Sun Java Communications Suite 5 Deployment Planning Guide

Planning for the Calendar Server LDAP Data Cache

The LDAP data cache option ensures that LDAP data is available immediately after it has been committed. In some configurations of LDAP, an update might need to be referred to a (remote) master server from which the update is then replicated down to the local LDAP directory. These kinds of configurations can induce a delay in the availability of committed data on the local LDAP server.

The LDAP data cache can ensure that your Calendar Server clients have accurate LDAP data, but can introduce a delay in the availability of committed LDAP data. For example, if your site has deployed a master/slave LDAP configuration, with Calendar Server accessing the master LDAP directory through a slave LDAP directory server, it introduces a delay.

This section covers the following topics:

Considerations for

Use these guidelines to determine if your site should configure the LDAP data cache:

You don’t need to configure the LDAP data cache if your Calendar Server accesses the master (or root) LDAP directory directly with no delays in the availability of committed LDAP data.
If your site has deployed a Using the LDAP Data Cache in a Master/Slave LDAP Configuration where Calendar Server accesses the master LDAP directory through a slave LDAP directory server, which in turn introduces a delay in the availability of committed LDAP data, configure the LDAP data cache to ensure that your end users have the most recent data.

Using the LDAP Data Cache in a Master/Slave LDAP Configuration

A Master/Slave LDAP configuration includes a master (root) directory server and one or more slave (consumer or replica) directory servers. Calendar Server can access the master LDAP directory server either directly or through a slave directory server:

If Calendar Server accesses the master LDAP directory server directly, the LDAP should be accurate, and you do not need to configure the LDAP data cache. In this case, make sure that the local.ldap.cache.enable parameter is set to “no” (which is the default).
If Calendar Server accesses the master LDAP directory server through a slave directory server, LDAP data changes are usually written to the master directory server transparently using an LDAP referral, which in turn replicates the data back to each slave directory server. This introduces a delay in the availability of committed LDAP data. For example, Calendar Server commits an LDAP data change, but the new data is not available for a specific amount of time because of the delay in the master directory server updating each slave directory server. A subsequent Calendar Server client operation uses the old LDAP data and presents an out-of-date view.

LDAP Attributes Affected by Delays

If the delay in updating the slave directory servers is short (only a few seconds), clients might not experience a problem. However, if the delay is longer (minutes or hours), clients will display inaccurate LDAP data for the length of the delay.

The following table lists the LDAP attributes that are affected by a delay in a master/slave LDAP server configuration where Calendar Server accesses the master LDAP directory server through a slave LDAP directory server.

Table 18–1 Calendar Server LDAP Attributes Affected by Delays


Operation	LDAP Attributes Affected
Auto provisioning	`icsCalendar, icsSubscribed, icsCalendarOwned, icsDWPHost`
Calendar groups	`icsSet`
Calendar creation	`icsCalendarOwned, icsSubscribed`
Calendar subscription	`icsSubscribed`
User options	`icsExtendedUserPrefs, icsFirstDay, icsTimeZone, icsFreeBusy`
Calendar searches	`icsCalendarOwned`

To ensure that your end uses have the most recent LDAP data, configure the LDAP data cache as described in the following section, Resolving the Master-Slave Delay Problem.

Resolving the Master-Slave Delay Problem

The LDAP data cache resolves the master/slave LDAP configuration problem by providing Calendar Server clients with the most recent LDAP data, even when the master directory server has not updated each slave directory server.

If the LDAP data cache is enabled, Calendar Server writes committed LDAP data to the cache database (ldapcache.db file). By default, the LDAP cache database is located in the /var/opt/SUNWics5/csdb/ldap_cache directory, but you can configure a different location if you prefer.

When a client makes a change to the LDAP data for a single user, Calendar Server writes the revised data to the LDAP cache database (as well as to the slave directory server). A subsequent client operation retrieves the LDAP data from the cache database. This data retrieval applies to the following operations for a single user:

User’s attributes at login
User’s options (such as color scheme or time zone)
User’s calendar groups
User’s subscribed list of calendars

Thus, the LDAP data cache database provides for:

Data consistency across processes on a single system—The database is available to all Calendar Server processes on a multiprocessor system.
Data persistence across user sessions—The database is permanent and does not require refreshing. You can configure the time to live (TTL) for an LDAP data cache entry and the interval between each database cleanup.

Limitations to the LDAP Data Cache Solution

The LDAP data cache does not provide for:

Reading the cache for searches where a list of entries is expected, for example, searching for attendees for a meeting. This type of search is subject to any LDAP delay. For instance, a newly created calendar will not appear in a calendar search if the LDAP search option is active and the search is performed within the delay period following the creation of a new calendar.
Reading and writing of the cache across multiple front-end servers. Each front-end server has its own cache, which is not aware of data in other caches.
The capability to handle a user who doesn’t always log into the same server. Since each server has its own LDAP cache, within the delay period, one cache will not know about the user's activities while logged into the another cache.

Configuring the LDAP Data Cache

Configure the LDAP data cache by setting the appropriate parameters in the ics.conf file. See the Sun Java System Calendar Server 6.3 Administration Guide for more information.

Caution –

If Calendar Server or the server where Calendar Server is running is not properly shut down, manually delete all files in the ldap_cache directory to avoid any database corruption that might cause problems during a subsequent restart.