fix space problems which ide results in
Signed-off-by: tim-zju <21651152@zju.edu.cn>reviewable/pr2036/r4
tim-zju
parent
8edcfc05b8
commit
1f7b3148f2
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@ -20,9 +20,9 @@ Thankfully, there is a system we can use to manage our containers in a cluster e
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Before we jump in and start kube'ing it up, it's important to understand some of the fundamentals of Kubernetes.
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* Containers: These are the Docker, rtk, AppC, or whatever Container you are running. You can think of these like subatomic particles; everything is made up of them, but you rarely (if ever) interact with them directly.
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* Pods: Pods are the basic component of Kubernetes. They are a group of Containers that are scheduled, live, and die together. Why would you want to have a group of containers instead of just a single container? Let's say you had a log processor, a web server, and a database. If you couldn't use Pods, you would have to bundle the log processor in the web server and database containers, and each time you updated one you would have to update the other. With Pods, you can just reuse the same log processor for both the web server and database.
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* Pods: Pods are the basic component of Kubernetes. They are a group of Containers that are scheduled, live, and die together. Why would you want to have a group of containers instead of just a single container? Let’s say you had a log processor, a web server, and a database. If you couldn't use Pods, you would have to bundle the log processor in the web server and database containers, and each time you updated one you would have to update the other. With Pods, you can just reuse the same log processor for both the web server and database.
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* Deployments: A Deployment provides declarative updates for Pods. You can define Deployments to create new Pods, or replace existing Pods. You only need to describe the desired state in a Deployment object, and the deployment controller will change the actual state to the desired state at a controlled rate for you. You can define Deployments to create new resources, or replace existing ones by new ones.
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* Services: A service is the single point of contact for a group of Pods. For example, let's say you have a Deployment that creates four copies of a web server pod. A Service will split the traffic to each of the four copies. Services are "permanent" while the pods behind them can come and go, so it's a good idea to use Services.
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* Services: A service is the single point of contact for a group of Pods. For example, let’s say you have a Deployment that creates four copies of a web server pod. A Service will split the traffic to each of the four copies. Services are "permanent" while the pods behind them can come and go, so it’s a good idea to use Services.
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## Step 1: Creating the Container
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@ -371,7 +371,7 @@ At this point, the local directory looks like this
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```shell
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$ ls
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Dockerfile
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Dockerfile
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app
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db-deployment.yml
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db-service.yml
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@ -15,7 +15,7 @@ In Kubernetes version 1.5, Windows Server Containers for Kubernetes is supported
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4. Docker Version 1.12.2-cs2-ws-beta or later for Windows Server nodes (Linux nodes and Kubernetes control plane can run any Kubernetes supported Docker Version)
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## Networking
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Network is achieved using L3 routing. Because third-party networking plugins (e.g. flannel, calico, etc) don't natively work on Windows Server, existing technology that is built into the Windows and Linux operating systems is relied on. In this L3 networking approach, a /16 subnet is chosen for the cluster nodes, and a /24 subnet is assigned to each worker node. All pods on a given worker node will be connected to the /24 subnet. This allows pods on the same node to communicate with each other. In order to enable networking between pods running on different nodes, routing features that are built into Windows Server 2016 and Linux are used.
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Network is achieved using L3 routing. Because third-party networking plugins (e.g. flannel, calico, etc) don’t natively work on Windows Server, existing technology that is built into the Windows and Linux operating systems is relied on. In this L3 networking approach, a /16 subnet is chosen for the cluster nodes, and a /24 subnet is assigned to each worker node. All pods on a given worker node will be connected to the /24 subnet. This allows pods on the same node to communicate with each other. In order to enable networking between pods running on different nodes, routing features that are built into Windows Server 2016 and Linux are used.
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### Linux
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The above networking approach is already supported on Linux using a bridge interface, which essentially creates a private network local to the node. Similar to the Windows side, routes to all other pod CIDRs must be created in order to send packets via the "public" NIC.
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@ -11,15 +11,15 @@ title: Running ZooKeeper, A CP Distributed System
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---
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{% capture overview %}
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This tutorial demonstrates [Apache Zookeeper](https://zookeeper.apache.org) on
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Kubernetes using [StatefulSets](/docs/concepts/abstractions/controllers/statefulsets/),
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[PodDisruptionBudgets](/docs/admin/disruptions/#specifying-a-poddisruptionbudget),
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This tutorial demonstrates [Apache Zookeeper](https://zookeeper.apache.org) on
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Kubernetes using [StatefulSets](/docs/concepts/abstractions/controllers/statefulsets/),
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[PodDisruptionBudgets](/docs/admin/disruptions/#specifying-a-poddisruptionbudget),
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and [PodAntiAffinity](/docs/user-guide/node-selection/).
