Passive health checks implemented (#2888)

Signed-off-by: Roman Zavodskikh <roman.zavodskikh@zalando.de>
Co-authored-by: Roman Zavodskikh <roman.zavodskikh@zalando.de>

config/config.go

@@ -285,6 +285,8 @@ type Config struct {
 	OpenPolicyAgentStartupTimeout       time.Duration `yaml:"open-policy-agent-startup-timeout"`
 	OpenPolicyAgentMaxRequestBodySize   int64         `yaml:"open-policy-agent-max-request-body-size"`
 	OpenPolicyAgentMaxMemoryBodyParsing int64         `yaml:"open-policy-agent-max-memory-body-parsing"`
+
+	PassiveHealthCheck mapFlags `yaml:"passive-health-check"`
 }
 
 const (
@@ -571,6 +573,9 @@ func NewConfig() *Config {
 	flag.Var(cfg.LuaModules, "lua-modules", "comma separated list of lua filter modules. Use <module>.<symbol> to selectively enable module symbols, for example: package,base._G,base.print,json")
 	flag.Var(cfg.LuaSources, "lua-sources", `comma separated list of lua input types for the lua() filter. Valid sources "", "file", "inline", "file,inline" and "none". Use "file" to only allow lua file references in lua filter. Default "" is the same as "file","inline". Use "none" to disable lua filters.`)
 
+	// Passive Health Checks
+	flag.Var(&cfg.PassiveHealthCheck, "passive-health-check", "sets the parameters for passive health check feature")
+
 	cfg.flags = flag
 	return cfg
 }
@@ -912,6 +917,8 @@ func (c *Config) ToOptions() skipper.Options {
 		OpenPolicyAgentStartupTimeout:       c.OpenPolicyAgentStartupTimeout,
 		OpenPolicyAgentMaxRequestBodySize:   c.OpenPolicyAgentMaxRequestBodySize,
 		OpenPolicyAgentMaxMemoryBodyParsing: c.OpenPolicyAgentMaxMemoryBodyParsing,
+
+		PassiveHealthCheck: c.PassiveHealthCheck.values,
 	}
 	for _, rcci := range c.CloneRoute {
 		eskipClone := eskip.NewClone(rcci.Reg, rcci.Repl)

