Add Prometheus support for APK

adapter/config/default_config.go

@@ -32,6 +32,11 @@ var defaultConfig = &Config{
 			Namespaces: nil,
 		},
 		Environment: "Default",
+		Metrics: metrics{
+			Enabled: false,
+			Type:    "prometheus",
+			Port:    18006,
+		},
 	},
 	Envoy: envoy{
 		ListenerCodecType: "AUTO",

adapter/config/types.go

@@ -93,6 +93,8 @@ type adapter struct {
 	Operator operator
 	// Environment of the Adapter
 	Environment string
+	// Metric represents configurations to expose/export go metrics
+	Metrics metrics
 }
 
 // Envoy Listener Component related configurations.
@@ -299,8 +301,10 @@ type tracing struct {
 }
 
 type metrics struct {
-	Enabled bool
-	Type    string
+	Enabled            bool
+	Type               string
+	Port               int32
+	CollectionInterval int32
 }
 
 type analyticsAdapter struct {

adapter/go.mod

@@ -10,6 +10,7 @@ require (
 	github.com/onsi/ginkgo/v2 v2.11.0
 	github.com/onsi/gomega v1.27.10
 	github.com/pelletier/go-toml v1.9.5
+	github.com/prometheus/client_golang v1.17.0
 	github.com/sirupsen/logrus v1.9.0
 	github.com/wso2/apk/common-go-libs v0.0.0-20231208100153-24bee7b4bd81
 	golang.org/x/exp v0.0.0-20231206192017-f3f8817b8deb
@@ -34,6 +35,7 @@ require (
 	github.com/evanphx/json-patch/v5 v5.7.0 // indirect
 	github.com/go-logr/logr v1.2.4 // indirect
 	github.com/go-logr/zapr v1.2.4 // indirect
+	github.com/go-ole/go-ole v1.2.6 // indirect
 	github.com/go-openapi/jsonpointer v0.20.0 // indirect
 	github.com/go-openapi/jsonreference v0.20.2 // indirect
 	github.com/go-openapi/swag v0.22.4 // indirect
@@ -47,19 +49,25 @@ require (
 	github.com/imdario/mergo v0.3.16 // indirect
 	github.com/josharian/intern v1.0.0 // indirect
 	github.com/json-iterator/go v1.1.12 // indirect
+	github.com/lufia/plan9stats v0.0.0-20211012122336-39d0f177ccd0 // indirect
 	github.com/mailru/easyjson v0.7.7 // indirect
 	github.com/matttproud/golang_protobuf_extensions/v2 v2.0.0 // indirect
 	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
 	github.com/modern-go/reflect2 v1.0.2 // indirect
 	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
 	github.com/pkg/errors v0.9.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
-	github.com/prometheus/client_golang v1.17.0 // indirect
+	github.com/power-devops/perfstat v0.0.0-20210106213030-5aafc221ea8c // indirect
 	github.com/prometheus/client_model v0.5.0 // indirect
 	github.com/prometheus/common v0.45.0 // indirect
 	github.com/prometheus/procfs v0.12.0 // indirect
+	github.com/shirou/gopsutil/v3 v3.24.2 // indirect
+	github.com/shoenig/go-m1cpu v0.1.6 // indirect
 	github.com/spf13/pflag v1.0.5 // indirect
+	github.com/tklauser/go-sysconf v0.3.12 // indirect
+	github.com/tklauser/numcpus v0.6.1 // indirect
 	github.com/vektah/gqlparser v1.3.1 // indirect
+	github.com/yusufpapurcu/wmi v1.2.4 // indirect
 	go.uber.org/multierr v1.11.0 // indirect
 	go.uber.org/zap v1.26.0 // indirect
 	golang.org/x/net v0.21.0 // indirect

