add support for diskio name templates & udev tags

closes #1453
closes #1386
closes #1428

plugins/inputs/system/disk_linux_test.go

@@ -0,0 +1,101 @@
+// +build linux
+
+package system
+
+import (
+	"io/ioutil"
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+var nullDiskInfo = []byte(`
+E:MY_PARAM_1=myval1
+E:MY_PARAM_2=myval2
+`)
+
+// setupNullDisk sets up fake udev info as if /dev/null were a disk.
+func setupNullDisk(t *testing.T) func() error {
+	td, err := ioutil.TempDir("", ".telegraf.TestDiskInfo")
+	require.NoError(t, err)
+
+	origUdevPath := udevPath
+
+	cleanFunc := func() error {
+		udevPath = origUdevPath
+		return os.RemoveAll(td)
+	}
+
+	udevPath = td
+	err = ioutil.WriteFile(td+"/b1:3", nullDiskInfo, 0644) // 1:3 is the 'null' device
+	if err != nil {
+		cleanFunc()
+		t.Fatal(err)
+	}
+
+	return cleanFunc
+}
+
+func TestDiskInfo(t *testing.T) {
+	clean := setupNullDisk(t)
+	defer clean()
+
+	s := &DiskIOStats{}
+	di, err := s.diskInfo("null")
+	require.NoError(t, err)
+	assert.Equal(t, "myval1", di["MY_PARAM_1"])
+	assert.Equal(t, "myval2", di["MY_PARAM_2"])
+
+	// test that data is cached
+	err = clean()
+	require.NoError(t, err)
+
+	di, err = s.diskInfo("null")
+	require.NoError(t, err)
+	assert.Equal(t, "myval1", di["MY_PARAM_1"])
+	assert.Equal(t, "myval2", di["MY_PARAM_2"])
+
+	// unfortunately we can't adjust mtime on /dev/null to test cache invalidation
+}
+
+// DiskIOStats.diskName isn't a linux specific function, but dependent
+// functions are a no-op on non-Linux.
+func TestDiskIOStats_diskName(t *testing.T) {
+	defer setupNullDisk(t)()
+
+	tests := []struct {
+		templates []string
+		expected  string
+	}{
+		{[]string{"$MY_PARAM_1"}, "myval1"},
+		{[]string{"${MY_PARAM_1}"}, "myval1"},
+		{[]string{"x$MY_PARAM_1"}, "xmyval1"},
+		{[]string{"x${MY_PARAM_1}x"}, "xmyval1x"},
+		{[]string{"$MISSING", "$MY_PARAM_1"}, "myval1"},
+		{[]string{"$MY_PARAM_1", "$MY_PARAM_2"}, "myval1"},
+		{[]string{"$MISSING"}, "null"},
+		{[]string{"$MY_PARAM_1/$MY_PARAM_2"}, "myval1/myval2"},
+		{[]string{"$MY_PARAM_2/$MISSING"}, "null"},
+	}
+
+	for _, tc := range tests {
+		s := DiskIOStats{
+			NameTemplates: tc.templates,
+		}
+		assert.Equal(t, tc.expected, s.diskName("null"), "Templates: %#v", tc.templates)
+	}
+}
+
+// DiskIOStats.diskTags isn't a linux specific function, but dependent
+// functions are a no-op on non-Linux.
+func TestDiskIOStats_diskTags(t *testing.T) {
+	defer setupNullDisk(t)()
+
+	s := &DiskIOStats{
+		DeviceTags: []string{"MY_PARAM_2"},
+	}
+	dt := s.diskTags("null")
+	assert.Equal(t, map[string]string{"MY_PARAM_2": "myval2"}, dt)
+}