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{% endcapture %}
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{% capture prerequisites %}
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Before starting this tutorial, you should be familiar with the following
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Before starting this tutorial, you should be familiar with the following
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Kubernetes concepts.
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* [Pods](/docs/user-guide/pods/single-container/)
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@ -34,16 +34,16 @@ Kubernetes concepts.
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* [kubectl CLI](/docs/user-guide/kubectl)
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You will require a cluster with at least four nodes, and each node will require
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at least 2 CPUs and 4 GiB of memory. In this tutorial you will cordon and
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drain the cluster's nodes. **This means that all Pods on the cluster's nodes
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will be terminated and evicted, and the nodes will, temporarily, become
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unschedulable.** You should use a dedicated cluster for this tutorial, or you
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should ensure that the disruption you cause will not interfere with other
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at least 2 CPUs and 4 GiB of memory. In this tutorial you will cordon and
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drain the cluster's nodes. **This means that all Pods on the cluster's nodes
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will be terminated and evicted, and the nodes will, temporarily, become
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unschedulable.** You should use a dedicated cluster for this tutorial, or you
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should ensure that the disruption you cause will not interfere with other
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tenants.
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This tutorial assumes that your cluster is configured to dynamically provision
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This tutorial assumes that your cluster is configured to dynamically provision
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PersistentVolumes. If your cluster is not configured to do so, you
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will have to manually provision three 20 GiB volumes prior to starting this
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will have to manually provision three 20 GiB volumes prior to starting this
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tutorial.
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{% endcapture %}
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@ -60,51 +60,51 @@ After this tutorial, you will know the following.
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#### ZooKeeper Basics
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[Apache ZooKeeper](https://zookeeper.apache.org/doc/current/) is a
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[Apache ZooKeeper](https://zookeeper.apache.org/doc/current/) is a
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distributed, open-source coordination service for distributed applications.
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ZooKeeper allows you to read, write, and observe updates to data. Data are
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organized in a file system like hierarchy and replicated to all ZooKeeper
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servers in the ensemble (a set of ZooKeeper servers). All operations on data
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are atomic and sequentially consistent. ZooKeeper ensures this by using the
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[Zab](https://pdfs.semanticscholar.org/b02c/6b00bd5dbdbd951fddb00b906c82fa80f0b3.pdf)
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ZooKeeper allows you to read, write, and observe updates to data. Data are
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organized in a file system like hierarchy and replicated to all ZooKeeper
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servers in the ensemble (a set of ZooKeeper servers). All operations on data
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are atomic and sequentially consistent. ZooKeeper ensures this by using the
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[Zab](https://pdfs.semanticscholar.org/b02c/6b00bd5dbdbd951fddb00b906c82fa80f0b3.pdf)
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consensus protocol to replicate a state machine across all servers in the ensemble.
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The ensemble uses the Zab protocol to elect a leader, and
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data can not be written until a leader is elected. Once a leader is
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elected, the ensemble uses Zab to ensure that all writes are replicated to a
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data can not be written until a leader is elected. Once a leader is
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elected, the ensemble uses Zab to ensure that all writes are replicated to a
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quorum before they are acknowledged and made visible to clients. Without respect
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to weighted quorums, a quorum is a majority component of the ensemble containing
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the current leader. For instance, if the ensemble has three servers, a component
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that contains the leader and one other server constitutes a quorum. If the
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to weighted quorums, a quorum is a majority component of the ensemble containing
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the current leader. For instance, if the ensemble has three servers, a component
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that contains the leader and one other server constitutes a quorum. If the
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ensemble can not achieve a quorum, data can not be written.
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ZooKeeper servers keep their entire state machine in memory, but every mutation
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is written to a durable WAL (Write Ahead Log) on storage media. When a server
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crashes, it can recover its previous state by replaying the WAL. In order to
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prevent the WAL from growing without bound, ZooKeeper servers will periodically
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snapshot their in memory state to storage media. These snapshots can be loaded
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directly into memory, and all WAL entries that preceded the snapshot may be
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ZooKeeper servers keep their entire state machine in memory, but every mutation
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is written to a durable WAL (Write Ahead Log) on storage media. When a server
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crashes, it can recover its previous state by replaying the WAL. In order to
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prevent the WAL from growing without bound, ZooKeeper servers will periodically
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snapshot their in memory state to storage media. These snapshots can be loaded
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directly into memory, and all WAL entries that preceded the snapshot may be
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safely discarded.
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### Creating a ZooKeeper Ensemble
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The manifest below contains a
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[Headless Service](/docs/user-guide/services/#headless-services),
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a [ConfigMap](/docs/user-guide/configmap/),
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a [PodDisruptionBudget](/docs/admin/disruptions/#specifying-a-poddisruptionbudget),
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and a [StatefulSet](/docs/concepts/abstractions/controllers/statefulsets/).