adapter/go.sum

@@ -41,6 +41,8 @@ github.com/go-logr/logr v1.2.4 h1:g01GSCwiDw2xSZfjJ2/T9M+S6pFdcNtFYsp+Y43HYDQ=
 github.com/go-logr/logr v1.2.4/go.mod h1:jdQByPbusPIv2/zmleS9BjJVeZ6kBagPoEUsqbVz/1A=
 github.com/go-logr/zapr v1.2.4 h1:QHVo+6stLbfJmYGkQ7uGHUCu5hnAFAj6mDe6Ea0SeOo=
 github.com/go-logr/zapr v1.2.4/go.mod h1:FyHWQIzQORZ0QVE1BtVHv3cKtNLuXsbNLtpuhNapBOA=
+github.com/go-ole/go-ole v1.2.6 h1:/Fpf6oFPoeFik9ty7siob0G6Ke8QvQEuVcuChpwXzpY=
+github.com/go-ole/go-ole v1.2.6/go.mod h1:pprOEPIfldk/42T2oK7lQ4v4JSDwmV0As9GaiUsvbm0=
 github.com/go-openapi/jsonpointer v0.19.6/go.mod h1:osyAmYz/mB/C3I+WsTTSgw1ONzaLJoLCyoi6/zppojs=
 github.com/go-openapi/jsonpointer v0.20.0 h1:ESKJdU9ASRfaPNOPRx12IUyA1vn3R9GiE3KYD14BXdQ=
 github.com/go-openapi/jsonpointer v0.20.0/go.mod h1:6PGzBjjIIumbLYysB73Klnms1mwnU4G3YHOECG3CedA=
@@ -62,6 +64,7 @@ github.com/golang/protobuf v1.5.3/go.mod h1:XVQd3VNwM+JqD3oG2Ue2ip4fOMUkwXdXDdiu
 github.com/google/gnostic-models v0.6.8 h1:yo/ABAfM5IMRsS1VnXjTBvUb61tFIHozhlYvRgGre9I=
 github.com/google/gnostic-models v0.6.8/go.mod h1:5n7qKqH0f5wFt+aWF8CW6pZLLNOfYuF5OpfBSENuI8U=
 github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
+github.com/google/go-cmp v0.5.6/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/go-cmp v0.5.9/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
 github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
@@ -88,6 +91,8 @@ github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
 github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
 github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
 github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
+github.com/lufia/plan9stats v0.0.0-20211012122336-39d0f177ccd0 h1:6E+4a0GO5zZEnZ81pIr0yLvtUWk2if982qA3F3QD6H4=
+github.com/lufia/plan9stats v0.0.0-20211012122336-39d0f177ccd0/go.mod h1:zJYVVT2jmtg6P3p1VtQj7WsuWi/y4VnjVBn7F8KPB3I=
 github.com/mailru/easyjson v0.7.7 h1:UGYAvKxe3sBsEDzO8ZeWOSlIQfWFlxbzLZe7hwFURr0=
 github.com/mailru/easyjson v0.7.7/go.mod h1:xzfreul335JAWq5oZzymOObrkdz5UnU4kGfJJLY9Nlc=
 github.com/matttproud/golang_protobuf_extensions/v2 v2.0.0 h1:jWpvCLoY8Z/e3VKvlsiIGKtc+UG6U5vzxaoagmhXfyg=
@@ -110,6 +115,8 @@ github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
 github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/power-devops/perfstat v0.0.0-20210106213030-5aafc221ea8c h1:ncq/mPwQF4JjgDlrVEn3C11VoGHZN7m8qihwgMEtzYw=
+github.com/power-devops/perfstat v0.0.0-20210106213030-5aafc221ea8c/go.mod h1:OmDBASR4679mdNQnz2pUhc2G8CO2JrUAVFDRBDP/hJE=
 github.com/prometheus/client_golang v1.17.0 h1:rl2sfwZMtSthVU752MqfjQozy7blglC+1SOtjMAMh+Q=
 github.com/prometheus/client_golang v1.17.0/go.mod h1:VeL+gMmOAxkS2IqfCq0ZmHSL+LjWfWDUmp1mBz9JgUY=
 github.com/prometheus/client_model v0.5.0 h1:VQw1hfvPvk3Uv6Qf29VrPF32JB6rtbgI6cYPYQjL0Qw=
@@ -121,6 +128,12 @@ github.com/prometheus/procfs v0.12.0/go.mod h1:pcuDEFsWDnvcgNzo4EEweacyhjeA9Zk3c
 github.com/rogpeppe/go-internal v1.11.0 h1:cWPaGQEPrBb5/AsnsZesgZZ9yb1OQ+GOISoDNXVBh4M=
 github.com/sergi/go-diff v1.0.0/go.mod h1:0CfEIISq7TuYL3j771MWULgwwjU+GofnZX9QAmXWZgo=
 github.com/sergi/go-diff v1.3.1 h1:xkr+Oxo4BOQKmkn/B9eMK0g5Kg/983T9DqqPHwYqD+8=
+github.com/shirou/gopsutil/v3 v3.24.2 h1:kcR0erMbLg5/3LcInpw0X/rrPSqq4CDPyI6A6ZRC18Y=
+github.com/shirou/gopsutil/v3 v3.24.2/go.mod h1:tSg/594BcA+8UdQU2XcW803GWYgdtauFFPgJCJKZlVk=
