We had a strange issue that we don't know where to look for answer. We are using Cassandra (2.0.10) cluster with 4 nodes. The OS is using CentOS 6.4. We are monitoring those Dell machines using rsh command every minute by dumping their ps and top list. Once a while (about 2 weeks to more than one month), we found rsh command return from one of the machines was very slow (more than 5 sec as compared to less than 1 sec) . At those moment, we noticed that it was very slow to putty to that specific machine as well, while it was fine with other nodes in the same cluster. On the problematic machine, even after we stopped cassandra service, things didn't improve. SSH and ps command still came back much slower than other machines. This didn't get improved until we rebooted the machine. This happened to two of the 4 machines used in the cluster. We looked at the message logs, hardware logs, cassandra logs and can't find the source of this issue. Has anybody experienced this? We love to hear any suggestions.
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I have a test cluster on 3 machines where 2 are seeds all centos7 and all cassandra 3.4.
Yesterday all was fine they were chating and i had the "brilliant" idea to ....power all those machines off to simulate a power failure.
As a newbie that i am, i simply powered the machines back and i expected probably some kind of supermagic, but here it is my cluster is not up again, each individual refuses to connect.
And yes, my firewalld is disabled.
My question : what damage was made and how can i recover the cluster to the previous running state?
Since you abruptly shutdown your cluster, that simply means, nodes were not able to drain themselves.
Don't worry, it is unlikely any data loss happened because of this, as cassandra maintains commit logs, and will read from it when it is restarted.
First, find your seed node ip from cassandra.yaml
Start your seed node first.
Check the start up logs in cassandra.log and system.log and wait for it to start up completely, it will take sometime.
As it will read from commit log for pending actions, and will replay them.
Once it finishes starting up, start other nodes, and tail their log files.
I am learning Cassandra and want to run a cloud based cluster. I don't care much about speed.
What I want to really test is the replication and recovery features.
I would be running tests like
taking nodes offline every once in a while
kill -9 cassandra
powering off server
manually corrupting sstables/commitlog (not sure if this is recoverable)
I am thinking of going for a 4 node cluster.
Each node will have the following config:
2 GB RAM
10 GB SSD
2 CPUs (Virtual)
Two nodes will be in a European datacenter and other two will be in a North American data center.
I know 8GB is the recommended minimum for Cassandra. But that config would be quite expensive.
If it helps, I can run one more VM on a dedicated box. This VM can have 16 GB RAM and 8 virtual CPUs. I could also run 4 VMs with 4GB RAM each on this box. But I guess, having 4 separate VMs in different data centers would make a more realistic setup and bring to fore any issues that may arise out of network problems, latencies etc.
Is it okay to run Cassandra on machines with this config? Please share your thoughts.
Many people run multiple instances of cassandra on modern laptops using ccm ( https://github.com/pcmanus/ccm ). If you just want to get an idea of what it does (create a 3 node cluster, add data, add a 4th node, create a snapshot, remove a node, add it back, restore the snapshot, etc), using ccm on a PC may be 'good enough'.
Otherwise, you can certainly run with less than 1GB of ram, but it's not always fun. There have been some clusters on tiny hardware ( http://www.datastax.com/dev/blog/32-node-raspberry-pi-cassandra-cluster ). Depending on your budget, making a cluster on raspberry pi's may be as cost effective as your 2 VM cluster.
So I have a Cassandra cluster of 6 nodes on my Ubuntu machines, now I have got another machine running Windows Server 2008. I have installed DataStax Apache Cassandra on this new Windows machine, and I want to be able to run all the CQL commands from Windows machine onto Ubuntu machines. So its like remote command execution.
I tried opening cqlsh in cmd using cqlsh with the IP of my one of the nodes and port like cqlsh 192.168.4.7 9160
But I can't seem to make it work. Also I don't want to add the new machine to my existing cluster Please suggest.
Provided version 3.1.1 is not supported by this server (supported: 2.0.0, 3.0.5)
any workaround u could suggest?
Basically, you have two options here. The harder one would be to upgrade your cluster (the tough, long-term solution). But there have been many improvements since 1.2.9 that you could take advantage of. Not to mention bugs fixed long ago that you may be running into.
The other, quicker option would be to install 1.2.9 on your Windows machine. Probably the easiest way to do this, would be to zip-up your Cassandra dir on Ubuntu (minus the data, commitlog, and saved caches dirs of course), copy it to your Windows machine, and expand it. Then the cqlsh versions would match-up, and you could solve your immediate problem.
I'm running Datastax Enterprise in a cluster consisting of 3 nodes. They are all running under the same hardware: 2 Core Intel Xeon 2.2 Ghz, 7 GB RAM, 4 TB Raid-0
This should be enough for running a cluster with a light load, storing less than 1 GB of data.
Most of the time, everything is just fine but it appears that sometimes the running tasks related to the Repair Service in OpsCenter sometimes get stuck; this causes an instability in that node and an increase in load.
However, if the node is restarted, the stuck tasks don't show up and the load is at normal levels again.
Because of the fact that we don't have much data in our cluster we're using the min_repair_time parameter defined in opscenterd.conf to delay the repair service so that it doesn't complete too often.
It really seems a little bit weird that the tasks that says that are marked as "Complete" and are showing a progress of 100% don't go away, and yes, we've waited hours for them to go away but they won't; the only way that we've found to solve this is to restart the nodes.
Edit:
Here's the output from nodetool compactionstats
Edit 2:
I'm running under Datastax Enterprise v. 4.6.0 with Cassandra v. 2.0.11.83
Edit 3:
This is output from dstat on a node that behaving normally
This is output from dstat on a node with stucked compaction
Edit 4:
Output from iostat on node with stucked compaction, see the high "iowait"
azure storage
Azure divides disk resources among storage accounts under an individual user account. There can be many storage accounts in an individual user account.
