I am new to Cassandra. I install Apache Cassandra on ubuntu 16.04. What I do to know how many nodes my cluster have. if only one node by default?. what happens during the replication process? please help, Thank you.
Your new installation gives you one node of Cassandra, so at present you would have a single-node cluster.
Once Cassandra is started and up and running, you can display your cluster topology with the nodetool status command, it prints the cluster information.
http://cassandra.apache.org/doc/latest/tools/nodetool/status.html
With Cassandra, the data is replicated between nodes according to the replication strategies that you define; in the case of a single-node cluster, replication is not really applicable.
Related
Previously we had three nodes cluster with two Cassandra nodes datacenter in one dc and one spark enabled node in different dc.
Spark was running smoothly in that configurations.
Then we tried adding another node in analytics dc with spark enabled. We had configured GossipingPropertyFileSnitch as well as added seeds.
But now when we start the cluster, spark master is assigned to both the nodes separately. So spark job still runs on a single node. What configurations are we missing regarding running spark job in a cluster?
Most probably you didn't make an adjustments in the Analytics keyspace replication, or didn't run the repair after you added a node. Please refer to instructions in official documentation.
Also, please check that you configured the same DC for both of Analytics nodes, because the Spark master is elected per DC.
We have currently using DSE 4.8 and 5.12. we want to migrate to apache cassandra .since we don't use spark or search thought save some bucks moving to apache. can this be achieved without down time. i see sstableloader works other way. can any one share me the steps to follow to migrate from dse to apache cassandra. something like this from dse to apache.
https://support.datastax.com/hc/en-us/articles/204226209-Clarification-for-the-use-of-SSTABLELOADER
Figure out what version of Apache Cassandra is being run by DSE. Based on the DSE documentation DSE 4.8.14 is using Apache Cassandra 2.1 and DSE 5.1 is using Apache Cassandra 3.11
Simplest way to do this is to build another DC (Logical DC per Cassandra) and add it to the existing cluster.
As usual, with a "Nodetool Rebuild {from-old-DC}" on to the new DC nodes, let Cassandra take care of streaming data to the new Apache Cassandra nodes naturally.
Once data streaming is completed, based on the LoadBalancingPolicy being used by applications, switch their local_dc to DC2 (the new DC). Once the new DC starts taking traffic, shutdown nodes in old DC say DC1 one by one.
alter keyspace dse_system and dse_security not using everywhere
on non-seed nodes, cleanup cassandra data directory
turn on replace in cassandra-env.sh
start instance
monitoring streaming process using command 'nodetool netstats|grep Receiving'
change seeds node definition and rolling restart before finally migrate previous seeds nodes.
I had setup a 50 node Apache Cassandra cluster
I took one node and wanted to install DSE on it and make is a single node DSE cluster
I have removed /var/lib/cassandra and /var/log/cassandra
I have truncated systems.peers table on the single node
When I start dse cassandra on this node, I still see the remaining nodes doing handshake and being added to this cluster.
What is the best way to complete remove any traces of existing Cassandra cluster from this node?
You need to change the cluster_name directive in cassandra.yaml to a different name to the rest of the cluster.
I'm trying use Datastax Enterprise for deploying database system
My cluster:
2 dse cassandra node
2 dse solr node
I created a keyspace by cqlsh on one node but I could not drop that keyspace from another nodes on cluster, unless drop from node creating keyspace. Anybody know why?
This sounds like https://issues.apache.org/jira/browse/CASSANDRA-5202
I have had to delete the data directory for the troubled key space in all nodes and restart DSE to fix.
Do you have the output from cqlsh on the node that won't allow you to drop the keyspace?
What version of DSE are you using?
I already have a cassandra cluster of 4 nodes (version 1.2.5). I made an image of one of the cassandra instance in the existing cluster and created new cluster with 2 nodes. When i started new instances and checked nodetool status it is showing the old cluster ips also. Checked the cassandra.yaml file. Seeds are set for new nodes only. What else needs to be changed?
I think the cluster metainfo is stored in the system keyspace--check the peers table.
#Alex Popescu , Thanks that worked for me.
1)SELECT * FROM system.peers; - gave me the entries for the hosts .
2)REMOVED the entry for unwanted node.
3)Ran nodetool flush system.
4)Restarted cassandra on all nodes of the cluster.