+github.com/shoenig/go-m1cpu v0.1.6 h1:nxdKQNcEB6vzgA2E2bvzKIYRuNj7XNJ4S/aRSwKzFtM=
+github.com/shoenig/go-m1cpu v0.1.6/go.mod h1:1JJMcUBvfNwpq05QDQVAnx3gUHr9IYF7GNg9SUEw2VQ=
+github.com/shoenig/test v0.6.4 h1:kVTaSd7WLz5WZ2IaoM0RSzRsUD+m8wRR+5qvntpn4LU=
+github.com/shoenig/test v0.6.4/go.mod h1:byHiCGXqrVaflBLAMq/srcZIHynQPQgeyvkvXnjqq0k=
 github.com/sirupsen/logrus v1.9.0 h1:trlNQbNUG3OdDrDil03MCb1H2o9nJ1x4/5LYw7byDE0=
 github.com/sirupsen/logrus v1.9.0/go.mod h1:naHLuLoDiP4jHNo9R0sCBMtWGeIprob74mVsIT4qYEQ=
 github.com/spf13/pflag v1.0.5 h1:iy+VFUOCP1a+8yFto/drg2CJ5u0yRoB7fZw3DKv/JXA=
@@ -136,12 +149,18 @@ github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO
 github.com/stretchr/testify v1.8.1/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
 github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
 github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
+github.com/tklauser/go-sysconf v0.3.12 h1:0QaGUFOdQaIVdPgfITYzaTegZvdCjmYO52cSFAEVmqU=
+github.com/tklauser/go-sysconf v0.3.12/go.mod h1:Ho14jnntGE1fpdOqQEEaiKRpvIavV0hSfmBq8nJbHYI=
+github.com/tklauser/numcpus v0.6.1 h1:ng9scYS7az0Bk4OZLvrNXNSAO2Pxr1XXRAPyjhIx+Fk=
+github.com/tklauser/numcpus v0.6.1/go.mod h1:1XfjsgE2zo8GVw7POkMbHENHzVg3GzmoZ9fESEdAacY=
 github.com/vektah/gqlparser v1.3.1 h1:8b0IcD3qZKWJQHSzynbDlrtP3IxVydZ2DZepCGofqfU=
 github.com/vektah/gqlparser v1.3.1/go.mod h1:bkVf0FX+Stjg/MHnm8mEyubuaArhNEqfQhF+OTiAL74=
 github.com/yuin/goldmark v1.1.27/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
 github.com/yuin/goldmark v1.2.1/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9decYSb74=
 github.com/yuin/goldmark v1.3.5/go.mod h1:mwnBkeHKe2W/ZEtQ+71ViKU8L12m81fl3OWwC1Zlc8k=
 github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
+github.com/yusufpapurcu/wmi v1.2.4 h1:zFUKzehAFReQwLys1b/iSMl+JQGSCSjtVqQn9bBrPo0=
+github.com/yusufpapurcu/wmi v1.2.4/go.mod h1:SBZ9tNy3G9/m5Oi98Zks0QjeHVDvuK0qfxQmPyzfmi0=
 go.uber.org/atomic v1.7.0/go.mod h1:fEN4uk6kAWBTFdckzkM89CLk9XfWZrxpCo0nPH17wJc=
 go.uber.org/goleak v1.1.11/go.mod h1:cwTWslyiVhfpKIDGSZEM2HlOvcqm+tG4zioyIeLoqMQ=
 go.uber.org/goleak v1.2.1 h1:NBol2c7O1ZokfZ0LEU9K6Whx/KnwvepVetCUhtKja4A=
@@ -182,15 +201,19 @@ golang.org/x/sync v0.0.0-20210220032951-036812b2e83c/go.mod h1:RxMgew5VJxzue5/jJ
 golang.org/x/sync v0.0.0-20220722155255-886fb9371eb4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20190916202348-b4ddaad3f8a3/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20191204072324-ce4227a45e2e/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200930185726-fdedc70b468f/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20201204225414-ed752295db88/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20210330210617-4fbd30eecc44/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20210510120138-977fb7262007/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20220520151302-bc2c85ada10a/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20220715151400-c0bba94af5f8/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20220722155257-8c9f86f7a55f/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.8.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.11.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.17.0 h1:25cE3gD+tdBA7lp7QfhuV+rJiE9YXTcS3VG1SqssI/Y=
 golang.org/x/sys v0.17.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=

