Containers area a lightweight alternative to Virtual Machines for isolating applications within a single host machine. They are widely used in the web- and application-tiers of systems, but are they really appropriate for the stateful data tier? In this talk, we explore that subject and walk through how to get Cassandra running using Docker.

1. Running Apache Cassandra on Docker
Jim Hatcher
Solution Architect, DataStax
Twitter: @thejimhatcher
DFW Cassandra Meetup
September 24, 2018
© DataStax, All Rights Reserved.1

2. Agenda
© 2016 DataStax, All Rights Reserved. 2
● What is Cassandra?
● What is Docker?
● Demo
● Do we have a match?
● References

3. What is Cassandra?
3

4. Capabilities
© 2016 DataStax, All Rights Reserved. 4
● Scale Out
○ Data Size
○ Throughput
○ Concurrency
● Active Everywhere
○ Multiple active-active data centers

5. Cassandra is an I/O Intensive Database
© 2016 DataStax, All Rights Reserved. 5
Both in terms of IOPS and throughput
● Normal Read/Write Path
● Compaction
● Bootstrapping
● Repair

6. Best Practices
© 2016 DataStax, All Rights Reserved. 6
● Don’t use Shared Storage (NAS, SAN, NFS, etc.)
○ Single Point of Failure
○ Performance Limitation
● Use Locally-Attached Storage
○ SSD
○ No RAID necessary -- RAID0 is OK
● Unit of failure is the server, not the disk
○ Swap disabled
● No Virtualization
○ Physical preferred
○ Overhead

7. Wait a minute...
© 2016 DataStax, All Rights Reserved. 7
● Doesn’t Cassandra run well in the cloud?
● Example in AWS
○ EBS drives (i.e., shared storage)
○ Ephemeral SSD
■ Is this really any different than running with local storage?
● Tips
○ Have strong backup and restore measures in place
■ Test backups! Test restores!
○ Know how long it takes to bootstrap nodes, rebuild nodes, rebuild
DCs
■ Adjust node density accordingly
○ Test failure scenarios! Not just the happy path

8. What is Docker?
8

9. Containers
© 2016 DataStax, All Rights Reserved. 9
● Building Blocks
○ Namespaces
■ Provide isolation for processes, network, file systems, and kernel
○ Control groups
■ Provides limitations on resources (CPU, memory)
○ UnionFS
Lighter Weight than Virtual Machines

10. Containers
© 2016 DataStax, All Rights Reserved. 10
Source: https://www.youtube.com/watch?v=TvnZTi_gaNc

11. © 2016 DataStax, All Rights Reserved. 11
Demo

12. Install Docker on host machine
© 2016 DataStax, All Rights Reserved. 12
sudo apt install apt-transport-https ca-certificates curl software-properties-common
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu bionic stable"
sudo apt update
apt-cache policy docker-ce
sudo apt install docker-ce
sudo systemctl status docker
sudo usermod -aG docker ${USER}
Reference:
https://www.digitalocean.com/community/tutorials/how-to-install-and-use-docker-on-ubuntu-18-04

13. Installing Cassandra Image on host machine
© 2016 DataStax, All Rights Reserved. 13
docker pull cassandra
docker images
sudo mkdir /var/lib/container_data
sudo mkdir /var/lib/container_data/cassandra-node-01
sudo mkdir /var/lib/container_data/cassandra-node-02
sudo mkdir /var/lib/container_data/cassandra-node-03
Reference:
https://hub.docker.com/_/cassandra/

14. Running Cassandra Containers
© 2016 DataStax, All Rights Reserved. 14
docker run --name cassandra-node-01 -d
-e CASSANDRA_CLUSTER_NAME="docker_test"
-e CASSANDRA_NUM_TOKENS="8"
-e CASSANDRA_DC="dc1"
-e CASSANDRA_RACK="rack1"
-e CASSANDRA_ENDPOINT_SNITCH="GossipingPropertyFileSnitch"
-v /var/lib/container_data/cassandra-node-01:/var/lib/cassandra/data
cassandra:latest
docker run --name cassandra-node-02 -d
-e CASSANDRA_CLUSTER_NAME="docker_test"
-e CASSANDRA_NUM_TOKENS="8"
-e CASSANDRA_DC="dc1"
-e CASSANDRA_RACK="rack2"
-e CASSANDRA_ENDPOINT_SNITCH="GossipingPropertyFileSnitch"
-e CASSANDRA_SEEDS="$(docker inspect --format='{{ .NetworkSettings.IPAddress }}' cassandra-node-01)"
-v /var/lib/container_data/cassandra-node-02:/var/lib/cassandra/data
cassandra:3.11
docker run --name cassandra-node-03 -d
-e CASSANDRA_CLUSTER_NAME="docker_test"
-e CASSANDRA_NUM_TOKENS="8"
-e CASSANDRA_DC="dc1"
-e CASSANDRA_RACK="rack3"
-e CASSANDRA_ENDPOINT_SNITCH="GossipingPropertyFileSnitch"
-e CASSANDRA_SEEDS="$(docker inspect --format='{{ .NetworkSettings.IPAddress }}' cassandra-node-01)"
-v /var/lib/container_data/cassandra-node-03:/var/lib/cassandra/data
cassandra:3.11

15. Running Cassandra Containers (zoomed in)
© 2016 DataStax, All Rights Reserved. 15
docker run --name cassandra-node-02 -d
-e CASSANDRA_CLUSTER_NAME="docker_test"
-e CASSANDRA_NUM_TOKENS="8"
-e CASSANDRA_DC="dc1"
-e CASSANDRA_RACK="rack2"
-e CASSANDRA_ENDPOINT_SNITCH="GossipingPropertyFileSnitch"
-e CASSANDRA_SEEDS="$(docker inspect --format='{{ .NetworkSettings.IPAddress }}'
cassandra-node-01)"
-v /var/lib/container_data/cassandra-node-02:/var/lib/cassandra/data
cassandra:3.11

16. © 2016 DataStax, All Rights Reserved. 16
Do we have a match?

17. Conclusions
© 2016 DataStax, All Rights Reserved. 17
Great option for Dev / Test / Training Instances
Questions to answer before trying in Production
How much "safety factor" do you need to give for resources?
Too much safety factor -- why are you using containers?
Too little safety factor -- running a risk for dropping nodes,
etc.
How well tested are operational procedures (scaling out, scaling in,
rebuilding nodes, rebuilding DCs, etc.)?

18. Resources - Docker on DSE
© 2016 DataStax, All Rights Reserved. 18
https://github.com/datastax/docker-images
https://hub.docker.com/u/datastax/
https://academy.datastax.com/content/docker-tutorial
https://academy.datastax.com/content/visualizing-your-data-tableau-using-dse-6-docker-images
https://academy.datastax.com/units/docker-tour-video?resource=guided-tour-dse-6-using-docker
https://academy.datastax.com/content/success-segment-getting-started-datastax-docker-images
https://docs.datastax.com/en/docker/doc/index.html
https://docs.datastax.com/en/docker/doc/docker/docker51/dockerReadme.html

19. Resources - Docker on Cassandra
© 2016 DataStax, All Rights Reserved. 19
https://hub.docker.com/_/cassandra/
http://blog.ditullio.fr/2016/06/10/docker-docker-basics-cassandra/
https://docs.docker.com/engine/docker-overview/

20. Continue Learning…
academy.datastax.com/developer-days
20