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The manifest below contains a
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[Headless Service](/docs/user-guide/services/#headless-services),
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a [ConfigMap](/docs/user-guide/configmap/),
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a [PodDisruptionBudget](/docs/admin/disruptions/#specifying-a-poddisruptionbudget),
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and a [StatefulSet](/docs/concepts/abstractions/controllers/statefulsets/).
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{% include code.html language="yaml" file="zookeeper.yaml" ghlink="/docs/tutorials/stateful-application/zookeeper.yaml" %}
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Open a command terminal, and use
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[`kubectl create`](/docs/user-guide/kubectl/kubectl_create/) to create the
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Open a command terminal, and use
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[`kubectl create`](/docs/user-guide/kubectl/kubectl_create/) to create the
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manifest.
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```shell
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kubectl create -f http://k8s.io/docs/tutorials/stateful-application/zookeeper.yaml
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```
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This creates the `zk-headless` Headless Service, the `zk-config` ConfigMap,
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This creates the `zk-headless` Headless Service, the `zk-config` ConfigMap,
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the `zk-budget` PodDisruptionBudget, and the `zk` StatefulSet.
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```shell
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@ -142,29 +142,29 @@ zk-2 0/1 Running 0 19s
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zk-2 1/1 Running 0 40s
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```
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The StatefulSet controller creates three Pods, and each Pod has a container with
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The StatefulSet controller creates three Pods, and each Pod has a container with
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a [ZooKeeper 3.4.9](http://www-us.apache.org/dist/zookeeper/zookeeper-3.4.9/) server.
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#### Facilitating Leader Election
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As there is no terminating algorithm for electing a leader in an anonymous
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network, Zab requires explicit membership configuration in order to perform
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leader election. Each server in the ensemble needs to have a unique
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As there is no terminating algorithm for electing a leader in an anonymous
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network, Zab requires explicit membership configuration in order to perform
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leader election. Each server in the ensemble needs to have a unique
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identifier, all servers need to know the global set of identifiers, and each
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identifier needs to be associated with a network address.
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Use [`kubectl exec`](/docs/user-guide/kubectl/kubectl_exec/) to get the hostnames
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Use [`kubectl exec`](/docs/user-guide/kubectl/kubectl_exec/) to get the hostnames
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of the Pods in the `zk` StatefulSet.
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```shell
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for i in 0 1 2; do kubectl exec zk-$i -- hostname; done
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```
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The StatefulSet controller provides each Pod with a unique hostname based on its
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ordinal index. The hostnames take the form `<statefulset name>-<ordinal index>`.
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As the `replicas` field of the `zk` StatefulSet is set to `3`, the Set's
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controller creates three Pods with their hostnames set to `zk-0`, `zk-1`, and
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`zk-2`.
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The StatefulSet controller provides each Pod with a unique hostname based on its
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ordinal index. The hostnames take the form `<statefulset name>-<ordinal index>`.
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As the `replicas` field of the `zk` StatefulSet is set to `3`, the Set's
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controller creates three Pods with their hostnames set to `zk-0`, `zk-1`, and
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`zk-2`.
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```shell
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zk-0
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@ -172,9 +172,9 @@ zk-1
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zk-2
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```
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The servers in a ZooKeeper ensemble use natural numbers as unique identifiers, and
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each server's identifier is stored in a file called `myid` in the server's
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data directory.
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The servers in a ZooKeeper ensemble use natural numbers as unique identifiers, and
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each server's identifier is stored in a file called `myid` in the server’s
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data directory.
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Examine the contents of the `myid` file for each server.
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@ -182,7 +182,7 @@ Examine the contents of the `myid` file for each server.
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for i in 0 1 2; do echo "myid zk-$i";kubectl exec zk-$i -- cat /var/lib/zookeeper/data/myid; done
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```
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As the identifiers are natural numbers and the ordinal indices are non-negative
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As the identifiers are natural numbers and the ordinal indices are non-negative
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integers, you can generate an identifier by adding one to the ordinal.
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```shell
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@ -200,7 +200,7 @@ Get the FQDN (Fully Qualified Domain Name) of each Pod in the `zk` StatefulSet.
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for i in 0 1 2; do kubectl exec zk-$i -- hostname -f; done
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```
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The `zk-headless` Service creates a domain for all of the Pods,
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The `zk-headless` Service creates a domain for all of the Pods,
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`zk-headless.default.svc.cluster.local`.
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```shell
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@ -209,11 +209,11 @@ zk-1.zk-headless.default.svc.cluster.local
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zk-2.zk-headless.default.svc.cluster.local
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```
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The A records in [Kubernetes DNS](/docs/admin/dns/) resolve the FQDNs to the Pods' IP addresses.
