lnd.xprv/nursery_store.go

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package main
import (
"bytes"
"errors"
"fmt"
"github.com/btcsuite/btcd/chaincfg/chainhash"
"github.com/btcsuite/btcd/wire"
"github.com/coreos/bbolt"
"github.com/lightningnetwork/lnd/channeldb"
)
// 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 PURGED + FINALIZED HEIGHTS
// |
// | Each nursery store tracks a "last graduated height", which records the
// | most recent block height for which the nursery store has successfully
// | graduated all outputs. It also tracks a "last finalized height", which
// | records the last block height that the nursery attempted to graduate
// | If a finalized height has kindergarten outputs, the sweep txn for these
// | outputs will be stored in the height bucket. This ensure that the same
// | txid will be used after restarts. Otherwise, the nursery will be unable
// | to recover the txid of kindergarten sweep transaction it has already
// | broadcast.
// |
// ├── last-finalized-height-key: <last-finalized-height>
// ├── last-graduated-height-key: <last-graduated-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 containing 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, or graduated 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/
// │   ├── <chan-point-1>/ <- CHANNEL BUCKET
// | |   ├── <state-prefix><outpoint-1>: <spendable-output-1>
// | |   └── <state-prefix><outpoint-2>: <spendable-output-2>
// │   ├── <chan-point-2>/
// | |   └── <state-prefix><outpoint-3>: <spendable-output-3>
// │   └── <chan-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 scheduled 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. If a height bucket is less than or equal to the current last
// | finalized height and has a non-zero number of kindergarten outputs, a
// | height bucket will also contain the finalized kindergarten sweep txn
// | under the "finalized-kndr-txn" key.
// |
// └── 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>: ""
//    | └── finalized-kndr-txn: "" | <kndr-sweep-tnx>
//    └── <height-2>/
//    └── <chan-point-1>/
//    └── <state-prefix><outpoint-1>: ""
//    └── <state-prefix><outpoint-2>: ""
// NurseryStore abstracts the persistent storage layer for the utxo nursery.
// Concretely, it stores commitment and htlc outputs 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 {
// Incubate registers a set of CSV delayed outputs (incoming HTLC's on
// our commitment transaction, or a commitment output), and a slice of
// outgoing htlc outputs to be swept back into the user's wallet. The
// event is persisted to disk, such that the nursery can resume the
// incubation process after a potential crash.
Incubate([]kidOutput, []babyOutput) error
// CribToKinder atomically moves a babyOutput in the crib bucket to the
// kindergarten bucket. Baby outputs are outgoing HTLC's which require
// us to go to the second-layer to claim. 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.
// Incoming HTLC's we need to go to the second-layer to claim, and also
// our commitment outputs fall into this class.
PreschoolToKinder(*kidOutput) error
// GraduateKinder atomically moves the kindergarten class at the
// provided height into the graduated status. This involves removing the
// kindergarten entries from both the height and channel indexes, and
// cleaning up the finalized kindergarten sweep txn. The height bucket
// will be opportunistically pruned from the height index as outputs are
// removed.
GraduateKinder(height uint32) error
// FetchPreschools returns a list of all outputs currently stored in
// the preschool bucket.
FetchPreschools() ([]kidOutput, error)
// FetchClass returns a list of kindergarten and crib outputs whose
// timelocks expire at the given height. If the kindergarten class at
// this height hash been finalized previously, via FinalizeKinder, it
// will also returns the finalized kindergarten sweep txn.
FetchClass(height uint32) (*wire.MsgTx, []kidOutput, []babyOutput, error)
// FinalizeKinder accepts a block height and the kindergarten sweep txn
// computed for this height. Upon startup, we will rebroadcast any
// finalized kindergarten txns instead of signing a new txn, as this
// result in a different txid from a preceding broadcast.
FinalizeKinder(height uint32, tx *wire.MsgTx) error
// LastFinalizedHeight returns the last block height for which the
// nursery store finalized a kindergarten class.
LastFinalizedHeight() (uint32, error)
// GraduateHeight records the provided height as the last height for
// which the nursery store successfully graduated all outputs.
GraduateHeight(height uint32) error
// LastGraduatedHeight returns the last block height for which the
// nursery store successfully graduated all outputs.
LastGraduatedHeight() (uint32, error)
// HeightsBelowOrEqual returns the lowest non-empty heights in the
// height index, that exist at or below the provided upper bound.
