runtime: add filter metrics with specific names

The kata monitor metrics API returns a huge size response,
if containers or sandboxs are a large number,
focus on what we need will be harder.

Fixes: #6500

Signed-off-by: Miao Xia <xia.miao1@zte.com.cn>

src/runtime/cmd/kata-monitor/README.md

@@ -52,6 +52,8 @@ The **log-level** allows the chose how verbose the logs should be. The default i
 
 **NOTE: The debug endpoints are available only if the [Kata Containers configuration file](https://github.com/kata-containers/kata-containers/blob/9d5b03a1b70bbd175237ec4b9f821d6ccee0a1f6/src/runtime/config/configuration-qemu.toml.in#L590-L592) includes** `enable_pprof = true` **in the** `[runtime]` **section**.
 
+The `/metrics` has a query parameter `filter_family`, which filter Kata sandboxes metrics with specific names. If `filter_family` is set to `A` (and `B`, split with `,`), metrics with prefix `A` (and `B`) will only be returned.
+
 The `/sandboxes` endpoint lists the _sandbox ID_ of all the detected Kata runtimes. If accessed via a web browser, it provides html links to the endpoints available for each sandbox.
 
 In order to retrieve data for a specific Kata workload, the _sandbox ID_ should be passed in the query string using the _sandbox_ key. The `/agent-url`, and all the `/debug/`* endpoints require `sandbox_id` to be specified in the query string.

src/runtime/pkg/kata-monitor/metrics.go

@@ -114,9 +114,15 @@ func (km *KataMonitor) ProcessMetricsRequest(w http.ResponseWriter, r *http.Requ
 		writer = gz
 	}
 
+	filterFamilies, err := getFilterFamilyFromReq(r)
+	if err != nil {
+		return
+	}
+
 	// create encoder to encode metrics.
 	encoder := expfmt.NewEncoder(writer, contentType)
 
+	if len(filterFamilies) == 0 {
 		// gather metrics collected for management agent.
 		mfs, err := prometheus.DefaultGatherer.Gather()
 		if err != nil {
@@ -130,9 +136,10 @@ func (km *KataMonitor) ProcessMetricsRequest(w http.ResponseWriter, r *http.Requ
 		if err := encodeMetricFamily(mfs, encoder); err != nil {
 			monitorLog.WithError(err).Warnf("failed to encode metrics")
 		}
+	}
 
 	// aggregate sandboxes metrics and write to response by encoder
-	if err := km.aggregateSandboxMetrics(encoder); err != nil {
+	if err := km.aggregateSandboxMetrics(encoder, filterFamilies); err != nil {
 		monitorLog.WithError(err).Errorf("failed aggregateSandboxMetrics")
 		scrapeFailedCount.Inc()
 	}
@@ -155,7 +162,7 @@ func encodeMetricFamily(mfs []*dto.MetricFamily, encoder expfmt.Encoder) error {
 }
 
 // aggregateSandboxMetrics will get metrics from one sandbox and do some process
-func (km *KataMonitor) aggregateSandboxMetrics(encoder expfmt.Encoder) error {
+func (km *KataMonitor) aggregateSandboxMetrics(encoder expfmt.Encoder, filterFamilies []string) error {
 	// get all kata sandboxes from cache
 	sandboxes := km.sandboxCache.getSandboxList()
 	// save running kata pods as a metrics.
@@ -230,11 +237,23 @@ func (km *KataMonitor) aggregateSandboxMetrics(encoder expfmt.Encoder) error {
 	}
 
 	// write metrics to response.
+	if len(filterFamilies) > 0 {
+		for _, filterName := range filterFamilies {
+			for fullName, mf := range metricsMap {
+				if strings.HasPrefix(fullName, filterName) {
+					if err := encoder.Encode(mf); err != nil {
+						return err
+					}
+				}
+			}
+		}
+	} else {
 		for _, mf := range metricsMap {
 			if err := encoder.Encode(mf); err != nil {
 				return err
 			}
 		}
+	}
 	return nil
 
 }

src/runtime/pkg/kata-monitor/shim_client.go

@@ -8,6 +8,7 @@ package katamonitor
 import (
 	"fmt"
 	"net/http"
+	"strings"
 	"time"
 
 	shim "github.com/kata-containers/kata-containers/src/runtime/pkg/containerd-shim-v2"
@@ -36,3 +37,11 @@ func getSandboxIDFromReq(r *http.Request) (string, error) {
 func getSandboxFS() string {
 	return shim.GetSandboxesStoragePath()
 }
+
+func getFilterFamilyFromReq(r *http.Request) ([]string, error) {
+	filterFamilies := r.URL.Query().Get("filter_family")
+	if filterFamilies != "" {
+		return strings.Split(filterFamilies, ","), nil
+	}
+	return nil, nil
+}