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diff --git a/kubernetes/common/music/charts/zookeeper/README.md b/kubernetes/common/music/charts/zookeeper/README.md new file mode 100644 index 0000000000..22bbac49dc --- /dev/null +++ b/kubernetes/common/music/charts/zookeeper/README.md @@ -0,0 +1,140 @@ +# incubator/zookeeper + +This helm chart provides an implementation of the ZooKeeper [StatefulSet](http://kubernetes.io/docs/concepts/abstractions/controllers/statefulsets/) found in Kubernetes Contrib [Zookeeper StatefulSet](https://github.com/kubernetes/contrib/tree/master/statefulsets/zookeeper). + +## Prerequisites +* Kubernetes 1.6+ +* PersistentVolume support on the underlying infrastructure +* A dynamic provisioner for the PersistentVolumes +* A familiarity with [Apache ZooKeeper 3.4.x](https://zookeeper.apache.org/doc/current/) + +## Chart Components +This chart will do the following: + +* Create a fixed size ZooKeeper ensemble using a [StatefulSet](http://kubernetes.io/docs/concepts/abstractions/controllers/statefulsets/). +* Create a [PodDisruptionBudget](https://kubernetes.io/docs/tasks/configure-pod-container/configure-pod-disruption-budget/) so kubectl drain will respect the Quorum size of the ensemble. +* Create a [Headless Service](https://kubernetes.io/docs/concepts/services-networking/service/) to control the domain of the ZooKeeper ensemble. +* Create a Service configured to connect to the available ZooKeeper instance on the configured client port. +* Optionally apply a [Pod Anti-Affinity](https://kubernetes.io/docs/concepts/configuration/assign-pod-node/#inter-pod-affinity-and-anti-affinity-beta-feature) to spread the ZooKeeper ensemble across nodes. +* Optionally start JMX Exporter and Zookeeper Exporter containers inside Zookeeper pods. +* Optionally create a job which creates Zookeeper chroots (e.g. `/kafka1`). + +## Installing the Chart +You can install the chart with the release name `zookeeper` as below. + +```console +$ helm repo add incubator http://storage.googleapis.com/kubernetes-charts-incubator +$ helm install --name zookeeper incubator/zookeeper +``` + +If you do not specify a name, helm will select a name for you. + +### Installed Components +You can use `kubectl get` to view all of the installed components. + +```console{%raw} +$ kubectl get all -l app=zookeeper +NAME: zookeeper +LAST DEPLOYED: Wed Apr 11 17:09:48 2018 +NAMESPACE: default +STATUS: DEPLOYED + +RESOURCES: +==> v1beta1/PodDisruptionBudget +NAME MIN AVAILABLE MAX UNAVAILABLE ALLOWED DISRUPTIONS AGE +zookeeper N/A 1 1 2m + +==> v1/Service +NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE +zookeeper-headless ClusterIP None <none> 2181/TCP,3888/TCP,2888/TCP 2m +zookeeper ClusterIP 10.98.179.165 <none> 2181/TCP 2m + +==> v1beta1/StatefulSet +NAME DESIRED CURRENT AGE +zookeeper 3 3 2m +``` + +1. `statefulsets/zookeeper` is the StatefulSet created by the chart. +1. `po/zookeeper-<0|1|2>` are the Pods created by the StatefulSet. Each Pod has a single container running a ZooKeeper server. +1. `svc/zookeeper-headless` is the Headless Service used to control the network domain of the ZooKeeper ensemble. +1. `svc/zookeeper` is a Service that can be used by clients to connect to an available ZooKeeper server. + +## Configuration +You can specify each parameter using the `--set key=value[,key=value]` argument to `helm install`. + +Alternatively, a YAML file that specifies the values for the parameters can be provided while installing the chart. For example, + +```console +$ helm install --name my-release -f values.yaml incubator/zookeeper +``` + +## Default Values + +- You can find all user-configurable settings, their defaults and commentary about them in [values.yaml](values.yaml). + +## Deep Dive + +## Image Details +The image used for this chart is based on Ubuntu 16.04 LTS. This image is larger than Alpine or BusyBox, but it provides glibc, rather than ulibc or mucl, and a JVM release that is built against it. You can easily convert this chart to run against a smaller image with a JVM that is built against that image's libc. However, as far as we know, no Hadoop vendor supports, or has verified, ZooKeeper running on such a JVM. + +## JVM Details +The Java Virtual Machine used for this chart is the OpenJDK JVM 8u111 JRE (headless). + +## ZooKeeper Details +The ZooKeeper version is the latest stable version (3.4.10). The distribution is installed into /opt/zookeeper-3.4.10. This directory is symbolically linked to /opt/zookeeper. Symlinks are created to simulate a rpm installation into /usr. + +## Failover +You can test failover by killing the leader. Insert a key: +```console +$ kubectl exec zookeeper-0 -- /opt/zookeeper/bin/zkCli.sh create /foo bar; +$ kubectl exec zookeeper-2 -- /opt/zookeeper/bin/zkCli.sh get /foo; +``` + +Watch existing members: +```console +$ kubectl run --attach bbox --image=busybox --restart=Never -- sh -c 'while true; do for i in 0 1 2; do echo zk-${i} $(echo stats | nc <pod-name>-${i}.<headless-service-name>:2181 | grep Mode); sleep 1; done; done'; + +zk-2 Mode: follower +zk-0 Mode: follower +zk-1 Mode: leader +zk-2 Mode: follower +``` + +Delete Pods and wait for the StatefulSet controller to bring them back up: +```console +$ kubectl delete po -l app=zookeeper +$ kubectl get po --watch-only +NAME READY STATUS RESTARTS AGE +zookeeper-0 0/1 Running 0 35s +zookeeper-0 1/1 Running 0 50s +zookeeper-1 0/1 Pending 0 0s +zookeeper-1 0/1 Pending 0 0s +zookeeper-1 0/1 ContainerCreating 0 0s +zookeeper-1 0/1 Running 0 19s +zookeeper-1 1/1 Running 0 40s +zookeeper-2 0/1 Pending 0 0s +zookeeper-2 0/1 Pending 0 0s +zookeeper-2 0/1 ContainerCreating 0 0s +zookeeper-2 0/1 Running 0 19s +zookeeper-2 1/1 Running 0 41s +``` + +Check the previously inserted key: +```console +$ kubectl exec zookeeper-1 -- /opt/zookeeper/bin/zkCli.sh get /foo +ionid = 0x354887858e80035, negotiated timeout = 30000 + +WATCHER:: + +WatchedEvent state:SyncConnected type:None path:null +bar +``` + +## Scaling +ZooKeeper can not be safely scaled in versions prior to 3.5.x. This chart currently uses 3.4.x. There are manual procedures for scaling a 3.4.x ensemble, but as noted in the [ZooKeeper 3.5.2 documentation](https://zookeeper.apache.org/doc/r3.5.2-alpha/zookeeperReconfig.html) these procedures require a rolling restart, are known to be error prone, and often result in a data loss. + +While ZooKeeper 3.5.x does allow for dynamic ensemble reconfiguration (including scaling membership), the current status of the release is still alpha, and 3.5.x is therefore not recommended for production use. + +## Limitations +* StatefulSet and PodDisruptionBudget are beta resources. +* Only supports storage options that have backends for persistent volume claims. |