# $OpenLDAP$
# Copyright 1999-2021 The OpenLDAP Foundation, All Rights Reserved.
# COPYING RESTRICTIONS APPLY, see COPYRIGHT.
H1: Monitoring

{{slapd}}(8) supports an optional {{TERM:LDAP}} monitoring interface
you can use to obtain information regarding the current state of
your {{slapd}} instance.  For instance, the interface allows you
to determine how many clients are connected to the server currently.
The monitoring information is provided by a specialized backend,
the {{monitor}} backend.  A manual page, {{slapd-monitor}}(5) is
available.

When the monitoring interface is enabled, LDAP clients may be used
to access information provided by the {{monitor}} backend, subject
to access and other controls.

When enabled, the {{monitor}} backend dynamically generates and
returns objects in response to search requests in the {{cn=Monitor}}
subtree.  Each object contains information about a particular aspect
of the server.  The information is held in a combination of user
applications and operational attributes.   This information can be
access with {{ldapsearch(1)}}, with any general-purpose LDAP browser,
or with specialized monitoring tools.  The {{SECT:Accessing Monitoring
Information}} section provides a brief tutorial on how to use
{{ldapsearch}}(1) to access monitoring information, while the
{{SECT:Monitor information}} section details monitoring information
base and its organization.

While support for the monitor backend is included in default builds
of slapd(8), this support requires some configuration to become
active.  This may be done using either {{EX:cn=config}} or
{{slapd.conf}}(5).  The former is discussed in the {{SECT:Monitor
configuration via cn=config}} section of this of this chapter.  The
latter is discussed in the {{SECT:Monitor configuration via
slapd.conf(5)}} section of this chapter.  These sections assume
monitor backend is built into {{slapd}} (e.g., {{EX:--enable-monitor=yes}},
the default).  If the monitor backend was built as a module (e.g.,
{{EX:--enable-monitor=mod}}, this module must loaded.  Loading of
modules is discussed in the {{SECT:Configuring slapd}} and {{SECT:The
slapd Configuration File}} chapters.


H2: Monitor configuration via cn=config(5)

The {{monitor backend}} is statically built into slapd and can be
instantiated via ldapadd.

> dn: olcDatabase=monitor,cn=config
> objectClass: olcDatabaseConfig
> olcDatabase: monitor

H2: Monitor configuration via slapd.conf(5)

Configuration of the slapd.conf(5) to support LDAP monitoring
is quite simple.

First, ensure {{core.schema}} schema configuration file is included
by your {{slapd.conf}}(5) file.  The {{monitor}} backend requires
it.

Second, instantiate the {{monitor backend}} by adding a
{{database monitor}} directive below your existing database
sections.  For instance:

>	database monitor

Lastly, add additional global or database directives as needed.

Like most other database backends, the monitor backend does honor
slapd(8) access and other administrative controls.   As some monitor
information may be sensitive, it is generally recommend access to
cn=monitor be restricted to directory administrators and their
monitoring agents.  Adding an {{access}} directive immediately below
the {{database monitor}} directive is a clear and effective approach
for controlling access.  For instance, the addition of the following
{{access}} directive immediately below the {{database monitor}}
directive restricts access to monitoring information to the specified
directory manager.

>	access to *
>		by dn.exact="cn=Manager,dc=example,dc=com
>		by * none

More information on {{slapd}}(8) access controls, see {{The access
Control Directive}} section of the {{SECT:The slapd Configuration
File}} chapter and {{slapd.access}}(5).

After restarting {{slapd}}(8), you are ready to start exploring the
monitoring information provided in {{EX:cn=config}} as discussed
in the {{SECT:Accessing Monitoring Information}} section of this
chapter.

One can verify slapd(8) is properly configured to provide monitoring
information by attempting to read the {{EX:cn=monitor}} object.
For instance, if the following {{ldapsearch}}(1) command returns the
cn=monitor object (with, as requested, no attributes), it's working.

>	ldapsearch -x -D 'cn=Manager,dc=example,dc=com' -W \
>		-b 'cn=Monitor' -s base 1.1

Note that unlike general purpose database backends, the database
suffix is hardcoded.  It's always {{EX:cn=Monitor}}.  So no {{suffix}}
directive should be provided.  Also note that general purpose
database backends, the monitor backend cannot be instantiated
multiple times.  That is, there can only be one (or zero) occurrences
of {{EX:database monitor}} in the server's configuration.


