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watch.go
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watch.go
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package mysql
import (
"context"
"errors"
"time"
"github.com/authzed/spicedb/internal/datastore/common"
"github.com/authzed/spicedb/pkg/datastore"
"github.com/authzed/spicedb/pkg/datastore/revision"
core "github.com/authzed/spicedb/pkg/proto/core/v1"
sq "github.com/Masterminds/squirrel"
)
const (
watchSleep = 100 * time.Millisecond
)
// Watch notifies the caller about all changes to tuples.
//
// All events following afterRevision will be sent to the caller.
//
// TODO (@vroldanbet) dupe from postgres datastore - need to refactor
func (mds *Datastore) Watch(ctx context.Context, afterRevisionRaw datastore.Revision) (<-chan *datastore.RevisionChanges, <-chan error) {
afterRevision := afterRevisionRaw.(revision.Decimal)
updates := make(chan *datastore.RevisionChanges, mds.watchBufferLength)
errs := make(chan error, 1)
go func() {
defer close(updates)
defer close(errs)
currentTxn := transactionFromRevision(afterRevision)
for {
var stagedUpdates []datastore.RevisionChanges
var err error
stagedUpdates, currentTxn, err = mds.loadChanges(ctx, currentTxn)
if err != nil {
if errors.Is(ctx.Err(), context.Canceled) {
errs <- datastore.NewWatchCanceledErr()
} else {
errs <- err
}
return
}
// Write the staged updates to the channel
for _, changeToWrite := range stagedUpdates {
changeToWrite := changeToWrite
select {
case updates <- &changeToWrite:
default:
errs <- datastore.NewWatchDisconnectedErr()
return
}
}
// If there were no changes, sleep a bit
if len(stagedUpdates) == 0 {
sleep := time.NewTimer(watchSleep)
select {
case <-sleep.C:
break
case <-ctx.Done():
errs <- datastore.NewWatchCanceledErr()
return
}
}
}
}()
return updates, errs
}
// TODO (@vroldanbet) dupe from postgres datastore - need to refactor
func (mds *Datastore) loadChanges(
ctx context.Context,
afterRevision uint64,
) (changes []datastore.RevisionChanges, newRevision uint64, err error) {
newRevision, err = mds.loadRevision(ctx)
if err != nil {
return
}
if newRevision == afterRevision {
return
}
sql, args, err := mds.QueryChangedQuery.Where(sq.Or{
sq.And{
sq.Gt{colCreatedTxn: afterRevision},
sq.LtOrEq{colCreatedTxn: newRevision},
},
sq.And{
sq.Gt{colDeletedTxn: afterRevision},
sq.LtOrEq{colDeletedTxn: newRevision},
},
}).ToSql()
if err != nil {
return
}
rows, err := mds.db.QueryContext(ctx, sql, args...)
if err != nil {
if errors.Is(err, context.Canceled) {
err = datastore.NewWatchCanceledErr()
}
return
}
defer common.LogOnError(ctx, rows.Close)
stagedChanges := common.NewChanges(revision.DecimalKeyFunc)
for rows.Next() {
nextTuple := &core.RelationTuple{
ResourceAndRelation: &core.ObjectAndRelation{},
Subject: &core.ObjectAndRelation{},
}
var createdTxn uint64
var deletedTxn uint64
var caveatName string
var caveatContext caveatContextWrapper
err = rows.Scan(
&nextTuple.ResourceAndRelation.Namespace,
&nextTuple.ResourceAndRelation.ObjectId,
&nextTuple.ResourceAndRelation.Relation,
&nextTuple.Subject.Namespace,
&nextTuple.Subject.ObjectId,
&nextTuple.Subject.Relation,
&caveatName,
&caveatContext,
&createdTxn,
&deletedTxn,
)
if err != nil {
return
}
nextTuple.Caveat, err = common.ContextualizedCaveatFrom(caveatName, caveatContext)
if err != nil {
return
}
if createdTxn > afterRevision && createdTxn <= newRevision {
stagedChanges.AddChange(ctx, revisionFromTransaction(createdTxn), nextTuple, core.RelationTupleUpdate_TOUCH)
}
if deletedTxn > afterRevision && deletedTxn <= newRevision {
stagedChanges.AddChange(ctx, revisionFromTransaction(deletedTxn), nextTuple, core.RelationTupleUpdate_DELETE)
}
}
if err = rows.Err(); err != nil {
return
}
changes = stagedChanges.AsRevisionChanges(revision.DecimalKeyLessThanFunc)
return
}