I have configured cassandra 3.0.9 on 3 nodes but I have to use only 1 node for sometime. I have disconnected other 2 nodes from network also removed the entries of both the nodes from Cassandra.yaml, rackdc and topology files.
When I check node tool status it shows me both the down nodes. When I try to execute any query on cqlsh it gives me below error:
Blockquote
OperationTimedOut: errors={'127.0.0.1': 'Request timed out while waiting for schema agreement. See Session.execute_async and Cluster.max_schema_agreement_wait.'}, last_host=127.0.0.1
Blockquote
Warning: schema version mismatch detected; check the schema versions of your nodes in system.local and system.peers.
How I can resolve this?
That's not how you remove a node from a Cassandra cluster. In fact, what you're doing is quite dangerous. Typically, you'd use nodetool decommission. If your other two nodes are still intact and just offline, I suggest bringing them back online temporarily and let decommission do its thing.
I'm going to also throw this out there - it's possible you're missing a good portion of your data with the steps you did above unless all keyspaces had RF=3. Cassandra distributes data evenly between the nodes in a respective DC. The decommission step I mention above redistributes the data.
Now if you don't have the other 2 nodes to run a nodetool decommission, you may have to remove the node with nodetool removenode and in the worst case, nodetool assassinate.
Check these docs for reference and the full steps to removing a node: https://docs.datastax.com/en/cassandra/3.0/cassandra/operations/opsAddingRemovingNodeTOC.html
Related
I have a 6 node Cassandra cluster and i've tested following scenario
i'm turn off 3 nodes, and on remaining 3 nodes i'm drop the table and re-create it, and after 3 node comes up, i'm unable to do repair, its says
[Uzbekistan#Gentoo]: nodetool repair --full
Repair command #2 failed with error Got negative replies from endpoints [ ip's of nodes that i turned off ]
and in the logs from node that i turned off
ERROR [AntiEntropyStage:1] 2020-08-21 16:13:12,497 RepairMessageVerbHandler.java:177 - Table with id 6a483210-e395-11ea-8da8-990844948c57 was dropped during prepare phase of repair
but why this case happens? and how to fix this? thanks
You are having schema disagreement between nodes of the cluster. If you run nodetool describecluster, then you will see that. For resolving it restart all the nodes and run nodetool describecluster. If no schema mismatch, then you should be able to run repair.
I tried removing a node from a cluster by issuing "nodetool decommission"
and have seen netstats to find out how much data is being distributed to other nodes which is all fine.
After the node has been decommissioned, I could see the status of few nodes in a cluster as 'UD' when I run nodetool status on few nodes(Not the one I decommissioned) and few nodes are showing 'UN' as status
I'm quite confused about why the status on nodes is showing such behavior, and not same on all nodes after the decommissioned the node.
Am I missing any steps before and after?
Any comments/Help is highly appreciated!
If gossip information is not the same in all nodes, then you should do a rolling restart on the cluster. That will make gossip reset in all nodes.
Was the node you removed a seed node? If it was, don't forget to remove the IP from the cassandra.yaml in all nodes.
I've been tasked with re-writing some sub-par Ansible playbooks to stand up a Cassandra cluster in CentOS. Quite frankly, there doesn't seem to be much information on Cassandra out there.
I've managed to get the service running on all three nodes at the same time, using the following configuration file, info scrubbed.
HOSTIP=10.0.0.1
MSIP=10.10.10.10
ADMIN_EMAIL=my#email.com
LICENSE_FILE=/tmp/license.conf
USE_LDAP_REMOTE_HOST=n
ENABLE_AX=y
MP_POD=gateway
REGION=test-1
USE_ZK_CLUSTER=y
ZK_HOSTS="10.0.0.1 10.0.0.2 10.0.0.3"
ZK_CLIENT_HOSTS="10.0.0.1 10.0.0.2 10.0.0.3"
USE_CASS_CLUSTER=y
CASS_HOSTS="10.0.0.1:1,1 10.0.0.2:1,1 10.0.0.3:1,1"
CASS_USERNAME=test
CASS_PASSWORD=test
The HOSTIP changes depending on which node the configuration file is on.
The problem is, when I run nodetool ring, each node says there's only two nodes in the cluster: itself and one other, seemingly random from the other two.
What are some basic sanity checks to determine a "healthy" Cassandra cluster? Why is nodetool saying each one thinks there's a different node missing from the cluster?
nodetool status - overview of the cluster (load, state, ownership)
nodetool info - more granular details at the node-level
As for the node mismatch I would check the following:
cassandra-topology.properties - identical across the cluster (all 3 IPs listed)
cassandra.yaml - I typically keep this file the same across all nodes. The parameters that MUST stay the same across the cluster are: cluster_name, seeds, partitioner, snitch).
verify all nodes can reach each other (ping, telnet, etc)
DataStax (Cassandra Vendor) has some good documentation. Please note that some features are only available on DataStax Enterprise -
http://docs.datastax.com/en/landing_page/doc/landing_page/current.html
Also check out the Apache Cassandra site -
http://cassandra.apache.org/community/
As well as the user forums -
https://www.mail-archive.com/user#cassandra.apache.org/
Actually, the thing you really want to check is if all the nodes "AGREE" on schema_id. nodetool status shows if nodes or up, down, joining, yet it does not really mean 'healthy' enough to make schema changes or do other changes.
