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multi: remove the need for the graphsession package

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In this commit, we add a `GraphSession` method to the `ChannelGraph`.
This method provides a caller with access to a `NodeTraverser`. This is
used by pathfinding to create a graph "session" overwhich to perform a
set of queries for a pathfinding attempt. With this refactor, we hide
details such as DB transaction creation and transaction commits from the
caller. So with this, pathfinding does not need to remember to "close
the graph session". With this commit, the `graphsession` package may be
completely removed.
This commit is contained in:
Elle Mouton
2025-02-13 09:44:14 +02:00
parent dfe2314a2a
commit e004447da6
11 changed files with 117 additions and 297 deletions
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68
graph/db/graph.go
View File

@@ -403,16 +403,6 @@ func initChannelGraph(db kvdb.Backend) error {
return nil
}
// NewPathFindTx returns a new read transaction that can be used for a single
// path finding session. Will return nil if the graph cache is enabled.
func (c *ChannelGraph) NewPathFindTx() (kvdb.RTx, error) {
if c.graphCache != nil {
return nil, nil
}
return c.db.BeginReadTx()
}
// AddrsForNode returns all known addresses for the target node public key that
// the graph DB is aware of. The returned boolean indicates if the given node is
// unknown to the graph DB or not.
@@ -3907,6 +3897,64 @@ func (c *ChannelGraph) IsClosedScid(scid lnwire.ShortChannelID) (bool, error) {
return isClosed, nil
}
// GraphSession will provide the call-back with access to a NodeTraverser
// instance which can be used to perform queries against the channel graph. If
// the graph cache is not enabled, then the call-back will be provided with
// access to the graph via a consistent read-only transaction.
func (c *ChannelGraph) GraphSession(cb func(graph NodeTraverser) error) error {
var (
tx kvdb.RTx
err error
commit = func() {}
)
if c.graphCache == nil {
tx, err = c.db.BeginReadTx()
if err != nil {
return err
}
commit = func() {
if err := tx.Rollback(); err != nil {
log.Errorf("Unable to rollback tx: %v", err)
}
}
}
defer commit()
return cb(&nodeTraverserSession{
db: c,
tx: tx,
})
}
// nodeTraverserSession implements the NodeTraverser interface but with a
// backing read only transaction for a consistent view of the graph in the case
// where the graph Cache has not been enabled.
type nodeTraverserSession struct {
tx kvdb.RTx
db *ChannelGraph
}
// ForEachNodeDirectedChannel calls the callback for every channel of the given
// node.
//
// NOTE: Part of the NodeTraverser interface.
func (c *nodeTraverserSession) ForEachNodeDirectedChannel(nodePub route.Vertex,
cb func(channel *DirectedChannel) error) error {
return c.db.ForEachNodeDirectedChannelTx(c.tx, nodePub, cb)
}
// FetchNodeFeatures returns the features of the given node. If the node is
// unknown, assume no additional features are supported.
//
// NOTE: Part of the NodeTraverser interface.
func (c *nodeTraverserSession) FetchNodeFeatures(nodePub route.Vertex) (
*lnwire.FeatureVector, error) {
return c.db.FetchNodeFeaturesTx(c.tx, nodePub)
}
func putLightningNode(nodeBucket kvdb.RwBucket, aliasBucket kvdb.RwBucket, // nolint:dupl
updateIndex kvdb.RwBucket, node *models.LightningNode) error {

