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addpartial Overlay README
DESCRIPTION
This package contains an OpenLDAP overlay called "addpartial" that
intercepts add requests, determines if the entry exists, determines what
attributes, if any, have changed, and modifies those attributes. If the
entry does not exist, the add request falls through and proceeds normally.
If the entry exists but no changes have been detected, the client receives
LDAP_SUCCESS (I suppose it is debatable what to do in this case, but this is
the most clean for my use. The LDAP_SUCCESS lets me know that the entry I
sent slapd == the entry already in my slapd DB. Perhaps this behavior
should be configurable in the future).
When a change is found, the addpartial overlay will replace all values for
the attribute (if an attribute does not exist in the new entry but exists
in the entry in the slapd DB, a replace will be done with an empty list of
values).
Once a modify takes place, the syncprov overlay will properly process the
change, provided that addpartial is the first overlay to run. Please see
the CAVEATS for more specifics about this.
The addpartial overlay makes it easy to replicate full entries to a slapd
instance without worrying about the differences between entries or even if
the entry exists. Using ldapadd to add entries, the addpartial overlay can
compare about 500 records per second. The intent of the addpartial overlay
is to make it easy to replicate records from a source that is not an LDAP
instance, such as a database. The overlay is also useful in places where it
is easier to create full entries rather than comparing an entry with an
entry that must be retrieved (with ldapsearch or similar) from an existing
slapd DB to find changes.
The addpartial overlay has been used in production since August 2004 and has
processed millions of records without incident.
BUILDING
A Makefile is included, please set your LDAP_SRC directory properly.
INSTALLATION
After compiling the addpartial overlay, add the following to your
slapd.conf:
### slapd.conf
...
moduleload addpartial.so
...
# after database directive...
# this overlay should be the last overlay in the config file to ensure that
# it properly intercepts the add request
overlay addpartial
...
### end slapd.conf
CAVEATS
- In order to ensure that addpartial does what it needs to do, it should be
the last overlay configured so it will run before the other overlays.
This is especially important if you are using syncrepl, as the modify that
addpartial does will muck with the locking that takes place in the
syncprov overlay.
---
Copyright 2004-2021 The OpenLDAP Foundation.
Portions Copyright (C) Virginia Tech, David Hawes.
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted only as authorized by the OpenLDAP
Public License.
A copy of this license is available in file LICENSE in the
top-level directory of the distribution or, alternatively, at
http://www.OpenLDAP.org/license.html.
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