docs/operation/operation.md

@@ -893,6 +893,34 @@ to get the results paginated or getting all of them at the same time.
 curl localhost:9911/routes?offset=200&limit=100
 ```
 
+## Passive health check (*experimental*)
+
+Skipper has an option to automatically detect and mitigate faulty backend endpoints, this feature is called
+Passive Health Check(PHC).
+
+PHC works the following way: the entire uptime is divided in chunks of `period`, per every period Skipper calculates
+the total amount of requests and amount of requests failed per every endpoint. While next period is going on,
+the Skipper takes a look at previous period and if the amount of requests in the previous period is more than `min-requests`
+for the given endpoints then Skipper will send reduced (the more `max-drop-probability`
+and failed requests ratio in previous period are, the stronger reduction is)
+amount of requests compared to amount sent without PHC.
+
+Having this, we expect less requests to fail because a lot of them would be sent to endpoints that seem to be healthy instead.
+
+To enable this feature, you need to provide `-passive-health-check` option having all forementioned parameters
+(`period`, `min-requests`, `max-drop-probability`) defined,
+for instance: `-passive-health-check=period=1s,min-requests=10,max-drop-probability=0.9`.
+
+You need to define all parameters on your side, there are no defaults, and skipper will not run if PHC params are passed only partially.
+
+However, Skipper will run without this feature, if no `-passive-health-check` is provided at all.
+
+The parameters of `-passive-health-check` option are:
++ `period=<duration>` - the duration of stats reset period
++ `min-requests=<int>` - the minimum number of requests per `period` per backend endpoint required to activate PHC for this endpoint
++ `max-drop-probabilty=<float more than/equal to 0 and less than/equal to 1>` - the maximum possible probability of unhealthy endpoint being not considered
+while choosing the endpoint for the given request
+
 ## Memory consumption
 
 While Skipper is generally not memory bound, some features may require

filters/fadein/fadein_test.go

@@ -236,6 +236,7 @@ func TestPostProcessor(t *testing.T) {
 		`
 
 		endpointRegistry := routing.NewEndpointRegistry(routing.RegistryOptions{})
+		defer endpointRegistry.Close()
 		rt, _ := createRouting(t, routes, endpointRegistry)
 
 		foo := route(rt, "/foo")
@@ -266,6 +267,7 @@ func TestPostProcessor(t *testing.T) {
 		`
 
 		endpointRegistry := routing.NewEndpointRegistry(routing.RegistryOptions{})
+		defer endpointRegistry.Close()
 		rt, _ := createRouting(t, routes, endpointRegistry)
 		r := route(rt, "/")
 		if r != nil {
@@ -278,13 +280,14 @@ func TestPostProcessor(t *testing.T) {
 			* -> fadeIn("-1m") -> <"http://10.0.0.1:8080">
 		`
 
-		endpointRegisty := routing.NewEndpointRegistry(routing.RegistryOptions{})
-		rt, _ := createRouting(t, routes, endpointRegisty)
+		endpointRegistry := routing.NewEndpointRegistry(routing.RegistryOptions{})
+		defer endpointRegistry.Close()
+		rt, _ := createRouting(t, routes, endpointRegistry)
 		r := route(rt, "/")
 		if r == nil || len(r.LBEndpoints) == 0 {
 			t.Fatal("failed to ignore negative duration")
 		}
-		if endpointRegisty.GetMetrics(r.LBEndpoints[0].Host).DetectedTime().IsZero() {
+		if endpointRegistry.GetMetrics(r.LBEndpoints[0].Host).DetectedTime().IsZero() {
 			t.Fatal("failed to ignore negative duration")
 		}
 	})
@@ -295,6 +298,7 @@ func TestPostProcessor(t *testing.T) {
 		`
 
 		endpointRegistry := routing.NewEndpointRegistry(routing.RegistryOptions{})
+		defer endpointRegistry.Close()
 		rt, update := createRouting(t, routes, endpointRegistry)
 		firstDetected := time.Now()
 
@@ -327,6 +331,7 @@ func TestPostProcessor(t *testing.T) {
