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