// MergeLabels handles merging of any number of labels throughout the various label data
// structures. It assumes that the merges aren't cascading, e.g., there is no attempt
// to merge label 3 into 4 and also 4 into 5. The caller should have flattened the merges.
// TODO: Provide some indication that subset of labels are under evolution, returning
// an "unavailable" status or 203 for non-authoritative response. This might not be
// feasible for clustered DVID front-ends due to coordination issues.
//
// EVENTS
//
// labels.MergeStartEvent occurs at very start of merge and transmits labels.DeltaMergeStart struct.
//
// labels.MergeBlockEvent occurs for every block of a merged label and transmits labels.DeltaMerge struct.
//
// labels.MergeEndEvent occurs at end of merge and transmits labels.DeltaMergeEnd struct.
//
func (d *Data) MergeLabels(v dvid.VersionID, m labels.MergeOp) error {
dvid.Infof("Merging data %q (labels %s) into label %d ...\n", d.DataName(), m.Merged, m.Target)
// Mark these labels as dirty until done, and make sure we can actually initiate the merge.
if err := labels.MergeStart(d.getMergeIV(v), m); err != nil {
return err
}
d.StartUpdate()
// Signal that we are starting a merge.
evt := datastore.SyncEvent{d.DataUUID(), labels.MergeStartEvent}
msg := datastore.SyncMessage{labels.MergeStartEvent, v, labels.DeltaMergeStart{m}}
if err := datastore.NotifySubscribers(evt, msg); err != nil {
d.StopUpdate()
return err
}
// Asynchronously perform merge and handle any concurrent requests using the cache map until
// labelvol and labelblk are updated and consistent.
go func() {
d.asyncMergeLabels(v, m)
// Remove dirty labels and updating flag when done.
labels.MergeStop(d.getMergeIV(v), m)
d.StopUpdate()
dvid.Infof("Finished with merge of labels %s.\n", m)
}()
return nil
}
func (d *Data) processMerge(v dvid.VersionID, delta labels.DeltaMerge) {
mutID := d.NewMutationID()
for izyxStr := range delta.Blocks {
n := izyxStr.Hash(numBlockHandlers)
d.MutAdd(mutID)
op := mergeOp{mutID: mutID, MergeOp: delta.MergeOp, block: izyxStr}
d.procCh[n] <- procMsg{op: op, v: v}
}
// When we've processed all the delta blocks, we can remove this merge op
// from the merge cache since all labels will have completed.
iv := dvid.InstanceVersion{d.DataUUID(), v}
go func() {
d.MutWait(mutID)
d.MutDelete(mutID)
labels.MergeStop(iv, delta.MergeOp)
d.publishDownresCommit(v, mutID)
}()
}