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reverseproxy: SRV dynamic upstream failover (#5832) 

* Implement grace period, but probably needs sync

* Update cached freshness value

* D'oh, actually use the grace period

* Fix freshness math
This commit is contained in:
Matt Holt 2024-03-05 12:08:31 -07:00 committed by GitHub
parent 8f8204708a
commit 72ce78d9af
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1 changed files with 13 additions and 0 deletions
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13
modules/caddyhttp/reverseproxy/upstreams.go
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@ -49,6 +49,13 @@ type SRVUpstreams struct {
// Results are cached between lookups. Default: 1m
Refresh caddy.Duration `json:"refresh,omitempty"`
// If > 0 and there is an error with the lookup,
// continue to use the cached results for up to
// this long before trying again, (even though they
// are stale) instead of returning an error to the
// client. Default: 0s.
GracePeriod caddy.Duration `json:"grace_period,omitempty"`
// Configures the DNS resolver used to resolve the
// SRV address to SRV records.
Resolver *UpstreamResolver `json:"resolver,omitempty"`
@ -140,6 +147,12 @@ func (su SRVUpstreams) GetUpstreams(r *http.Request) ([]*Upstream, error) {
// out and an error will be returned alongside the remaining results, if any." Thus, we
// only return an error if no records were also returned.
if len(records) == 0 {
if su.GracePeriod > 0 {
su.logger.Error("SRV lookup failed; using previously cached", zap.Error(err))
cached.freshness = time.Now().Add(time.Duration(su.GracePeriod) - time.Duration(su.Refresh))
srvs[suAddr] = cached
return allNew(cached.upstreams), nil
}
return nil, err
}
su.logger.Warn("SRV records filtered", zap.Error(err))