Replicators can have one of four roles, Extractor(master),Applier(slave), thl-server or thl-client.
A replicator in a master role
extracts data from a source database (for example, by reading the
binary log from a MySQL server), and generates THL. As a
master the replicator also
provides the THL to other replicators over the network connection.
A slave replicator pulls THL
data from a master and then
applies that data to a target database.
A thl-server replicator is a special role
that Extractor replicators can be changed to temporarily when a Primary is taken offline.
This will allow downstream Applier replicators to download and apply any THL that hasn't
yet been processed by the Applier.
To enable this role, first you must place the cluster into MAINTENANCE mode
and then issue the following statements
shell>trepctl offlineshell>trepctl setrole -role thl-servershell>trepctl online
To revert back to the original Extractor role, issue the following
shell>trepctl offlineshell>trepctl setrole -role mastershell>trepctl online
A thl-client replicator is a special role
that Applier replicators can be changed to. This will allow the Applier replicator
to download any THL available from the upstream Extractor, but does NOT apply the THL to
the target database.
To enable this role, first you must place the cluster into MAINTENANCE mode
and then issue the following statements
shell>trepctl offlineshell>trepctl setrole -role thl-clientshell>trepctl online
To revert back to the original Applier role, issue the following
shell>trepctl offlineshell>trepctl setrole -role slaveshell>trepctl online