Stateful Containers: Flocker on CoreOS
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Stephen Nguyen a Developer Evangelist for ClusterHQ reviews how volumes work and overviews the benefits of allowing Flocker to orchestrate your Volumes. (video coming soon)
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Stateful Containers: Flocker on CoreOS
- 2. Hi my name is Stephen I’m a developer evangelist at ClusterHQ I was previously at Iron.io advoca<ng stateless workloads
- 4. docker docs… • Volumes are ini.alized when a container is created. If the container’s base image contains data at the specified mount point, that exis.ng data is copied into the new volume upon volume ini.aliza.on. • Volumes can be shared and reused among containers. • Changes to a volume are made directly. • Changes to a volume will not be included when you update an image. • Volumes persist even if the container itself is deleted. External Volumes
- 5. docker run -v /data ubuntu docker run -v /data2 ubuntu host /DATA /DATA2 Volumes inside a container
- 6. docker rm <container_1> host /DATA /DATA2 Volumes inside a container
- 7. Mount a host directory as a data volume docker run -v $HOME:/data ubuntu host $HOME/data
- 8. Mount a host directory as a data volume host docker rm <container_id> $HOME/data
- 9. Mount a host directory as a data volume $HOME/data host docker run -v $HOME:/data ubuntu
- 10. Mount a host directory as a data volume /data docker run -v /data ubuntu coreos-‐host-‐node—1 coreos-‐host-‐node—2
- 11. That container is not guaranteed to be scheduled to that host /data coreos-‐host-‐node—1 /data My data is still here! fresh host volume :( coreos-‐host-‐node—2 docker run -v /data ubuntudocker run rm <container_id>
- 12. That container is not guaranteed to be scheduled to that host /host/logs/container/logs coreos-‐host-‐node—1 /host/logs/container/logs My data is still here! fresh host volume :( coreos-‐host-‐node—2 copy host volume?
- 13. • Keep track of Host Volumes? • What if the volume is extremely large? • BitTorrent Sync? • Use NFS? GlusterFS? OtherDistributedFileSystemFS Problems to address
- 14. Distributed Synchronized Filesystems coreos-‐host-‐node—N… /data /data /data /data /data from what I have read so far • Network uniformity • CPU intensive • Maintenance
- 17. Limita<on of ~40 EBS volumes to a Linux Host before Boot Failures become a thing coreos-‐host-‐node—1
- 18. • MounKng correct ebs volumes to the correct containers/host machine • Provisioning EBS volumes happens manually not dynamically • you need to interact with the the AWS EBS API or Console Problems to address
- 19. Enter Flocker
- 20. coreos-‐host-‐node—1 ectd docker flocker Redundant Cloud Storage! demo:/data redis:latest docker run -d -v demo:/data --volume-driver=flocker --name=redis redis:latest CREATE
- 21. Redundant Cloud Storage! coreos-‐host-‐node—1 demo:/data redis:latest ectd docker docker run -d -e USE_REDIS_HOST=redis --link redis:redis -p 80:80 --name=app stephenitis/bird-counter:latest flocker bird-‐counter
- 23. Redundant Cloud Storage! coreos-‐host-‐node—1 demo:/data redis:latest ectd docker flocker bird-‐counter coreos-‐host-‐node—2 redis:latest ectd docker flocker docker run -d -e USE_REDIS_HOST=redis --link redis:redis -p 80:80 --name=app stephenitis/bird-counter:latest remount volume moby-‐counter
- 25. demo?
- 26. coreos-‐host-‐node—1 ectd docker flocker Flocker Create and Mount a Volume demo:/data redis:latest docker run -d -v demo:/data --volume-driver=flocker --name=redis redis:latest CREATE
- 27. coreos-‐host-‐node—1 demo:/data redis:latest ectd docker docker run -d -e USE_REDIS_HOST=redis --link redis:redis -p 80:80 --name=app stephenitis/bird-counter:latest flocker bird-‐counter
- 29. Flocker Magic coreos-‐host-‐node—1 demo:/data redis:latest ectd docker $ docker run -d -v demo:/data --volume-driver=flocker --name=redis redis:latest $ docker run -d -e USE_REDIS_HOST=redis --link redis:redis -p 80:80 --name=app stephenitis/bird-counter flocker bird-‐counter coreos-‐host-‐node—2 redis:latest ectd docker flocker bird-‐counter
- 31. how it works
- 32. Magic.
- 33. • All Flocker services to be Containerized • run our containers in “privileged” mode • When the operator executes docker run -‐-‐privileged • We need to to communicate the state of mounted volumes to the host system back to our containerized flocker service Problems to address to get this to work on CoreOS
- 34. coreos-‐host-‐master-‐node docker flocker-‐docker-‐plugin flocker-‐container-‐agent flocker-‐dataset-‐agent flocker-‐control-‐service docker run -d -v demo:/data --volume-driver=flocker --name=redis redis:latest redis
- 35. Installing the tools across all cores nodes was brainlessly easy with our uft-flocker tool $ uft-flocker-install cluster.yml $ uft-flocker-config cluster.yml $ uft-flocker-plugin-install cluster.yml $ # boom shaka laka Making installa<on of all the pieces easier
- 36. wrapping flocker in nsenter wrap commands that interact with host with nsenter `mount`, `umount`, `lsblk`, `losetup` https://github.com/jpetazzo/nsenter
- 37. nsenter it can enter existing namespaces, or spawn a process into a new set of namespaces. https://github.com/jpetazzo/nsenter
- 38. syncing /etc/mtab for `psutil` /etc/mtab psutil
- 39. Installing the tools across all cores nodes was brainlessly easy with our uft-flocker tools /etc/mtab psutil /bin/nsenter --mount=/host/proc/1/ns/mnt -- cat /etc/ mtab > /etc/mtab.tmp - mv /etc/mtab.tmp /etc/mtab
- 41. Thanks to ClusterHQ team Madhuri Yechuri / Luke Marsden /Kai Davenport CoreOS (for teaching us how our services would work in a dockerized format) Giant Swarm (for pushing us forward) Jérôme Petazzoni (nsenter _w)
- 42. demo instruc.ons at goo.gl/Wymh74
- 43. Q’s @stepheniKs stephen@clusterhq.com San Francisco | Bristol | Remote Hiring like ClusterHQ.com/careers/