H2: Accessing Monitoring Information

As previously discussed, when enabled, the {{monitor}} backend
dynamically generates and returns objects in response to search
requests in the {{cn=Monitor}} subtree.  Each object contains
information about a particular aspect of the server.  The information
is held in a combination of user applications and operational
attributes.  This information can be accessed with {{ldapsearch(1)}},
with any general-purpose LDAP browser, or with specialized monitoring
tools.

This section provides a provides a brief tutorial on how to use
{{ldapsearch}}(1) to access monitoring information.

To inspect any particular monitor object, one performs search
operation on the object with a baseObject scope and a
{{EX:(objectClass=*)}} filter.  As the monitoring information is
contained in a combination of user applications and operational
attributes, the return all user applications attributes (e.g.,
{{EX:'*'}}) and all operational attributes (e.g., {{EX:'+'}}) should
be requested.   For instance, to read the {{EX:cn=Monitor}} object
itself, the {{ldapsearch}}(1) command (modified to fit your configuration)
can be used:

>	ldapsearch -x -D 'cn=Manager,dc=example,dc=com' -W \
>		-b 'cn=Monitor' -s base '(objectClass=*)' '*' '+'

When run against your server, this should produce output
similar to:

>	dn: cn=Monitor
>	objectClass: monitorServer
>	structuralObjectClass: monitorServer
>	cn: Monitor
>	creatorsName:
>	modifiersName:
>	createTimestamp: 20061208223558Z
>	modifyTimestamp: 20061208223558Z
>	description: This subtree contains monitoring/managing objects.
>	description: This object contains information about this server.
>	description: Most of the information is held in operational attributes, which 
>	 must be explicitly requested.
>	monitoredInfo: OpenLDAP: slapd 2.5 (Dec  7 2006 17:30:29)
>	entryDN: cn=Monitor
>	subschemaSubentry: cn=Subschema
>	hasSubordinates: TRUE

To reduce the number of uninteresting attributes returned, one
can be more selective when requesting which attributes are to be
returned.  For instance, one could request the return of all
attributes allowed by the {{monitorServer}} object class (e.g.,
{{EX:@objectClass}}) instead of all user and all operational
attributes:

>	ldapsearch -x -D 'cn=Manager,dc=example,dc=com' -W \
>		-b 'cn=Monitor' -s base '(objectClass=*)' '@monitorServer'

This limits the output as follows:

>	dn: cn=Monitor
>	objectClass: monitorServer
>	cn: Monitor
>	description: This subtree contains monitoring/managing objects.
>	description: This object contains information about this server.
>	description: Most of the information is held in operational attributes, which 
>	 must be explicitly requested.
>	monitoredInfo: OpenLDAP: slapd 2.X (Dec  7 2006 17:30:29)

To return the names of all the monitoring objects, one performs a
search of {{EX:cn=Monitor}} with subtree scope and {{EX:(objectClass=*)}}
filter and requesting no attributes (e.g., {{EX:1.1}}) be returned.

>	ldapsearch -x -D 'cn=Manager,dc=example,dc=com' -W -b 'cn=Monitor' -s sub 1.1

If you run this command you will discover that there are many objects
in the {{cn=Monitor}} subtree.  The following section describes
some of the commonly available monitoring objects.


H2: Monitor Information

The {{monitor}} backend provides a wealth of information useful
for monitoring the slapd(8) contained in set of monitor objects.
Each object contains information about a particular aspect of
the server, such as a backends, a connection, or a thread.
Some objects serve as containers for other objects and used
to construct a hierarchy of objects.

In this hierarchy, the most superior object is {cn=Monitor}.
While this object primarily serves as a container for other
objects, most of which are containers, this object provides
information about this server.  In particular, it provides the
slapd(8) version string.  Example:

>	dn: cn=Monitor
>	monitoredInfo: OpenLDAP: slapd 2.X (Dec  7 2006 17:30:29)

Note: Examples in this section (and its subsections) have been
trimmed to show only key information.