HeightsBelowOrEqual(height uint32) ([]uint32, error)
// 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
// ListChannels returns all channels the nursery is currently tracking.
ListChannels() ([]wire.OutPoint, error)
// IsMatureChannel determines the whether or not all of the outputs in a
// particular channel bucket have been marked as graduated.
IsMatureChannel(*wire.OutPoint) (bool, error)
// RemoveChannel channel erases all entries from the channel bucket for
// the provided channel point, this method should only be called if
// IsMatureChannel indicates the channel is ready for removal.
RemoveChannel(*wire.OutPoint) error
}
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")
// lastGraduatedHeightKey is a static key used to retrieve the height of
// the last bucket that successfully graduated all outputs.
lastGraduatedHeightKey = []byte("last-graduated-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")
// finalizedKndrTxnKey is a static key that can be used to locate a
// finalized kindergarten sweep txn.
finalizedKndrTxnKey = []byte("finalized-kndr-txn")
)
// Defines the state prefixes that will be used to persistently track an
// output's progress through the nursery.
// NOTE: Each state prefix MUST be exactly 4 bytes in length, the nursery logic
// depends on the ability to create keys for a different state by overwriting
// an existing state prefix.
var (
// 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 within the nursery,
// and will be swept into the wallet after waiting out the relative
// timelock.
kndrPrefix = []byte("kndr")
// gradPrefix is the state prefix given to all outputs that have been
// completely incubated. Once all outputs have been marked as graduated,
// this serves as a persistent marker that the nursery should mark the
// channel fully closed in the channeldb.
gradPrefix = []byte("grad")
)
// 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
}
// nurseryStore is a concrete instantiation of a NurseryStore that is backed by
// a channeldb.DB instance.
type nurseryStore struct {
chainHash chainhash.Hash
db *channeldb.DB
pfxChainKey []byte
}
// 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,
db: db,
pfxChainKey: pfxChainKey,
}, nil
}
// Incubate persists the beginning of the incubation process for the
// CSV-delayed outputs (commitment and incoming HTLC's), commitment output and
// a list of outgoing two-stage htlc outputs.
func (ns *nurseryStore) Incubate(kids []kidOutput, babies []babyOutput) error {
return ns.db.Update(func(tx *bbolt.Tx) error {
// If we have any kid outputs to incubate, then we'll attempt
// to add each of them to the nursery store. Any duplicate
// outputs will be ignored.
for _, kid := range kids {
if err := ns.enterPreschool(tx, &kid); err != nil {
return err
}
}
// Next, we'll Add all htlc outputs to the crib bucket.
// Similarly, we'll ignore any outputs that have already been
// inserted.
for _, baby := range babies {
if err := ns.enterCrib(tx, &baby); err != nil {
return err
}
}
return nil
})
}
// 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 *bbolt.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
}
// Remove the crib output's entry in the height index.
err = ns.removeOutputFromHeight(tx, bby.expiry, chanPoint,
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()
// Retrieve 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
}
utxnLog.Tracef("Transitioning (crib -> baby) output for "+
"chan_point=%v at height_index=%v", chanPoint,
maturityHeight)
// 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.
return hghtChanBucketCsv.Put(pfxOutputKey, []byte{})
})
}
// 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 *bbolt.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
}
// If this output has an absolute time lock, then we'll set the
// maturity height directly.
var maturityHeight uint32
if kid.BlocksToMaturity() == 0 {
maturityHeight = kid.absoluteMaturity
} else {
// Otherwise, 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()
}
// In the case of a Late Registration, we've already graduated
// the class that this kid is destined for. So we'll bump its
// height by one to ensure we don't forget to graduate it.
lastGradHeight, err := ns.getLastGraduatedHeight(tx)
if err != nil {
return err
}
if maturityHeight <= lastGradHeight {
utxnLog.Debugf("Late Registration for kid output=%v "+
"detected: class_height=%v, "+
"last_graduated_height=%v", kid.OutPoint(),
maturityHeight, lastGradHeight)
maturityHeight = lastGradHeight + 1
}
utxnLog.Infof("Transitioning (crib -> kid) output for "+
"chan_point=%v at height_index=%v", chanPoint,
maturityHeight)
// 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 key in the height-channel created above.
