resultdb/cli/poll.go

// Copyright 2019 The LUCI Authors.
//
// 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 cli

import (
	"context"
	"time"

	"go.chromium.org/luci/common/clock"
	"go.chromium.org/luci/common/errors"
	"go.chromium.org/luci/common/retry"
)

var notReady = errors.BoolTag{Key: errors.NewTagKey("not ready")}

// pollingIter implements the polling policy matching the one used by
// `swarming collect`:
// https://source.chromium.org/chromium/_/chromium/infra/luci/client-py.git/+/885b3febcc170a60f25795304e60927b77d1e92d:swarming.py;l=546;drc=7a76117d3fc4543d7e76c6fb3d39cc2977da0ab9
// which is
//   Start with 1 sec delay and for each 30 sec of waiting add another second
//   of delay, until hitting 15 sec ceiling.
//
// The error must be tagged with notReady for polling to continue.
type pollingIter struct {
	start time.Time
}

func newPollingIter() retry.Iterator {
	return &pollingIter{}
}

// Next implements Iterator.
func (c *pollingIter) Next(ctx context.Context, err error) time.Duration {
	if !notReady.In(err) {
		return retry.Stop
	}

	now := clock.Now(ctx)
	if c.start.IsZero() {
		c.start = now
	}
	delay := now.Sub(c.start) / 30 / time.Second
	switch {
	case delay < time.Second:
		delay = time.Second
	case delay > 15*time.Second:
		delay = 15 * time.Second
	}
	return delay
}