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If the Pods are rescheduled, the A records will be updated with the Pods' new IP
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The A records in [Kubernetes DNS](/docs/admin/dns/) resolve the FQDNs to the Pods' IP addresses.
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If the Pods are rescheduled, the A records will be updated with the Pods' new IP
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addresses, but the A record's names will not change.
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ZooKeeper stores its application configuration in a file named `zoo.cfg`. Use
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ZooKeeper stores its application configuration in a file named `zoo.cfg`. Use
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`kubectl exec` to view the contents of the `zoo.cfg` file in the `zk-0` Pod.
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```
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@ -222,8 +222,8 @@ kubectl exec zk-0 -- cat /opt/zookeeper/conf/zoo.cfg
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For the `server.1`, `server.2`, and `server.3` properties at the bottom of
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the file, the `1`, `2`, and `3` correspond to the identifiers in the
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ZooKeeper servers' `myid` files. They are set to the FQDNs for the Pods in
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the `zk` StatefulSet.
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ZooKeeper servers' `myid` files. They are set to the FQDNs for the Pods in
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the `zk` StatefulSet.
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```shell
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clientPort=2181
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@ -244,16 +244,16 @@ server.3=zk-2.zk-headless.default.svc.cluster.local:2888:3888
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#### Achieving Consensus
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Consensus protocols require that the identifiers of each participant be
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unique. No two participants in the Zab protocol should claim the same unique
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identifier. This is necessary to allow the processes in the system to agree on
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which processes have committed which data. If two Pods were launched with the
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Consensus protocols require that the identifiers of each participant be
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unique. No two participants in the Zab protocol should claim the same unique
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identifier. This is necessary to allow the processes in the system to agree on
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which processes have committed which data. If two Pods were launched with the
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same ordinal, two ZooKeeper servers would both identify themselves as the same
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server.
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When you created the `zk` StatefulSet, the StatefulSet's controller created
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each Pod sequentially, in the order defined by the Pods' ordinal indices, and it
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waited for each Pod to be Running and Ready before creating the next Pod.
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When you created the `zk` StatefulSet, the StatefulSet's controller created
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each Pod sequentially, in the order defined by the Pods' ordinal indices, and it
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waited for each Pod to be Running and Ready before creating the next Pod.
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```shell
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kubectl get pods -w -l app=zk
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@ -277,7 +277,7 @@ zk-2 1/1 Running 0 40s
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The A records for each Pod are only entered when the Pod becomes Ready. Therefore,
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the FQDNs of the ZooKeeper servers will only resolve to a single endpoint, and that
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endpoint will be the unique ZooKeeper server claiming the identity configured
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endpoint will be the unique ZooKeeper server claiming the identity configured
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in its `myid` file.
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```shell
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@ -286,7 +286,7 @@ zk-1.zk-headless.default.svc.cluster.local
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zk-2.zk-headless.default.svc.cluster.local
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```
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This ensures that the `servers` properties in the ZooKeepers' `zoo.cfg` files
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This ensures that the `servers` properties in the ZooKeepers' `zoo.cfg` files
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represents a correctly configured ensemble.
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```shell
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@ -295,16 +295,16 @@ server.2=zk-1.zk-headless.default.svc.cluster.local:2888:3888
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server.3=zk-2.zk-headless.default.svc.cluster.local:2888:3888
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```
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When the servers use the Zab protocol to attempt to commit a value, they will
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either achieve consensus and commit the value (if leader election has succeeded
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and at least two of the Pods are Running and Ready), or they will fail to do so
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(if either of the aforementioned conditions are not met). No state will arise
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When the servers use the Zab protocol to attempt to commit a value, they will
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either achieve consensus and commit the value (if leader election has succeeded
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and at least two of the Pods are Running and Ready), or they will fail to do so
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(if either of the aforementioned conditions are not met). No state will arise
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where one server acknowledges a write on behalf of another.
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#### Sanity Testing the Ensemble
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The most basic sanity test is to write some data to one ZooKeeper server and
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to read the data from another.
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The most basic sanity test is to write some data to one ZooKeeper server and
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to read the data from another.
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Use the `zkCli.sh` script to write `world` to the path `/hello` on the `zk-0` Pod.
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@ -327,7 +327,7 @@ Get the data from the `zk-1` Pod.
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kubectl exec zk-1 zkCli.sh get /hello
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```
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The data that you created on `zk-0` is available on all of the servers in the
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The data that you created on `zk-0` is available on all of the servers in the
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ensemble.
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```shell
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@ -351,12 +351,12 @@ numChildren = 0
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#### Providing Durable Storage
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As mentioned in the [ZooKeeper Basics](#zookeeper-basics) section,
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ZooKeeper commits all entries to a durable WAL, and periodically writes snapshots
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in memory state, to storage media. Using WALs to provide durability is a common
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ZooKeeper commits all entries to a durable WAL, and periodically writes snapshots
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in memory state, to storage media. Using WALs to provide durability is a common
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technique for applications that use consensus protocols to achieve a replicated
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state machine and for storage applications in general.