// The key 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.
return hghtChanBucket.Put(pfxOutputKey, []byte{})
})
}
// GraduateKinder atomically moves the kindergarten class at the provided height
// into the graduated status. This involves removing the kindergarten entries
// from both the height and channel indexes, and cleaning up the finalized
// kindergarten sweep txn. The height bucket will be opportunistically pruned
// from the height index as outputs are removed.
func (ns *nurseryStore) GraduateKinder(height uint32) error {
return ns.db.Update(func(tx *bbolt.Tx) error {
// Since all kindergarten outputs at a particular height are
// swept in a single txn, we can now safely delete the finalized
// txn, since it has already been broadcast and confirmed.
hghtBucket := ns.getHeightBucket(tx, height)
if hghtBucket == nil {
// Nothing to delete, bucket has already been removed.
return nil
}
// Remove the finalized kindergarten txn, we do this before
// removing the outputs so that the extra entry doesn't prevent
// the height bucket from being opportunistically pruned below.
if err := hghtBucket.Delete(finalizedKndrTxnKey); err != nil {
return err
}
// For each kindergarten found output, delete its entry from the
// height and channel index, and create a new grad output in the
// channel index.
return ns.forEachHeightPrefix(tx, kndrPrefix, height,
func(v []byte) error {
var kid kidOutput
err := kid.Decode(bytes.NewReader(v))
if err != nil {
return err
}
outpoint := kid.OutPoint()
chanPoint := kid.OriginChanPoint()
// Construct the key under which the output is
// currently stored height and channel indexes.
pfxOutputKey, err := prefixOutputKey(kndrPrefix,
outpoint)
if err != nil {
return err
}
// Remove the grad output's entry in the height
// index.
err = ns.removeOutputFromHeight(tx, height,
chanPoint, pfxOutputKey)
if err != nil {
return err
}
chanBucket := ns.getChannelBucket(tx,
chanPoint)
if chanBucket == nil {
return ErrContractNotFound
}
// Remove previous output with kindergarten
// prefix.
err = chanBucket.Delete(pfxOutputKey)
if 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
}
// Insert serialized output into channel bucket
// using graduate-prefixed key.
return chanBucket.Put(pfxOutputKey,
gradBuffer.Bytes())
},
)
})
}
// FinalizeKinder accepts a block height and a finalized kindergarten sweep
// transaction, persisting the transaction at the appropriate height bucket. The
// nursery store's last finalized height is also updated with the provided
// height.
func (ns *nurseryStore) FinalizeKinder(height uint32,
finalTx *wire.MsgTx) error {
return ns.db.Update(func(tx *bbolt.Tx) error {
return ns.finalizeKinder(tx, height, finalTx)
})
}
// GraduateHeight persists the provided height as the nursery store's last
// graduated height.
func (ns *nurseryStore) GraduateHeight(height uint32) error {
return ns.db.Update(func(tx *bbolt.Tx) error {
return ns.putLastGraduatedHeight(tx, height)
})
}
// FetchClass returns a list of babyOutputs in the crib bucket whose CLTV
// delay expires at the provided block height.
// FetchClass returns a list of the kindergarten and crib outputs whose timeouts
// are expiring
func (ns *nurseryStore) FetchClass(
height uint32) (*wire.MsgTx, []kidOutput, []babyOutput, error) {
// Construct list of all crib and kindergarten outputs that need to be
// processed at the provided block height.
var finalTx *wire.MsgTx
var kids []kidOutput
var babies []babyOutput
if err := ns.db.View(func(tx *bbolt.Tx) error {
var err error
finalTx, err = ns.getFinalizedTxn(tx, height)
if err != nil {
return err
}
// Append each crib output to our list of babyOutputs.
if err = ns.forEachHeightPrefix(tx, 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 baby babyOutput
babyReader := bytes.NewReader(buf)
if err := baby.Decode(babyReader); err != nil {
return err
}
babies = append(babies, baby)
return nil
},
); err != nil {
return err
}
// Append each kindergarten output to our list of kidOutputs.
return ns.forEachHeightPrefix(tx, kndrPrefix, height,
func(buf []byte) error {
// 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
kidReader := bytes.NewReader(buf)
if err := kid.Decode(kidReader); err != nil {
return err
}
kids = append(kids, kid)
return nil
})
}); err != nil {
return nil, nil, nil, err
}
return finalTx, kids, babies, 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 *bbolt.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()
for k, v := c.Seek(psclPrefix); bytes.HasPrefix(
k, psclPrefix); k, v = c.Next() {
// 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(v)
err := psclOutput.Decode(psclReader)
if err != nil {
return err
}
// Add the deserialized output to our list of
// preschool outputs.
