Add 'logind' exporter

logind provides a nice interface to find out about the numbers of sessions
on a system; it is used on most Linux distributions, even those which
aren't using systemd.

The exporter exposes the total number of sessions indexed by the following
attributes:

* seat
* type ("tty", "x11", ...)
* class ("user", "greeter", ...)
* remote ("true"/"false")

1 files changed, 102 insertions, 0 deletions

diff --git a/collector/logind_linux_test.go b/collector/logind_linux_test.go
new file mode 100644
index 0000000..7c94158
--- /dev/null
+++ b/collector/logind_linux_test.go
@@ -0,0 +1,102 @@
+// Copyright 2016 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.
+
+package collector
+
+import (
+        "testing"
+
+        "github.com/godbus/dbus"
+        "github.com/prometheus/client_golang/prometheus"
+)
+
+type testLogindInterface struct{}
+
+var testSeats = []string{"seat0", ""}
+
+func (c *testLogindInterface) listSeats() ([]string, error) {
+        return testSeats, nil
+}
+
+func (c *testLogindInterface) listSessions() ([]logindSessionEntry, error) {
+        return []logindSessionEntry{
+                {
+                        SessionId:         "1",
+                        UserId:            0,
+                        UserName:          "",
+                        SeatId:            "",
+                        SessionObjectPath: dbus.ObjectPath("/org/freedesktop/login1/session/1"),
+                },
+                {
+                        SessionId:         "2",
+                        UserId:            0,
+                        UserName:          "",
+                        SeatId:            "seat0",
+                        SessionObjectPath: dbus.ObjectPath("/org/freedesktop/login1/session/2"),
+                },
+        }, nil
+}
+
+func (c *testLogindInterface) getSession(session logindSessionEntry) *logindSession {
+        sessions := map[dbus.ObjectPath]*logindSession{
+                dbus.ObjectPath("/org/freedesktop/login1/session/1"): {
+                        seat:        session.SeatId,
+                        remote:      "true",
+                        sessionType: knownStringOrOther("tty", attrTypeValues),
+                        class:       knownStringOrOther("user", attrClassValues),
+                },
+                dbus.ObjectPath("/org/freedesktop/login1/session/2"): {
+                        seat:        session.SeatId,
+                        remote:      "false",
+                        sessionType: knownStringOrOther("x11", attrTypeValues),
+                        class:       knownStringOrOther("greeter", attrClassValues),
+                },
+        }
+
+        return sessions[session.SessionObjectPath]
+}
+
+func TestLogindCollectorKnownStringOrOther(t *testing.T) {
+        known := []string{"foo", "bar"}
+
+        actual := knownStringOrOther("foo", known)
+        expected := "foo"
+        if actual != expected {
+                t.Errorf("knownStringOrOther failed: got %q, expected %q.", actual, expected)
+        }
+
+        actual = knownStringOrOther("baz", known)
+        expected = "other"
+        if actual != expected {
+                t.Errorf("knownStringOrOther failed: got %q, expected %q.", actual, expected)
+        }
+
+}
+
+func TestLogindCollectorCollectMetrics(t *testing.T) {
+        ch := make(chan prometheus.Metric)
+        go func() {
+                collectMetrics(ch, &testLogindInterface{})
+                close(ch)
+        }()
+
+        count := 0
+        for range ch {
+                count++
+        }
+
+        expected := len(testSeats) * len(attrRemoteValues) * len(attrTypeValues) * len(attrClassValues)
+        if count != expected {
+                t.Errorf("collectMetrics did not generate the expected number of metrics: got %d, expected %d.", count, expected)
+        }
+}