I was searching about Cassandra, and as I understood you have to manually start all nodes. Is there way to start cluster(all nodes) from just one machine like in Hadoop or HBase.
For example I have 5 machines with Cassandra, each has its own configuration(some are seeds for example) can I log in to first machine and type something like this "Cassandra -start-all" or something similar?
No. But you can write a script that does this. SSH into the machine and start the node, or configure Cassandra to run as a service, that way it will start up on it's own.
The CCM tool for running multiple nodes on one machine does scripting to start multiple nodes. Take a look at the source.
Related
We have a 6 node cassandra 3.11.3 cluster with ubuntu 16.04. These are virtual machines.
We are switching to physical machines on brand (8!) new servers that will have debian 11 and presumably cassandra 3.11.12.
Since the main version is always 3.11.x and ubuntu 16.04 is out of support, the question is: can we just let the new machines join the old cluster and then decommission the outdated?
I hope to get a tips about this becouse intuitively it seems fine but we are not too sure about that.
Thank you.
We have a 6 node cassandra 3.11.3 cluster with ubuntu 16.04. These are virtual machines. We are switching to physical machines on brand (8!)
Quick tip here; but it's a good idea to build your clusters in multiples of your RF. Not sure what your RF is, but if RF=3, I'd either stay with six or get one more and go to nine. It's all about even data distribution.
can we just let the new machines join the old cluster and then decommission the outdated?
In short, no. You'll want to upgrade the existing nodes to 3.11.12, first. I can't recall if 3.11.3 and 3.11.12 are SSTable compatible, but I wouldn't risk it.
Secondly, the best way to do this, is to build your new (physical) nodes in the cluster as their own logical data center. Start them up empty, and then run a nodetool rebuild on each. Once that's complete, then decommission the old nodes.
There is a bit simpler solution - move data from each virtual machine into a physical server, as following:
Prepare Cassandra installation on a physical machine, configure the same cluster name, etc.
1.Stop Cassandra in a virtual machine & make sure that it won't start
Copy all Cassandra data /var/lib/cassandra or something like from VM to the physical server
Start Cassandra process on a physical server
Repeat that process for all VM nodes, at some point, updating seeds, etc. After process is finished, you can add two physical servers that are left. Also, to speedup process, you can do initial copy of the data before stopping Cassandra in the VM, and after it's stopped, re-sync data with rsync or something like. This way you can minimize the downtime.
This approach would be much faster compared to the adding a new node & decommissioning the old one as we won't need to stream data twice. This works because after node is initialized, Cassandra identify nodes by assigned UUID, not by IP address.
Another approach is to follow instructions on replacement of the dead node. In this case streaming of data will happen only once, but it could be a bit slower compared to the direct copy of the data.
I'm running Hadoop and Spark on a four-node cluster in AWS EC2.
After doing a lot of web research, it seems the accepted way to start Spark on a cluster (once Hadoop is running) is to:
1) Log into the master node and run start-master.sh.
2) Log into each slave node and run start-slave.sh, passing it the DNS and port information for the master node.
My question is: If there are, let's say 20 nodes, this is pretty tedious and time consuming. Is there a way to start Spark from some localized location the way Hadoop is started? When you run Hadoop from the master node, it starts all the slave nodes remotely. I'm looking for a solution like that, or for a python script that can SSH into the nodes and start them.
You could use Apache Ambari to manage the whole cluster, which would SSH to all nodes for you
Otherwise, you could use a system like Ansible to configure and start all the services
Sounds like you're only using Spark Standalone, though, not YARN, because there is no start-slaves script for YARN
I am trying to test out Spark so I can summarize some data I have in Cassandra. I've been through all the DataStax tutorials and they are very vague as to how you actually enable spark. The only indication I can find is that it comes enabled automatically when you select "Analytics" node during install. However, I have an existing Cassandra node and I don't want to have to use a different machine for testing as I am just evaluating everything on my laptop.
Is it possible to just enable Spark on the same node and deal with any performance implications? If so how can I enable it so that it can be tested?
I see the folders there for Spark (although I'm not positive all the files are present) but when I check to see if it's set to Spark master, it says that no spark nodes are enabled.
dsetool sparkmaster
I am using Linux Ubuntu Mint.
I'm just looking for a quick and dirty way to get my data averaged and so forth and Spark seems like the way to go since it's a massive amount of data, but I want to avoid having to pay to host multiple machines (at least for now while testing).
Yes, Spark is also able to interact with a cluster even if it is not on all the nodes.
Package install
Edit the /etc/default/dse file, and then edit the appropriate line
to this file, depending on the type of node you want:
...
Spark nodes:
SPARK_ENABLED=1
HADOOP_ENABLED=0
SOLR_ENABLED=0
Then restart the DSE service
http://docs.datastax.com/en/datastax_enterprise/4.5/datastax_enterprise/reference/refDseServ.html
Tar Install
Stop DSE on the node and the restart it using the following command
From the install directory:
...
Spark only node: $ bin/dse cassandra -k - Starts Spark trackers on a cluster of Analytics nodes.
http://docs.datastax.com/en/datastax_enterprise/4.5/datastax_enterprise/reference/refDseStandalone.html
Enable spark by changing SPARK_ENABLED=1
using the command: sudo nano /usr/share/dse/resources/dse/conf/dse.default
I have a cassandra cluster (2.1.0) running fine.
After installing titan 5.1, and editing the titan-cassandra.properties to point to cluster hostname list rather than localhost, i run following -
titan.sh -c conf/titan-cassandra.properties start
It is able to recognize running cassandra instance, starts elastic search, but times out while connecting to rexster.
If i run it with local cassandra, everything runs fine using following ->br>
titan.sh start
do i need to make any change in rexster properties to point to running cassandra cluster..
Thanks in advance
Titan Server started by titan.sh represents a quick way to get started with Titan/Rexster/ES. It is designed to simplify running all those things with one startup script. Once you start breaking things apart (e.g. a separate cassandra cluster), you might not want to use titan.sh anymore because, it still forks a cassandra process when it starts up. Presumably, you don't need that anymore, given that you have a separate cassandra cluster.
Given the more advanced nature of your environment, I would simply download Rexster and configure it to connect to your cluster.
I would like know is there any way to run multiple Cassandra servers on a single machine, so tall the servers on that machine form one ring (cluster).
I would like know is there any way to run the cassandra servers in a single machine ?
There's always a way!
There is an excellent tool available that allows you to configure a multi-node cluster locally, but it's currently not supported under windows. When you build a cluster and start it, it will configure the ring for you. You can check out the ring using ./nodetool -h 127.0.0.1 -p 7100 ring after it has started.
*Just a side-note, the ccm tool starts the cluster as a background process.