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Use [`kubectl delete`](/docs/user-guide/kubectl/kubectl_delete/) to delete the
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Use [`kubectl delete`](/docs/user-guide/kubectl/kubectl_delete/) to delete the
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`zk` StatefulSet.
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```shell
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|
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@ -392,7 +392,7 @@ Reapply the manifest in `zookeeper.yaml`.
|
|||
kubectl apply -f http://k8s.io/docs/tutorials/stateful-application/zookeeper.yaml
|
||||
```
|
||||
|
||||
The `zk` StatefulSet will be created, but, as they already exist, the other API
|
||||
The `zk` StatefulSet will be created, but, as they already exist, the other API
|
||||
Objects in the manifest will not be modified.
|
||||
|
||||
```shell
|
||||
|
|
@ -429,14 +429,14 @@ zk-2 0/1 Running 0 19s
|
|||
zk-2 1/1 Running 0 40s
|
||||
```
|
||||
|
||||
Get the value you entered during the [sanity test](#sanity-testing-the-ensemble),
|
||||
Get the value you entered during the [sanity test](#sanity-testing-the-ensemble),
|
||||
from the `zk-2` Pod.
|
||||
|
||||
```shell
|
||||
kubectl exec zk-2 zkCli.sh get /hello
|
||||
```
|
||||
|
||||
Even though all of the Pods in the `zk` StatefulSet have been terminated and
|
||||
Even though all of the Pods in the `zk` StatefulSet have been terminated and
|
||||
recreated, the ensemble still serves the original value.
|
||||
|
||||
```shell
|
||||
|
|
@ -457,8 +457,8 @@ dataLength = 5
|
|||
numChildren = 0
|
||||
```
|
||||
|
||||
The `volumeClaimTemplates` field, of the `zk` StatefulSet's `spec`, specifies a
|
||||
PersistentVolume that will be provisioned for each Pod.
|
||||
The `volumeClaimTemplates` field, of the `zk` StatefulSet's `spec`, specifies a
|
||||
PersistentVolume that will be provisioned for each Pod.
|
||||
|
||||
```yaml
|
||||
volumeClaimTemplates:
|
||||
|
|
@ -474,8 +474,8 @@ volumeClaimTemplates:
|
|||
```
|
||||
|
||||
|
||||
The StatefulSet controller generates a PersistentVolumeClaim for each Pod in
|
||||
the StatefulSet.
|
||||
The StatefulSet controller generates a PersistentVolumeClaim for each Pod in
|
||||
the StatefulSet.
|
||||
|
||||
Get the StatefulSet's PersistentVolumeClaims.
|
||||
|
||||
|
|
@ -483,7 +483,7 @@ Get the StatefulSet's PersistentVolumeClaims.
|
|||
kubectl get pvc -l app=zk
|
||||
```
|
||||
|
||||
When the StatefulSet recreated its Pods, the Pods' PersistentVolumes were
|
||||
When the StatefulSet recreated its Pods, the Pods' PersistentVolumes were
|
||||
remounted.
|
||||
|
||||
```shell
|
||||
|
|
@ -502,19 +502,19 @@ volumeMounts:
|
|||
mountPath: /var/lib/zookeeper
|
||||
```
|
||||
|
||||
When a Pod in the `zk` StatefulSet is (re)scheduled, it will always have the
|
||||
same PersistentVolume mounted to the ZooKeeper server's data directory.
|
||||
Even when the Pods are rescheduled, all of the writes made to the ZooKeeper
|
||||
When a Pod in the `zk` StatefulSet is (re)scheduled, it will always have the
|
||||
same PersistentVolume mounted to the ZooKeeper server's data directory.
|
||||
Even when the Pods are rescheduled, all of the writes made to the ZooKeeper
|
||||
servers' WALs, and all of their snapshots, remain durable.
|
||||
|
||||
### Ensuring Consistent Configuration
|
||||
|
||||
As noted in the [Facilitating Leader Election](#facilitating-leader-election) and
|
||||
[Achieving Consensus](#achieving-consensus) sections, the servers in a
|
||||
ZooKeeper ensemble require consistent configuration in order to elect a leader
|
||||
[Achieving Consensus](#achieving-consensus) sections, the servers in a
|
||||
ZooKeeper ensemble require consistent configuration in order to elect a leader
|
||||
and form a quorum. They also require consistent configuration of the Zab protocol
|
||||
in order for the protocol to work correctly over a network. You can use
|
||||
ConfigMaps to achieve this.
|
||||
in order for the protocol to work correctly over a network. You can use
|
||||
ConfigMaps to achieve this.
