Ok so this might be a basic question, but i'm new to kubernetes and tried to install wordpress using helm unto it, using the stable/wordpress chart, but i keep getting an error "pod has unbound immediate PersistentVolumeClaims (repeated 2 times)" is this because of the requirement in here https://github.com/helm/charts/tree/master/stable/wordpress. "PV provisioner support in the underlying infrastructure" how do i enable this in my infrastructure, i have setup my cluster across three nodes on digitalocean, i've tried searching for tutorials on this, with no luck until now. Please let me know what i'm missing, thanks.
PersistentVolume types are implemented as plugins. Kubernetes currently supports the following plugins:
GCEPersistentDisk
AWSElasticBlockStore
AzureFile
AzureDisk
FC (Fibre Channel)
Flexvolume
Flocker
NFS
iSCSI
RBD (Ceph Block Device)
CephFS
Cinder (OpenStack block storage)
Glusterfs
VsphereVolume
Quobyte Volumes
HostPath (Single node testing only – local storage is not supported in any way and WILL NOT WORK in a multi-node cluster)
Portworx Volumes
ScaleIO Volumes
StorageOS
You can enable support for PVs or Dynamic PVs using thoese plugins.
detail reference
On Digital Ocean you can use block storage for volumes.
details
Kubernetes can be set-up for Dynamic Volume Provisioning. This would allow the Chart to run to completion using the default configuration as the PVs would be provisioned on-demand.
Related
I want to setup HA for airflow(2.3.1) on centos7. Messaging queue - Rabbitmq and metadata db - postgres. Anybody knows how to setup it.
Your question is very large, because the high availability has multiple level and definition:
Airflow availability: multiple scheduler, multiple workers, auto scaling to avoid pressure, high storage volume, ...
The databases: a HA cluster for Rabbitmq and a HA cluster for postgres
Even if you have the first two levels, how many node you want to use? you cannot put everything in the same node, you need to run one service replica per node
Suppose you did that, and now you have 3 different nodes running in the same data center, what if there is a fire in the data center? So you need to use multiple nodes in different regions
After doing all of above, is there a risk for network problem? of course there is
If you just want to run airflow in HA mode, you have multiple option to do that on any OS:
docker compose: usually we use it for developing, but you can use it for production too, you can create multiple scheduler instances, with multiple workers, it can help you to improve the availability of your service
docker swarm: similar to docker compose with additional features (scaling, multi nodes, ...), you will not find much resources to install it, but you can use the compose files and just do some changes
kubernetes: the best solution, K8S can help you to ensure the availability of your services, easy install with helm
or just running the different services on your host: not recommended, because of manual tasks, and applying the HA is complicated
I'm learning Kubernetes, and trying to setup a cluster that could handle a single Wordpress site with high traffic. From reading multiple examples online from both Google Cloud and Kubernetes.io - they all set the "accessMode" - "readWriteOnce" when creating the PVCs.
Does this mean if I scaled the Wordpress Deployment to use multiple replicas, they all use the same single PVC to store persistent data - read/write data. (Just like they use the single DB instance?)
The google example here only uses a single-replica, single-db instance - https://cloud.google.com/kubernetes-engine/docs/tutorials/persistent-disk
My question is how do you handle persistent storage on a multiple-replica instance?
ReadWriteOnce means all replicas will use the same volume and therefore they will all run on one node. This can be suboptimal.
You can set up ReadWriteMany volume (NFS, GlusterFS, CephFS and others) storage class that will allow multiple nodes to mount one volume.
Alternatively you can run your application as StatefulSet with volumeClaimTemplate which ensures that each replica will mount its own ReadWriteOnce volume.
If on AWS (and therefore blocked by the limitation of EBS volumes only mountable on a single instance at a time), another option here is setting up the Pod Affinity to schedule on the same node. Not ideal from an HA standpoint, but it is an option.
If after setting that up you start running into any wonky issues (e.g. unable to login to the admin, redirect loops, disappearing media), I wrote a guide on some of the more common issues people run into when running Wordpress on Kubernetes, might be worth having a look!
