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tka: make storage a parameter rather than an Authority struct member

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Updates #5435

Based on the discussion in #5435, we can better support transactional data models
by making the underlying storage layer a parameter (which can be specialized for
the request) rather than a long-lived member of Authority.

Now that Authority is just an instantaneous snapshot of state, we can do things
like provide idempotent methods and make it cloneable, too.

Signed-off-by: Tom DNetto <tom@tailscale.com>
This commit is contained in:
Tom DNetto
2022-08-26 09:45:16 -07:00
committed by Tom
parent 7d1357162e
commit 79905a1162
9 changed files with 158 additions and 114 deletions
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56
tka/sync.go
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@@ -43,7 +43,19 @@ const (
ancestorsSkipShift = 2
)
func (a *Authority) syncOffer() (SyncOffer, error) {
// SyncOffer returns an abbreviated description of the current AUM
// chain, which can be used to synchronize with another (untrusted)
// Authority instance.
//
// The returned SyncOffer structure should be transmitted to the remote
// Authority, which should call MissingAUMs() using it to determine
// AUMs which need to be transmitted. This list of AUMs from the remote
// can then be applied locally with Inform().
//
// This SyncOffer + AUM exchange should be performed by both ends,
// because its possible that either end has AUMs that the other needs
// to find out about.
func (a *Authority) SyncOffer(storage Chonk) (SyncOffer, error) {
oldest := a.oldestAncestor.Hash()
out := SyncOffer{
@@ -65,7 +77,7 @@ func (a *Authority) syncOffer() (SyncOffer, error) {
skipAmount = skipAmount << ancestorsSkipShift
}
parent, err := a.storage.AUM(curs)
parent, err := storage.AUM(curs)
if err != nil {
if err != os.ErrNotExist {
return SyncOffer{}, err
@@ -84,22 +96,6 @@ func (a *Authority) syncOffer() (SyncOffer, error) {
return out, nil
}
// SyncOffer returns an abbreviated description of the current AUM
// chain, which can be used to synchronize with another (untrusted)
// Authority instance.
//
// The returned SyncOffer structure should be transmitted to the remote
// Authority, which should call MissingAUMs() using it to determine
// AUMs which need to be transmitted. This list of AUMs from the remote
// can then be applied locally with Inform().
//
// This SyncOffer + AUM exchange should be performed by both ends,
// because its possible that either end has AUMs that the other needs
// to find out about.
func (a *Authority) SyncOffer() (SyncOffer, error) {
return a.syncOffer()
}
// intersection describes how to synchronize AUMs with a remote
// authority.
type intersection struct {
@@ -119,7 +115,7 @@ type intersection struct {
// computeSyncIntersection determines the common AUMs between a local and
// remote SyncOffer. This intersection can be used to synchronize both
// sides.
func computeSyncIntersection(authority *Authority, localOffer, remoteOffer SyncOffer) (*intersection, error) {
func computeSyncIntersection(storage Chonk, localOffer, remoteOffer SyncOffer) (*intersection, error) {
// Simple case: up to date.
if remoteOffer.Head == localOffer.Head {
return &intersection{upToDate: true, headIntersection: &localOffer.Head}, nil
@@ -136,7 +132,7 @@ func computeSyncIntersection(authority *Authority, localOffer, remoteOffer SyncO
// <Them> A -> B
// ∴ their head intersects with our chain, we need to send C
var hasRemoteHead bool
_, err := authority.storage.AUM(remoteOffer.Head)
_, err := storage.AUM(remoteOffer.Head)
if err != nil {
if err != os.ErrNotExist {
return nil, err
@@ -148,7 +144,7 @@ func computeSyncIntersection(authority *Authority, localOffer, remoteOffer SyncO
if hasRemoteHead {
curs := localOffer.Head
for i := 0; i < maxSyncHeadIntersectionIter; i++ {
parent, err := authority.storage.AUM(curs)
parent, err := storage.AUM(curs)
if err != nil {
if err != os.ErrNotExist {
return nil, err
@@ -176,7 +172,7 @@ func computeSyncIntersection(authority *Authority, localOffer, remoteOffer SyncO
// a bit of luck we can use an earlier one and hence do less work /
// transmit fewer AUMs.
for _, a := range remoteOffer.Ancestors {
state, err := computeStateAt(authority.storage, maxSyncIter, a)
state, err := computeStateAt(storage, maxSyncIter, a)
if err != nil {
if err != os.ErrNotExist {
return nil, fmt.Errorf("computeStateAt: %v", err)
@@ -184,7 +180,7 @@ func computeSyncIntersection(authority *Authority, localOffer, remoteOffer SyncO
continue
}
end, _, err := fastForward(authority.storage, maxSyncIter, state, func(curs AUM, _ State) bool {
end, _, err := fastForward(storage, maxSyncIter, state, func(curs AUM, _ State) bool {
return curs.Hash() == localOffer.Head
})
if err != nil {
@@ -203,12 +199,12 @@ func computeSyncIntersection(authority *Authority, localOffer, remoteOffer SyncO
// MissingAUMs returns AUMs a remote may be missing based on the
// remotes' SyncOffer.
func (a *Authority) MissingAUMs(remoteOffer SyncOffer) ([]AUM, error) {
localOffer, err := a.syncOffer()
func (a *Authority) MissingAUMs(storage Chonk, remoteOffer SyncOffer) ([]AUM, error) {
localOffer, err := a.SyncOffer(storage)
if err != nil {
return nil, fmt.Errorf("local syncOffer: %v", err)
}
intersection, err := computeSyncIntersection(a, localOffer, remoteOffer)
intersection, err := computeSyncIntersection(storage, localOffer, remoteOffer)
if err != nil {
return nil, fmt.Errorf("intersection: %v", err)
}
@@ -218,12 +214,12 @@ func (a *Authority) MissingAUMs(remoteOffer SyncOffer) ([]AUM, error) {
out := make([]AUM, 0, 12) // 12 chosen arbitrarily.
if intersection.headIntersection != nil {
state, err := computeStateAt(a.storage, maxSyncIter, *intersection.headIntersection)
state, err := computeStateAt(storage, maxSyncIter, *intersection.headIntersection)
if err != nil {
return nil, err
}
_, _, err = fastForward(a.storage, maxSyncIter, state, func(curs AUM, _ State) bool {
_, _, err = fastForward(storage, maxSyncIter, state, func(curs AUM, _ State) bool {
if curs.Hash() != *intersection.headIntersection {
out = append(out, curs)
}
@@ -233,12 +229,12 @@ func (a *Authority) MissingAUMs(remoteOffer SyncOffer) ([]AUM, error) {
}
if intersection.tailIntersection != nil {
state, err := computeStateAt(a.storage, maxSyncIter, *intersection.tailIntersection)
state, err := computeStateAt(storage, maxSyncIter, *intersection.tailIntersection)
if err != nil {
return nil, err
}
_, _, err = fastForward(a.storage, maxSyncIter, state, func(curs AUM, _ State) bool {
_, _, err = fastForward(storage, maxSyncIter, state, func(curs AUM, _ State) bool {
if curs.Hash() != *intersection.tailIntersection {
out = append(out, curs)
}