 		`
 
 		endpointRegistry := routing.NewEndpointRegistry(routing.RegistryOptions{})
+		defer endpointRegistry.Close()
 		rt, update := createRouting(t, initialRoutes, endpointRegistry)
 		firstDetected := time.Now()
 
@@ -362,6 +367,7 @@ func TestPostProcessor(t *testing.T) {
 
 		const lastSeenTimeout = 2 * time.Second
 		endpointRegistry := routing.NewEndpointRegistry(routing.RegistryOptions{LastSeenTimeout: lastSeenTimeout})
+		defer endpointRegistry.Close()
 		rt, update := createRouting(t, initialRoutes, endpointRegistry)
 		firstDetected := time.Now()
 
@@ -397,6 +403,7 @@ func TestPostProcessor(t *testing.T) {
 		`
 
 		endpointRegistry := routing.NewEndpointRegistry(routing.RegistryOptions{})
+		defer endpointRegistry.Close()
 		routes := fmt.Sprintf(routesFmt, nows(t))
 		rt, update := createRouting(t, routes, endpointRegistry)
 		firstDetected := time.Now()

loadbalancer/algorithm_test.go

@@ -31,6 +31,7 @@ func TestSelectAlgorithm(t *testing.T) {
 	t.Run("LB route with default algorithm", func(t *testing.T) {
 		p := NewAlgorithmProvider()
 		endpointRegistry := routing.NewEndpointRegistry(routing.RegistryOptions{})
+		defer endpointRegistry.Close()
 		r := &routing.Route{
 			Route: eskip.Route{
 				BackendType: eskip.LBBackend,
@@ -59,6 +60,7 @@ func TestSelectAlgorithm(t *testing.T) {
 	t.Run("LB route with explicit round-robin algorithm", func(t *testing.T) {
 		p := NewAlgorithmProvider()
 		endpointRegistry := routing.NewEndpointRegistry(routing.RegistryOptions{})
+		defer endpointRegistry.Close()
 		r := &routing.Route{
 			Route: eskip.Route{
 				BackendType: eskip.LBBackend,
@@ -88,6 +90,7 @@ func TestSelectAlgorithm(t *testing.T) {
 	t.Run("LB route with explicit consistentHash algorithm", func(t *testing.T) {
 		p := NewAlgorithmProvider()
 		endpointRegistry := routing.NewEndpointRegistry(routing.RegistryOptions{})
+		defer endpointRegistry.Close()
 		r := &routing.Route{
 			Route: eskip.Route{
 				BackendType: eskip.LBBackend,
@@ -117,6 +120,7 @@ func TestSelectAlgorithm(t *testing.T) {
 	t.Run("LB route with explicit random algorithm", func(t *testing.T) {
 		p := NewAlgorithmProvider()
 		endpointRegistry := routing.NewEndpointRegistry(routing.RegistryOptions{})
+		defer endpointRegistry.Close()
 		r := &routing.Route{
 			Route: eskip.Route{
 				BackendType: eskip.LBBackend,
@@ -146,6 +150,7 @@ func TestSelectAlgorithm(t *testing.T) {
 	t.Run("LB route with explicit powerOfRandomNChoices algorithm", func(t *testing.T) {
 		p := NewAlgorithmProvider()
 		endpointRegistry := routing.NewEndpointRegistry(routing.RegistryOptions{})
+		defer endpointRegistry.Close()
 		r := &routing.Route{
 			Route: eskip.Route{
 				BackendType: eskip.LBBackend,
@@ -260,6 +265,7 @@ func TestApply(t *testing.T) {
 			req, _ := http.NewRequest("GET", "http://127.0.0.1:1234/foo", nil)
 			p := NewAlgorithmProvider()
 			endpointRegistry := routing.NewEndpointRegistry(routing.RegistryOptions{})
+			defer endpointRegistry.Close()
 			r := &routing.Route{
 				Route: eskip.Route{
 					BackendType: eskip.LBBackend,
@@ -293,6 +299,7 @@ func TestConsistentHashSearch(t *testing.T) {
 	apply := func(key string, endpoints []string) string {
 		p := NewAlgorithmProvider()
 		endpointRegistry := routing.NewEndpointRegistry(routing.RegistryOptions{})
+		defer endpointRegistry.Close()
 		r := &routing.Route{
 			Route: eskip.Route{
 				BackendType: eskip.LBBackend,
@@ -349,6 +356,7 @@ func TestConsistentHashBoundedLoadSearch(t *testing.T) {
 		Params:      map[string]interface{}{ConsistentHashBalanceFactor: 1.25},
 	}
 	endpointRegistry := routing.NewEndpointRegistry(routing.RegistryOptions{})
+	defer endpointRegistry.Close()
 	endpointRegistry.Do([]*routing.Route{route})
 	noLoad := ch.Apply(ctx)
