syncthing/lib/connections/dialqueue.go

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// Copyright (C) 2021 The Syncthing Authors.
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at https://mozilla.org/MPL/2.0/.
package connections
import (
"sort"
"time"
"github.com/syncthing/syncthing/lib/protocol"
"github.com/syncthing/syncthing/lib/rand"
)
type dialQueueEntry struct {
id protocol.DeviceID
lastSeen time.Time
shortLived bool
targets []dialTarget
}
type dialQueue []dialQueueEntry
func (queue dialQueue) Sort() {
// Sort the queue with the most recently seen device at the head,
// increasing the likelihood of connecting to a device that we're
// already almost up to date with, index wise.
sort.Slice(queue, func(a, b int) bool {
qa, qb := queue[a], queue[b]
if qa.shortLived != qb.shortLived {
return qb.shortLived
}
return qa.lastSeen.After(qb.lastSeen)
})
// Shuffle the part of the connection queue that are devices we haven't
// connected to recently, so that if we only try a limited set of
// devices (or they in turn have limits and we're trying to load balance
// over several) and the usual ones are down it won't be the same ones
// in the same order every time.
idx := 0
cutoff := time.Now().Add(-recentlySeenCutoff)
for idx < len(queue) {
if queue[idx].lastSeen.Before(cutoff) {
break
}
idx++
}
if idx < len(queue)-1 {
rand.Shuffle(queue[idx:])
}
}