|
||||
|
||||
Get the `zk-config` ConfigMap.
|
||||
|
||||
|
|
@ -532,8 +532,8 @@ data:
|
|||
tick: "2000"
|
||||
```
|
||||
|
||||
The `env` field of the `zk` StatefulSet's Pod `template` reads the ConfigMap
|
||||
into environment variables. These variables are injected into the containers
|
||||
The `env` field of the `zk` StatefulSet's Pod `template` reads the ConfigMap
|
||||
into environment variables. These variables are injected into the containers
|
||||
environment.
|
||||
|
||||
```yaml
|
||||
|
|
@ -581,7 +581,7 @@ env:
|
|||
```
|
||||
|
||||
The entry point of the container invokes a bash script, `zkConfig.sh`, prior to
|
||||
launching the ZooKeeper server process. This bash script generates the
|
||||
launching the ZooKeeper server process. This bash script generates the
|
||||
ZooKeeper configuration files from the supplied environment variables.
|
||||
|
||||
```yaml
|
||||
|
|
@ -597,8 +597,8 @@ Examine the environment of all of the Pods in the `zk` StatefulSet.
|
|||
for i in 0 1 2; do kubectl exec zk-$i env | grep ZK_*;echo""; done
|
||||
```
|
||||
|
||||
All of the variables populated from `zk-config` contain identical values. This
|
||||
allows the `zkGenConfig.sh` script to create consistent configurations for all
|
||||
All of the variables populated from `zk-config` contain identical values. This
|
||||
allows the `zkGenConfig.sh` script to create consistent configurations for all
|
||||
of the ZooKeeper servers in the ensemble.
|
||||
|
||||
```shell
|
||||
|
|
@ -653,16 +653,16 @@ ZK_LOG_DIR=/var/log/zookeeper
|
|||
|
||||
#### Configuring Logging
|
||||
|
||||
One of the files generated by the `zkConfigGen.sh` script controls ZooKeeper's logging.
|
||||
ZooKeeper uses [Log4j](http://logging.apache.org/log4j/2.x/), and, by default,
|
||||
it uses a time and size based rolling file appender for its logging configuration.
|
||||
One of the files generated by the `zkConfigGen.sh` script controls ZooKeeper's logging.
|
||||
ZooKeeper uses [Log4j](http://logging.apache.org/log4j/2.x/), and, by default,
|
||||
it uses a time and size based rolling file appender for its logging configuration.
|
||||
Get the logging configuration from one of Pods in the `zk` StatefulSet.
|
||||
|
||||
```shell
|
||||
kubectl exec zk-0 cat /usr/etc/zookeeper/log4j.properties
|
||||
```
|
||||
|
||||
The logging configuration below will cause the ZooKeeper process to write all
|
||||
The logging configuration below will cause the ZooKeeper process to write all
|
||||
of its logs to the standard output file stream.
|
||||
|
||||
```shell
|
||||
|
|
@ -675,20 +675,20 @@ log4j.appender.CONSOLE.layout=org.apache.log4j.PatternLayout
|
|||
log4j.appender.CONSOLE.layout.ConversionPattern=%d{ISO8601} [myid:%X{myid}] - %-5p [%t:%C{1}@%L] - %m%n
|
||||
```
|
||||
|
||||
This is the simplest possible way to safely log inside the container. As the
|
||||
application's logs are being written to standard out, Kubernetes will handle
|
||||
log rotation for you. Kubernetes also implements a sane retention policy that
|
||||
ensures application logs written to standard out and standard error do not
|
||||
This is the simplest possible way to safely log inside the container. As the
|
||||
application's logs are being written to standard out, Kubernetes will handle
|
||||
log rotation for you. Kubernetes also implements a sane retention policy that
|
||||
ensures application logs written to standard out and standard error do not
|
||||
exhaust local storage media.
|
||||
|
||||
Use [`kubectl logs`](/docs/user-guide/kubectl/kubectl_logs/) to retrieve the last
|
||||
Use [`kubectl logs`](/docs/user-guide/kubectl/kubectl_logs/) to retrieve the last
|
||||
few log lines from one of the Pods.
|
||||
|
||||
```shell
|
||||
kubectl logs zk-0 --tail 20
|
||||
```
|
||||
|
||||
Application logs that are written to standard out or standard error are viewable
|
||||
Application logs that are written to standard out or standard error are viewable
|
||||
using `kubectl logs` and from the Kubernetes Dashboard.
|
||||
|
||||
```shell
|
||||
|
|
@ -714,19 +714,19 @@ using `kubectl logs` and from the Kubernetes Dashboard.
