := chanBuffer.Bytes()
// Retrieve the existing channel bucket. If none exists, then our job is
// complete and it is safe to return nil.
chanBucket := chanIndex.Bucket(chanBytes)
if chanBucket == nil {
return nil
}
// Otherwise, the bucket still exists. Serialize the outpoint that needs
// deletion, prefixing the key with kindergarten prefix. Since all
// outputs eventually make their way to becoming kindergarten outputs,
// we can safely assume that they will be stored with a kindergarten
// prefix.
pfxOutputBytes, err := prefixOutputKey(kndrPrefix, outpoint)
if err != nil {
return err
}
// Remove the output in question using the kindergarten-prefixed key we
// generated above.
if err := chanBucket.Delete(pfxOutputBytes); err != nil {
return err
}
// Finally, now that the outpoint has been removed from this channel
// bucket, try to remove the channel bucket altogether if it is now
// empty.
return ns.removeBucketIfEmpty(chanIndex, chanBytes)
}
func (ns *nurseryStore) RemoveChannel(chanPoint *wire.OutPoint) error {
return ns.db.Update(func(tx *bolt.Tx) error {
// Retrieve the existing chain bucket for this nursery store.
chainBucket := tx.Bucket(ns.pfxChainKey)
if chainBucket == nil {
return nil
}
// Retrieve the channel index stored in the chain bucket.
chanIndex := chainBucket.Bucket(channelIndexKey)
if chanIndex == nil {
return nil
}
// Serialize the provided channel point, such that we can delete
// the mature channel bucket.
var chanBuffer bytes.Buffer
if err := writeOutpoint(&chanBuffer, chanPoint); err != nil {
return err
}
return chanIndex.DeleteBucket(chanBuffer.Bytes())
})
}
// pruneHeight
// NOTE: This method returns two concrete errors apart from those returned by
// the underlying database: ErrBucketDoesNotExist and ErrBucketNotEmpty. These
// should be handled in the context of the caller so as they may be benign
// depending on context. Errors returned other than these two should be
// interpreted as database errors.
func (ns *nurseryStore) pruneHeight(tx *bolt.Tx, height uint32) error {
// Fetch the existing chain bucket for this nursery store.
chainBucket := tx.Bucket(ns.pfxChainKey)
if chainBucket == nil {
return nil
}
// Load the existing height bucket for the height in question.
hghtIndex := chainBucket.Bucket(heightIndexKey)
if hghtIndex == nil {
return nil
}
// Serialize the provided block height, such that it can be used as the
// key to locate the desired height bucket.
var heightBytes [4]byte
byteOrder.PutUint32(heightBytes[:], height)
// Retrieve the height bucket using the serialized height as the bucket
// name.
hghtBucket := hghtIndex.Bucket(heightBytes[:])
if hghtBucket == nil {
return ErrBucketDoesNotExist
}
// Iterate over the contents of this height bucket, which is comprised
// of sub-buckets named after the channel points that need attention at
// this block height. We will attempt to remove each one if they are
// empty, keeping track of the number of height-channel buckets that
// still have active outputs.
var nActiveBuckets int
if err := hghtBucket.ForEach(func(chanBytes, _ []byte) error {
// Attempt to each height-channel bucket from the height bucket
// located above.
err := ns.removeBucketIfEmpty(hghtBucket, chanBytes)
switch err {
case nil:
// The height-channel bucket was removed successfully!
return nil
case ErrBucketDoesNotExist:
// The height-channel bucket could not be located--no
// harm, no foul.
return nil
case ErrBucketNotEmpty:
// The bucket still has active outputs at this height,
// increment our number of still active height-channel
// buckets.
nActiveBuckets++
return nil
default:
// Database error!
return err
}
}); err != nil {
return err
}
// If we located any height-channel buckets that still have active
// outputs, it is unsafe to delete this height bucket. Signal this event
// to the caller so that they can determine the appropriate action.
if nActiveBuckets > 0 {
return ErrBucketNotEmpty
}
// All of the height-channel buckets are empty or have been previously
// removed, proceed by attempting to remove the height bucket
// altogether.
return ns.removeBucketIfEmpty(hghtIndex, heightBytes[:])
}
// removeBucketIfEmpty attempts to delete a bucket specified by name from the
// provided parent bucket.
// NOTE: This method returns two concrete errors apart from those returned by
// the underlying database: ErrBucketDoesNotExist and ErrBucketNotEmpty. These
// should be handled in the context of the caller so as they may be benign
// depending on context. Errors returned other than these two should be
// interpreted as database errors.
func (ns *nurseryStore) removeBucketIfEmpty(parent *bolt.Bucket,
bktName []byte) error {
// Attempt to fetch the named bucket from its parent.
bkt := parent.Bucket(bktName)
if bkt == nil {
// No bucket was found, signal this to the caller.
return ErrBucketDoesNotExist
}
// The bucket exists, now compute how many children *it* has.
nChildren, err := ns.numChildrenInBucket(bkt)
if err != nil {
return err
}
// If the number of children is non-zero, alert the caller that the
// named bucket is not being removed.
if nChildren > 0 {
return ErrBucketNotEmpty
}
// Otherwise, remove the empty bucket from its parent.
return parent.DeleteBucket(bktName)
}
// numChildrenInBucket computes the number of children contained in the given
// boltdb bucket.
func (ns *nurseryStore) numChildrenInBucket(parent *bolt.Bucket) (int, error) {
var nChildren int
if err := parent.ForEach(func(_, _ []byte) error {
nChildren++
return nil
}); err != nil {
return 0, err
}
return nChildren, nil
}
// Compile-time constraint to ensure nurseryStore implements NurseryStore.
var _ NurseryStore = (*nurseryStore)(nil)