kids = append(kids, psclOutput)
}
}
return nil
}); err != nil {
return nil, err
}
return kids, nil
}
// HeightsBelowOrEqual returns a slice of all non-empty heights in the height
// index at or below the provided upper bound.
func (ns *nurseryStore) HeightsBelowOrEqual(height uint32) ([]uint32, error) {
var activeHeights []uint32
err := ns.db.View(func(tx *bbolt.Tx) error {
// Ensure that the chain bucket for this nursery store exists.
chainBucket := tx.Bucket(ns.pfxChainKey)
if chainBucket == nil {
return nil
}
// Ensure that the height index has been properly initialized for this
// chain.
hghtIndex := chainBucket.Bucket(heightIndexKey)
if hghtIndex == nil {
return nil
}
// Serialize the provided height, as this will form the name of the
// bucket.
var lower, upper [4]byte
byteOrder.PutUint32(upper[:], height)
c := hghtIndex.Cursor()
for k, _ := c.Seek(lower[:]); bytes.Compare(k, upper[:]) <= 0 &&
len(k) == 4; k, _ = c.Next() {
activeHeights = append(activeHeights, byteOrder.Uint32(k))
}
return nil
})
if err != nil {
return nil, err
}
return activeHeights, nil
}
// 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 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 *bbolt.Tx) error {
return ns.forChanOutputs(tx, chanPoint, callback)
})
}
// ListChannels returns all channels the nursery is currently tracking.
func (ns *nurseryStore) ListChannels() ([]wire.OutPoint, error) {
var activeChannels []wire.OutPoint
if err := ns.db.View(func(tx *bbolt.Tx) error {
// 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
}
return chanIndex.ForEach(func(chanBytes, _ []byte) error {
var chanPoint wire.OutPoint
err := readOutpoint(bytes.NewReader(chanBytes), &chanPoint)
if err != nil {
return err
}
activeChannels = append(activeChannels, chanPoint)
return nil
})
}); err != nil {
return nil, err
}
return activeChannels, nil
}
// IsMatureChannel determines the whether or not all of the outputs in a
// particular channel bucket have been marked as graduated.
func (ns *nurseryStore) IsMatureChannel(chanPoint *wire.OutPoint) (bool, error) {
err := ns.db.View(func(tx *bbolt.Tx) error {
// Iterate over the contents of the channel bucket, computing
// both total number of outputs, and those that have the grad
// prefix.
return ns.forChanOutputs(tx, chanPoint,
func(pfxKey, _ []byte) error {
if !bytes.HasPrefix(pfxKey, gradPrefix) {
return ErrImmatureChannel
}
return nil
})
})
if err != nil && err != ErrImmatureChannel {
return false, err
}
return err == nil, nil
}
// ErrImmatureChannel signals a channel cannot be removed because not all of its
// outputs have graduated.
var ErrImmatureChannel = errors.New("cannot remove immature channel, " +
"still has ungraduated outputs")
// RemoveChannel channel erases all entries from the channel bucket for the
// provided channel point.
// NOTE: The channel's entries in the height index are assumed to be removed.
func (ns *nurseryStore) RemoveChannel(chanPoint *wire.OutPoint) error {
return ns.db.Update(func(tx *bbolt.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
}
chanBytes := chanBuffer.Bytes()
err := ns.forChanOutputs(tx, chanPoint, func(k, v []byte) error {
if !bytes.HasPrefix(k, gradPrefix) {
return ErrImmatureChannel
}
// Construct a kindergarten prefixed key, since this
// would have been the preceding state for a grad
// output.
kndrKey := make([]byte, len(k))
copy(kndrKey, k)
copy(kndrKey[:4], kndrPrefix)
// Decode each to retrieve the output's maturity height.
var kid kidOutput
if err := kid.Decode(bytes.NewReader(v)); err != nil {
return err
}
maturityHeight := kid.ConfHeight() + kid.BlocksToMaturity()
hghtBucket := ns.getHeightBucket(tx, maturityHeight)
if hghtBucket == nil {
return nil
}
return removeBucketIfExists(hghtBucket, chanBytes)
})
if err != nil {
return err
}
return removeBucketIfExists(chanIndex, chanBytes)
})
}
// LastFinalizedHeight returns the last block height for which the nursery
// store has finalized a kindergarten class.