adapter/internal/adapter/adapter.go

@@ -20,6 +20,7 @@ package adapter
 
 import (
 	"crypto/tls"
+	"strings"
 	"time"
 
 	discoveryv3 "github.com/envoyproxy/go-control-plane/envoy/service/discovery/v3"
@@ -33,6 +34,7 @@ import (
 	wso2_server "github.com/wso2/apk/adapter/pkg/discovery/protocol/server/v3"
 	"github.com/wso2/apk/adapter/pkg/health"
 	healthservice "github.com/wso2/apk/adapter/pkg/health/api/wso2/health/service"
+	metrics "github.com/wso2/apk/adapter/pkg/metrics"
 	"github.com/wso2/apk/adapter/pkg/utils/tlsutils"
 
 	"context"
@@ -154,6 +156,13 @@ func Run(conf *config.Config) {
 	}
 
 	logger.LoggerAPK.Info("Starting adapter ....")
+
+	// Start the metrics server
+	if conf.Adapter.Metrics.Enabled && strings.EqualFold(conf.Adapter.Metrics.Type, metrics.PrometheusMetricType) {
+		logger.LoggerAPK.Info("Starting Prometheus Metrics Server ....")
+		go metrics.StartPrometheusMetricsServer(conf.Adapter.Metrics.Port)
+	}
+
 	cache := xds.GetXdsCache()
 	enforcerCache := xds.GetEnforcerCache()
 	enforcerAPICache := xds.GetEnforcerAPICache()

adapter/internal/discovery/xds/server.go

@@ -779,3 +779,48 @@ func SanitizeGateway(gatewayName string, create bool) error {
 	}
 	return nil
 }
+
+// GetEnvoyGatewayConfigClusters method gets the number of clusters in envoy gateway config
+func GetEnvoyGatewayConfigClusters() int {
+	totalClusters := 0
+	for _, config := range gatewayLabelConfigMap {
+		// Add the number of clusters in this EnvoyGatewayConfig instance to the total
+		totalClusters += len(config.clusters)
+	}
+	return totalClusters
+}
+
+// GetEnvoyInternalAPIRoutes method gets the number of routes in envoy internal API
+func GetEnvoyInternalAPIRoutes() int {
+	totalRoutes := 0
+	for _, orgMap := range orgAPIMap {
+		for _, api := range orgMap {
+			// Add the number of routes in this EnvoyInternalAPI instance to the total
+			totalRoutes += len(api.routes)
+		}
+	}
+	return totalRoutes
+}
+
+// GetEnvoyInternalAPIClusters method gets the number of clusters in envoy internal API
+func GetEnvoyInternalAPIClusters() int {
+	totalClusters := 0
+	for _, orgMap := range orgAPIMap {
+		for _, api := range orgMap {
+			// Add the number of clusters in this EnvoyInternalAPI instance to the total
+			totalClusters += len(api.clusters)
+		}
+	}
+	return totalClusters
+}
+
+// GetEnvoyInternalAPICount method gets the number of APIs deployed in Envoy
+func GetEnvoyInternalAPICount() int {
+	totalCount := 0
+	for _, apiMap := range orgAPIMap {
+		for range apiMap {
+			totalCount++
+		}
+	}
+	return totalCount
+}

