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reverseproxy: Add ability to clear dynamic upstreams cache during retries

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This is an optional interface for dynamic upstream modules to implement if they cache results.

TODO: More documentation; this is an experiment.
This commit is contained in:
Matthew Holt 2026-04-20 16:55:16 -06:00
parent 4430756d5c
commit 5609d12e5e
No known key found for this signature in database
2 changed files with 33 additions and 4 deletions
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16
modules/caddyhttp/reverseproxy/reverseproxy.go
View File

@ -574,6 +574,15 @@ func (h *Handler) proxyLoopIteration(r *http.Request, origReq *http.Request, w h
// get the updated list of upstreams
upstreams := h.Upstreams
if h.DynamicUpstreams != nil {
if retries > 0 {
if cachingDynamicUpstreams, ok := h.DynamicUpstreams.(cachingUpstreamSource); ok {
if err := cachingDynamicUpstreams.ResetCache(r); err != nil {
if c := h.logger.Check(zapcore.ErrorLevel, "failed clearing dynamic upstream source's cache"); c != nil {
c.Write(zap.Error(err))
}
}
}
}
dUpstreams, err := h.DynamicUpstreams.GetUpstreams(r)
if err != nil {
if c := h.logger.Check(zapcore.ErrorLevel, "failed getting dynamic upstreams; falling back to static upstreams"); c != nil {
@ -1590,6 +1599,13 @@ type UpstreamSource interface {
GetUpstreams(*http.Request) ([]*Upstream, error)
}
// cachingUpstreamSource is an upstream source that caches its upstreams.
// EXPERIMENTAL: Subject to change.
type cachingUpstreamSource interface {
UpstreamSource
ResetCache(*http.Request) error
}
// Hop-by-hop headers. These are removed when sent to the backend.
// As of RFC 7230, hop-by-hop headers are required to appear in the
// Connection header field. These are the headers defined by the

21
modules/caddyhttp/reverseproxy/upstreams.go
View File

@ -119,6 +119,18 @@ func (su *SRVUpstreams) Provision(ctx caddy.Context) error {
return nil
}
func (su *SRVUpstreams) ResetCache(r *http.Request) error {
srvsMu.Lock()
if r == nil {
srvs = make(map[string]srvLookup)
} else {
suAddr, _, _, _ := su.expandedAddr(r)
delete(srvs, suAddr)
}
srvsMu.Unlock()
return nil
}
func (su SRVUpstreams) GetUpstreams(r *http.Request) ([]*Upstream, error) {
suAddr, service, proto, name := su.expandedAddr(r)
@ -554,8 +566,9 @@ var (
// Interface guards
var (
_ caddy.Provisioner = (*SRVUpstreams)(nil)
_ UpstreamSource = (*SRVUpstreams)(nil)
_ caddy.Provisioner = (*AUpstreams)(nil)
_ UpstreamSource = (*AUpstreams)(nil)
_ caddy.Provisioner = (*SRVUpstreams)(nil)
_ UpstreamSource = (*SRVUpstreams)(nil)
_ cachingUpstreamSource = (*SRVUpstreams)(nil)
_ caddy.Provisioner = (*AUpstreams)(nil)
_ UpstreamSource = (*AUpstreams)(nil)
)