If not use simulator or devstack, but use real production cluster, very necessary need will cost how many hosts(or nodes)?
CloudStack: 2 (management-servers and DBs) + 2 (Hypervisors) + 1 Storage(If you do not have a Storage Device, maybe you need a server for NFS or iSCSI)
Total: 5 servers for a minimal environment with load-balance and HA.
OpenStack: It depends on the component you have chosen. Every component can be installed in the right one server. But you need one more server for load-balance and HA.
Total: 2 servers for a minimal environment with load-balance and HA.
When planning a cloud platform, the total resource = ManagementServer*2 + Hypervisor*N + Storage(Server Or Storage Device)
Hypervisor number is the total cpus and memorys of how much vms you planned to run.
Storage is how much volumes you want to allocate for all vms.
For Cloudstack, unlike OpenStack, you can use just one physical machine or server for the installation of both the management server as well as agent (for execution of VMs) and yes, the database and NFS shares can be set up on the same machine too (assuming you need it for testing purpose).
You can follow the quick installation guide of Cloudstack here: http://docs.cloudstack.apache.org/projects/cloudstack-installation/en/4.11/qig.html
I have personally installed using the above documentation and can assure you the above works fine with CentOS 7.4 too. For more complex setup and architecture you can find more documentation here: http://docs.cloudstack.apache.org. Just be sure to have some free IPs available ;)
I'm working on a project to run a Kubernetes cluster on GCE. My goal is to run a cluster containing a WordPress site in multiple zones. I've been reading a lot of documentation, but I can't seem to find anything that is direct and to the point on persistent volumes and statefulsets in a multiple zone scenario. Is this not a supported configuration? I can get the cluster up and the statefulsets deployed, but I'm not getting the state replicated throughout the cluster. Any suggestions?
Thanks,
Darryl
Reading the docs, I see that the recommended configuration would be to create a MySQL cluster with replication: https://kubernetes.io/docs/tasks/run-application/run-replicated-stateful-application/. This way, you would have the data properly replicated between the instances of your cluster (if you are in a multi-zone deployment you may have to create an external endpoint).
Regarding the Wordpress data, my advice would be to go for an immutable deployment: https://engineering.bitnami.com/articles/why-your-next-web-service-should-be-immutable.html . This way, if you need to add a plugin or perform upgrades, you would create a new container image and re-deploy it. Regarding the media library assets and immutability, I think the best option would be to use an external storage service like S3 https://wordpress.org/plugins/amazon-s3-and-cloudfront/
So, to answer the original question: I think that statefulset synchronization is not available in K8s (at the moment). Maybe using a volume provider that allows ReadWriteMany access mode could fit your needs (https://kubernetes.io/docs/concepts/storage/persistent-volumes/#access-modes), though I am quite unsure about the stability of it.
I am wondering what is a stack in openslack.
It seems to be components (network, containers and stuff)
Can i mix thoses items with docker containers for example ?
Thanks
OpenStack version of AWS cloudformation (infrastructure as a code) is performed trough HEAT (OpenStack Component). A "stack" is a set of resources that can be deployed in the cloud. What are those resources ?: Everything that can be created withing the cloud environment:
- A network port...
- A set of instances (virtual machines).
- A load balancer.
- A storage device (block or object).
Basically, you use a template (or a set of templates) in order to create a complete infrastructure inside the cloud (database servers, web servers, a load balancer for the web servers, maybe the storage too... etc.).
The template uses a common language to define those components and how are they created in the cloud.
Note that, many "AWS Cloudformation" objects can be defined in OpenStack HEAT templates, but, HEAT also has it's very own set of objects definitions for OpenStack.
At the end of my site you will find a sample HEAT template for a stack that include servers, loadbalancer and autoscalling:
https://tigerlinux.github.io/recipes/openstack/index.html
Also, more examples directly from the OpenStack community:
https://git.openstack.org/cgit/openstack/heat-templates/tree/hot