test(monitoring): add integration tests for kernel reader metrics (#4318)

* Add metrics test for Kernel reader

Author: vipnydav

tools/integration_tests/monitoring/kernel_reader_prom_test.go

@@ -0,0 +1,61 @@
+// Copyright 2026 Google LLC
+//
+// Licensed 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 monitoring
+
+import (
+	"log"
+	"os"
+	"path"
+	"strings"
+	"testing"
+
+	"github.com/googlecloudplatform/gcsfuse/v3/tools/integration_tests/util/client"
+	"github.com/googlecloudplatform/gcsfuse/v3/tools/integration_tests/util/setup"
+	"github.com/stretchr/testify/require"
+	"github.com/stretchr/testify/suite"
+)
+
+type PromKernelReaderTest struct {
+	PromTestBase
+}
+
+func (p *PromKernelReaderTest) TestKernelReaderMetrics() {
+	testName := strings.ReplaceAll(p.T().Name(), "/", "_")
+	gcsDir := path.Join(testDirName, testName)
+	fileName := "mrd_test_file.txt"
+	client.SetupFileInTestDirectory(testEnv.ctx, testEnv.storageClient, gcsDir, fileName, 10*1024*1024, p.T())
+
+	// Read file to trigger metrics
+	_, err := os.ReadFile(path.Join(testEnv.testDirPath, fileName))
+
+	require.NoError(p.T(), err)
+	assertNonZeroCountMetric(p.T(), "fs_ops_count", "fs_op", "ReadFile", p.prometheusPort)
+	assertNonZeroCountMetric(p.T(), "gcs_download_bytes_count", "read_type", "Parallel", p.prometheusPort)
+	assertNonZeroCountMetric(p.T(), "gcs_read_bytes_count", "", "", p.prometheusPort)
+	assertNonZeroCountMetric(p.T(), "gcs_read_count", "read_type", "Parallel", p.prometheusPort)
+	assertNonZeroCountMetric(p.T(), "gcs_request_count", "gcs_method", "MultiRangeDownloader::Add", p.prometheusPort)
+	assertNonZeroHistogramMetric(p.T(), "gcs_request_latencies", "gcs_method", "MultiRangeDownloader::Add", p.prometheusPort)
+}
+
+func TestPromKernelReaderSuite(t *testing.T) {
+	ts := &PromKernelReaderTest{}
+	flagSets := setup.BuildFlagSets(*testEnv.cfg, testEnv.bucketType, t.Name())
+	for _, flags := range flagSets {
+		ts.flags = flags
+		ts.prometheusPort = parsePortFromFlags(flags)
+		log.Printf("Running prom kernel reader tests with flags: %s", ts.flags)
+		suite.Run(t, ts)
+	}
+}

tools/integration_tests/monitoring/setup_test.go

@@ -176,7 +176,7 @@ func TestMain(m *testing.M) {
 		testEnv.cfg.LogFile = setup.LogFile()
 		testEnv.cfg.GKEMountedDirectory = setup.MountedDirectory()
 
-		testEnv.cfg.Configs = make([]test_suite.ConfigItem, 6)
+		testEnv.cfg.Configs = make([]test_suite.ConfigItem, 7)
 		testEnv.cfg.Configs[0].Flags = []string{"--prometheus-port=9190 --cache-dir=/gcsfuse-tmp/PromOTELSuite --log-file=/gcsfuse-tmp/monitoring.log --enable-kernel-reader=false"}
 		testEnv.cfg.Configs[0].Compatible = map[string]bool{"flat": true, "hns": false, "zonal": false}
 		testEnv.cfg.Configs[0].Run = "TestPromOTELSuite"
@@ -197,6 +197,10 @@ func TestMain(m *testing.M) {
 		testEnv.cfg.Configs[5].Flags = []string{"--client-protocol=grpc --experimental-enable-grpc-metrics=true --prometheus-port=10192 --cache-dir=/gcsfuse-tmp/TestPromGrpcMetricsSuite --log-file=/gcsfuse-tmp/prom_grpc_metrics_hns.log --enable-kernel-reader=false"}
 		testEnv.cfg.Configs[5].Compatible = map[string]bool{"flat": false, "hns": true, "zonal": true}
 		testEnv.cfg.Configs[5].Run = "TestPromGrpcMetricsSuite"
+
+		testEnv.cfg.Configs[6].Flags = []string{"--prometheus-port=9193 --log-file=/gcsfuse-tmp/prom_kernel_reader.log"}
+		testEnv.cfg.Configs[6].Compatible = map[string]bool{"flat": false, "hns": false, "zonal": true}
+		testEnv.cfg.Configs[6].Run = "TestPromKernelReaderSuite"
 	}
 	testEnv.cfg = &configFile.Monitoring[0]
 	testEnv.ctx = context.Background()

tools/integration_tests/test_config.yaml

@@ -882,3 +882,11 @@ monitoring:
           zonal: true
         run: "TestPromGrpcMetricsSuite"
         run_on_gke: true
+      - flags:
+        - "--prometheus-port=9193 --log-file=/gcsfuse-tmp/prom_kernel_reader.log"
+        compatible:
+          flat: false
+          hns: false
+          zonal: true
+        run: "TestPromKernelReaderSuite"
+        run_on_gke: false