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Add random delay to periodic peer update thread #1277

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Sep 16, 2021
Merged

Add random delay to periodic peer update thread #1277

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2fbd987
add random delay to periodic peer update thread
jordanschalm Sep 10, 2021
9ab6c98
exit goroutine launched periodically while in initial delay
jordanschalm Sep 10, 2021
e7f9d37
add test case for stopping during delay
jordanschalm Sep 10, 2021
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7 changes: 6 additions & 1 deletion engine/unit.go
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Original file line number Diff line number Diff line change
Expand Up @@ -74,7 +74,12 @@ func (u *Unit) LaunchAfter(delay time.Duration, f func()) {
// If f is executed, the unit will not shut down until after f returns.
func (u *Unit) LaunchPeriodically(f func(), interval time.Duration, delay time.Duration) {
u.Launch(func() {
<-time.After(delay)
select {
case <-u.ctx.Done():
return
case <-time.After(delay):
}

ticker := time.NewTicker(interval)
defer ticker.Stop()
for {
Expand Down
17 changes: 15 additions & 2 deletions engine/unit_test.go
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Expand Up @@ -7,6 +7,7 @@ import (
"github.com/stretchr/testify/require"

"github.com/onflow/flow-go/engine"
"github.com/onflow/flow-go/utils/unittest"
)

func TestReadyDone(t *testing.T) {
Expand All @@ -19,7 +20,7 @@ func TestReadyDone(t *testing.T) {
// takes longer than the interval, the next call will be blocked
func TestLaunchPeriod(t *testing.T) {
u := engine.NewUnit()
<-u.Ready()
unittest.RequireCloseBefore(t, u.Ready(), time.Second, "ready did not close")
logs := make([]string, 0)
u.LaunchPeriodically(func() {
logs = append(logs, "running")
Expand All @@ -38,11 +39,23 @@ func TestLaunchPeriod(t *testing.T) {
"running", "finish",
"running",
}, logs)
<-u.Done()
unittest.RequireCloseBefore(t, u.Done(), time.Second, "done did not close")

require.Equal(t, []string{
"running", "finish",
"running", "finish",
"running", "finish",
}, logs)
}

func TestLaunchPeriod_Delay(t *testing.T) {
u := engine.NewUnit()
unittest.RequireCloseBefore(t, u.Ready(), time.Second, "ready did not close")

// launch f with a large initial delay (30s)
// the function f should never be invoked, so we use t.Fail
u.LaunchPeriodically(t.Fail, time.Millisecond, time.Second*30)

// ensure we can stop the unit quickly (we should not need to wait for initial delay)
unittest.RequireCloseBefore(t, u.Done(), time.Second, "done did not close")
}
10 changes: 7 additions & 3 deletions network/p2p/peerManager.go
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Expand Up @@ -3,6 +3,7 @@ package p2p
import (
"context"
"fmt"
mrand "math/rand"
"time"

"github.com/libp2p/go-libp2p-core/host"
Expand Down Expand Up @@ -83,12 +84,15 @@ func PeerManagerFactory(peerManagerOptions []Option, connectorOptions ...Connect

// Ready kicks off the ambient periodic connection updates.
func (pm *PeerManager) Ready() <-chan struct{} {
// makes sure that peer update request is invoked
// once before returning
// makes sure that peer update request is invoked once before returning
pm.RequestPeerUpdate()

// also starts running it periodically
pm.unit.LaunchPeriodically(pm.RequestPeerUpdate, pm.peerUpdateInterval, time.Duration(0))
//
// add a random delay to initial launch to avoid synchronizing this
// potentially expensive operation across the network
delay := time.Duration(mrand.Int63n(pm.peerUpdateInterval.Nanoseconds()))
pm.unit.LaunchPeriodically(pm.RequestPeerUpdate, pm.peerUpdateInterval, delay)
Comment on lines +94 to +95
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This delay becomes a static configuration parameter of the update loop of the node when inserted here.

Would it be possible to instead choose the delay as part of each run through the loop? That way a node isn't "stuck" with a long delay.

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The delay only happens once (here), before the static-period ticker starts. The time between each peer update is still 10m, it's just the time before the first peer update that can have a longer delay.

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😲 got it!


pm.unit.Launch(pm.updateLoop)

Expand Down