Hello, I am sorry it took us (the community) more than a day to answer to this rather critical situation. That being said, my recommendation at this point would be for you to make sure about the impacts of whatever you would try. Working on a broken cluster, as an emergency might lead you to a second mistake, possibly more destructive than the first one. It happened to me and around, for many clusters. Move forward even more carefuly in these situations as a global advice.
Suddenly i lost all disks of cassandar-data on one of my racks With RF=2, I guess operations use LOCAL_ONE consistency, thus you should have all the data in the safe rack(s) with your configuration, you probably did not lose anything yet and have the service only using the nodes up, that got the right data. tried to replace the nodes with same ip using this: > > https://blog.alteroot.org/articles/2014-03-12/replace-a-dead-node-in-cassandra.html > As a side note, I would recommend you to use 'replace_address_first_boot' instead of 'replace_address'. This does basically the same but will be ignored after the first bootstrap. A detail, but hey, it's there and somewhat safer, I would use this one. java.lang.IllegalStateException: unable to find sufficient sources for > streaming range in keyspace system_traces By default, non-user keyspace use 'SimpleStrategy' and a small RF. Ideally, this should be changed in a production cluster, and you're having an example of why. Now when i altered the system_traces keyspace startegy to > NetworkTopologyStrategy and RF=2 > but then running nodetool repair failed: Endpoint not alive /IP of dead > node that i'm trying to replace. > Changing the replication strategy you made the dead rack owner of part of the token ranges, thus repairs just can't work as there will always be one of the nodes involved down as the whole rack is down. Repair won't work, but you probably do not need it! 'system_traces' is a temporary / debug table. It's probably empty or with irrelevant data. Here are some thoughts: * It would be awesome at this point for us (and for you if you did not) to see the status of the cluster: ** 'nodetool status' ** *'nodetool describecluster' *--> This one will tell if the nodes agree on the schema (nodes up). I have seen schema changes with nodes down inducing some issues. *** *Cassandra version ** Number of racks (I assumer #racks >= 2 in this email) *Option 1: (Change schema and) use replace method (preferred method)* * Did you try to have the replace going, without any former repairs, ignoring the fact 'system_traces' might be inconsistent? You probably don't care about this table, so if Cassandra allows it with some of the nodes down, going this way is relatively safe probably. I really do not see what you could lose that matters in this table. * Another option, if the schema first change was accepted, is to make the second one, to drop this table. You can always rebuild it in case you need it I assume. *Option 2: Remove all the dead nodes *(try to avoid this option 2, if option 1 works, it is better). Please do not take an apply this like this. It's a thought on how you could get rid of the issue, yet it's rather brutal and risky and I did not consider it deeply and have no clue about your architecture and the context. Consider it carefully on your side. * You can also 'nodetool removenode' on each of the dead nodes. This will have nodes streaming around and the rack isolation guarantee will no longer be valid. It's hard to reason about what would happen to the data and in terms of streaming. * Alternatively, if you don't have enough space, you can even '*force*' the 'nodetool removenode'. See the documentation. Forcing it will prevent streaming and remove the node (token ranges handover, but not the data). If that does not work you can use the 'nodetool assassinate' command as well. When adding nodes back to the broken DC, the first nodes will take probably 100% of the ownership, which is often too much. You can consider adding back all the nodes with 'auto_bootstrap: false' before repairing them once they have their final token ownership, the same ways we do when building a new data center. This option is not really clean, and have some caveats that* you need to consider before starting* as there are token range movements and nodes available that do not have the data. Yet this should work. I imagine it would work nicely with RF=3 and QUORUM and with RF=2 (if you have 2+ racks), I guess it should work as well but you will have to pick one of availability or consistency while repairing the data. *Be aware that read requests hitting these nodes will not find data!* Plus, you are using an *RF=2*. Thus using consistency of 2+ (TWO, QUORUM, ALL), for at least one of reads or writes is needed to preserve consistency while re-adding the nodes in this case. Otherwise, reads will not detect the mismatch with certainty and might show inconsistent data the time for the nodes to be repaired. I must say, that I really prefer odd values for the RF, starting with RF=3. Using RF=2 you will have to pick. Consistency or Availability. With a consistency of ONE everywhere, the service is available, no single point of failure. using anything bigger than this, for writes or read, brings consistency but it creates single points of failures (actually any node becomes a point of failure). RF=3 and QUORUM for both write and reads take the best of the 2 worlds somehow. The tradeoff with RF=3 and quorum reads is the latency increase and the resource usage. Maybe is there a better approach, I am not too sure, but I think I would try option 1 first in any case. It's less destructive, less risky, no token range movements, no empty nodes available. I am not sure about limitation you might face though and that's why I suggest a second option for you to consider if the first is not actionable. Let us know how it goes, C*heers, ----------------------- Alain Rodriguez - @arodream - al...@thelastpickle.com France / Spain The Last Pickle - Apache Cassandra Consulting http://www.thelastpickle.com Le lun. 10 sept. 2018 à 09:09, onmstester onmstester <onmstes...@zoho.com> a écrit : > Any idea? > > Sent using Zoho Mail <https://www.zoho.com/mail/> > > > ---- On Sun, 09 Sep 2018 11:23:17 +0430 *onmstester onmstester > <onmstes...@zoho.com <onmstes...@zoho.com>>* wrote ---- > > > Hi, > > Cluster Spec: > 30 nodes > RF = 2 > NetworkTopologyStrategy > GossipingPropertyFileSnitch + rack aware > > Suddenly i lost all disks of cassandar-data on one of my racks, after > replacing the disks, tried to replace the nodes with same ip using this: > > https://blog.alteroot.org/articles/2014-03-12/replace-a-dead-node-in-cassandra.html > > starting the to-be-replace-node fails with: > java.lang.IllegalStateException: unable to find sufficient sources for > streaming range in keyspace system_traces > > the problem is that i did not changed default replication config for > System keyspaces, but Now when i altered the system_traces keyspace > startegy to NetworkTopologyStrategy and RF=2 > but then running nodetool repair failed: Endpoint not alive /IP of dead > node that i'm trying to replace. > > What should i do now? > Can i just remove previous nodes, change dead nodes IPs and re-join them > to cluster? > > Sent using Zoho Mail <https://www.zoho.com/mail/> > > > >
