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> 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 ---- On Mon, 10 Sep 2018 16:20:10
+0430 Alain RODRIGUEZ <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 ---- On Sun, 09 Sep 2018 11:23:17 +0430 onmstester onmstester
<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