137
graph/graphsession/graph_session.go
View File

@@ -1,137 +0,0 @@
package graphsession
import (
"fmt"
graphdb "github.com/lightningnetwork/lnd/graph/db"
"github.com/lightningnetwork/lnd/kvdb"
"github.com/lightningnetwork/lnd/lnwire"
"github.com/lightningnetwork/lnd/routing"
"github.com/lightningnetwork/lnd/routing/route"
)
// Factory implements the routing.GraphSessionFactory and can be used to start
// a session with a ReadOnlyGraph.
type Factory struct {
graph ReadOnlyGraph
}
// NewGraphSessionFactory constructs a new Factory which can then be used to
// start a new session.
func NewGraphSessionFactory(graph ReadOnlyGraph) routing.GraphSessionFactory {
return &Factory{
graph: graph,
}
}
// NewGraphSession will produce a new Graph to use for a path-finding session.
// It returns the Graph along with a call-back that must be called once Graph
// access is complete. This call-back will close any read-only transaction that
// was created at Graph construction time.
//
// NOTE: This is part of the routing.GraphSessionFactory interface.
func (g *Factory) NewGraphSession() (routing.Graph, func() error, error) {
tx, err := g.graph.NewPathFindTx()
if err != nil {
return nil, nil, err
}
session := &session{
graph: g.graph,
tx: tx,
}
return session, session.close, nil
}
// A compile-time check to ensure that Factory implements the
// routing.GraphSessionFactory interface.
var _ routing.GraphSessionFactory = (*Factory)(nil)
// session is an implementation of the routing.Graph interface where the same
// read-only transaction is held across calls to the graph and can be used to
// access the backing channel graph.
type session struct {
graph graph
tx kvdb.RTx
}
// close closes the read-only transaction being used to access the backing
// graph. If no transaction was started then this is a no-op.
func (g *session) close() error {
if g.tx == nil {
return nil
}
err := g.tx.Rollback()
if err != nil {
return fmt.Errorf("error closing db tx: %w", err)
}
return nil
}
// ForEachNodeDirectedChannel calls the callback for every channel of the given
// node.
//
// NOTE: Part of the routing.Graph interface.
func (g *session) ForEachNodeDirectedChannel(nodePub route.Vertex,
cb func(channel *graphdb.DirectedChannel) error) error {
return g.graph.ForEachNodeDirectedChannelTx(g.tx, nodePub, cb)
}
// FetchNodeFeatures returns the features of the given node. If the node is
// unknown, assume no additional features are supported.
//
// NOTE: Part of the routing.Graph interface.
func (g *session) FetchNodeFeatures(nodePub route.Vertex) (
*lnwire.FeatureVector, error) {
return g.graph.FetchNodeFeaturesTx(g.tx, nodePub)
}
// A compile-time check to ensure that *session implements the
// routing.Graph interface.
var _ routing.Graph = (*session)(nil)
// ReadOnlyGraph is a graph extended with a call to create a new read-only
// transaction that can then be used to make further queries to the graph.
type ReadOnlyGraph interface {
// NewPathFindTx returns a new read transaction that can be used for a
// single path finding session. Will return nil if the graph cache is
// enabled.
NewPathFindTx() (kvdb.RTx, error)
graph
}
// graph describes the API necessary for a graph source to have access to on a
// database implementation, like channeldb.ChannelGraph, in order to be used by
// the Router for pathfinding.
type graph interface {
// ForEachNodeDirectedChannelTx iterates through all channels of a given
// node, executing the passed callback on the directed edge representing
// the channel and its incoming policy. If the callback returns an
// error, then the iteration is halted with the error propagated back
// up to the caller.
//
// Unknown policies are passed into the callback as nil values.
//
// NOTE: if a nil tx is provided, then it is expected that the
// implementation create a read only tx.
ForEachNodeDirectedChannelTx(tx kvdb.RTx, node route.Vertex,
cb func(channel *graphdb.DirectedChannel) error) error
// FetchNodeFeaturesTx returns the features of a given node. If no
// features are known for the node, an empty feature vector is returned.
//
// NOTE: if a nil tx is provided, then it is expected that the
// implementation create a read only tx.
FetchNodeFeaturesTx(tx kvdb.RTx, node route.Vertex) (
*lnwire.FeatureVector, error)
}
// A compile-time check to ensure that *channeldb.ChannelGraph implements the
// graph interface.
var _ graph = (*graphdb.ChannelGraph)(nil)