adapter/pkg/metrics/metrics.go

@@ -0,0 +1,110 @@
+/*
+ * Copyright (c) 2024, WSO2 LLC. (https://www.wso2.com)
+ *
+ * WSO2 LLC. licenses this file to you 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 metrics holds the implementation for exposing adapter metrics to prometheus
+package metrics
+
+import (
+	"fmt"
+	"net/http"
+	"strconv"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+	xds "github.com/wso2/apk/adapter/internal/discovery/xds"
+	logger "github.com/wso2/apk/adapter/internal/loggers"
+	"github.com/wso2/apk/adapter/pkg/logging"
+	commonmetrics "github.com/wso2/apk/common-go-libs/pkg/metrics"
+)
+
+var (
+	prometheusMetricRegistry = prometheus.NewRegistry()
+)
+
+// AdapterCollector contains the descriptions of the custom metrics exposed by the adapter.
+// It also uses the metrics defined in common-go-libs
+type AdapterCollector struct {
+	commonmetrics.Collector
+	apis                 *prometheus.Desc
+	internalClusterCount *prometheus.Desc
+	internalRouteCount   *prometheus.Desc
+}
+
+func adapterMetricsCollector() *AdapterCollector {
+	return &AdapterCollector{
+		Collector: *commonmetrics.CustomMetricsCollector(),
+		apis: prometheus.NewDesc(
+			"api_count",
+			"Number of APIs created.",
+			nil, nil,
+		),
+		internalClusterCount: prometheus.NewDesc(
+			"internal_cluster_count",
+			"Number of internal clusters created.",
+			nil, nil,
+		),
+		internalRouteCount: prometheus.NewDesc(
+			"internal_route_count",
+			"Number of internal routes created.",
+			nil, nil,
+		),
+	}
+}
+
+// Describe sends all the descriptors of the metrics collected by this Collector
+// to the provided channel.
+func (collector *AdapterCollector) Describe(ch chan<- *prometheus.Desc) {
+	collector.Collector.Describe(ch)
+	ch <- collector.apis
+	ch <- collector.internalClusterCount
+	ch <- collector.internalRouteCount
+}
+
+// Collect collects all the relevant Prometheus metrics.
+func (collector *AdapterCollector) Collect(ch chan<- prometheus.Metric) {
+	collector.Collector.Collect(ch)
+	var apisCount float64
+	var internalClusterCount float64
+	var internalRouteCount float64
+
+	apiCount := xds.GetEnvoyInternalAPICount()
+	apisCount = float64(apiCount)
+
+	internalRouteCount = float64(xds.GetEnvoyInternalAPIRoutes())
+	internalClusterCount = float64(xds.GetEnvoyInternalAPIClusters())
+
+	ch <- prometheus.MustNewConstMetric(collector.apis, prometheus.GaugeValue, apisCount)
+	ch <- prometheus.MustNewConstMetric(collector.internalRouteCount, prometheus.GaugeValue, internalRouteCount)
+	ch <- prometheus.MustNewConstMetric(collector.internalClusterCount, prometheus.GaugeValue, internalClusterCount)
+}
+
+// StartPrometheusMetricsServer initializes and starts the metrics server to expose metrics to prometheus.
+func StartPrometheusMetricsServer(port int32) {
+
+	collector := adapterMetricsCollector()
+	prometheus.MustRegister(collector)
+	http.Handle("/metrics", promhttp.Handler())
+	err := http.ListenAndServe(":"+strconv.Itoa(int(port)), nil)
+	if err != nil {
+		logger.LoggerAPK.ErrorC(logging.ErrorDetails{
+			Message:   fmt.Sprintln("Prometheus metrics server error:", err),
+			Severity:  logging.MAJOR,
+			ErrorCode: 1110,
+		})
+	}
+}

adapter/pkg/metrics/types.go

@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) 2024, WSO2 LLC. (https://www.wso2.com)
+ *
+ * WSO2 LLC. licenses this file to you 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 metrics
+
+ const (
+	 // PrometheusMetricType prometheus metric type
+	 PrometheusMetricType = "prometheus"
+ )