support expose metrics

Author: wonderflow

api/pkg/filtermanager/config.go

@@ -216,6 +216,11 @@ func (p *FilterManagerConfigParser) Parse(any *anypb.Any, callbacks capi.ConfigC
 
 	for _, proto := range plugins {
 		name := proto.Name
+
+		if registerMetrics := pkgPlugins.LoadMetricsCallback(name); registerMetrics != nil {
+			registerMetrics(callbacks)
+		}
+
 		if plugin := pkgPlugins.LoadHTTPFilterFactoryAndParser(name); plugin != nil {
 			config, err := plugin.ConfigParser.Parse(proto.Config)
 			if err != nil {

api/pkg/plugins/plugins.go

@@ -20,6 +20,7 @@ import (
 	"errors"
 	"runtime/debug"
 
+	capi "github.com/envoyproxy/envoy/contrib/golang/common/go/api"
 	"mosn.io/htnn/api/internal/proto"
 	"mosn.io/htnn/api/pkg/filtermanager/api"
 	"mosn.io/htnn/api/pkg/log"
@@ -31,6 +32,7 @@ var (
 	pluginTypes                = map[string]Plugin{}
 	plugins                    = map[string]Plugin{}
 	httpFilterFactoryAndParser = map[string]*FilterFactoryAndParser{}
+	metricsRegister            = map[string]func(capi.ConfigCallbacks){}
 )
 
 // Here we introduce extra struct to avoid cyclic import between pkg/filtermanager and pkg/plugins
@@ -188,6 +190,14 @@ func (cp *PluginConfigParser) Parse(any interface{}) (res interface{}, err error
 	return conf, nil
 }
 
+func RegisterMetricsCallback(pluginName string, registerMetricFunc func(capi.ConfigCallbacks)) {
+	metricsRegister[pluginName] = registerMetricFunc
+}
+
+func LoadMetricsCallback(pluginName string) func(capi.ConfigCallbacks) {
+	return metricsRegister[pluginName]
+}
+
 // PluginMethodDefaultImpl provides reasonable implementation for optional methods
 type PluginMethodDefaultImpl struct{}