For the purposes of running DSE [or cassandra], it is important to note that a single storage account should not should not be shared between more than two nodes if DSE [or cassandra] is configured like the examples in the scripts in this document. This document configures each node to have 16 disks. Each disk has a limit of 500 IOPS. This yields 8000 IOPS when configured in RAID-0. So, two nodes will hit 16,000 IOPS and three would exceed the limit.
See details here
So, this has been an issue that have been under investigation for a long time now and we've found a solution, however, we aren't sure what the underlaying problem that were causing the issues were but we got a clue even tho that, nothing can be confirmed.
Basically what we did was setting up a RAID-0 also known as Striping consisting of four disks, each at 1 TB of size. We should have seen somewhere 4x one disks IOPS when using the Stripe, but we didn't, so something was clearly wrong with the setup of the RAID.
We used multiple utilities to confirm that the CPU were waiting for the IO to respond most of the time when we said to ourselves that the node was "stucked". Clearly something with the IO and most probably our RAID-setup was causing this. We tried a few differences within MDADM-settings etc, but didn't manage to solve the problems using the RAID-setup.
We started investigating Azure Premium Storage (which still is in preview). This enables attaching disks to VMs whose underlaying physical storage actually are SSDs. So we said, well, SSDs => more IOPS, so let us give this a try. We did not setup any RAID using the SSDs. We are only using one single SSD-disk per VM.
We've been running the Cluster for almost 3 days now and we've stress tested it a lot but haven't been able to reproduce the issues.
I guess we didn't came down to the real cause but the conclusion is that some of the following must have been the underlaying cause for our problems.
Too slow disks (writes > IOPS)
RAID was setup incorrectly which caused the disks to function non-normally
These two problems go hand-in-hand and most likely is that we basically just was setting up the disks in the wrong way. However, SSDs = more power to the people, so we will definitely continue using SSDs.
If someone experience the same problems that we had on Azure with RAID-0 on large disks, don't hesitate to add to here.
Part of the problem you have is that you do not have a lot of memory on those systems and it is likely that even with only 1GB of data per node, your nodes are experiencing GC pressure. Check in the system.log for errors and warnings as this will provide clues as to what is happening on your cluster.
The rollups_60 table in the OpsCenter schema contains the lowest (minute level) granularity time series data for all your Cassandra, OS, and DSE metrics. These metrics are collected regardless of whether you have built charts for them in your dashboard so that you can pick up historical views when needed. It may be that this table is outgrowing your small hardware.
You can try tuning OpsCenter to avoid this kind of issues. Here are some options for configuration in your opscenterd.conf file:
Adding keyspaces (for example the opsc keyspace) to your ignored_keyspaces setting
You can also decrease the TTL on this table by tuning the 1min_ttlsetting
Sources:
Opscenter Config DataStax docs
Metrics Config DataStax Docs
We're hosting Cassandra 2.0.2 cluster on AWS. We've recently started upgrading from normal to SSD drives, by bootstrapping new and decommissioning old nodes. It went fairly well, aside from two nodes hanging forever on decommission. Now, after the new 6 nodes are operational, we noticed that some of our old tools, using phpcassa stopped working. Nothing has changed with security groups, all ports TCP/UDP are open, telnet can connect via 9160, cqlsh can 'use' a cluster, select data, however, 'describe cluster' fails, in cli, 'show keyspaces' also fails - and by fail, I mean never exits back to prompt, nor returns any results. The queries work perfectly from the new nodes, but even the old nodes waiting to be decommissioned cannot perform them. The production system, also using phpcassa, does normal data requests - it works fine.
All cassandras have the same config, the same versions, the same package they were installed from. All nodes were recently restarted, due to seed node change.
Versions:
Connected to ### at ####.compute-1.amazonaws.com:9160.
[cqlsh 4.1.0 | Cassandra 2.0.2 | CQL spec 3.1.1 | Thrift protocol 19.38.0]
I've run out out of ideas. Any hints would be greatly appreciated.
Update:
After a bit of random investigating, here's a bit more detailed description.
If I cassandra-cli to any machine, and do "show keyspaces", it works.
If I cassandra-cli to a remote machine, and do "show keyspaces", it hangs indefinitely.
If I cqlsh to a remote cassandra, and do a describe keyspaces, it hangs. ctrl+c, repeat the same query, it instantly responds.
If I cqlsh to a local cassandra, and do a describe keyspaces, it works.
If I cqlsh to a local cassandra, and do a select * from Keyspace limit x, it will return data up to a certain limit. I was able to return data with limit 760, the 761 would fail.
If I do a consistency all, and select the same, it hangs.
If I do a trace, different machines return the data, though sometimes source_elapsed is "null"
Not to forget, applications querying the cluster sometimes do get results, after several attempts.
Update 2
Further playing introduced failed bootstrapping of two nodes, one hanging on bootstrap for 4 days, and eventually failing, possibly due to a rolling restart, and the other plain failing after 2 days. Repairs wouldn't function, and introduced "Stream failed" errors, as well as "Exception in thread Thread[StorageServiceShutdownHook,5,main] java.lang.NullPointerException". Also, after executing repair, started getting "Read an invalid frame size of 0. Are you using tframedtransport on the client side?", so..
Solution
Switch rpc_server_type from hsha to sync. All problems gone. We worked with hsha for months without issues.
If someone also stumbles here:
http://planetcassandra.org/blog/post/hsha-thrift-server-corruption-cassandra-2-0-2-5/
In cassandra.yaml:
Switch rpc_server_type from hsha to sync.