openldap/servers/slapd/back-relay/README
2004-03-17 22:37:59 +00:00

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Relay backend sets up a relay virtual database that allows
to access other databases in the same instance of slapd
through different naming contexts and remapping attribute
values.
The DN rewrite, filter rewrite and attributeType/objectClass
mapping is done by means of the rewrite-remap overlay.
The database containing the real naming context can be
explicitly selected by means of the "relay" directive,
which must contain the naming context of the target
database. This also causes the rewrite-remap overlay
to be automatically instantiated. If the optional keyword
"massage" is present, the rewrite-remap overlay is
automatically configured to map the virtual to the real
naming context and vice-versa.
Otherwise, the rewrite-remap overlay must be explicitly
instantiated, by using the "overlay" directive, as
illustrated below. This allows much more freedom in target
database selection and DN rewriting.
If the "relay" directive is not present, the backend is
not bound to a single target database; on the contrary,
the target database is selected on a per-operation basis.
This allows, for instance, to relay one database for
authentication and anotheir for search/modify, or allows
to use one target for persons and another for groups
and so on.
To summarize: the "relay" directive:
- explicitly bounds the database to a single database
holding the real naming context;
- automatically instantiates the rewrite-remap overlay;
- automatically configures the naming context massaging
if the optional "massage" keyword is added
If the "relay" directive is not used, the rewrite-remap
overlay must be explicitly instantiated and the massaging
must be configured, either by using the "suffixmassage"
directive, or by issuing more sophisticate rewrite
instructions.
AttributeType/objectClass mapping must be explicitly
required.
Note that the rewrite-remap overlay is not complete nor
production- ready yet.
Examples are given of all the suggested usages.
# automatically massage from virtual to real naming context
database relay
suffix "dc=virtual,dc=naming,dc=context"
relay "dc=real,dc=naming,dc=context" massage
# explicitly massage (same as above)
database relay
suffix "dc=virtual,dc=naming,dc=context"
relay "dc=real,dc=naming,dc=context"
suffixmassage "dc=virtual,dc=naming,dc=context" \
"dc=real,dc=naming,dc=context"
# explicitly massage (same as above, but dynamic backend resolution)
database relay
suffix "dc=virtual,dc=naming,dc=context"
overlay rewrite-remap
suffixmassage "dc=virtual,dc=naming,dc=context" \
"dc=real,dc=naming,dc=context"
# old fashioned suffixalias, applied also to DN-valued attributes
# from virtual to real naming context, but not the reverse...
database relay
suffix "dc=virtual,dc=naming,dc=context"
relay "dc=real,dc=naming,dc=context"
rewriteContext default
rewriteRule "(.*)dc=virtual,dc=naming,dc=context$" \
"$1dc=real,dc=naming,dc=context"
rewriteContext searchFilter
rewriteContext searchResult
rewriteContext searchResultAttrDN
rewriteContext matchedDN