I've found modified Carlos' article (more recent than that I was referring to) and this one contains the same method as you described, Oleksandr:
https://mrcalonso.com/2016/01/26/cassandra-instantaneous-in-place-node-replacement Thank you for your readiness to help! Kind Regards, Kyrill ________________________________ From: Kyrylo Lebediev <kyrylo_lebed...@epam.com> Sent: Saturday, February 3, 2018 12:23:15 PM To: User Subject: Re: Cassandra 2.1: replace running node without streaming Thank you Oleksandr, Just tested on 3.11.1 and it worked for me (you may see the logs below). Just comprehended that there is one important prerequisite this method to work: new node MUST be located in the same rack (in terms of C*) as the old one. Otherwise correct replicas placement order will be violated (I mean when replicas of the same token range should be placed in different racks). Anyway, even having successful run of node replacement in sandbox I'm still in doubt. Just wondering why this procedure which seems to be much easier than [add/remove node] or [replace a node] which are documented ways for live node replacement, has never been included into documentation. Does anybody in the ML know the reason for this? Also, for some reason in his article Carlos drops files of system keyspace (which contains system.local table): In the new node, delete all system tables except for the schema ones. This will ensure that the new Cassandra node will not have any corrupt or previous configuration assigned. 1. sudo cd /var/lib/cassandra/data/system && sudo ls | grep -v schema | xargs -I {} sudo rm -rf {} http://engineering.mydrivesolutions.com/posts/cassandra_nodes_replacement/ [Carlos, if you are here might you, please, comment ] So still a mystery to me..... ----- Logs for 3.1.11 ----- ====== Before: -- Address Load Tokens Owns (effective) Host ID Rack UN 10.10.10.222 256.61 KiB 3 100.0% bd504008-5ff0-4b6c-a3a6-a07049e61c31 rack1 UN 10.10.10.223 225.65 KiB 3 100.0% c562263f-4126-4935-b9f7-f4e7d0dc70b4 rack1 <<<<<< UN 10.10.10.221 187.39 KiB 3 100.0% d312c083-8808-4c98-a3ab-72a7cd18b31f rack1 ======= After: -- Address Load Tokens Owns (effective) Host ID Rack UN 10.10.10.222 245.84 KiB 3 100.0% bd504008-5ff0-4b6c-a3a6-a07049e61c31 rack1 UN 10.10.10.221 192.8 KiB 3 100.0% d312c083-8808-4c98-a3ab-72a7cd18b31f rack1 UN 10.10.10.224 266.61 KiB 3 100.0% c562263f-4126-4935-b9f7-f4e7d0dc70b4 rack1 <<<<< ====== Logs from another node (10.10.10.221): INFO [HANDSHAKE-/10.10.10.224] 2018-02-03 11:33:01,397 OutboundTcpConnection.java:560 - Handshaking version with /10.10.10.224 INFO [GossipStage:1] 2018-02-03 11:33:01,431 Gossiper.java:1067 - Node /10.10.10.224 is now part of the cluster INFO [RequestResponseStage-1] 2018-02-03 11:33:02,190 Gossiper.java:1031 - InetAddress /10.10.10.224 is now UP INFO [RequestResponseStage-1] 2018-02-03 11:33:02,190 Gossiper.java:1031 - InetAddress /10.10.10.224 is now UP WARN [GossipStage:1] 2018-02-03 11:33:08,375 StorageService.java:2313 - Host ID collision for c562263f-4126-4935-b9f7-f4e7d0dc70b4 between /10.10.10.223 and /10.10.10.224; /10.10.10.224 is the new owner INFO [GossipTasks:1] 2018-02-03 11:33:08,806 Gossiper.java:810 - FatClient /10.10.10.223 has been silent for 30000ms, removing from gossip ====== Logs from new node: INFO [main] 2018-02-03 11:33:01,926 StorageService.java:1442 - JOINING: Finish joining ring INFO [GossipStage:1] 2018-02-03 11:33:02,659 Gossiper.java:1067 - Node /10.10.10.223 is now part of the cluster WARN [GossipStage:1] 2018-02-03 11:33:02,676 StorageService.java:2307 - Not updating host ID c562263f-4126-4935-b9f7-f4e7d0dc70b4 for /10.10.10.223 because it's mine INFO [GossipStage:1] 2018-02-03 11:33:02,683 StorageService.java:2365 - Nodes /10.10.10.223 and /10.10.10.224 have the same token -7774421781914237508. Ignoring /10.10.10.223 INFO [GossipStage:1] 2018-02-03 11:33:02,686 StorageService.java:2365 - Nodes /10.10.10.223 and /10.10.10.224 have the same token 2257660731441815305. Ignoring /10.10.10.223 INFO [GossipStage:1] 2018-02-03 11:33:02,692 StorageService.java:2365 - Nodes /10.10.10.223 and /10.10.10.224 have the same token 51879124242594885. Ignoring /10.10.10.223 WARN [GossipTasks:1] 2018-02-03 11:33:03,985 Gossiper.java:789 - Gossip stage has 5 pending tasks; skipping status check (no nodes will be marked down) INFO [main] 2018-02-03 11:33:04,394 SecondaryIndexManager.java:509 - Executing pre-join tasks for: CFS(Keyspace='test', ColumnFamily='usr') WARN [GossipTasks:1] 2018-02-03 11:33:05,088 Gossiper.java:789 - Gossip stage has 7 pending tasks; skipping status check (no nodes will be marked down) INFO [GossipStage:1] 2018-02-03 11:33:05,718 Gossiper.java:1046 - InetAddress /10.10.10.223 is now DOWN INFO [main] 2018-02-03 11:33:06,872 StorageService.java:2268 - Node /10.10.10.224 state jump to NORMAL INFO [main] 2018-02-03 11:33:06,998 Gossiper.java:1655 - Waiting for gossip to settle... INFO [main] 2018-02-03 11:33:15,004 Gossiper.java:1686 - No gossip backlog; proceeding INFO [GossipTasks:1] 2018-02-03 11:33:20,114 Gossiper.java:1046 - InetAddress /10.10.10.222 is now DOWN <<<<< have no idea why this appeared in logs INFO [main] 2018-02-03 11:33:20,566 NativeTransportService.java:70 - Netty using native Epoll event loop INFO [HANDSHAKE-/10.10.10.222] 2018-02-03 11:33:20,714 OutboundTcpConnection.java:560 - Handshaking version with /10.10.10.222 Kind Regards, Kyrill ________________________________ From: Oleksandr Shulgin <oleksandr.shul...@zalando.de> Sent: Saturday, February 3, 2018 10:44:26 AM To: User Subject: Re: Cassandra 2.1: replace running node without streaming On 3 Feb 2018 08:49, "Jürgen Albersdorfer" <jalbersdor...@gmail.com<mailto:jalbersdor...@gmail.com>> wrote: Cool, good to know. Do you know this is still true for 3.11.1? Well, I've never tried with that specific version, but this is pretty fundamental, so I would expect it to work the same way. Test in isolation if you want to be sure, though. I don't think this is documented anywhere, however, since I had the same doubts before seeing it worked for the first time. -- Alex Am 03.02.2018 um 08:19 schrieb Oleksandr Shulgin <oleksandr.shul...@zalando.de<mailto:oleksandr.shul...@zalando.de>>: On 3 Feb 2018 02:42, "Kyrylo Lebediev" <kyrylo_lebed...@epam.com<mailto:kyrylo_lebed...@epam.com>> wrote: Thanks, Oleksandr, In my case I'll need to replace all nodes in the cluster (one-by-one), so streaming will introduce perceptible overhead. My question is not about data movement/copy itself, but more about all this token magic. Okay, let's say we stopped old node, moved data to new node. Once it's started with auto_bootstrap=false it will be added to the cluster like an usual node, just skipping streaming stage, right? For a cluster with vnodes enabled, during addition of new node its token ranges are calculated automatically by C* on startup. So, how will C* know that this new node must be responsible for exactly the same token ranges as the old node was? How would the rest of nodes in the cluster ('peers') figure out that old node should be replaced in ring by the new one? Do you know about some limitation for this process in case of C* 2.1.x with vnodes enabled? A node stores its tokens and host id in the system.local table. Next time it starts up, it will use the same tokens as previously and the host id allows the rest of the cluster to see that it is the same node and ignore the IP address change. This happens regardless of auto_bootstrap setting. Try "select * from system.local" to see what is recorded for the old node. When the new node starts up it should log "Using saved tokens" with the list of numbers. Other nodes should log something like "ignoring IP address change" for the affected node addresses. Be careful though, to make sure that you put the data directory exactly where the new node expects to find it: otherwise it might just join as a brand new one, allocating new tokens. As a precaution it helps to ensure that the system user running the Cassandra process has no permission to create the data directory: this should stop the startup in case of misconfiguration. Cheers, -- Alex