|
|||
2016-12-06 19:34:46,230 [myid:1] - INFO [Thread-1142:NIOServerCnxn@1008] - Closed socket connection for client /127.0.0.1:52768 (no session established for client)
|
||||
```
|
||||
|
||||
Kubernetes also supports more powerful, but more complex, logging integrations
|
||||
with [Google Cloud Logging](https://github.com/kubernetes/contrib/blob/master/logging/fluentd-sidecar-gcp/README.md)
|
||||
Kubernetes also supports more powerful, but more complex, logging integrations
|
||||
with [Google Cloud Logging](https://github.com/kubernetes/contrib/blob/master/logging/fluentd-sidecar-gcp/README.md)
|
||||
and [ELK](https://github.com/kubernetes/contrib/blob/master/logging/fluentd-sidecar-es/README.md).
|
||||
For cluster level log shipping and aggregation, you should consider deploying a
|
||||
[sidecar](http://blog.kubernetes.io/2015/06/the-distributed-system-toolkit-patterns.html)
|
||||
[sidecar](http://blog.kubernetes.io/2015/06/the-distributed-system-toolkit-patterns.html)
|
||||
container to rotate and ship your logs.
|
||||
|
||||
#### Configuring a Non-Privileged User
|
||||
|
||||
The best practices with respect to allowing an application to run as a privileged
|
||||
user inside of a container are a matter of debate. If your organization requires
|
||||
that applications be run as a non-privileged user you can use a
|
||||
[SecurityContext](/docs/user-guide/security-context/) to control the user that
|
||||
The best practices with respect to allowing an application to run as a privileged
|
||||
user inside of a container are a matter of debate. If your organization requires
|
||||
that applications be run as a non-privileged user you can use a
|
||||
[SecurityContext](/docs/user-guide/security-context/) to control the user that
|
||||
the entry point runs as.
|
||||
|
||||
The `zk` StatefulSet's Pod `template` contains a SecurityContext.
|
||||
|
|
@ -737,7 +737,7 @@ securityContext:
|
|||
fsGroup: 1000
|
||||
```
|
||||
|
||||
In the Pods' containers, UID 1000 corresponds to the zookeeper user and GID 1000
|
||||
In the Pods' containers, UID 1000 corresponds to the zookeeper user and GID 1000
|
||||
corresponds to the zookeeper group.
|
||||
|
||||
Get the ZooKeeper process information from the `zk-0` Pod.
|
||||
|
|
@ -746,7 +746,7 @@ Get the ZooKeeper process information from the `zk-0` Pod.
|
|||
kubectl exec zk-0 -- ps -elf
|
||||
```
|
||||
|
||||
As the `runAsUser` field of the `securityContext` object is set to 1000,
|
||||
As the `runAsUser` field of the `securityContext` object is set to 1000,
|
||||
instead of running as root, the ZooKeeper process runs as the zookeeper user.
|
||||
|
||||
```shell
|
||||
|
|
@ -755,8 +755,8 @@ F S UID PID PPID C PRI NI ADDR SZ WCHAN STIME TTY TIME CMD
|
|||
0 S zookeep+ 27 1 0 80 0 - 1155556 - 20:46 ? 00:00:19 /usr/lib/jvm/java-8-openjdk-amd64/bin/java -Dzookeeper.log.dir=/var/log/zookeeper -Dzookeeper.root.logger=INFO,CONSOLE -cp /usr/bin/../build/classes:/usr/bin/../build/lib/*.jar:/usr/bin/../share/zookeeper/zookeeper-3.4.9.jar:/usr/bin/../share/zookeeper/slf4j-log4j12-1.6.1.jar:/usr/bin/../share/zookeeper/slf4j-api-1.6.1.jar:/usr/bin/../share/zookeeper/netty-3.10.5.Final.jar:/usr/bin/../share/zookeeper/log4j-1.2.16.jar:/usr/bin/../share/zookeeper/jline-0.9.94.jar:/usr/bin/../src/java/lib/*.jar:/usr/bin/../etc/zookeeper: -Xmx2G -Xms2G -Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.local.only=false org.apache.zookeeper.server.quorum.QuorumPeerMain /usr/bin/../etc/zookeeper/zoo.cfg
|
||||
```
|
||||
|
||||
By default, when the Pod's PersistentVolume is mounted to the ZooKeeper server's
|
||||
data directory, it is only accessible by the root user. This configuration
|
||||
By default, when the Pod's PersistentVolume is mounted to the ZooKeeper server's
|
||||
data directory, it is only accessible by the root user. This configuration
|
||||
prevents the ZooKeeper process from writing to its WAL and storing its snapshots.
|
||||
|
||||
Get the file permissions of the ZooKeeper data directory on the `zk-0` Pod.
|
||||
|
|
@ -765,8 +765,8 @@ Get the file permissions of the ZooKeeper data directory on the `zk-0` Pod.
