18. Monitoring

slapd(8) supports an optional 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 Accessing Monitoring Information section provides a brief tutorial on how to use ldapsearch(1) to access monitoring information, while the 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 cn=config or slapd.conf(5). The former is discussed in the Monitor configuration via cn=config section of this of this chapter. The latter is discussed in the Monitor configuration via slapd.conf(5) section of this chapter. These sections assume monitor backend is built into slapd (e.g., --enable-monitor=yes, the default). If the monitor backend was built as a module (e.g., --enable-monitor=mod, this module must loaded. Loading of modules is discussed in the Configuring slapd and The slapd Configuration File chapters.


18.1. Monitor configuration via cn=config(5)

This section has yet to be written.


18.2. 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 The slapd Configuration File chapter and slapd.access(5).

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

One can verify slapd(8) is properly configured to provide monitoring information by attempting to read the 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 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 database monitor in the server's configuration.


18.3. 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 access 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 (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., '*') and all operational attributes (e.g., '+') should be requested. For instance, to read the 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 2.4 (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., @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 cn=Monitor with subtree scope and (objectClass=*) filter and requesting no attributes (e.g., 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.


18.4. 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.

18.4.1. Backends

The 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: bdb
        monitoredInfo: hdb

This indicates the config, ldif, monitor, bdb, and hdb backends are available.

The 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: bdb
        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
        seeAlso: cn=Database 1,cn=Databases,cn=Monitor

        dn: cn=Backend 4,cn=Backends,cn=Monitor
        monitoredInfo: hdb
        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 cn=Backend 3,cn=Backends,cn=Monitor object contains (in the example) information about the bdb backend.

Attribute Description
monitoredInfo Name of backend
supportedControl supported LDAP control extensions
seeAlso Database objects of instances of this backend

18.4.2. 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

18.4.3. 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

18.4.4. 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

18.4.5. 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               (useless)
   ACL
   Stats
   Stats2
   Shell
   Parse
   Cache                (deprecated)
   Index

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

18.4.6. 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 Monitor search example

18.4.7. 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

18.4.8. SASL

Currently empty.

18.4.9. 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

18.4.10. 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

18.4.11. 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

18.4.12. TLS

Currently empty.

18.4.13. 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