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repair.go
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repair.go
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package farm
import (
"sync"
"github.com/SimonRichardson/coherence/pkg/cluster/hashring"
"github.com/SimonRichardson/coherence/pkg/cluster/nodes"
"github.com/SimonRichardson/coherence/pkg/selectors"
"github.com/pkg/errors"
)
type repairStrategy struct {
nodes hashring.Snapshot
}
func (r *repairStrategy) Repair(members []selectors.KeyFieldValue) error {
clues := make([]selectors.Clue, 0)
for _, v := range members {
// This can be optimised to send all of them at once, but could flood the
// hosts
clue, err := r.readScoreRepair(v.Key, func(n nodes.Node) <-chan selectors.Element {
return n.Score(v.Key, v.Field)
})
if err != nil {
continue
}
// Ignore the clue, we don't want to perform any read repairs.
if clue.Ignore {
continue
}
clues = append(clues, clue.SetKeyFieldValue(v.Key, v.Field, v.Value))
}
var (
inserts = make(map[selectors.Key][]selectors.FieldValueScore)
deletes = make(map[selectors.Key][]selectors.FieldValueScore)
)
for _, v := range clues {
// If we've not met quorum then we shouldn't be doing anything.
if v.Ignore || !v.Quorum {
continue
}
if v.Insert {
inserts[v.Key] = append(inserts[v.Key], selectors.FieldValueScore{
Field: v.Field,
Value: v.Value,
Score: v.Score + 1,
})
} else {
deletes[v.Key] = append(deletes[v.Key], selectors.FieldValueScore{
Field: v.Field,
Value: v.Value,
Score: v.Score + 1,
})
}
}
var errs []error
for key, members := range inserts {
if err := r.write(key, func(n nodes.Node) <-chan selectors.Element {
return n.Insert(key, members)
}); err != nil {
errs = append(errs, err)
}
}
for key, members := range deletes {
if err := r.write(key, func(n nodes.Node) <-chan selectors.Element {
return n.Delete(key, members)
}); err != nil {
errs = append(errs, err)
}
}
if len(errs) > 0 {
return errors.Wrapf(joinErrors(errs), "repair error")
}
return nil
}
func (r *repairStrategy) readScoreRepair(key selectors.Key, fn func(nodes.Node) <-chan selectors.Element) (selectors.Clue, error) {
var (
retrieved = 0
returned = 0
nodes = r.nodes.Read(key, selectors.Strong)
elements = make(chan selectors.Element, len(nodes))
errs []error
presences = make([]selectors.Presence, len(nodes))
wg = &sync.WaitGroup{}
)
wg.Add(len(nodes))
go func() { wg.Wait(); close(elements) }()
if err := scatterRequests(nodes, fn, wg, elements); err != nil {
return selectors.Clue{}, err
}
for element := range elements {
retrieved++
if err := selectors.ErrorFromElement(element); err != nil {
errs = append(errs, err)
continue
}
returned++
presence := selectors.PresenceFromElement(element)
presences = append(presences, presence)
}
// We should just send everything again, as we have no idea what the condition
// of the clusters are in.
if !consensus(selectors.Consensus, len(nodes), returned) {
return selectors.Clue{}, errors.Errorf("unable to perform repair")
}
var (
present = 0
found = false
wasInserted = false
highestScore = int64(0)
)
for _, presence := range presences {
if presence.Present {
present++
if presence.Score > highestScore {
found = true
highestScore = presence.Score
wasInserted = wasInserted || presence.Inserted
}
}
}
return selectors.Clue{
Ignore: !found,
Insert: wasInserted,
Score: highestScore,
Quorum: consensus(selectors.Consensus, len(nodes), present),
}, nil
}
func (r *repairStrategy) write(key selectors.Key, fn func(nodes.Node) <-chan selectors.Element) error {
var (
retrieved = 0
returned = 0
nodes, finish = r.nodes.Write(key, selectors.Strong)
elements = make(chan selectors.Element, len(nodes))
errs []error
hashes []uint32
records = &changeSetRecords{}
wg = &sync.WaitGroup{}
)
wg.Add(len(nodes))
go func() { wg.Wait(); close(elements) }()
if err := scatterRequests(nodes, fn, wg, elements); err != nil {
return err
}
for element := range elements {
retrieved++
if err := selectors.ErrorFromElement(element); err != nil {
errs = append(errs, err)
continue
}
returned++
changeSet := selectors.ChangeSetFromElement(element)
records.Add(changeSet)
hashes = append(hashes, element.Hash())
}
// Finish and close the snapshot back to the node set
go finish(hashes)
if len(errs) > 0 {
return errors.Wrapf(joinErrors(errs), "partial error")
}
if err := records.Err(); err != nil {
return errPartial{err}
}
return nil
}