H3: Backends

The {{EX:cn=Backends,cn=Monitor}} object, itself, provides a list
of available backends.  The list of available backends all builtin
backends, as well as backends loaded by modules.  For example:

>	dn: cn=Backends,cn=Monitor          
>	monitoredInfo: config                 
>	monitoredInfo: ldif     
>	monitoredInfo: monitor
>	monitoredInfo: mdb

This indicates the {{config}}, {{ldif}}, {{monitor}},
and {{mdb}} backends are available.

The {{EX:cn=Backends,cn=Monitor}} object is also a container
for available backend objects.  Each available backend object
contains information about a particular backend.  For example:

>	dn: cn=Backend 0,cn=Backends,cn=Monitor 
>	monitoredInfo: config
>	monitorRuntimeConfig: TRUE
>	supportedControl: 2.16.840.1.113730.3.4.2  
>	seeAlso: cn=Database 0,cn=Databases,cn=Monitor
>	
>	dn: cn=Backend 1,cn=Backends,cn=Monitor  
>	monitoredInfo: ldif          
>	monitorRuntimeConfig: TRUE     
>	supportedControl: 2.16.840.1.113730.3.4.2
>	
>	dn: cn=Backend 2,cn=Backends,cn=Monitor
>	monitoredInfo: monitor
>	monitorRuntimeConfig: TRUE
>	supportedControl: 2.16.840.1.113730.3.4.2
>	seeAlso: cn=Database 2,cn=Databases,cn=Monitor
>	
>	dn: cn=Backend 3,cn=Backends,cn=Monitor
>	monitoredInfo: mdb
>	monitorRuntimeConfig: TRUE
>	supportedControl: 1.3.6.1.1.12
>	supportedControl: 2.16.840.1.113730.3.4.2
>	supportedControl: 1.3.6.1.4.1.4203.666.5.2
>	supportedControl: 1.2.840.113556.1.4.319
>	supportedControl: 1.3.6.1.1.13.1
>	supportedControl: 1.3.6.1.1.13.2
>	supportedControl: 1.3.6.1.4.1.4203.1.10.1
>	supportedControl: 1.2.840.113556.1.4.1413
>	supportedControl: 1.3.6.1.4.1.4203.666.11.7.2

For each of these objects, monitorInfo indicates which backend the
information in the object is about.  For instance, the {{EX:cn=Backend
5,cn=Backends,cn=Monitor}} object contains (in the example) information
about the {{mdb}} backend. 

!block table
Attribute|Description
monitoredInfo|Name of backend
supportedControl|supported LDAP control extensions
seeAlso|Database objects of instances of this backend
!endblock

H3: Connections

The main entry is empty; it should contain some statistics on the number 
of connections.

Dynamic child entries are created for each open connection, with stats on
the activity on that connection (the format will be detailed later).
There are two special child entries that show the number of total and
current connections respectively.

For example:

Total Connections:

>   dn: cn=Total,cn=Connections,cn=Monitor
>   structuralObjectClass: monitorCounterObject
>   monitorCounter: 4
>   entryDN: cn=Total,cn=Connections,cn=Monitor
>   subschemaSubentry: cn=Subschema
>   hasSubordinates: FALSE

Current Connections:

>   dn: cn=Current,cn=Connections,cn=Monitor
>   structuralObjectClass: monitorCounterObject
>   monitorCounter: 2
>   entryDN: cn=Current,cn=Connections,cn=Monitor
>   subschemaSubentry: cn=Subschema
>   hasSubordinates: FALSE


H3: Databases

The main entry contains the naming context of each configured database; 
the child entries contain, for each database, the type and the naming
context.

