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reverseproxy: Implement retry count, alternative to try_duration (#4756)

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* reverseproxy: Implement retry count, alternative to try_duration

* Add Caddyfile support for `retry_match`

* Refactor to deduplicate matcher parsing logic

* Fix lint
This commit is contained in:
Francis Lavoie 2022-07-13 16:15:00 -04:00 committed by GitHub
parent 04a14ee37a
commit 7d1f7771c9
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GPG key ID: 4AEE18F83AFDEB23
4 changed files with 189 additions and 69 deletions
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64
caddytest/integration/caddyfile_adapt/reverse_proxy_load_balance.txt Normal file
View file

@ -0,0 +1,64 @@
:8884
reverse_proxy 127.0.0.1:65535 {
lb_policy first
lb_retries 5
lb_try_duration 10s
lb_try_interval 500ms
lb_retry_match {
path /foo*
method POST
}
lb_retry_match path /bar*
}
----------
{
"apps": {
"http": {
"servers": {
"srv0": {
"listen": [
":8884"
],
"routes": [
{
"handle": [
{
"handler": "reverse_proxy",
"load_balancing": {
"retries": 5,
"retry_match": [
{
"method": [
"POST"
],
"path": [
"/foo*"
]
},
{
"path": [
"/bar*"
]
}
],
"selection_policy": {
"policy": "first"
},
"try_duration": 10000000000,
"try_interval": 500000000
},
"upstreams": [
{
"dial": "127.0.0.1:65535"
}
]
}
]
}
]
}
}
}
}
}

99
modules/caddyhttp/matchers.go
View file

@ -1003,57 +1003,12 @@ func (MatchNot) CaddyModule() caddy.ModuleInfo {
// UnmarshalCaddyfile implements caddyfile.Unmarshaler.
func (m *MatchNot) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
// first, unmarshal each matcher in the set from its tokens
type matcherPair struct {
raw caddy.ModuleMap
decoded MatcherSet
}
for d.Next() {
var mp matcherPair
matcherMap := make(map[string]RequestMatcher)
// in case there are multiple instances of the same matcher, concatenate
// their tokens (we expect that UnmarshalCaddyfile should be able to
// handle more than one segment); otherwise, we'd overwrite other
// instances of the matcher in this set
tokensByMatcherName := make(map[string][]caddyfile.Token)
for nesting := d.Nesting(); d.NextArg() || d.NextBlock(nesting); {
matcherName := d.Val()
tokensByMatcherName[matcherName] = append(tokensByMatcherName[matcherName], d.NextSegment()...)
}
for matcherName, tokens := range tokensByMatcherName {
mod, err := caddy.GetModule("http.matchers." + matcherName)
if err != nil {
return d.Errf("getting matcher module '%s': %v", matcherName, err)
}
unm, ok := mod.New().(caddyfile.Unmarshaler)
if !ok {
return d.Errf("matcher module '%s' is not a Caddyfile unmarshaler", matcherName)
}
err = unm.UnmarshalCaddyfile(caddyfile.NewDispenser(tokens))
matcherSet, err := ParseCaddyfileNestedMatcherSet(d)
if err != nil {
return err
}
rm, ok := unm.(RequestMatcher)
if !ok {
return fmt.Errorf("matcher module '%s' is not a request matcher", matcherName)
}
matcherMap[matcherName] = rm
mp.decoded = append(mp.decoded, rm)
}
// we should now have a functional 'not' matcher, but we also
// need to be able to marshal as JSON, otherwise config
// adaptation will be missing the matchers!
mp.raw = make(caddy.ModuleMap)
for name, matcher := range matcherMap {
jsonBytes, err := json.Marshal(matcher)
if err != nil {
return fmt.Errorf("marshaling %T matcher: %v", matcher, err)
}
mp.raw[name] = jsonBytes
}
m.MatcherSetsRaw = append(m.MatcherSetsRaw, mp.raw)
m.MatcherSetsRaw = append(m.MatcherSetsRaw, matcherSet)
}
return nil
}
@ -1352,6 +1307,56 @@ func (mre *MatchRegexp) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
return nil
}
// ParseCaddyfileNestedMatcher parses the Caddyfile tokens for a nested
// matcher set, and returns its raw module map value.
func ParseCaddyfileNestedMatcherSet(d *caddyfile.Dispenser) (caddy.ModuleMap, error) {
matcherMap := make(map[string]RequestMatcher)
// in case there are multiple instances of the same matcher, concatenate
// their tokens (we expect that UnmarshalCaddyfile should be able to
// handle more than one segment); otherwise, we'd overwrite other
// instances of the matcher in this set
tokensByMatcherName := make(map[string][]caddyfile.Token)
for nesting := d.Nesting(); d.NextArg() || d.NextBlock(nesting); {
matcherName := d.Val()
tokensByMatcherName[matcherName] = append(tokensByMatcherName[matcherName], d.NextSegment()...)
}
for matcherName, tokens := range tokensByMatcherName {
mod, err := caddy.GetModule("http.matchers." + matcherName)
if err != nil {
return nil, d.Errf("getting matcher module '%s': %v", matcherName, err)
}
unm, ok := mod.New().(caddyfile.Unmarshaler)
if !ok {
return nil, d.Errf("matcher module '%s' is not a Caddyfile unmarshaler", matcherName)
}
err = unm.UnmarshalCaddyfile(caddyfile.NewDispenser(tokens))
if err != nil {
return nil, err
}
rm, ok := unm.(RequestMatcher)
if !ok {
return nil, fmt.Errorf("matcher module '%s' is not a request matcher", matcherName)
}
matcherMap[matcherName] = rm
}
// we should now have a functional matcher, but we also
// need to be able to marshal as JSON, otherwise config
// adaptation will be missing the matchers!
matcherSet := make(caddy.ModuleMap)
for name, matcher := range matcherMap {
jsonBytes, err := json.Marshal(matcher)
if err != nil {
return nil, fmt.Errorf("marshaling %T matcher: %v", matcher, err)
}
matcherSet[name] = jsonBytes
}
return matcherSet, nil
}
var (
wordRE = regexp.MustCompile(`\w+`)
)