 	nonBounded := ch.Apply(&routing.LBContext{Request: r, Route: route, LBEndpoints: route.LBEndpoints, Params: map[string]interface{}{}})
@@ -429,6 +437,7 @@ func TestConsistentHashBoundedLoadDistribution(t *testing.T) {
 		Params:      map[string]interface{}{ConsistentHashBalanceFactor: balanceFactor},
 	}
 	endpointRegistry := routing.NewEndpointRegistry(routing.RegistryOptions{})
+	defer endpointRegistry.Close()
 	endpointRegistry.Do([]*routing.Route{route})
 
 	for i := 0; i < 100; i++ {

metricsinit_test.go

@@ -53,6 +53,11 @@ func TestInitOrderAndDefault(t *testing.T) {
 			SwarmRedisURLs:                []string{fmt.Sprintf("localhost:%d", redisPort)},
 			EnableRatelimiters:            true,
 			SwarmRedisConnMetricsInterval: ringMetricsUpdatePeriod,
+			PassiveHealthCheck: map[string]string{
+				"period":               "1m",
+				"min-requests":         "10",
+				"max-drop-probability": "0.9",
+			},
 		}
 
 		tornDown := make(chan struct{})

proxy/fadein_internal_test.go

@@ -92,7 +92,7 @@ func initializeEndpoints(endpointAges []float64, algorithmName string, fadeInDur
 		registry.GetMetrics(eps[i]).SetDetected(detectionTimes[i])
 	}
 
-	proxy := &Proxy{registry: registry, fadein: &fadeIn{rnd: rand.New(loadbalancer.NewLockedSource()), endpointRegistry: registry}}
+	proxy := &Proxy{registry: registry, fadein: &fadeIn{rnd: rand.New(loadbalancer.NewLockedSource()), endpointRegistry: registry}, quit: make(chan struct{})}
 	return route, proxy, eps
 }
 
@@ -103,6 +103,7 @@ func calculateFadeInDuration(t *testing.T, algorithmName string, endpointAges []
 	const precalculateRatio = 10
 
 	route, proxy, _ := initializeEndpoints(endpointAges, algorithmName, defaultFadeInDuration)
+	defer proxy.Close()
 	rnd := rand.New(rand.NewSource(time.Now().UnixNano()))
 
 	t.Log("preemulation start", time.Now())
@@ -125,6 +126,7 @@ func testFadeInMonotony(
 	t.Run(name, func(t *testing.T) {
 		fadeInDuration := calculateFadeInDuration(t, algorithmName, endpointAges)
 		route, proxy, eps := initializeEndpoints(endpointAges, algorithmName, fadeInDuration)
+		defer proxy.Close()
 
 		t.Log("test start", time.Now())
 		var stats []string
@@ -273,6 +275,7 @@ func testFadeInLoadBetweenOldAndNewEps(
 		}
 
 		route, proxy, eps := initializeEndpoints(endpointAges, algorithmName, defaultFadeInDurationHuge)
+		defer proxy.Close()
 		rnd := rand.New(rand.NewSource(time.Now().UnixNano()))
 		nReqs := map[string]int{}
 
@@ -330,6 +333,7 @@ func testSelectEndpointEndsWhenAllEndpointsAreFading(
 		// Initialize every endpoint with zero: every endpoint is new
 		endpointAges := make([]float64, nEndpoints)
 		route, proxy, _ := initializeEndpoints(endpointAges, algorithmName, defaultFadeInDurationHuge)
+		defer proxy.Close()
 		applied := make(chan struct{})
 
 		go func() {
@@ -364,6 +368,7 @@ func benchmarkFadeIn(
 ) {
 	b.Run(name, func(b *testing.B) {
 		route, proxy, _ := initializeEndpoints(endpointAges, algorithmName, defaultFadeInDurationHuge)
+		defer proxy.Close()
 		var wg sync.WaitGroup
 
 		// Emulate the load balancer loop, sending requests to it with random hash keys

proxy/healthy_endpoints.go

@@ -0,0 +1,34 @@
+package proxy
+
+import (
+	"math/rand"
+
+	"github.com/zalando/skipper/routing"
+)
+
+type healthyEndpoints struct {
+	rnd              *rand.Rand
+	endpointRegistry *routing.EndpointRegistry
+}
+
+func (h *healthyEndpoints) filterHealthyEndpoints(endpoints []routing.LBEndpoint, rt *routing.Route) []routing.LBEndpoint {
+	if h == nil {
+		return endpoints
+	}
+
+	p := h.rnd.Float64()
+
+	filtered := make([]routing.LBEndpoint, 0, len(endpoints))
+	for _, e := range endpoints {
+		if p < e.Metrics.HealthCheckDropProbability() {
+			/* drop */
+		} else {
+			filtered = append(filtered, e)
+		}
+	}
+
+	if len(filtered) == 0 {
+		return endpoints
+	}
+	return filtered
+}