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watch.go
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watch.go
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package crdb
import (
"context"
"encoding/json"
"errors"
"fmt"
"sort"
"time"
"github.com/jackc/pgx/v5"
"github.com/authzed/spicedb/internal/datastore/common"
"github.com/authzed/spicedb/pkg/datastore"
core "github.com/authzed/spicedb/pkg/proto/core/v1"
)
const (
queryChangefeed = "EXPERIMENTAL CHANGEFEED FOR %s WITH updated, cursor = '%s', resolved = '1s', min_checkpoint_frequency = '0';"
queryChangefeedPreV22 = "EXPERIMENTAL CHANGEFEED FOR %s WITH updated, cursor = '%s', resolved = '1s';"
)
type changeDetails struct {
Resolved string
Updated string
After *struct {
CaveatContext map[string]any `json:"caveat_context"`
CaveatName string `json:"caveat_name"`
}
}
func (cds *crdbDatastore) Watch(ctx context.Context, afterRevision datastore.Revision) (<-chan *datastore.RevisionChanges, <-chan error) {
updates := make(chan *datastore.RevisionChanges, cds.watchBufferLength)
errs := make(chan error, 1)
features, err := cds.Features(ctx)
if err != nil {
errs <- err
return updates, errs
}
if !features.Watch.Enabled {
errs <- datastore.NewWatchDisabledErr(fmt.Sprintf("%s. See https://spicedb.dev/d/enable-watch-api-crdb", features.Watch.Reason))
return updates, errs
}
// get non-pooled connection for watch
// "applications should explicitly create dedicated connections to consume
// changefeed data, instead of using a connection pool as most client
// drivers do by default."
// see: https://www.cockroachlabs.com/docs/v22.2/changefeed-for#considerations
conn, err := pgx.Connect(ctx, cds.dburl)
if err != nil {
errs <- err
return updates, errs
}
interpolated := fmt.Sprintf(cds.beginChangefeedQuery, tableTuple, afterRevision)
go func() {
defer close(updates)
defer close(errs)
pendingChanges := make(map[string]*datastore.RevisionChanges)
changes, err := conn.Query(ctx, interpolated)
if err != nil {
if errors.Is(ctx.Err(), context.Canceled) {
errs <- datastore.NewWatchCanceledErr()
} else {
errs <- err
}
return
}
// We call Close async here because it can be slow and blocks closing the channels. There is
// no return value so we're not really losing anything.
defer func() { go changes.Close() }()
for changes.Next() {
var unused interface{}
var changeJSON []byte
var primaryKeyValuesJSON []byte
if err := changes.Scan(&unused, &primaryKeyValuesJSON, &changeJSON); err != nil {
if errors.Is(ctx.Err(), context.Canceled) {
errs <- datastore.NewWatchCanceledErr()
} else {
errs <- err
}
return
}
var details changeDetails
if err := json.Unmarshal(changeJSON, &details); err != nil {
errs <- err
return
}
if details.Resolved != "" {
// This entry indicates that we are ready to potentially emit some changes
resolved, err := cds.RevisionFromString(details.Resolved)
if err != nil {
errs <- err
return
}
var toEmit []*datastore.RevisionChanges
for ts, values := range pendingChanges {
if resolved.GreaterThan(values.Revision) {
delete(pendingChanges, ts)
toEmit = append(toEmit, values)
}
}
sort.Slice(toEmit, func(i, j int) bool {
return toEmit[i].Revision.LessThan(toEmit[j].Revision)
})
for _, change := range toEmit {
select {
case updates <- change:
default:
errs <- datastore.NewWatchDisconnectedErr()
return
}
}
continue
}
var pkValues [6]string
if err := json.Unmarshal(primaryKeyValuesJSON, &pkValues); err != nil {
errs <- err
return
}
revision, err := cds.RevisionFromString(details.Updated)
if err != nil {
errs <- fmt.Errorf("malformed update timestamp: %w", err)
return
}
var caveatName string
var caveatContext map[string]any
if details.After != nil && details.After.CaveatName != "" {
caveatName = details.After.CaveatName
caveatContext = details.After.CaveatContext
}
ctxCaveat, err := common.ContextualizedCaveatFrom(caveatName, caveatContext)
if err != nil {
errs <- err
return
}
oneChange := &core.RelationTupleUpdate{
Tuple: &core.RelationTuple{
ResourceAndRelation: &core.ObjectAndRelation{
Namespace: pkValues[0],
ObjectId: pkValues[1],
Relation: pkValues[2],
},
Subject: &core.ObjectAndRelation{
Namespace: pkValues[3],
ObjectId: pkValues[4],
Relation: pkValues[5],
},
Caveat: ctxCaveat,
},
}
if details.After == nil {
oneChange.Operation = core.RelationTupleUpdate_DELETE
} else {
oneChange.Operation = core.RelationTupleUpdate_TOUCH
}
pending, ok := pendingChanges[details.Updated]
if !ok {
pending = &datastore.RevisionChanges{
Revision: revision,
}
pendingChanges[details.Updated] = pending
}
pending.Changes = append(pending.Changes, oneChange)
}
if changes.Err() != nil {
if errors.Is(ctx.Err(), context.Canceled) {
closeCtx, closeCancel := context.WithTimeout(context.Background(), 5*time.Second)
defer closeCancel()
if err := conn.Close(closeCtx); err != nil {
errs <- err
}
errs <- datastore.NewWatchCanceledErr()
} else {
errs <- changes.Err()
}
return
}
}()
return updates, errs
}