Add input plugin for OpenLDAP (#2612)

plugins/inputs/openldap/README.md

@@ -0,0 +1,82 @@
+# Openldap Input Plugin
+
+This plugin gathers metrics from OpenLDAP's cn=Monitor backend.
+
+### Configuration:
+
+```toml
+[[inputs.openldap]]
+  host = "localhost"
+  port = 389
+
+  # ldaps, starttls, or no encryption. default is an empty string, disabling all encryption.
+  # note that port will likely need to be changed to 636 for ldaps
+  # valid options: "" | "starttls" | "ldaps"
+  ssl = ""
+
+  # skip peer certificate verification. Default is false.
+  insecure_skip_verify = false
+
+  # Path to PEM-encoded Root certificate to use to verify server certificate
+  ssl_ca = "/etc/ssl/certs.pem"
+
+  # dn/password to bind with. If bind_dn is empty, an anonymous bind is performed.
+  bind_dn = ""
+  bind_password = ""
+```
+
+### Measurements & Fields:
+
+All **monitorCounter**, **monitorOpInitiated**, and **monitorOpCompleted** attributes are gathered based on this LDAP query:
+
+```(|(objectClass=monitorCounterObject)(objectClass=monitorOperation))```
+
+Metric names are based on their entry DN.
+
+Metrics for the **monitorOp*** attributes have **_initiated** and **_completed** added to the base name.
+
+An OpenLDAP 2.4 server will provide these metrics:
+
+- openldap
+	- max_file_descriptors_connections
+	- current_connections
+	- total_connections
+	- abandon_operations_completed
+	- abandon_operations_initiated
+	- add_operations_completed
+	- add_operations_initiated
+	- bind_operations_completed
+	- bind_operations_initiated
+	- compare_operations_completed
+	- compare_operations_initiated
+	- delete_operations_completed
+	- delete_operations_initiated
+	- extended_operations_completed
+	- extended_operations_initiated
+	- modify_operations_completed
+	- modify_operations_initiated
+	- modrdn_operations_completed
+	- modrdn_operations_initiated
+	- search_operations_completed
+	- search_operations_initiated
+	- unbind_operations_completed
+	- unbind_operations_initiated
+	- bytes_statistics
+	- entries_statistics
+	- pdu_statistics
+	- referrals_statistics
+	- read_waiters
+	- write_waiters
+
+### Tags:
+
+- server= # value from config
+- port= # value from config
+
+### Example Output:
+
+```
+$ telegraf -config telegraf.conf -input-filter openldap -test --debug
+* Plugin: inputs.openldap, Collection 1
+> openldap,server=localhost,port=389,host=zirzla search_operations_completed=2i,delete_operations_completed=0i,read_waiters=1i,total_connections=1004i,bind_operations_completed=3i,unbind_operations_completed=3i,referrals_statistics=0i,current_connections=1i,bind_operations_initiated=3i,compare_operations_completed=0i,add_operations_completed=2i,delete_operations_initiated=0i,unbind_operations_initiated=3i,search_operations_initiated=3i,add_operations_initiated=2i,max_file_descriptors_connections=4096i,abandon_operations_initiated=0i,write_waiters=0i,modrdn_operations_completed=0i,abandon_operations_completed=0i,pdu_statistics=23i,modify_operations_initiated=0i,bytes_statistics=1660i,entries_statistics=17i,compare_operations_initiated=0i,modrdn_operations_initiated=0i,extended_operations_completed=0i,modify_operations_completed=0i,extended_operations_initiated=0i 1499990455000000000
+```