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	== Design ==		== Design ==
		+	To define plug-in execution order, it will be possible to set a plug-in precedence in a plug-in configuration entry. This precedence value will then be used to determine the order in which to call the plug-ins within a given plug-in type. The precedence will be defined as an integer value between '''00-99''' with '''00''' being the highest priority and '''99''' being the lowest priority. The precedence value will be stored in the '''nsslapd-pluginPrecedence''' attribute within a plug-in configuration entry. Here is an example configuration entry:
		+
		+	dn: cn=ACL Plugin,cn=plugins,cn=config
		+	objectClass: top
		+	objectClass: nsSlapdPlugin
		+	objectClass: extensibleObject
		+	cn: ACL Plugin
		+	nsslapd-pluginPath: libacl-plugin
		+	nsslapd-pluginInitfunc: acl_init
		+	nsslapd-pluginType: accesscontrol
		+	nsslapd-pluginEnabled: on
		+	nsslapd-plugin-depends-on-type: database
		+	nsslapd-pluginId: acl
		+	nsslapd-pluginVersion: 1.2.3
		+	nsslapd-pluginVendor: 389 Project
		+	nsslapd-pluginDescription: acl access check plugin
		+	nsslapd-pluginPrecedence: 50
		+
		+	If the precedence attribute is not set for a particular plug-in, the value will default to '''50''' internally.
	== Implementation ==		== Implementation ==

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Revision as of 19:31, 2 November 2009

This document describes the design and implementation of a feature to allow Plug-in execution order to be defined.

Background

The current implementation of the SLAPI plug-in interface does not allow the execution order of plug-ins to be defined within the same plug-in type. It would be useful to plug-in developers to be able to define an order for plug-in execution. This would allow for more complex plug-in interaction, such as having a pre-operation plug-in that relies on another pre-operation plug-in completing it's job first.

Design

To define plug-in execution order, it will be possible to set a plug-in precedence in a plug-in configuration entry. This precedence value will then be used to determine the order in which to call the plug-ins within a given plug-in type. The precedence will be defined as an integer value between 00-99 with 00 being the highest priority and 99 being the lowest priority. The precedence value will be stored in the nsslapd-pluginPrecedence attribute within a plug-in configuration entry. Here is an example configuration entry:

dn: cn=ACL Plugin,cn=plugins,cn=config
objectClass: top
objectClass: nsSlapdPlugin
objectClass: extensibleObject
cn: ACL Plugin
nsslapd-pluginPath: libacl-plugin
nsslapd-pluginInitfunc: acl_init
nsslapd-pluginType: accesscontrol
nsslapd-pluginEnabled: on
nsslapd-plugin-depends-on-type: database
nsslapd-pluginId: acl
nsslapd-pluginVersion: 1.2.3
nsslapd-pluginVendor: 389 Project
nsslapd-pluginDescription: acl access check plugin
nsslapd-pluginPrecedence: 50

If the precedence attribute is not set for a particular plug-in, the value will default to 50 internally.

Implementation