NAME¶

SYNOPSIS¶

DESCRIPTION¶

overlay pcache

This directive adds the proxy cache overlay to the current backend. The proxy cache overlay may be used with any backend but is intended for use with the ldap, meta, and sql backends. Please note that the underlying backend must have a configured rootdn.

pcache <database> <max_entries> <numattrsets> <entry_limit> <cc_period>

The directive enables proxy caching in the current backend and sets general cache parameters. A <database> backend will be used internally to maintain the cached entries. The chosen database will need to be configured as well, as shown below. Cache replacement is invoked when the cache size grows to <max_entries> entries and continues till the cache size drops below this size. <numattrsets> should be equal to the number of following pcacheAttrset directives. Queries are cached only if they correspond to a cacheable template (specified by the pcacheTemplate directive) and the number of entries returned is less than <entry_limit>. Consistency check is performed every <cc_period> duration (specified in secs). In each cycle queries with expired "time to live( TTL)" are removed. A sample cache configuration is:

pcacheAttrset <index> <attrs...>

Used to associate a set of attributes <attrs..> with an <index>. Each attribute set is associated with an integer from 0 to <numattrsets>-1. These indices are used by the pcacheTemplate directive to define cacheable templates. A set of attributes cannot be empty. A set of attributes can contain the special attributes "*" (all user attributes), "+" (all operational attributes) or both; in the latter case, any other attribute is redundant and should be avoided for clarity. A set of attributes can contain "1.1" as the only attribute; in this case, only the presence of the entries is cached. Attributes prefixed by "undef:" need not be present in the schema.

 

pcacheMaxQueries <queries>

Specify the maximum number of queries to cache. The default is 10000.

 

pcacheValidate { TRUE | FALSE }

Check whether the results of a query being cached can actually be returned from the cache by the proxy DSA. When enabled, the entries being returned while caching the results of a query are checked to ensure consistency with the schema known to the proxy DSA. In case of failure, the query is not cached. By default, the check is off.

 

pcacheOffline { TRUE | FALSE }

Set the cache to offline mode. While offline, the consistency checker will be stopped and no expirations will occur. This allows the cache contents to be used indefinitely while the proxy is cut off from network access to the remote DSA. The default is FALSE, i.e. consistency checks and expirations will be performed.

 

pcachePersist { TRUE | FALSE }

Specify whether the cached queries should be saved across restarts of the caching proxy, to provide hot startup of the cache. Only non-expired queries are reloaded. The default is FALSE.

 

CAVEAT: of course, the configuration of the proxy cache must not change across restarts; the pcache overlay does not perform any consistency checks in this sense. In detail, this option should be disabled unless the existing pcacheAttrset and pcacheTemplate directives are not changed neither in order nor in contents. If new sets and templates are added, or if other details of the pcache overlay configuration changed, this feature should not be affected.

 

pcacheTemplate <template_string> <attrset_index> <ttl> [<negttl> [<limitttl> [<ttr>]]]

Specifies a cacheable template and "time to live" <ttl> of queries belonging to the template. An optional <negttl> can be used to specify that negative results (i.e., queries that returned zero entries) should also be cached for the specified amount of time. Negative results are not cached by default (<negttl> set to 0). An optional <limitttl> can be used to specify that results hitting a sizelimit should also be cached for the specified amount of time. Results hitting a sizelimit are not cached by default (<limitttl> set to 0). An optional <ttr> "time to refresh" can be used to specify that cached entries should be automatically refreshed after a certain time. Entries will only be refreshed while they have not expired, so the <ttl> should be larger than the <ttr> for this option to be useful. Entries are not refreshed by default (<ttr> set to 0).

 

pcacheBind <filter_template> <attrset_index> <ttr> <scope> <base>

Specifies a template for caching Simple Bind credentials based on an already defined pcacheTemplate. The <filter_template> is similar to a <template_string> except that it may have some values present. Its purpose is to allow the overlay to generate filters similar to what other applications do when they do a Search immediately before a Bind. E.g., if a client like nss_ldap is configured to search for a user with the filter "(&(objectClass=posixAccount)(uid=<username>))" then the corresponding template "(&(objectClass=posixAccount)(uid=))" should be used here. When converted to a regular template e.g. "(&(objectClass=)(uid=))" this template and the <attrset_index> must match an already defined pcacheTemplate clause. The "time to refresh" <ttr> determines the time interval after which the cached credentials may be refreshed. The first Bind request that occurs after that time will trigger the refresh attempt. Refreshes are not performed when the overlay is Offline. There is no "time to live" parameter for the Bind credentials; the credentials will expire according to the pcacheTemplate ttl. The <scope> and <base> should match the search scope and base used by the authentication clients. The cached credentials are not stored in cleartext, they are hashed using the default password hash. By default Bind caching is not enabled.

 

pcachePosition { head | tail }

Specifies whether the response callback should be placed at the tail (the default) or at the head (actually, wherever the stacking sequence would make it appear) of the callback list. This affects how the overlay interacts with other overlays, since the proxycache overlay should be executed as early as possible (and thus configured as late as possible), to get a chance to return the cached results; however, if executed early at response, it would cache entries that may be later "massaged" by other databases and thus returned after massaging the first time, and before massaging when cached.

 

There are some constraints:

 

all values must be positive;

 

<entry_limit> must be less than or equal to <max_entries>;

 

<numattrsets> attribute sets SHOULD be defined by using the directive pcacheAttrset;

 

all attribute sets SHOULD be referenced by (at least) one pcacheTemplate directive;

 

pcacheAttrset  0 mail postaladdress telephonenumber
pcacheTemplate  (&(sn=)(givenName=)) 0 3600

directory /var/tmp/cache
cachesize 100

BACKWARD COMPATIBILITY¶

proxycache

use pcache

 

proxyattrset

use pcacheAttrset

 

proxycachequeries

use pcacheMaxQueries

 

proxycheckcacheability

use pcacheValidate

 

proxysavequeries

use pcachePersist

 

proxytemplate

use pcacheTemplate

 

response-callback

use pcachePosition

 

CAVEATS¶

FILES¶

/etc/ldap/slapd.conf

default slapd configuration file

SEE ALSO¶

AUTHOR¶