func (ns *nurseryStore) LastFinalizedHeight() (uint32, error) {
var lastFinalizedHeight uint32
err := ns.db.View(func(tx *bbolt.Tx) error {
var err error
lastFinalizedHeight, err = ns.getLastFinalizedHeight(tx)
return err
})
return lastFinalizedHeight, err
}
// LastGraduatedHeight returns the last block height for which the nursery
// store has successfully graduated all outputs.
func (ns *nurseryStore) LastGraduatedHeight() (uint32, error) {
var lastGraduatedHeight uint32
err := ns.db.View(func(tx *bbolt.Tx) error {
var err error
lastGraduatedHeight, err = ns.getLastGraduatedHeight(tx)
return err
})
return lastGraduatedHeight, err
}
// Helper Methods
// 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 in the crib state, and will be
// revisited after the first-stage output's CLTV has expired.
func (ns *nurseryStore) enterCrib(tx *bbolt.Tx, baby *babyOutput) error {
// First, retrieve or create the channel bucket corresponding to the
// baby output's origin channel point.
chanPoint := baby.OriginChanPoint()
chanBucket, err := ns.createChannelBucket(tx, 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, baby.OutPoint())
if err != nil {
return err
}
// We'll first check that we don't already have an entry for this
// output. If we do, then we can exit early.
if rawBytes := chanBucket.Get(pfxOutputKey); rawBytes != nil {
return nil
}
// 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,
baby.expiry, chanPoint)
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 := baby.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.
return hghtChanBucket.Put(pfxOutputKey, []byte{})
}
// 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(tx *bbolt.Tx, kid *kidOutput) 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 kidOutput 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
}
// We'll first check if an entry for this key is already stored. If so,
// then we'll ignore this request, and return a nil error.
if rawBytes := chanBucket.Get(pfxOutputKey); rawBytes != nil {
return nil
}
// 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())
}
// createChannelBucket creates or retrieves a channel bucket for the provided
// channel point.
func (ns *nurseryStore) createChannelBucket(tx *bbolt.Tx,
chanPoint *wire.OutPoint) (*bbolt.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 *bbolt.Tx,
chanPoint *wire.OutPoint) *bbolt.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 *bbolt.Tx,
height uint32) (*bbolt.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[:])
}
// getHeightBucketPath 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) getHeightBucketPath(tx *bbolt.Tx,
height uint32) (*bbolt.Bucket, *bbolt.Bucket, *bbolt.Bucket) {
// Retrieve the existing chain bucket for this nursery store.
chainBucket := tx.Bucket(ns.pfxChainKey)
if chainBucket == nil {
return nil, nil, nil
}
// Retrieve the existing channel index.
hghtIndex := chainBucket.Bucket(heightIndexKey)
if hghtIndex == nil {
return nil, nil, nil
}
// Serialize the provided block height and return the bucket matching
// the serialized key.
var heightBytes [4]byte
byteOrder.PutUint32(heightBytes[:], height)
return chainBucket, hghtIndex, hghtIndex.Bucket(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 *bbolt.Tx,
height uint32) *bbolt.Bucket {
_, _, hghtBucket := ns.getHeightBucketPath(tx, height)
return hghtBucket
}
// 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 *bbolt.Tx,
height uint32, chanPoint *wire.OutPoint) (*bbolt.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 *bbolt.Tx,
height uint32, chanPoint *wire.OutPoint) *bbolt.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(tx *bbolt.Tx, prefix []byte,
height uint32, callback func([]byte) error) error {
// Start by retrieving the height bucket corresponding to the provided
// block height.
chainBucket, _, hghtBucket := ns.getHeightBucketPath(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, v []byte) error {
if v == nil {
channelsAtHeight = append(channelsAtHeight, chanBytes)
}
return nil
}); err != nil {
return err
}
// 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 errors.New("unable to retrieve channel index")
}
// Now, we are ready to enumerate all outputs with the desired prefix at
// 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 {
return fmt.Errorf("unable to retrieve height-channel "+
"bucket at height %d for %x", height, chanBytes)
}
// 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 {
return fmt.Errorf("unable to retrieve channel "+
"bucket: '%x'", chanBytes)
}
// 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()
for k, _ := c.Seek(prefix); bytes.HasPrefix(
k, prefix); k, _ = c.Next() {
// Use the prefix output key emitted from our scan to
// load the serialized babyOutput from the appropriate
// channel bucket.