25
modules/caddyhttp/reverseproxy/caddyfile.go
View file

@ -59,8 +59,10 @@ func parseCaddyfile(h httpcaddyfile.Helper) (caddyhttp.MiddlewareHandler, error)
//
// # load balancing
// lb_policy <name> [<options...>]
// lb_retries <retries>
// lb_try_duration <duration>
// lb_try_interval <interval>
// lb_retry_match <request-matcher>
//
// # active health checking
// health_uri <uri>
@ -247,6 +249,19 @@ func (h *Handler) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
}
h.LoadBalancing.SelectionPolicyRaw = caddyconfig.JSONModuleObject(sel, "policy", name, nil)
case "lb_retries":
if !d.NextArg() {
return d.ArgErr()
}
tries, err := strconv.Atoi(d.Val())
if err != nil {
return d.Errf("bad lb_retries number '%s': %v", d.Val(), err)
}
if h.LoadBalancing == nil {
h.LoadBalancing = new(LoadBalancing)
}
h.LoadBalancing.Retries = tries
case "lb_try_duration":
if !d.NextArg() {
return d.ArgErr()
@ -273,6 +288,16 @@ func (h *Handler) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
}
h.LoadBalancing.TryInterval = caddy.Duration(dur)
case "lb_retry_match":
matcherSet, err := caddyhttp.ParseCaddyfileNestedMatcherSet(d)
if err != nil {
return d.Errf("failed to parse lb_retry_match: %v", err)
}
if h.LoadBalancing == nil {
h.LoadBalancing = new(LoadBalancing)
}
h.LoadBalancing.RetryMatchRaw = append(h.LoadBalancing.RetryMatchRaw, matcherSet)
case "health_uri":
if !d.NextArg() {
return d.ArgErr()

