Add perf exporter (#1274)

Signed-off-by: Daniel Hodges <hodges.daniel.scott@gmail.com>

collector/perf_linux_test.go

@@ -0,0 +1,55 @@
+// Copyright 2019 The Prometheus Authors
+// 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.
+
+// +build !noprocesses
+
+package collector
+
+import (
+	"io/ioutil"
+	"strconv"
+	"strings"
+	"testing"
+
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+func TestPerfCollector(t *testing.T) {
+	paranoidBytes, err := ioutil.ReadFile("/proc/sys/kernel/perf_event_paranoid")
+	if err != nil {
+		t.Skip("Procfs not mounted, skipping perf tests")
+	}
+	paranoidStr := strings.Replace(string(paranoidBytes), "\n", "", -1)
+	paranoid, err := strconv.Atoi(paranoidStr)
+	if err != nil {
+		t.Fatalf("Expected perf_event_paranoid to be an int, got: %s", paranoidStr)
+	}
+	if paranoid >= 1 {
+		t.Skip("Skipping perf tests, set perf_event_paranoid to 0")
+	}
+	collector, err := NewPerfCollector()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Setup background goroutine to capture metrics.
+	metrics := make(chan prometheus.Metric)
+	defer close(metrics)
+	go func() {
+		for range metrics {
+		}
+	}()
+	if err := collector.Update(metrics); err != nil {
+		t.Fatal(err)
+	}
+}