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Building Clustered Applications with Kubernetes and Docker
- 1. @wattsteve Building Clustered Applications with Kubernetes and Docker Steve Watt Red Hat Emerging Technologies
- 2. @wattsteve Why Docker? CC flickr bibbit
- 4. @wattsteve Kubernetes Cluster Kubernetes Architectural Overview Kubernetes Master Server(s)Kubernetes Master Server(s) Linux Server(s) etcd API Server Controller Manager Kubernetes NodeKubernetes Node Linux Server KubeletDocker Kubernetes Proxy Kubernetes NodeKubernetes Node Linux Server KubeletDocker Kubernetes Proxy Kubernetes NodeKubernetes Node Linux Server KubeletDocker Kubernetes Proxy Scheduler
- 5. @wattsteve Installing Kubernetes • Hosted Services: Google Compute Engine • Support for a wide variety of Infrastructure (Azure, Rackspace, vSphere, AWS) • Support for several OS’ (RHEL, CentOS, Fedora, Debian, Ubuntu, Atomic, CoreOS) • Local but automated (Vagrant/Ansible) * Magic * • Local but manual (Fedora) * What I use * https://github.com/GoogleCloudPlatform/kubernetes/blob/mas ter/docs/getting-started- guides/fedora/fedora_manual_config.md
- 6. @wattsteve CC flickr kk Awesome! Now, lets build an application
- 7. @wattsteve Kubernetes MasterKubernetes Master Kubernetes Node 1Kubernetes Node 1 Kubernetes Cluster NGINX Pod NGINX ContainerNGINX ContainerBrowser Request Browser Request Kubernetes Node 2Kubernetes Node 2 Other Pods Other ContainersOther Containers We’ll start by Defining and Deploying a Pod
- 8. @wattsteve Kubernetes MasterKubernetes Master Kubernetes Node 1Kubernetes Node 1 Kubernetes Cluster NGINX Pod NGINX ContainerNGINX ContainerBrowser Request Browser Request Kubernetes Node 2Kubernetes Node 2 NGINX Pod NGINX Pod ReplicationController NGINX Pod ReplicationController NGINX ContainerNGINX ContainerBrowser Request Browser Request You might also want to add a ReplicationController
- 9. @wattsteve Kubernetes MasterKubernetes Master Kubernetes Node 1Kubernetes Node 1 Kubernetes Cluster NGINX Pod NGINX ContainerNGINX Container Browser Request Browser Request Kubernetes Node 2Kubernetes Node 2 NGINX Pod NGINX Pod ReplicationController NGINX Pod ReplicationController NGINX ContainerNGINX Container NGINX Master ServiceNGINX Master Service And add a Service to Proxy in front of it
- 10. @wattsteve What about Persistence? Lets try out Volumes Volumes are specified in a Pod and mounted onto a specified path within a container. There are several kinds of Volumes: •hostPath (mount a persistent directory provided by host) •NFS (mount NFS share provided by a 3rd Party) Ephemeral •emptyDir (mount an ephemeral directory provided by host) File •GlusterFS Distributed File System (mount an adjacent GlusterFS volume) •Ceph Distributed File System (mount an adjacent CephFS volume) Block •GCEPersistentDisk (mount a GCE Block Device when in GCE) •Ceph Block (mount an adjacent Ceph Block Device) •ISCSI Block Devices (mount an adjacent ISCSI Block Device)
- 11. @wattsteve Kubernetes MasterKubernetes Master Kubernetes Node 1Kubernetes Node 1 Kubernetes Cluster NGINX Pod NGINX ContainerNGINX Container Browser Request Browser Request Kubernetes Node 2Kubernetes Node 2 NGINX Pod NGINX Pod ReplicationController NGINX Pod ReplicationController NGINX ContainerNGINX Container NGINX Master ServiceNGINX Master Service GlusterFS Volume GlusterFS Volume For this example, we’re going to use GlusterFS
- 13. @wattsteve Thanks for Attending Interested in following up? Steve Watt swatt@redhat.com Examples: https://github.com/wattsteve/kubernetes/
Editor's Notes
- I feel like there is A LOT of info about Kubernetes but not a whole lot to get you quickly ramped up on the basics. Just to set expectations. My goal is that everybody leaving this talk will understand: The basics of what Kubernetes is (you can fork out for other talks on niche topics like etcd) How to set it up How to build and deploy a Kubernetes Application This talk won’t cover how Kubernetes is different from the other projects in the Container Orchestration and Management space Who here has tried out Docker? Who here has tried out Kubernetes?
