Creating a PostgreSQL Cluster Using Helm

http://blog.kubernetes.io/2016/09/creating-postgresql-cluster-using-helm.html

by charlieegan3 • 10 years ago

95 35 10 years ago

blog.kubernetes.io

kozikow• 10 years ago

I am curious why petsets were not mentioned? I was planning to move my postgres to petset. Do you do find running master within single pod enough?

pat2man4• 10 years ago

Pet sets aren't really stable yet. Once they are I assume people will start using them for DB masters. http://kubernetes.io/docs/user-guide/petset/#alpha-limitatio...

lobster_johnson4• 10 years ago

Alpha quality, not stable, several limitations in current release. Planned for beta in 1.5 (next year, probably).

tzaman2• 10 years ago

1.5 is scheduled for early december, according to this: https://github.com/kubernetes/kubernetes/milestones

smnscu• 10 years ago

I assumed at first this was about the emacs plugin (Google seems to agree that it's quite popular, see pic) and was a bit confused (yet intrigued!).

http://imgur.com/VlXfKoK

https://github.com/emacs-helm/helm

edit: search from incognito window (without my profile's emacs bias): http://imgur.com/QXkBlLq

pat2man4• 10 years ago

Yeah the title of the helm readme is "Kubernetes Helm" which would have been more appropriate here. On the kubernetes blog it's implied.

thesmallestcat• 10 years ago

Same reaction: "I mean, Helm can do anything but this is getting ridiculous."

fidget• 10 years ago

God I hate helm. Buggy piece of shit

meddlepal• 10 years ago

Slightly off topic, but I'm evaluating Helm for use and I'm wondering about people's experiences? Good? Bad? Run don't walk away?

pat2man4• 10 years ago

It's still very new. Getting better quickly but I wouldn't use it for anything too complicated.

jdubs• 10 years ago

When I looked at it two months ago, I was having issues getting it to build and deploy on my cluster. After having issues trying to dissect the simple examples, I eventually wrote something similar with python & bash wrapped up in a docker container.

My requirements were deploying 30 different apps using pretty much every kin do k8s objects and deploy custom consul configuration. It could have been done with helm, but the quick and dirty was jinja2 to the rescue.

elktea• 10 years ago

Is anyone else very wary about keeping things with persistent state in containers (like databases)?

pat2man4• 10 years ago

The persistent state is really just the data, not the process. With kubernetes you store the data on a persistent volume (which could be EBS, iSCSI, etc) and the process runs in the container. Host dies? Kubernetes can re-attach that volume on another host, start up a new container and you are back in business.

*Note: looks like in this example they are not setting up a persistent volume.

gtaylor• 10 years ago

Kubernetes can re-attach that volume on another host, start up a new container and you are back in business.

There are still some bugs with this, particularly on AWS. Getting better with every release, though.

olalonde• 10 years ago

Another strategy is to use https://github.com/wal-e/wal-e to continuously backup and restore from S3 on boot (e.g. https://github.com/deis/postgres). But restores will be slower and it probably doesn't come with strong durability guarantees.

haimez• 10 years ago

Ideally, yes. It's not actually the case though. Again, ideally.

Well tested databases have evolved to have to survive arbitrary power cuts- even in the middle of a transaction; and so have slowly become reliable enough to trust to start from on-disk state only.

Good f-in' luck bringing your db flavor of the month back online from disk state alone. Hope you didn't have any transactions open to your DB before it got rescheduled to a different node in your cluster.

djsumdog2• 10 years ago

I work at a shop that has everything in docker containers. We have mostly coreos clusters, but we're slowly moving to mesos/marathon.

And I do mean everything. We've got .NET apps running in docker containers, perl scripts .. they went hard in on docker.

But our databases: Amazon RDS instances.

It's one of the few things that isn't dockerized.

I've personally been looking at a lot of docker solutions for my own projects and I'm still weary of a lot of the data storage solutions out there.

polskibus• 10 years ago

What .net are you running on containers? Mono? .Net Core? Is it working for you well outside of Windows server?

xnxn• 10 years ago

Kubernetes rocks, but this post exemplifies a complaint of mine: there's a glaring lack of examples of production-capable database deployments.

In this Helm chart, your master is a single Pod (which is ephemeral and which you should usually not be creating directly) that stores data in an emptyDir (which is coupled to the lifecycle of the Pod).

alexk2• 10 years ago

Check this out:

https://github.com/gravitational/stolon

this is heavily modified version of

https://github.com/sorintlab/stolon

K8s-native deployment of PostgreSQL

drdaeman• 10 years ago

Thanks! That was exactly what I was looking for. From a first glance it seems it's well possible to use it with non-k8s environments (like Rancher's Cattle) as well, using Consul and, possibly, a bit of duct tape.

But can you please tell what's the general difference between the original and the fork? I see that both are active, but nothing in README tells what one has over another.

manojlds3• 10 years ago

Exactly. I was expecting use of the new PetSets. I go and look at Helm charts, and most of them are like some toy project setup.

lobster_johnson4• 10 years ago

Petsets are alpha quality (lots of bugs and some missing behaviour in 1.3) and will only reach beta in 1.5, which is probably next year. So it wouldn't really be fair to demo something that cannot be used in production.

Annatar• 10 years ago

One more completely custom method of provisioning, rather than using operating system packages and simple shell scripts inside of their preinstall, postinstall, preremove, and postremove sections. How wonderful.

tzaman2• 10 years ago

This is bad example, because it creates more questions than it answers:

- what if the master pod dies (or I transfer it to another node pool)?

- how do I make sure if everything dies, my data is safe?

- how do I use peristent disks in this scenario?

- how can I have a service that handles both the master and the replicas?

- what happens when I update the node pool to a new version of Kubernetes

- How can I achieve true HA?

x0rg• 10 years ago

We (https://tech.zalando.com) also made some work to use Helm to deploy Patroni (https://github.com/zalando/patroni), our solution HA PostgreSQL. We have a PR open, if you want to have a look: https://github.com/kubernetes/charts/pull/57 ... comments are always helpful.

Creating a PostgreSQL Cluster Using Helm

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