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-rw-r--r--modules/caddyhttp/reverseproxy/circuitbreaker.go152
1 files changed, 152 insertions, 0 deletions
diff --git a/modules/caddyhttp/reverseproxy/circuitbreaker.go b/modules/caddyhttp/reverseproxy/circuitbreaker.go
new file mode 100644
index 0000000..de2a6f9
--- /dev/null
+++ b/modules/caddyhttp/reverseproxy/circuitbreaker.go
@@ -0,0 +1,152 @@
+// Copyright 2015 Matthew Holt and The Caddy Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package reverseproxy
+
+import (
+ "fmt"
+ "sync/atomic"
+ "time"
+
+ "github.com/caddyserver/caddy/v2"
+ "github.com/vulcand/oxy/memmetrics"
+)
+
+func init() {
+ caddy.RegisterModule(localCircuitBreaker{})
+}
+
+// localCircuitBreaker implements circuit breaking functionality
+// for requests within this process over a sliding time window.
+type localCircuitBreaker struct {
+ tripped int32
+ cbType int32
+ threshold float64
+ metrics *memmetrics.RTMetrics
+ tripTime time.Duration
+ Config
+}
+
+// CaddyModule returns the Caddy module information.
+func (localCircuitBreaker) CaddyModule() caddy.ModuleInfo {
+ return caddy.ModuleInfo{
+ Name: "http.handlers.reverse_proxy.circuit_breakers.local",
+ New: func() caddy.Module { return new(localCircuitBreaker) },
+ }
+}
+
+// Provision sets up a configured circuit breaker.
+func (c *localCircuitBreaker) Provision(ctx caddy.Context) error {
+ t, ok := typeCB[c.Type]
+ if !ok {
+ return fmt.Errorf("type is not defined")
+ }
+
+ if c.TripTime == "" {
+ c.TripTime = defaultTripTime
+ }
+
+ tw, err := time.ParseDuration(c.TripTime)
+ if err != nil {
+ return fmt.Errorf("cannot parse trip_time duration, %v", err.Error())
+ }
+
+ mt, err := memmetrics.NewRTMetrics()
+ if err != nil {
+ return fmt.Errorf("cannot create new metrics: %v", err.Error())
+ }
+
+ c.cbType = t
+ c.tripTime = tw
+ c.threshold = c.Threshold
+ c.metrics = mt
+ c.tripped = 0
+
+ return nil
+}
+
+// Ok returns whether the circuit breaker is tripped or not.
+func (c *localCircuitBreaker) Ok() bool {
+ tripped := atomic.LoadInt32(&c.tripped)
+ return tripped == 0
+}
+
+// RecordMetric records a response status code and execution time of a request. This function should be run in a separate goroutine.
+func (c *localCircuitBreaker) RecordMetric(statusCode int, latency time.Duration) {
+ c.metrics.Record(statusCode, latency)
+ c.checkAndSet()
+}
+
+// Ok checks our metrics to see if we should trip our circuit breaker, or if the fallback duration has completed.
+func (c *localCircuitBreaker) checkAndSet() {
+ var isTripped bool
+
+ switch c.cbType {
+ case typeErrorRatio:
+ // check if amount of network errors exceed threshold over sliding window, threshold for comparison should be < 1.0 i.e. .5 = 50th percentile
+ if c.metrics.NetworkErrorRatio() > c.threshold {
+ isTripped = true
+ }
+ case typeLatency:
+ // check if threshold in milliseconds is reached and trip
+ hist, err := c.metrics.LatencyHistogram()
+ if err != nil {
+ return
+ }
+
+ l := hist.LatencyAtQuantile(c.threshold)
+ if l.Nanoseconds()/int64(time.Millisecond) > int64(c.threshold) {
+ isTripped = true
+ }
+ case typeStatusCodeRatio:
+ // check ratio of error status codes of sliding window, threshold for comparison should be < 1.0 i.e. .5 = 50th percentile
+ if c.metrics.ResponseCodeRatio(500, 600, 0, 600) > c.threshold {
+ isTripped = true
+ }
+ }
+
+ if isTripped {
+ c.metrics.Reset()
+ atomic.AddInt32(&c.tripped, 1)
+
+ // wait tripTime amount before allowing operations to resume.
+ t := time.NewTimer(c.tripTime)
+ <-t.C
+
+ atomic.AddInt32(&c.tripped, -1)
+ }
+}
+
+// Config represents the configuration of a circuit breaker.
+type Config struct {
+ Threshold float64 `json:"threshold"`
+ Type string `json:"type"`
+ TripTime string `json:"trip_time"`
+}
+
+const (
+ typeLatency = iota + 1
+ typeErrorRatio
+ typeStatusCodeRatio
+ defaultTripTime = "5s"
+)
+
+var (
+ // typeCB handles converting a Config Type value to the internal circuit breaker types.
+ typeCB = map[string]int32{
+ "latency": typeLatency,
+ "error_ratio": typeErrorRatio,
+ "status_ratio": typeStatusCodeRatio,
+ }
+)