For example:

>   dn: cn=Database 2,cn=Databases,cn=Monitor
>   structuralObjectClass: monitoredObject
>   monitoredInfo: monitor
>   monitorIsShadow: FALSE
>   monitorContext: cn=Monitor
>   readOnly: FALSE
>   entryDN: cn=Database 2,cn=Databases,cn=Monitor
>   subschemaSubentry: cn=Subschema
>   hasSubordinates: FALSE

H3: Listener

It contains the description of the devices the server is currently 
listening on:

>   dn: cn=Listener 0,cn=Listeners,cn=Monitor
>   structuralObjectClass: monitoredObject
>   monitorConnectionLocalAddress: IP=0.0.0.0:389
>   entryDN: cn=Listener 0,cn=Listeners,cn=Monitor
>   subschemaSubentry: cn=Subschema
>   hasSubordinates: FALSE


H3: Log

It contains the currently active log items.  The {{Log}} subsystem allows 
user modify operations on the {{description}} attribute, whose values {{MUST}} 
be in the list of admittable log switches:

>   Trace
>   Packets
>   Args
>   Conns
>   BER
>   Filter
>   Config
>   ACL
>   Stats
>   Stats2
>   Shell
>   Parse
>   Sync

These values can be added, replaced or deleted; they affect what 
messages are sent to the syslog device.
Custom values could be added by custom modules.

H3: Operations

It shows some statistics on the operations performed by the server:

>   Initiated
>   Completed

and for each operation type, i.e.:

>   Bind
>   Unbind
>   Add
>   Delete
>   Modrdn
>   Modify
>   Compare
>   Search
>   Abandon
>   Extended

There are too many types to list example here, so please try for yourself 
using {{SECT: Monitor search example}}

H3: Overlays

The main entry contains the type of overlays available at run-time;
the child entries, for each overlay, contain the type of the overlay.

It should also contain the modules that have been loaded if dynamic 
overlays are enabled:

>   # Overlays, Monitor
>   dn: cn=Overlays,cn=Monitor
>   structuralObjectClass: monitorContainer
>   monitoredInfo: syncprov
>   monitoredInfo: accesslog
>   monitoredInfo: glue
>   entryDN: cn=Overlays,cn=Monitor
>   subschemaSubentry: cn=Subschema
>   hasSubordinates: TRUE

H3: SASL

Currently empty.

H3: Statistics

It shows some statistics on the data sent by the server:

>   Bytes
>   PDU
>   Entries
>   Referrals

e.g.

>   # Entries, Statistics, Monitor
>   dn: cn=Entries,cn=Statistics,cn=Monitor
>   structuralObjectClass: monitorCounterObject
>   monitorCounter: 612248
>   entryDN: cn=Entries,cn=Statistics,cn=Monitor
>   subschemaSubentry: cn=Subschema
>   hasSubordinates: FALSE

H3: Threads

It contains the maximum number of threads enabled at startup and the 
current backload.

e.g.

>   # Max, Threads, Monitor
>   dn: cn=Max,cn=Threads,cn=Monitor
>   structuralObjectClass: monitoredObject
>   monitoredInfo: 16
>   entryDN: cn=Max,cn=Threads,cn=Monitor
>   subschemaSubentry: cn=Subschema
>   hasSubordinates: FALSE


H3: Time

It contains two child entries with the start time and the current time 
of the server.

e.g.

Start time:

>   dn: cn=Start,cn=Time,cn=Monitor
>   structuralObjectClass: monitoredObject
>   monitorTimestamp: 20061205124040Z
>   entryDN: cn=Start,cn=Time,cn=Monitor
>   subschemaSubentry: cn=Subschema
>   hasSubordinates: FALSE

Current time:

>   dn: cn=Current,cn=Time,cn=Monitor
>   structuralObjectClass: monitoredObject
>   monitorTimestamp: 20061207120624Z
>   entryDN: cn=Current,cn=Time,cn=Monitor
>   subschemaSubentry: cn=Subschema
>   hasSubordinates: FALSE

H3: TLS

Currently empty.

H3: Waiters

It contains the number of current read waiters.

e.g.

Read waiters:

>   dn: cn=Read,cn=Waiters,cn=Monitor
>   structuralObjectClass: monitorCounterObject
>   monitorCounter: 7
>   entryDN: cn=Read,cn=Waiters,cn=Monitor
>   subschemaSubentry: cn=Subschema
>   hasSubordinates: FALSE

Write waiters:

>   dn: cn=Write,cn=Waiters,cn=Monitor
>   structuralObjectClass: monitorCounterObject
>   monitorCounter: 0
>   entryDN: cn=Write,cn=Waiters,cn=Monitor
>   subschemaSubentry: cn=Subschema
>   hasSubordinates: FALSE

Add new monitored things here and discuss, referencing man pages and present
examples