outputBytes := chanBucket.Get(k)
if outputBytes == nil {
return errors.New("unable to retrieve output")
}
// 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
}
}
}
return nil
}
// forChanOutputs enumerates the outputs contained in a channel bucket to the
// provided callback. The callback accepts a key-value pair of byte slices
// corresponding to the prefixed-output key and the serialized output,
// respectively.
func (ns *nurseryStore) forChanOutputs(tx *bbolt.Tx, chanPoint *wire.OutPoint,
callback func([]byte, []byte) error) error {
chanBucket := ns.getChannelBucket(tx, chanPoint)
if chanBucket == nil {
return ErrContractNotFound
}
return chanBucket.ForEach(callback)
}
// getLastFinalizedHeight is a helper method that retrieves the last height for
// which the database finalized its persistent state.
func (ns *nurseryStore) getLastFinalizedHeight(tx *bbolt.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 heightBytes == nil {
// We have never finalized, return height 0.
return 0, nil
}
// If the resulting bytes are not sized like a uint32, then we have
// never finalized, so we return 0.
// Otherwise, parse the bytes and return the last finalized height.
return byteOrder.Uint32(heightBytes), nil
}
// finalizeKinder records a finalized kindergarten sweep txn to the given height
// bucket. It also updates the nursery store's last finalized height, so that we
// do not finalize the same height twice. If the finalized txn is nil, i.e. if
// the height has no kindergarten outputs, the height will be marked as
// finalized, and we skip the process of writing the txn. When the class is
// loaded, a nil value will be returned if no txn has been written to a
// finalized height bucket.
func (ns *nurseryStore) finalizeKinder(tx *bbolt.Tx, height uint32,
finalTx *wire.MsgTx) error {
// TODO(conner) ensure height is greater that current finalized height.
// 1. Write the last finalized height to the chain bucket.
// 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)
err = chainBucket.Put(lastFinalizedHeightKey, lastHeightBytes[:])
if err != nil {
return err
}
// 2. Write the finalized txn in the appropriate height bucket.
// If there is no finalized txn, we have nothing to do.
if finalTx == nil {
return nil
}
// Otherwise serialize the finalized txn and write it to the height
// bucket.
hghtBucket := ns.getHeightBucket(tx, height)
if hghtBucket == nil {
return nil
}
var finalTxnBuf bytes.Buffer
if err := finalTx.Serialize(&finalTxnBuf); err != nil {
return err
}
return hghtBucket.Put(finalizedKndrTxnKey, finalTxnBuf.Bytes())
}
// getFinalizedTxn retrieves the finalized kindergarten sweep txn at the given
// height, returning nil if one was not found.
func (ns *nurseryStore) getFinalizedTxn(tx *bbolt.Tx,
height uint32) (*wire.MsgTx, error) {
hghtBucket := ns.getHeightBucket(tx, height)
if hghtBucket == nil {
// No class to finalize.
return nil, nil
}
finalTxBytes := hghtBucket.Get(finalizedKndrTxnKey)
if finalTxBytes == nil {
// No finalized txn for this height.
return nil, nil
}
// Otherwise, deserialize and return the finalized transaction.
txn := &wire.MsgTx{}
if err := txn.Deserialize(bytes.NewReader(finalTxBytes)); err != nil {
return nil, err
}
return txn, nil
}
// getLastGraduatedHeight is a helper method that retrieves the last height for
// which the database graduated all outputs successfully.
func (ns *nurseryStore) getLastGraduatedHeight(tx *bbolt.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 graduated height in the top-level chain bucket.
heightBytes := chainBucket.Get(lastGraduatedHeightKey)
if heightBytes == nil {
// We have never graduated before, return height 0.
return 0, nil
}
// Otherwise, parse the bytes and return the last graduated height.
return byteOrder.Uint32(heightBytes), nil
}
// pubLastGraduatedHeight is a helper method that writes the provided height under
// the last graduated height key.
func (ns *nurseryStore) putLastGraduatedHeight(tx *bbolt.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-graduated 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(lastGraduatedHeightKey, lastHeightBytes[:])
}
// errBucketNotEmpty signals that an attempt to prune a particular
// bucket failed because it still has active outputs.
