restic/vendor/cloud.google.com/go/firestore/watch.go

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// Copyright 2018 Google Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package firestore
import (
"io"
"time"
gax "github.com/googleapis/gax-go"
"golang.org/x/net/context"
pb "google.golang.org/genproto/googleapis/firestore/v1beta1"
"google.golang.org/grpc/codes"
"google.golang.org/grpc/status"
)
// Implementation of realtime updates (a.k.a. watch).
// This code is closely based on the Node.js implementation,
// https://github.com/googleapis/nodejs-firestore/blob/master/src/watch.js.
var defaultBackoff = gax.Backoff{
// Values from https://github.com/googleapis/nodejs-firestore/blob/master/src/backoff.js.
Initial: 1 * time.Second,
Max: 60 * time.Second,
Multiplier: 1.5,
}
type watchStream struct {
ctx context.Context
c *Client
target *pb.Target // document or query being watched
lc pb.Firestore_ListenClient
backoff gax.Backoff
}
func newWatchStream(ctx context.Context, c *Client, target *pb.Target) *watchStream {
return &watchStream{
ctx: ctx,
c: c,
target: target,
backoff: defaultBackoff,
}
}
// recv receives the next message from the stream. It also handles opening the stream
// initially, and reopening it on non-permanent errors.
// recv doesn't have to be goroutine-safe.
func (s *watchStream) recv() (*pb.ListenResponse, error) {
var err error
for {
if s.lc == nil {
s.lc, err = s.open()
if err != nil {
// Do not retry if open fails.
return nil, err
}
}
res, err := s.lc.Recv()
if err == nil || isPermanentWatchError(err) {
return res, err
}
// Non-permanent error. Sleep and retry.
// TODO: from node:
// request.addTarget.resumeToken = resumeToken;
// changeMap.clear();
dur := s.backoff.Pause()
// If we're out of quota, wait a long time before retrying.
if status.Code(err) == codes.ResourceExhausted {
dur = s.backoff.Max
}
if err := gax.Sleep(s.ctx, dur); err != nil {
return nil, err
}
s.lc = nil
}
}
func (s *watchStream) open() (pb.Firestore_ListenClient, error) {
lc, err := s.c.c.Listen(s.ctx)
if err == nil {
err = lc.Send(&pb.ListenRequest{
Database: s.c.path(),
TargetChange: &pb.ListenRequest_AddTarget{AddTarget: s.target},
})
}
if err != nil {
return nil, err
}
return lc, nil
}
func isPermanentWatchError(err error) bool {
if err == io.EOF {
// Retry on normal end-of-stream.
return false
}
switch status.Code(err) {
case codes.Canceled, codes.Unknown, codes.DeadlineExceeded, codes.ResourceExhausted,
codes.Internal, codes.Unavailable, codes.Unauthenticated:
return false
default:
return true
}
}