Fix poolmanager terminates running function pod periodically (#1435)

The pool manager keeps terminating function pod periodically even there are
traffic to the function. The root cause is that executor, poolmgr, newdeploy
manage their own functionServiceCache separately. And when router taps a
function, executor updates the access time of the function service entry in its
own cache without notifying executor types to do the update as well. Hence,
the access time of function service entry in poolmanager cache never gets updated.
Due to the access time never gets updated, the idle pod reaper in poolmanager
then thinks the function pod is in idle state and recycle it.

This PR removes the cache in executor itself, and when router tries to tap a function,
executor will call executor type to tap the function and update access time.

pkg/executor/api.go

@@ -20,13 +20,13 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"github.com/hashicorp/go-multierror"
-	"github.com/pkg/errors"
 	"io/ioutil"
 	"net/http"
 	"strings"
 
 	"github.com/gorilla/mux"
+	"github.com/hashicorp/go-multierror"
+	"github.com/pkg/errors"
 	"go.opencensus.io/plugin/ochttp"
 	"go.uber.org/zap"
 	k8serrors "k8s.io/apimachinery/pkg/api/errors"
@@ -91,9 +91,15 @@ func (executor *Executor) getServiceForFunction(fn *fv1.Function) (string, error
 		zap.String("function_name", fn.Metadata.Name),
 		zap.String("function_namespace", fn.Metadata.Namespace))
 
-	fsvc, err := executor.fsCache.GetByFunction(&fn.Metadata)
+	t := fn.Spec.InvokeStrategy.ExecutionStrategy.ExecutorType
+	et, exists := executor.executorTypes[t]
+	if !exists {
+		return "", errors.Errorf("Unknown executor type '%v'", t)
+	}
+
+	fsvc, err := et.GetFuncSvcFromCache(fn)
 	if err == nil {
-		if executor.isValidAddress(fsvc) {
+		if et.IsValid(fsvc) {
 			// Cached, return svc address
 			return fsvc.Address, nil
 		} else {
@@ -101,7 +107,7 @@ func (executor *Executor) getServiceForFunction(fn *fv1.Function) (string, error
 				zap.String("function_name", fn.Metadata.Name),
 				zap.String("function_namespace", fn.Metadata.Namespace),
 				zap.String("address", fsvc.Address))
-			executor.fsCache.DeleteEntry(fsvc)
+			et.DeleteFuncSvcFromCache(fsvc)
 		}
 	}
 
@@ -120,24 +126,7 @@ func (executor *Executor) getServiceForFunction(fn *fv1.Function) (string, error
 // find funcSvc and update its atime
 // TODO: Deprecated tapService
 func (executor *Executor) tapService(w http.ResponseWriter, r *http.Request) {
-	body, err := ioutil.ReadAll(r.Body)
-	if err != nil {
-		executor.logger.Error("failed to read tap service request", zap.Error(err))
-		http.Error(w, "Failed to read request", http.StatusInternalServerError)
-		return
-	}
-	svcName := string(body)
-	svcHost := strings.TrimPrefix(svcName, "http://")
-
-	err = executor.fsCache.TouchByAddress(svcHost)
-	if err != nil {
-		executor.logger.Error("error tapping function service",
-			zap.Error(err),
-			zap.String("service", svcName),
-			zap.String("host", svcHost))
-		http.Error(w, "Not found", http.StatusNotFound)
-		return
-	}
+	// only for upgrade compatibility
 	w.WriteHeader(http.StatusOK)
 }
 
@@ -163,7 +152,16 @@ func (executor *Executor) tapServices(w http.ResponseWriter, r *http.Request) {
 	errs := &multierror.Error{}
 	for _, req := range tapSvcReqs {
 		svcHost := strings.TrimPrefix(req.ServiceUrl, "http://")
-		err = executor.fsCache.TouchByAddress(svcHost)
+
+		et, exists := executor.executorTypes[req.FnExecutorType]
+		if !exists {
+			errs = multierror.Append(errs,
+				errors.Errorf("error tapping service due to unknown executor type '%v' found",
+					req.FnExecutorType))
+			continue
+		}
+
+		err = et.TapService(svcHost)
 		if err != nil {
 			errs = multierror.Append(errs,
 				errors.Wrapf(err, "'%v' failed to tap function '%v/%v' with service url '%v'",
@@ -199,10 +197,11 @@ func (executor *Executor) Serve(port int) {
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
 
-	executor.ndm.Run(ctx)
-	executor.gpm.Run(ctx)
-	executor.cms.Run(ctx)
+	for _, et := range executor.executorTypes {
+		et.Run(ctx)
+	}
 
+	executor.cms.Run(ctx)
 	address := fmt.Sprintf(":%v", port)
 	err := http.ListenAndServe(address, &ochttp.Handler{
 		Handler: executor.GetHandler(),