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plugin/forward: cap default connect attempts (#8365)

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Default to two connect attempts per configured upstream so fast failures cannot spin until the request deadline. Track whether max_connect_attempts was explicitly configured so zero still opts into the legacy unbounded behavior.

Fixes #7723

Signed-off-by: houyuwushang <liuluoqianqiu@outlook.com>
This commit is contained in:
houyuwushang
2026-08-04 09:49:29 +08:00
committed by GitHub
parent dc1e3a96ad
commit 0fa6c66797
5 changed files with 98 additions and 17 deletions
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22
plugin/forward/forward.go
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@@ -30,9 +30,10 @@ import (
var log = clog.NewWithPlugin("forward")
const (
defaultExpire = 10 * time.Second
defaultReadTimeout = 2 * time.Second
hcInterval = 500 * time.Millisecond
defaultExpire = 10 * time.Second
defaultReadTimeout = 2 * time.Second
hcInterval = 500 * time.Millisecond
defaultConnectAttemptsPerUpstream = 2
)
// Forward represents a plugin instance that can proxy requests to another (DNS) server. It has a list
@@ -62,6 +63,7 @@ type Forward struct {
failfastUnhealthyUpstreams bool
failoverRcodes []int
maxConnectAttempts uint32
maxConnectAttemptsSet bool
sourceAddress net.IP
// Hostname resolution fields
@@ -135,9 +137,13 @@ func (f *Forward) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg
list := f.List()
deadline := time.Now().Add(defaultTimeout)
start := time.Now()
connectAttempts := uint32(0)
maxConnectAttempts := uint64(f.maxConnectAttempts)
if !f.maxConnectAttemptsSet {
maxConnectAttempts = uint64(defaultConnectAttemptsPerUpstream) * uint64(len(list))
}
connectAttempts := uint64(0)
for time.Now().Before(deadline) && ctx.Err() == nil && (f.maxConnectAttempts == 0 || connectAttempts < f.maxConnectAttempts) {
for time.Now().Before(deadline) && ctx.Err() == nil && (maxConnectAttempts == 0 || connectAttempts < maxConnectAttempts) {
if i >= len(list) {
// reached the end of list, reset to begin
i = 0
@@ -215,11 +221,9 @@ func (f *Forward) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg
proxy.Healthcheck()
}
// If a per-request connect-attempt cap is configured, count this
// failed connect attempt and stop retrying when the cap is hit.
if f.maxConnectAttempts > 0 {
if maxConnectAttempts > 0 {
connectAttempts++
if connectAttempts >= f.maxConnectAttempts {
if connectAttempts >= maxConnectAttempts {
break
}
}