mirror of https://github.com/hashicorp/consul
64 lines
2.5 KiB
Go
64 lines
2.5 KiB
Go
package leafcert
|
|
|
|
import (
|
|
"time"
|
|
|
|
"github.com/hashicorp/consul/agent/structs"
|
|
)
|
|
|
|
// calculateSoftExpiry encapsulates our logic for when to renew a cert based on
|
|
// it's age. It returns a pair of times min, max which makes it easier to test
|
|
// the logic without non-deterministic jitter to account for. The caller should
|
|
// choose a time randomly in between these.
|
|
//
|
|
// We want to balance a few factors here:
|
|
// - renew too early and it increases the aggregate CSR rate in the cluster
|
|
// - renew too late and it risks disruption to the service if a transient
|
|
// error prevents the renewal
|
|
// - we want a broad amount of jitter so if there is an outage, we don't end
|
|
// up with all services in sync and causing a thundering herd every
|
|
// renewal period. Broader is better for smoothing requests but pushes
|
|
// both earlier and later tradeoffs above.
|
|
//
|
|
// Somewhat arbitrarily the current strategy looks like this:
|
|
//
|
|
// 0 60% 90%
|
|
// Issued [------------------------------|===============|!!!!!] Expires
|
|
// 72h TTL: 0 ~43h ~65h
|
|
// 1h TTL: 0 36m 54m
|
|
//
|
|
// Where |===| is the soft renewal period where we jitter for the first attempt
|
|
// and |!!!| is the danger zone where we just try immediately.
|
|
//
|
|
// In the happy path (no outages) the average renewal occurs half way through
|
|
// the soft renewal region or at 75% of the cert lifetime which is ~54 hours for
|
|
// a 72 hour cert, or 45 mins for a 1 hour cert.
|
|
//
|
|
// If we are already in the softRenewal period, we randomly pick a time between
|
|
// now and the start of the danger zone.
|
|
//
|
|
// We pass in now to make testing easier.
|
|
func calculateSoftExpiry(now time.Time, cert *structs.IssuedCert) (min time.Time, max time.Time) {
|
|
certLifetime := cert.ValidBefore.Sub(cert.ValidAfter)
|
|
if certLifetime < 10*time.Minute {
|
|
// Shouldn't happen as we limit to 1 hour shortest elsewhere but just be
|
|
// defensive against strange times or bugs.
|
|
return now, now
|
|
}
|
|
|
|
// Find the 60% mark in diagram above
|
|
softRenewTime := cert.ValidAfter.Add(time.Duration(float64(certLifetime) * 0.6))
|
|
hardRenewTime := cert.ValidAfter.Add(time.Duration(float64(certLifetime) * 0.9))
|
|
|
|
if now.After(hardRenewTime) {
|
|
// In the hard renew period, or already expired. Renew now!
|
|
return now, now
|
|
}
|
|
|
|
if now.After(softRenewTime) {
|
|
// Already in the soft renew period, make now the lower bound for jitter
|
|
softRenewTime = now
|
|
}
|
|
return softRenewTime, hardRenewTime
|
|
}
|