HP-UX Directory Server 8.1 plug-in reference

function and library are part of the entry for the dc=example,dc=com suffix and appear as
follows:
nsslapd-distribution-plugin: /path/to/a/shared/library
nsslapd-distribution-funct: distribution-function-name
Each time the server gets a request for a suffix that contains the distribution function, the function
is called. The function then decides which database (back end) processes the request. The decision
made by the function is based on some piece of information present in the pblock at the time of
the request, such as the entry DN, a hash function, the time of day, or the type of operation.
For search operations, the function can forward the operation to a single database, or to all
databases.
The distribution function itself appears as follows:
int distribution_function(Slapi_PBlock *pb, Slapi_DN * dn, Slapi_Back end
**mtn_be, int be_count, Slapi_DN * node_dn);
The following table lists the parameters taken by the distribution function:
Table 12-1 Distribution function parameters
DescriptionParameter name
The pblock of the plug-in that contains all the information about the operations in
progress. This structure is the same as that for other plug-ins; for example, operation
type, IP address of the client, target DN, search filter, bind credentials, etc.
pb
A table of size be_count containing the list of databases defined for the suffix. If a
database is defined in the suffix entry but is not available, the corresponding pointer
in the table will be set to NULL.
mtn_be
The suffix containing the distribution function.
node_dn
The size of the table that contains the list of databases involved in the distribution of
entries.
be_count
The row number of the database in the mtn_be table. For search operations, you can
return a value of MTN_ALL_BACKENDS to specify that all databases must be searched.
int
The root entry for the suffix must be present in each database in order for the distribution function
to work properly. For example, for the suffix dc=example,dc=com, you need to create an entry
corresponding to dc=example,dc=com in each database involved in the distribution.
You can create the root entry in two ways:
• Import the same LDIF file into each database using the ldif2db command-line utility.
This LDIF file should contain the root entry as well as data that you want to distribute across
the databases. Only the data determined by the distribution function to be appropriate for
each database will be imported.
• Create an LDIF file that contains the root entry. You can do this by exporting the root entry
(for example, dc=example,dc=com) in LDIF format using the ldapsearch command-line
utility.
You then need to import the LDIF file into each database using the ldif2db command-line
utility. If you have three databases for a single suffix, you need to import the suffix entry
three times.
When a subtree search is performed above a suffix that is distributed among several databases,
the search will be performed on all databases. This means that the shared suffix entry that you
create on each database (in the example, dc=example,dc=com) can be returned multiple times.
102 Using the custom distribution logic