I don't like your cunning plan. Don't drop the system auth and distributed keyspaces, instead just change them to NTS and then do your replacement for each down node.
If you're actually using auth and worried about consistency I believe 3.11 has the feature to be able to exclude nodes during a repair which you could use just to repair the auth keyspace. But if you're not using auth go ahead and change them and then do all your replaces is the best method of recovery here. On Sun., 23 Sep. 2018, 00:33 onmstester onmstester, <onmstes...@zoho.com> wrote: > Another question, > Is there a management tool to do nodetool cleanup one by one (wait until > finish of cleaning up one node then start clean up for the next node in > cluster)? > ---- On Sat, 22 Sep 2018 16:02:17 +0330 *onmstester onmstester > <onmstes...@zoho.com <onmstes...@zoho.com>>* wrote ---- > > I have a cunning plan (Baldrick wise) to solve this problem: > > - stop client application > - run nodetool flush on all nodes to save memtables to disk > - stop cassandra on all of the nodes > - rename original Cassandra data directory to data-old > - start cassandra on all the nodes to create a fresh cluster including > the old dead nodes > - again create the application related keyspaces in cqlsh and this > time set rf=2 on system keyspaces (to never encounter this problem again!) > - move sstables from data-backup dir to current data dirs and restart > cassandra or reload sstables > > > Should this work and solve my problem? > > > ---- On Mon, 10 Sep 2018 17:12:48 +0430 *onmstester onmstester > <onmstes...@zoho.com <onmstes...@zoho.com>>* wrote ---- > > > > Thanks Alain, > First here it is more detail about my cluster: > > - 10 racks + 3 nodes on each rack > - nodetool status: shows 27 nodes UN and 3 nodes all related to single > rack as DN > - version 3.11.2 > > *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. > > I really love to let the replace going, but it stops with the error: > > java.lang.IllegalStateException: unable to find sufficient sources for > streaming range in keyspace system_traces > > > Also i could delete system_traces which is empty anyway, but there is a > system_auth and system_distributed keyspace too and they are not empty, > Could i delete them safely too? > If i could just somehow skip streaming the system keyspaces from node > replace phase, the option 1 would be great. > > P.S: Its clear to me that i should use at least RF=3 in production, but > could not manage to acquire enough resources yet (i hope would be fixed in > recent future) > > Again Thank you for your time > > Sent using Zoho Mail <https://www.zoho.com/mail/> > > > ---- On Mon, 10 Sep 2018 16:20:10 +0430 *Alain RODRIGUEZ > <arodr...@gmail.com <arodr...@gmail.com>>* wrote ---- > > > > 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/> > > > > >
