Preventing Monopolization Of The Consumer In Multi-Master Replication - Red Hat DIRECTORY SERVER 8.0 - ADMINISTRATION Administration Manual

NOTE
At the end of this procedure, all supplier servers will have mutual replication agreements,
which means that they can accept updates from each other.
NOTE
After creating a replication agreement, the connection type (SSL or non-SSL) cannot
be changed because LDAP and LDAPS connections use different ports. To change the
connection type, re-create the replication agreement.
8.5.4. Preventing Monopolization of the Consumer in Multi-Master
Replication
One of the features of multi-master replication is that a supplier acquires exclusive access to the
consumer for the replicated area. During this time, other suppliers are locked out of direct contact with
the consumer. If a supplier attempts to acquire access while locked out, the consumer sends back a
busy response, and the supplier sleeps for several seconds before making another attempt. Normally,
this is all right; the supplier simply sends its update to another consumer while the first consumer is
locked and then send updates when the first consumer is free again.
A problem can arise if the locking supplier is under a heavy update load or has a lot of pending
updates in the changelog. If the locking supplier finishes sending updates and then has more pending
changes to send, it will immediately attempt to reacquire the consumer and will most likely succeed,
since the other suppliers usually will be sleeping. This can cause a single supplier to monopolize a
consumer for several hours or longer.
Two attributes address this issue, nsds5ReplicaBusyWaitTime and
nsds5ReplicaSessionPauseTime.
• nsds5ReplicaBusyWaitTime. The nsds5ReplicaBusyWaitTime attribute sets the amount of time
in seconds a supplier should wait after a consumer sends back a busy response before making
another attempt to acquire access. The default is 3 seconds.
• nsds5ReplicaSessionPauseTime. The nsds5ReplicaSessionPauseTime attribute sets the
amount of time in seconds a supplier should wait between update sessions. Set this interval so
that it is at least one second longer than the interval specified for nsds5ReplicaBusyWaitTime.
Increase the interval as needed until there is an acceptable distribution of consumer access among
the suppliers. The default is 0.
These two attributes may be present in the nsds5ReplicationAgreement object class,
which is used to describe replication agreements. Set the attributes at any time by using
changetype:modify with the replace operation. The change takes effect for the next update
session if one is already in progress.
NOTE
If either attribute is set to a negative value, Directory Server sends the client a message
and an LDAP_UNWILLING_TO_PERFORM error code.

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