Seattle Cloud Native and Kubernetes Meetup on July 19, 2018

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Persistent Storage with Containers
Kaslin Fields – Solutions Architect at Oracle Cloud Infrastructure
Cloud-Native and Kubernetes Meetup – 7/19/2018
Twitter: @kaslinfields
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Safe Harbor Statement
The following is intended to outline our general product direction. It is intended for
information purposes only, and may not be incorporated into any contract. It is not a
commitment to deliver any material, code, or functionality, and should not be relied upon
in making purchasing decisions. The development, release, and timing of any features or
functionality described for Oracle’s products remains at the sole discretion of Oracle.
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The Promise of Containers
• Fast
• Efficient
• Portable
• Scalable
• Immutable
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Immutability
Adjective:
“unable to be changed”
- Mirriam-Webster
https://www.merriam-webster.com/dictionary/immutable

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Immutability and Containers
• Containers should never change on the fly
• No Patching
– Just recreate it!
• Dependencies included
– No more “It works on my machine”
• Application-focused
– Only the app and its dependencies!
• Made to Die
– Cattle, not pets
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Immutable Containers and Persistent Storage
• If my containers can never change while they’re running, then where’s all
my data supposed to go??
• Separate the App from the Data
– Containers for Apps
– Volumes for Data
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Use Case - Wordpress
• Surprisingly difficult to containerize IMMUTABLY
• A traditional app
– Database – Clearly needs to PERSIST
– Numerous (expected) local filesystem locations which store data which needs to
PERSIST
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Persistent Storage with Containers - Tools
• Docker
– Volumes
• Kubernetes
– Volumes
– Persistent Volumes
– Persistent Volume Claims
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Docker
• Docker is a container implementation format
• Docker Volumes
– Came out in 1.8.0 (July of 2015)
– Local
– Plugins
• Docker Swarm is a container orchestrator
– Docker Volumes work natively with Swarm
– Though generally a Docker Volume will get provisioned on every node in a Swarm*
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Docker Volume Plugin on OCI
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$ docker volume create
--driver oci --name persStor
Install Docker
OCI API
$ docker run -it --rm
-v persStor:/mnt busybox sh
Mount
Busybox

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Kubernetes
• Kubernetes is a container orchestrator
• Volumes
– Tied to pod lifetime
– Fun Fact: Kubernetes released 1.0 in July 2015
• Kubernetes Persistent Volumes (and Persistent Volume Claims)
– Now in Beta! (April 2018)
– Alpha in 1.8 (September 2017)
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OCI FlexVolume Driver - Setup
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https://github.com/oracle/oci-flexvolume-driver
AVAILABILITY DOMAIN 3AVAILABILITY DOMAIN 2AVAILABILITY DOMAIN 1
REGION
Kubernetes Workers
REGION
AVAILABILITY DOMAIN 3AVAILABILITY DOMAIN 2AVAILABILITY DOMAIN 1

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OCI FlexVolume Driver – Setup (Pod Definition)
https://github.com/oracle/oci-flexvolume-driver

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OCI FlexVolume Driver
https://github.com/oracle/oci-flexvolume-driver
REGION
AVAILABILITY DOMAIN 3AVAILABILITY DOMAIN 2AVAILABILITY DOMAIN 1
$ kubectl apply –f pod.yml

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REGION
AVAILABILITY DOMAIN 3AVAILABILITY DOMAIN 2AVAILABILITY DOMAIN 1
OCI Volume Provisioner
https://github.com/oracle/oci-volume-provisioner/
Flexvolume Driver
&
Volume Provisioner

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OCI Volume Provisioner
https://github.com/oracle/oci-volume-provisioner/

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OCI Volume Provisioner
https://github.com/oracle/oci-volume-provisioner/

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OCI Volume Provisioner
https://github.com/oracle/oci-volume-provisioner/
REGION
AVAILABILITY DOMAIN 3AVAILABILITY DOMAIN 2AVAILABILITY DOMAIN 1
$ kubectl apply –f pod.yml

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Persistent Storage Tools in Review
• Docker
– Works with Docker Containers or Swarm
• Can also be used with Docker containers running on Kubernetes – though this doesn’t take
advantage of Kubernetes’ orchestration features
– Use local storage or a plugin
• Kubernetes
– Be mindful of the physical state of WHERE your app is running
– Persistent Volume Claims & Persistent Volumes
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Let’s Talk About Databases
• Can you run them in containers?
– CERTAINLY!
• Oracle DB - https://github.com/oracle/docker-images/tree/master/OracleDatabase
• MySQL - https://hub.docker.com/_/mysql/
• Oracle RAC - https://github.com/oracle/docker-images/tree/master/OracleDatabase/RAC
• Should you run them in containers?
– Ehhh, it depends…
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Kaslin’s Guidelines for Databases in Containers
• Great for testing environments
• Great for applications which require a tightly coupled DB, like WordPress
– Kubernetes Pod-style
• Not so great if you have 0 tolerance for your DB APPLICATION going down
– Though stateful sets can help with this SOME
• Should be good if you expect the DB’s STORAGE to always be up!
– Granted you’ve planned out your storage requirements appropriately.
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A Simple Rule for Containerizing Databases
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1. If your DATA needs to be persistent, you’re probably good.
2. If your access point to that data, the DATABASE APPLICATION,
needs to be as close to 100% up-time as possible
- there are probably better options.

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Let’s Review
• Immutability means your container, once built, never changes.
– It gets remade instead!
• Application = Container
• Data = Volume
• Both Docker and Kubernetes have tooling to help manage data volumes
– With plugins available from various vendors
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Thanks!
Q&A
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