var errBucketNotEmpty = errors.New("bucket is not empty, cannot be pruned")
// removeOutputFromHeight will delete the given output from the specified
// height-channel bucket, and attempt to prune the upstream directories if they
// are empty.
func (ns *nurseryStore) removeOutputFromHeight(tx *bbolt.Tx, height uint32,
chanPoint *wire.OutPoint, pfxKey []byte) error {
// Retrieve the height-channel bucket and delete the prefixed output.
hghtChanBucket := ns.getHeightChanBucket(tx, height, chanPoint)
if hghtChanBucket == nil {
// Height-channel bucket already removed.
return nil
}
// Try to delete the prefixed output from the target height-channel
// bucket.
if err := hghtChanBucket.Delete(pfxKey); err != nil {
return err
}
// Retrieve the height bucket that contains the height-channel bucket.
hghtBucket := ns.getHeightBucket(tx, height)
if hghtBucket == nil {
return errors.New("height bucket not found")
}
var chanBuffer bytes.Buffer
if err := writeOutpoint(&chanBuffer, chanPoint); err != nil {
return err
}
// Try to remove the channel-height bucket if it this was the last
// output in the bucket.
err := removeBucketIfEmpty(hghtBucket, chanBuffer.Bytes())
if err != nil && err != errBucketNotEmpty {
return err
} else if err == errBucketNotEmpty {
return nil
}
// Attempt to prune the height bucket matching the kid output's
// confirmation height in case that was the last height-chan bucket.
pruned, err := ns.pruneHeight(tx, height)
if err != nil && err != errBucketNotEmpty {
return err
} else if err == nil && pruned {
utxnLog.Infof("Height bucket %d pruned", height)
}
return nil
}
// pruneHeight removes the height bucket at the provided height if and only if
// all active outputs at this height have been removed from their respective
// height-channel buckets. The returned boolean value indicated whether or not
// this invocation successfully pruned the height bucket.
func (ns *nurseryStore) pruneHeight(tx *bbolt.Tx, height uint32) (bool, error) {
// Fetch the existing height index and height bucket.
_, hghtIndex, hghtBucket := ns.getHeightBucketPath(tx, height)
if hghtBucket == nil {
return false, nil
}
// Iterate over all channels stored 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.
if err := hghtBucket.ForEach(func(chanBytes, v []byte) error {
// Skip the finalized txn key.
if v != nil {
return nil
}
// Attempt to each height-channel bucket from the height bucket
// located above.
hghtChanBucket := hghtBucket.Bucket(chanBytes)
if hghtChanBucket == nil {
return errors.New("unable to find height-channel bucket")
}
return isBucketEmpty(hghtChanBucket)
}); err != nil {
return false, err
}
// Serialize the provided block height, such that it can be used as the
// key to delete desired height bucket.
var heightBytes [4]byte
byteOrder.PutUint32(heightBytes[:], height)
// All of the height-channel buckets are empty or have been previously
// removed, proceed by removing the height bucket
// altogether.
if err := removeBucketIfExists(hghtIndex, heightBytes[:]); err != nil {
return false, err
}
return true, nil
}
// removeBucketIfEmpty attempts to delete a bucket specified by name from the
// provided parent bucket.
func removeBucketIfEmpty(parent *bbolt.Bucket, bktName []byte) error {
// Attempt to fetch the named bucket from its parent.
bkt := parent.Bucket(bktName)
if bkt == nil {
// No bucket was found, already removed?
return nil
}
// The bucket exists, fail if it still has children.
if err := isBucketEmpty(bkt); err != nil {
return err
}
return parent.DeleteBucket(bktName)
}
// removeBucketIfExists safely deletes the named bucket by first checking
// that it exists in the parent bucket.
func removeBucketIfExists(parent *bbolt.Bucket, bktName []byte) error {
// Attempt to fetch the named bucket from its parent.
bkt := parent.Bucket(bktName)
if bkt == nil {
// No bucket was found, already removed?
return nil
}
return parent.DeleteBucket(bktName)
}
// isBucketEmpty returns errBucketNotEmpty if the bucket has a non-zero number
// of children.
func isBucketEmpty(parent *bbolt.Bucket) error {
return parent.ForEach(func(_, _ []byte) error {
return errBucketNotEmpty
})
}
// Compile-time constraint to ensure nurseryStore implements NurseryStore.
var _ NurseryStore = (*nurseryStore)(nil)