Add logon collector documentation

README.md

@@ -17,6 +17,7 @@ Name     | Description | Enabled by default
 [hyperv](docs/collector.hyperv.md) | Hyper-V hosts |
 [iis](docs/collector.iis.md) | IIS sites and applications |
 [logical_disk](docs/collector.logical_disk.md) | Logical disks, disk I/O | ✓
+[logon](docs/collector.logon.md) | User logon sessions |
 [memory](docs/collector.memory.md) | Memory usage metrics |
 [msmq](docs/collector.msmq.md) | MSMQ queues |
 [mssql](docs/collector.mssql.md) | [SQL Server Performance Objects](https://docs.microsoft.com/en-us/sql/relational-databases/performance-monitor/use-sql-server-objects#SQLServerPOs) metrics  |

docs/collector.logon.md

@@ -0,0 +1,34 @@
+# logon collector
+
+The logon collector exposes metrics detailing the active user logon sessions.
+
+|||
+-|-
+Metric name prefix  | `logon`
+Classes             | [`Win32_LogonSession`](https://docs.microsoft.com/en-us/windows/win32/cimwin32prov/win32-logonsession)
+Enabled by default? | No
+
+## Flags
+
+None
+
+## Metrics
+
+Name | Description | Type | Labels
+-----|-------------|------|-------
+`wmi_logon_logon_type` | Number of active user logon sessions | gauge | status
+
+### Example metric
+Query the total number of interactive logon sessions
+```
+wmi_logon_logon_type{status="interactive"}
+```
+
+## Useful queries
+Query the total number of local and remote (I.E. Terminal Services) interactive sessions.
+```
+wmi_logon_logon_type{status=~"interactive|remoteinteractive"}
+```
+
+## Alerting examples
+_This collector does not yet have alerting examples, we would appreciate your help adding them!_