66
modules/caddyhttp/reverseproxy/reverseproxy.go
View file

@ -430,12 +430,14 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyht
// and because we may retry some number of times, carry over the error
// from previous tries because of the nuances of load balancing & retries
var proxyErr error
var retries int
for {
var done bool
done, proxyErr = h.proxyLoopIteration(clonedReq, r, w, proxyErr, start, repl, reqHeader, reqHost, next)
done, proxyErr = h.proxyLoopIteration(clonedReq, r, w, proxyErr, start, retries, repl, reqHeader, reqHost, next)
if done {
break
}
retries++
}
if proxyErr != nil {
@ -449,7 +451,7 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyht
// that has to be passed in, we brought this into its own method so that we could run defer more easily.
// It returns true when the loop is done and should break; false otherwise. The error value returned should
// be assigned to the proxyErr value for the next iteration of the loop (or the error handled after break).
func (h *Handler) proxyLoopIteration(r *http.Request, origReq *http.Request, w http.ResponseWriter, proxyErr error, start time.Time,
func (h *Handler) proxyLoopIteration(r *http.Request, origReq *http.Request, w http.ResponseWriter, proxyErr error, start time.Time, retries int,
repl *caddy.Replacer, reqHeader http.Header, reqHost string, next caddyhttp.Handler) (bool, error) {
// get the updated list of upstreams
upstreams := h.Upstreams
@ -479,7 +481,7 @@ func (h *Handler) proxyLoopIteration(r *http.Request, origReq *http.Request, w h
if proxyErr == nil {
proxyErr = caddyhttp.Error(http.StatusServiceUnavailable, fmt.Errorf("no upstreams available"))
}
if !h.LoadBalancing.tryAgain(h.ctx, start, proxyErr, r) {
if !h.LoadBalancing.tryAgain(h.ctx, start, retries, proxyErr, r) {
return true, proxyErr
}
return false, proxyErr
@ -542,7 +544,7 @@ func (h *Handler) proxyLoopIteration(r *http.Request, origReq *http.Request, w h
h.countFailure(upstream)
// if we've tried long enough, break
if !h.LoadBalancing.tryAgain(h.ctx, start, proxyErr, r) {
if !h.LoadBalancing.tryAgain(h.ctx, start, retries, proxyErr, r) {
return true, proxyErr
}
@ -944,16 +946,26 @@ func (h Handler) finalizeResponse(
return nil
}
// tryAgain takes the time that the handler was initially invoked
// as well as any error currently obtained, and the request being
// tried, and returns true if another attempt should be made at
// proxying the request. If true is returned, it has already blocked
// long enough before the next retry (i.e. no more sleeping is
// needed). If false is returned, the handler should stop trying to
// proxy the request.
func (lb LoadBalancing) tryAgain(ctx caddy.Context, start time.Time, proxyErr error, req *http.Request) bool {
// tryAgain takes the time that the handler was initially invoked,
// the amount of retries already performed, as well as any error
// currently obtained, and the request being tried, and returns
// true if another attempt should be made at proxying the request.
// If true is returned, it has already blocked long enough before
// the next retry (i.e. no more sleeping is needed). If false is
// returned, the handler should stop trying to proxy the request.
func (lb LoadBalancing) tryAgain(ctx caddy.Context, start time.Time, retries int, proxyErr error, req *http.Request) bool {
// no retries are configured
if lb.TryDuration == 0 && lb.Retries == 0 {
return false
}
// if we've tried long enough, break
if time.Since(start) >= time.Duration(lb.TryDuration) {
if lb.TryDuration > 0 && time.Since(start) >= time.Duration(lb.TryDuration) {
return false
}
// if we've reached the retry limit, break
if lb.Retries > 0 && retries >= lb.Retries {
return false
}
@ -976,6 +988,11 @@ func (lb LoadBalancing) tryAgain(ctx caddy.Context, start time.Time, proxyErr er
}
}
// fast path; if the interval is zero, we don't need to wait
if lb.TryInterval == 0 {
return true
}
// otherwise, wait and try the next available host
timer := time.NewTimer(time.Duration(lb.TryInterval))
select {
@ -1190,16 +1207,25 @@ type LoadBalancing struct {
// The default policy is random selection.
SelectionPolicyRaw json.RawMessage `json:"selection_policy,omitempty" caddy:"namespace=http.reverse_proxy.selection_policies inline_key=policy"`
// How many times to retry selecting available backends for each
// request if the next available host is down. If try_duration is
// also configured, then retries may stop early if the duration
// is reached. By default, retries are disabled (zero).
Retries int `json:"retries,omitempty"`
// How long to try selecting available backends for each request
// if the next available host is down. By default, this retry is
// disabled. Clients will wait for up to this long while the load
// balancer tries to find an available upstream host.
// if the next available host is down. Clients will wait for up
// to this long while the load balancer tries to find an available
// upstream host. If retries is also configured, tries may stop
// early if the maximum retries is reached. By default, retries
// are disabled (zero duration).
TryDuration caddy.Duration `json:"try_duration,omitempty"`
// How long to wait between selecting the next host from the pool. Default
// is 250ms. Only relevant when a request to an upstream host fails. Be
// aware that setting this to 0 with a non-zero try_duration can cause the
// CPU to spin if all backends are down and latency is very low.
// How long to wait between selecting the next host from the pool.
// Default is 250ms if try_duration is enabled, otherwise zero. Only
// relevant when a request to an upstream host fails. Be aware that
// setting this to 0 with a non-zero try_duration can cause the CPU
// to spin if all backends are down and latency is very low.
TryInterval caddy.Duration `json:"try_interval,omitempty"`
// A list of matcher sets that restricts with which requests retries are