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-rw-r--r--modules/caddyhttp/reverseproxy/healthchecks.go10
-rw-r--r--modules/caddyhttp/reverseproxy/hosts.go10
-rw-r--r--modules/caddyhttp/reverseproxy/reverseproxy.go18
3 files changed, 36 insertions, 2 deletions
diff --git a/modules/caddyhttp/reverseproxy/healthchecks.go b/modules/caddyhttp/reverseproxy/healthchecks.go
index 0b46d04..673f7c4 100644
--- a/modules/caddyhttp/reverseproxy/healthchecks.go
+++ b/modules/caddyhttp/reverseproxy/healthchecks.go
@@ -64,6 +64,14 @@ type PassiveHealthChecks struct {
UnhealthyLatency caddy.Duration `json:"unhealthy_latency,omitempty"`
}
+// CircuitBreaker is a type that can act as an early-warning
+// system for the health checker when backends are getting
+// overloaded.
+type CircuitBreaker interface {
+ OK() bool
+ RecordMetric(statusCode int, latency time.Duration)
+}
+
// activeHealthChecker runs active health checks on a
// regular basis and blocks until
// h.HealthChecks.Active.stopChan is closed.
@@ -202,7 +210,7 @@ func (h *Handler) doActiveHealthCheck(hostAddr string, host Host) error {
// remembers 1 failure for upstream for the configured
// duration. If passive health checks are disabled or
// failure expiry is 0, this is a no-op.
-func (h Handler) countFailure(upstream *Upstream) {
+func (h *Handler) countFailure(upstream *Upstream) {
// only count failures if passive health checking is enabled
// and if failures are configured have a non-zero expiry
if h.HealthChecks == nil || h.HealthChecks.Passive == nil {
diff --git a/modules/caddyhttp/reverseproxy/hosts.go b/modules/caddyhttp/reverseproxy/hosts.go
index 5100936..b40e614 100644
--- a/modules/caddyhttp/reverseproxy/hosts.go
+++ b/modules/caddyhttp/reverseproxy/hosts.go
@@ -69,21 +69,29 @@ type Upstream struct {
healthCheckPolicy *PassiveHealthChecks
hostURL *url.URL
+ cb CircuitBreaker
}
// Available returns true if the remote host
-// is available to receive requests.
+// is available to receive requests. This is
+// the method that should be used by selection
+// policies, etc. to determine if a backend
+// should be able to be sent a request.
func (u *Upstream) Available() bool {
return u.Healthy() && !u.Full()
}
// Healthy returns true if the remote host
// is currently known to be healthy or "up".
+// It consults the circuit breaker, if any.
func (u *Upstream) Healthy() bool {
healthy := !u.Host.Unhealthy()
if healthy && u.healthCheckPolicy != nil {
healthy = u.Host.Fails() < u.healthCheckPolicy.MaxFails
}
+ if healthy && u.cb != nil {
+ healthy = u.cb.OK()
+ }
return healthy
}
diff --git a/modules/caddyhttp/reverseproxy/reverseproxy.go b/modules/caddyhttp/reverseproxy/reverseproxy.go
index ca54741..16d7f7a 100644
--- a/modules/caddyhttp/reverseproxy/reverseproxy.go
+++ b/modules/caddyhttp/reverseproxy/reverseproxy.go
@@ -37,12 +37,14 @@ func init() {
// Handler implements a highly configurable and production-ready reverse proxy.
type Handler struct {
TransportRaw json.RawMessage `json:"transport,omitempty"`
+ CBRaw json.RawMessage `json:"circuit_breaker,omitempty"`
LoadBalancing *LoadBalancing `json:"load_balancing,omitempty"`
HealthChecks *HealthChecks `json:"health_checks,omitempty"`
Upstreams UpstreamPool `json:"upstreams,omitempty"`
FlushInterval caddy.Duration `json:"flush_interval,omitempty"`
Transport http.RoundTripper `json:"-"`
+ CB CircuitBreaker `json:"-"`
}
// CaddyModule returns the Caddy module information.
@@ -55,6 +57,7 @@ func (Handler) CaddyModule() caddy.ModuleInfo {
// Provision ensures that h is set up properly before use.
func (h *Handler) Provision(ctx caddy.Context) error {
+ // start by loading modules
if h.TransportRaw != nil {
val, err := ctx.LoadModuleInline("protocol", "http.handlers.reverse_proxy.transport", h.TransportRaw)
if err != nil {
@@ -73,6 +76,14 @@ func (h *Handler) Provision(ctx caddy.Context) error {
h.LoadBalancing.SelectionPolicy = val.(Selector)
h.LoadBalancing.SelectionPolicyRaw = nil // allow GC to deallocate - TODO: Does this help?
}
+ if h.CBRaw != nil {
+ val, err := ctx.LoadModuleInline("type", "http.handlers.reverse_proxy.circuit_breakers", h.CBRaw)
+ if err != nil {
+ return fmt.Errorf("loading circuit breaker module: %s", err)
+ }
+ h.CB = val.(CircuitBreaker)
+ h.CBRaw = nil // allow GC to deallocate - TODO: Does this help?
+ }
if h.Transport == nil {
h.Transport = defaultTransport
@@ -123,6 +134,8 @@ func (h *Handler) Provision(ctx caddy.Context) error {
}
for _, upstream := range h.Upstreams {
+ upstream.cb = h.CB
+
// url parser requires a scheme
if !strings.Contains(upstream.Address, "://") {
upstream.Address = "http://" + upstream.Address
@@ -307,6 +320,11 @@ func (h *Handler) reverseProxy(rw http.ResponseWriter, req *http.Request, upstre
return err
}
+ // update circuit breaker on current conditions
+ if upstream.cb != nil {
+ upstream.cb.RecordMetric(res.StatusCode, latency)
+ }
+
// perform passive health checks (if enabled)
if h.HealthChecks != nil && h.HealthChecks.Passive != nil {
// strike if the status code matches one that is "bad"