The simplest way is:
nodetool describecluster
Cluster Information:
Name: FooBarCluster
Snitch: org.apache.cassandra.locator.GossipingPropertyFileSnitch
DynamicEndPointSnitch: enabled
Partitioner: org.apache.cassandra.dht.Murmur3Partitioner
Schema versions:
43fe9177-382c-327e-904a-c8353a9df590: [10.136.2.1, 10.136.2.2, 10.136.2.3]
If schema IDs do not match, you need to wait for schema to settle, or run repairs, say for example like this:
43fe9177-382c-327e-904a-c8353a9df590: [10.136.2.1, 10.136.2.2]
43fe9177-382c-327e-904a-c8353a9dxxxx: [10.136.2.3]
However, running nodetool is 'heavy' and hard to parse.
The information is inside the database, you can check here:
'SELECT schema_version, release_version FROM system.local' and
'SELECT peer, schema_version, release_version FROM system.peers'
Then you compare schema_version across all nodes... if they match, the cluster is very likely healthy. You should ALWAYS check this before making any changes to schema.
Now, during a rolling upgrade, when changing engine versions, the release_version is different, so to support automatic rolling upgrades, you need to check schema_id matching within release_versions separately.
I'm not sure all of the problems you might be having, but...
Check the cassandra.yaml file. You need minimum 3 things to be the same - seeds: list (but do not list all nodes as seeds!), cluster_name, and snitch. Make sure your listen_address is correct.
If you are using gossipingPropertyFileSnitch then check cassandra-topology.properties and/or cassandra-rackdc.properties files for accuracy.
Don't start all the nodes at the same time. Start the seed nodes 1st - the other nodes will "gossip" with the seed node to learn cluster topology. Shutdown the seed nodes last.
Don't use shared storage. That defeats the purpose of distributed data and is considered a cassandra anti-pattern.
If you're in AWS, don't use auto-scaling groups unless you know what you're doing.
Once you've done all that, use nodetool status | ring | info or jmx to see what the cluster is doing.
Datastax does have decent documentation for cassandra.
I am using Cassandra 2.0 and cluster has been setup with 3 nodes. Nodetool status and ring showing all the three nodes. I have specified tokens for all the nodes.
I followed the below steps to change the configuration in one node:
1) sudo service cassandra stop
2) updated cassandra.yaml (to update thrift_framed_transport_size_in_mb)
3) sudo srevice cassandra start
The specific not started successfully and system.log shows below exception:
org.apache.cassandra.exceptions.ConfigurationException: Cannot change
the number of tokens from 1 to 256
What is best mechanism to restart the node without losing the existing data in the node or cluster ?
Switching from Non-Vnodes to Vnodes has been a slightly tricky proposition for C* and the mechanism for previously performing this switch (shuffle) is slightly notorious for instability.
The easiest way forward is to start fresh nodes (in a new datacenter) with vnodes enabled and to transfer data to those nodes via repair.
I was also getting this error while I was trying to change the number of tokens from 1 to 256. To solve this I tried the following:
Scenario:
I have 4 node DSE (4.6.1) cassandra cluster. Let say their FQDNs are: d0.cass.org, d1.cass.org, d2.cass.org, d3.cass.org. Here, the nodes d0.cass.org and d1.cass.org are the seed providers. My aim is to enable nodes by changing the num_token attribute in the cassandra.yaml file.
Procedure to be followed for each node (one at a time):
Run nodetool decommission on one node: nodetool decommission
Kil the cassandra process on the decommissioned node. Find the process id for dse cassandra using ps ax | grep dse and kill <pid>
Once the decommissioning of the node is successful, go to one of the remaining nodes and check the status of the cassandra cluster using nodetool status. The decommissioned node should not appear in the list.
Go to one of the active seed_providers and type nodetool rebuild
On the decommissioned node, open the cassandra.yaml file and uncomment the num_tokens: 256. Save and close the file. If this node was originally seed provider, make sure that it's ip-address is removed from the seeds: lists from cassandra.yaml file. If this is not done, the stale information about the cluster topology it has will hinder with the new topology which is being provided by the new seed node. On successful start, it can be added again in the seed list.
Restart the remaining cluster either using the corresponding option in opscenter or manually stopping cassandra on each node and starting it again.
Finally, start cassandra on it using dse cassandra command.
This should work.
I am trying to connect Apache Cassandra nodes into a ring. They are not Datastax versions, but Cassandra 1.2.8 from the Apache website. When trying to add one as the seed of the other I get following exception:
Unable to find compaction strategy class 'com.datastax.bdp.hadoop.cfs.compaction.CFSCompactionStrategy'
Before that I change the "listen_address" and "rpc_address" to local IP address of each node. Next step I add one IP as a seed to another node. The nodes start up, an exception is printed but both nodes run fine until restart. After restarting either node the exception is printed and nodes do not run.
This is very strange - I do not have any DSE components.
Did you previously use any DSE components? If you did and are using the same data directory on any of your nodes, it may find old column families that were created with this compaction strategy. If you have no data you want in the data directories on all your nodes, you should clear them by stopping all nodes, deleting the directories, then starting the nodes.
Or if you have any DSE nodes still up, they may be joining the new cluster and propagating their schema, so creating column families with this compaction strategy. You can find out by looking in the logs and seeing which nodes try to connect. If any aren't from your 1.2.8 ring then this is probably the cause.
That error means you either had a DSE Analytics node in your ring at some point, or you restored your schema from someplace that had an Analytics node.
I would check if you have the folder /etc/dse/ on your VM, that would mean DSE was installed there.
To just wipe the node and start from scratch schema wise, you can stop the node, remove the /system/schema_* folders, then start the node. When it starts it will have no schema. Re-create any keyspaces/column families you had before, and they will get read from disk.