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fix: Refactor tailnet conn AwaitReachable to allow for pings >1s RTT #5096

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Merged
merged 2 commits into from
Nov 15, 2022
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fix: Refactor tailnet conn AwaitReachable to allow for pings >1s RTT #5096

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b0d789b
fix: Refactor tailnet conn AwaitReachable to allow for pings >1s RTT
mafredri Nov 15, 2022
b7256c5
fix: Add exponential backoff
mafredri Nov 15, 2022
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34 changes: 27 additions & 7 deletions tailnet/conn.go
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,7 @@ import (
"sync"
"time"

"github.com/cenkalti/backoff/v4"
"github.com/google/uuid"
"go4.org/netipx"
"golang.org/x/xerrors"
Expand Down Expand Up @@ -424,24 +425,43 @@ func (c *Conn) Ping(ctx context.Context, ip netip.Addr) (time.Duration, error) {
// address is reachable. It's the callers responsibility to provide
// a timeout, otherwise this function will block forever.
func (c *Conn) AwaitReachable(ctx context.Context, ip netip.Addr) bool {
ticker := time.NewTicker(time.Millisecond * 100)
defer ticker.Stop()
completedCtx, completed := context.WithCancel(ctx)
ctx, cancel := context.WithCancel(ctx)
defer cancel() // Cancel all pending pings on exit.

completedCtx, completed := context.WithCancel(context.Background())
defer completed()

run := func() {
ctx, cancelFunc := context.WithTimeout(completedCtx, time.Second)
defer cancelFunc()
// Safety timeout, initially we'll have around 10-20 goroutines
// running in parallel. The exponential backoff will converge
// around ~1 ping / 30s, this means we'll have around 10-20
// goroutines pending towards the end as well.
ctx, cancel := context.WithTimeout(ctx, 5*time.Minute)
defer cancel()

_, err := c.Ping(ctx, ip)
if err == nil {
completed()
}
}

eb := backoff.NewExponentialBackOff()
eb.MaxElapsedTime = 0
eb.InitialInterval = 50 * time.Millisecond
eb.MaxInterval = 30 * time.Second
// Consume the first interval since
// we'll fire off a ping immediately.
_ = eb.NextBackOff()

t := backoff.NewTicker(eb)
defer t.Stop()

go run()
defer completed()
for {
select {
case <-completedCtx.Done():
return true
case <-ticker.C:
case <-t.C:
// Pings can take a while, so we can run multiple
// in parallel to return ASAP.
go run()
Expand Down