- Packaging, Consistency, Portability using the same Image across Dev, Build, Test and Production to easily maintain consistency. Same Image pulled down from Registry. This solves a lot of complex deployment and migration issues. [ DEMO ] ssh demo-1; docker images; ls –l /opt/data; docker run -v /opt/data:/var/www/html/ -d dockerfile/nginx; docker ps; docker inspect {containerID}| grep "IPAddress”; curl {ipaddress|/hello.html Docker stop {containerID}
- But, we need to re-examine Docker’s Deployment efficacy through the lens of Scale Up and Scale Out Architectures: Scale Up – Easy: Fairly trivial to launch and manage images on just a few servers. Scale Out – Hard: Too much to track when you have images across 400+ nodes. So we clearly lack an elegant solution Orchestrating and Managing clusters of containers. Kubernetes provides a framework for you to describe your Application and the Images it needs and its dependencies as a Pod file and handles the deployment and availability for you
- This is Runtime View. Typical Scale Out Architecture. Devs and POCs usually just use a single master with multiple nodes. Kube Master Server – etcd? Distributed Key/Value Store that the API Server uses to persist configuration information. Kube API Server? RESTFul and Command Line interface. Handles the Creation of Objects. Scheduler – ensures Pods are scheduled. Can apply scheduling policies. Kube Controller Manager? Ensures Pod Replication Policies are implemented consistently. Kube Node – What is the Kube Proxy? Network Proxy for Containers and Service Endpoints. What does the Kubelet do? Provisions the resources in the Pods provided it. Interacts with Docker to launch containers. Kubernetes is written in GO, but you don’t have to know anything about GO to use it.
- [ Show Github Community Docs – get folks comfortable with navigating the project ] 2 Config Files on the Master cat /etc/kubernetes/apiserver/etc/kubernetes/config Demo start-master, stop-master on Master 2 Config Files on each Nodecat /etc/kubernetes/kubelet /etc/kubernetes/config Demo start-node, stop-node on Node Demo kubectl get nodes
- So it sounds good in theory, lets check it out in practice. We’re going to build a scale out containerized web application using NGINX. We are going to build a layered application. So we’ll start small and then build up.
- We are going to build a Pod to achieve what we see in this picture, which is …(Mgmt Layer + App Layer) Pods describe a tightly coupled group of containers that typically need to be deployed on the same server because they share resources. Pods are deployed on Kubernetes Nodes. Pods are described in Pod Files which also articulate what shared resources the containers in the Pod require. An example of a Shared Resource is a Volume. Demo You can pretty much do every thing with the kubectl command line: Ssh demo-1; cat /opt/data/hello.html Ssh demo-master Create the Podcat nginx-pod.yaml Submit the Podkubectl create -f nginx-host.yaml View Pod Status kubectl get pods Delete Pods kubectl delete pods {MyPodName} Ssh demo-1; curl 172.17.0.11/test/hello.html Affinity you can also ensure Pod Affinity using labels kubectl label nodes test-node Disks=SSD Then add NodeSelector with Key and Value in your Pod File
- Used to ensure that there are always a certain amount of Kube Nodes running a particular pod. Even if its just one (Singleton). ReplicationControllers are described in Files that also include the Pod definition. No need for a separate Pod file. # kubectl create –f nginx-rc.yaml # kubectl get rc # kubectl get pods # ssh demo-1; curl IP/test/hello.html # kubectl delete rc {MyReplicationControllerName} Kubernetes uses Labels to organize its assets. Replication Controllers uses these labels to loosely couple co-operating pods You can turn up/down the replicas using the following command: kubectl resize --replicas=1 rc nginxrep
- When using ReplicationControllers you have the same Pod running on multiple hosts. A Kubernetes “Service” is a Load Balancer that will proxy inbound connections and route requests round-robin between the containers launched by the Pod. Kubectl create –f service.json kubectl label services nginxrep version=1.0
- Great Demo of the Declarative Power of Kubernetes. We are going to mount network storage (GlusterFS Distributed File) into the containers on the web serving directory This provides central storage for all the web servers. Change the files in just one place. You could also do this collocated on top of GlusterFS directly to improve performance. Show/Create the Endpoints:kubectl create –f gluster-endpoints.json Show/Create the RC:kubectl create –f nginx-rc-gluster.json Show RC and Podskubectl get rc/pods Show Mounts Createdssh demo-1; mount Show Web Servingssh demo-1; curl {IPAddress}/test/hello.html Change the Data/Re-Show