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forward/up: HC every 0.5 seconds, do not do exponential backoff (#4371)

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* remove hc backoff

Signed-off-by: Chris O'Haver <cohaver@infoblox.com>

* fix mutex

Signed-off-by: Chris O'Haver <cohaver@infoblox.com>

* Update plugin/pkg/up/up.go

* fmt

Signed-off-by: Miek Gieben <miek@miek.nl>

Co-authored-by: Chris O'Haver <cohaver@infoblox.com>
This commit is contained in:
Miek Gieben 2021-01-12 13:55:01 +01:00 • committed by GitHub
parent ed891c5c4e
commit fd705b4783
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1 changed files with 10 additions and 23 deletions
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33
plugin/pkg/up/up.go
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@ -5,17 +5,21 @@ package up
import (
"sync"
"time"
"github.com/cenkalti/backoff/v4"
)
// Probe is used to run a single Func until it returns true (indicating a target is healthy). If an Func
// is already in progress no new one will be added, i.e. there is always a maximum of 1 checks in flight.
// When failures start to happen we will back off every second failure up to maximum of 4 intervals.
//
// There is a tradeoff to be made in figuring out quickly that an upstream is healthy and not doing to much work
// (sending queries) to find that out. Having some kind of exp. backoff here won't help much, because you don't won't
// to backoff too much. You then also need random queries to be perfomed every so often to quickly detect a working
// upstream. In the end we just send a query every 0.5 second to check the upstream. This hopefully strikes a balance
// between getting information about the upstream state quickly and not doing too much work. Note that 0.5s is still an
// eternity in DNS, so we may actually want to shorten it.
type Probe struct {
sync.Mutex
inprogress int
expBackoff backoff.ExponentialBackOff
interval time.Duration
}
// Func is used to determine if a target is alive. If so this function must return nil.
@ -32,13 +36,7 @@ func (p *Probe) Do(f Func) {
return
}
p.inprogress = active
interval := p.expBackoff.NextBackOff()
// If exponential backoff has reached the maximum elapsed time (15 minutes),
// reset it and try again
if interval == -1 {
p.expBackoff.Reset()
interval = p.expBackoff.NextBackOff()
}
interval := p.interval
p.Unlock()
// Passed the lock. Now run f for as long it returns false. If a true is returned
// we return from the goroutine and we can accept another Func to run.
@ -72,20 +70,9 @@ func (p *Probe) Stop() {
}
// Start will initialize the probe manager, after which probes can be initiated with Do.
// Initializes exponential backoff using the given interval duration
func (p *Probe) Start(interval time.Duration) {
p.Lock()
eB := &backoff.ExponentialBackOff{
InitialInterval: interval,
RandomizationFactor: backoff.DefaultRandomizationFactor,
Multiplier: backoff.DefaultMultiplier,
MaxInterval: 15 * time.Second,
MaxElapsedTime: 2 * time.Minute,
Stop: backoff.Stop,
Clock: backoff.SystemClock,
}
p.expBackoff = *eB
p.expBackoff.Reset()
p.interval = interval
p.Unlock()
}