Hi Colin, I guess currently we may have to restart almost all the daemons/services in order to swap out a standby NameNode (SBN):
1. The current active NameNode (ANN) needs to know the new SBN since in the current implementation the SBN tries to send rollEditLog RPC request to ANN periodically (thus if a NN failover happens later, the original ANN needs to send this RPC to the correct NN). 2. Looks like the DataNode currently cannot do real refreshment for NN. Look at the code in BPOfferService: void refreshNNList(ArrayList<InetSocketAddress> addrs) throws IOException { Set<InetSocketAddress> oldAddrs = Sets.newHashSet(); for (BPServiceActor actor : bpServices) { oldAddrs.add(actor.getNNSocketAddress()); } Set<InetSocketAddress> newAddrs = Sets.newHashSet(addrs); if (!Sets.symmetricDifference(oldAddrs, newAddrs).isEmpty()) { // Keep things simple for now -- we can implement this at a later date. throw new IOException( "HA does not currently support adding a new standby to a running DN. " + "Please do a rolling restart of DNs to reconfigure the list of NNs."); } } 3. If you're using automatic failover, you also need to update the configuration of the ZKFC on the current ANN machine, since ZKFC will do gracefully fencing by sending RPC to the other NN. 4. Looks like we do not need to restart JournalNodes for the new SBN but I have not tried before. Thus in general we may still have to restart all the services (except JNs) and update their configurations. But this may be a rolling restart process I guess: 1. Shutdown the old SBN, bootstrap the new SBN, and start the new SBN. 2. Keep the ANN and its corresponding ZKFC running, do a rolling restart of all the DN to update their configurations 3. After restarting all the DN, stop ANN and the ZKFC, and update their configuration. The new SBN should become active. I have not tried the upper steps, thus please let me know if this works or not. And I think we should also document the correct steps in Apache. Could you please file an Apache jira? Thanks, -Jing On Thu, Jul 31, 2014 at 9:37 AM, Colin Kincaid Williams <disc...@uw.edu> wrote: > Hello, > > I'm trying to swap out a standby NameNode in a QJM / HA configuration. I > believe the steps to achieve this would be something similar to: > > Use the Bootstrap standby command to prep the replacment standby. Or rsync > if the command fails. > > Somehow update the datanodes, so they push the heartbeat / journal to the > new standby > > Update the xml configuration on all nodes to reflect the replacment > standby. > > Start the replacment standby > > Use some hadoop command to refresh the datanodes to the new NameNode > configuration. > > I am not sure how to deal with the Journal switch, or if I am going about > this the right way. Can anybody give me some suggestions here? > > > Regards, > > Colin Williams > > -- CONFIDENTIALITY NOTICE NOTICE: This message is intended for the use of the individual or entity to which it is addressed and may contain information that is confidential, privileged and exempt from disclosure under applicable law. If the reader of this message is not the intended recipient, you are hereby notified that any printing, copying, dissemination, distribution, disclosure or forwarding of this communication is strictly prohibited. If you have received this communication in error, please contact the sender immediately and delete it from your system. Thank You.