From 06ac7020e25bb3e9f9791a99d60cc05d2afaf9af Mon Sep 17 00:00:00 2001
From: Mustafa Abdelrahman <mustafa.abdelrahman@zalando.de>
Date: Mon, 22 Apr 2024 16:47:05 +0200
Subject: [PATCH] add a counter for endpoints that opted out before
 loadbalancing

Signed-off-by: Mustafa Abdelrahman <mustafa.abdelrahman@zalando.de>
---
 docs/operation/operation.md | 6 ++++++
 proxy/healthy_endpoints.go  | 4 +++-
 proxy/proxy.go              | 2 +-
 3 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/docs/operation/operation.md b/docs/operation/operation.md
index b530f1f339..6239a6e47b 100644
--- a/docs/operation/operation.md
+++ b/docs/operation/operation.md
@@ -921,6 +921,12 @@ The parameters of `-passive-health-check` option are:
 + `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
 
+### Metrics
+
+A set of metrics will be exposed to track passive health checks:
+
+* `routing.endpoint.drop.loadbalancer`: Number of endpoints dropped before load balancing the requests 
+
 ## Memory consumption
 
 While Skipper is generally not memory bound, some features may require
diff --git a/proxy/healthy_endpoints.go b/proxy/healthy_endpoints.go
index b79a132769..c902a2949d 100644
--- a/proxy/healthy_endpoints.go
+++ b/proxy/healthy_endpoints.go
@@ -3,6 +3,7 @@ package proxy
 import (
 	"math/rand"
 
+	"github.com/zalando/skipper/metrics"
 	"github.com/zalando/skipper/routing"
 )
 
@@ -11,7 +12,7 @@ type healthyEndpoints struct {
 	endpointRegistry *routing.EndpointRegistry
 }
 
-func (h *healthyEndpoints) filterHealthyEndpoints(endpoints []routing.LBEndpoint, rt *routing.Route) []routing.LBEndpoint {
+func (h *healthyEndpoints) filterHealthyEndpoints(endpoints []routing.LBEndpoint, metrics metrics.Metrics) []routing.LBEndpoint {
 	if h == nil {
 		return endpoints
 	}
@@ -22,6 +23,7 @@ func (h *healthyEndpoints) filterHealthyEndpoints(endpoints []routing.LBEndpoint
 	for _, e := range endpoints {
 		if p < e.Metrics.HealthCheckDropProbability() {
 			/* drop */
+			metrics.IncCounter("routing.endpoint.drop.loadbalancer")
 		} else {
 			filtered = append(filtered, e)
 		}
diff --git a/proxy/proxy.go b/proxy/proxy.go
index 6e0616530b..a7f309f49d 100644
--- a/proxy/proxy.go
+++ b/proxy/proxy.go
@@ -540,7 +540,7 @@ func (p *Proxy) selectEndpoint(ctx *context) *routing.LBEndpoint {
 	rt := ctx.route
 	endpoints := rt.LBEndpoints
 	endpoints = p.fadein.filterFadeIn(endpoints, rt)
-	endpoints = p.heathlyEndpoints.filterHealthyEndpoints(endpoints, rt)
+	endpoints = p.heathlyEndpoints.filterHealthyEndpoints(endpoints, p.metrics)
 
 	lbctx := &routing.LBContext{
 		Request:     ctx.request,