Although the takeover of a failed broker’s persistent data by a failover broker in an enhanced cluster is normally automatic, there may be times when you want to prevent such failover from occurring. To suppress automatic failover when shutting down a broker, use the -nofailover option to the imqcmd shutdown bkr subcommand:
imqcmd shutdown bkr -nofailover -b hostName:portNumber
where hostName and portNumber are the host name and port number of the broker to be shut down.
Conversely, you may sometimes need to force a broker failover to occur manually. (This might be necessary, for instance, if a failover broker were to itself fail before completing the takeover process.) In such cases, you can initiate a failover manually from the command line: first shut down the broker to be taken over with the -nofailover option, as shown above, then issue the command
imqcmd takeover bkr -n brokerID
where brokerID is the broker identifier of the broker to be taken over. If the specified broker appears to be running, the Command utility will display a confirmation message:
The broker associated with brokerID last accessed the database # seconds ago. Do you want to take over for this broker?
You can suppress this message, and force the takeover to occur unconditionally, by using the -f option to the imqcmd takeover bkr command:
imqcmd takeover bkr -f -n brokerID
The imqcmd takeover bkr subcommand is intended only for use in failed-takeover situations. You should use it only as a last resort, and not as a general way of forcibly taking over a running broker.