|
|||
kubectl exec -ti zk-0 -- ls -ld /var/lib/zookeeper/data
|
||||
```
|
||||
|
||||
As the `fsGroup` field of the `securityContext` object is set to 1000,
|
||||
the ownership of the Pods' PersistentVolumes is set to the zookeeper group,
|
||||
As the `fsGroup` field of the `securityContext` object is set to 1000,
|
||||
the ownership of the Pods' PersistentVolumes is set to the zookeeper group,
|
||||
and the ZooKeeper process is able to successfully read and write its data.
|
||||
|
||||
```shell
|
||||
|
|
@ -775,21 +775,21 @@ drwxr-sr-x 3 zookeeper zookeeper 4096 Dec 5 20:45 /var/lib/zookeeper/data
|
|||
|
||||
### Managing the ZooKeeper Process
|
||||
|
||||
The [ZooKeeper documentation](https://zookeeper.apache.org/doc/current/zookeeperAdmin.html#sc_supervision)
|
||||
documentation indicates that "You will want to have a supervisory process that
|
||||
manages each of your ZooKeeper server processes (JVM)." Utilizing a watchdog
|
||||
(supervisory process) to restart failed processes in a distributed system is a
|
||||
common pattern. When deploying an application in Kubernetes, rather than using
|
||||
an external utility as a supervisory process, you should use Kubernetes as the
|
||||
The [ZooKeeper documentation](https://zookeeper.apache.org/doc/current/zookeeperAdmin.html#sc_supervision)
|
||||
documentation indicates that "You will want to have a supervisory process that
|
||||
manages each of your ZooKeeper server processes (JVM)." Utilizing a watchdog
|
||||
(supervisory process) to restart failed processes in a distributed system is a
|
||||
common pattern. When deploying an application in Kubernetes, rather than using
|
||||
an external utility as a supervisory process, you should use Kubernetes as the
|
||||
watchdog for your application.
|
||||
|
||||
#### Handling Process Failure
|
||||
#### Handling Process Failure
|
||||
|
||||
|
||||
[Restart Policies](/docs/user-guide/pod-states/#restartpolicy) control how
|
||||
[Restart Policies](/docs/user-guide/pod-states/#restartpolicy) control how
|
||||
Kubernetes handles process failures for the entry point of the container in a Pod.
|
||||
For Pods in a StatefulSet, the only appropriate RestartPolicy is Always, and this
|
||||
is the default value. For stateful applications you should **never** override
|
||||
is the default value. For stateful applications you should **never** override
|
||||
the default policy.
|
||||
|
||||
|
||||
|
|
@ -799,7 +799,7 @@ Examine the process tree for the ZooKeeper server running in the `zk-0` Pod.
|
|||
kubectl exec zk-0 -- ps -ef
|
||||
```
|
||||
|
||||
The command used as the container's entry point has PID 1, and the
|
||||
The command used as the container's entry point has PID 1, and the
|
||||
the ZooKeeper process, a child of the entry point, has PID 23.
|
||||
|
||||
|
||||
|
|
@ -824,8 +824,8 @@ In another terminal, kill the ZooKeeper process in Pod `zk-0`.
|
|||
```
|
||||
|
||||
|
||||
The death of the ZooKeeper process caused its parent process to terminate. As
|
||||
the RestartPolicy of the container is Always, the parent process was relaunched.
|
||||
The death of the ZooKeeper process caused its parent process to terminate. As
|
||||
the RestartPolicy of the container is Always, the parent process was relaunched.
|
||||
|
||||
|
||||
```shell
|
||||
|
|
@ -840,19 +840,19 @@ zk-0 1/1 Running 1 29m
|
|||
```
|
||||
|
||||
|
||||
If your application uses a script (such as zkServer.sh) to launch the process
|
||||
If your application uses a script (such as zkServer.sh) to launch the process
|
||||
that implements the application's business logic, the script must terminate with the
|
||||
child process. This ensures that Kubernetes will restart the application's
|
||||
container when the process implementing the application's business logic fails.
|
||||
container when the process implementing the application's business logic fails.
|
||||
|
||||
|
||||
#### Testing for Liveness
|
||||
|
||||
|
||||
Configuring your application to restart failed processes is not sufficient to
|
||||
keep a distributed system healthy. There are many scenarios where
|
||||
a system's processes can be both alive and unresponsive, or otherwise
|
||||
unhealthy. You should use liveness probes in order to notify Kubernetes
|
||||
Configuring your application to restart failed processes is not sufficient to
|
||||
keep a distributed system healthy. There are many scenarios where
|
||||
a system's processes can be both alive and unresponsive, or otherwise
|
||||
unhealthy. You should use liveness probes in order to notify Kubernetes
|
||||
that your application's processes are unhealthy and should be restarted.
|
||||
|
||||
|
||||
|
|
@ -869,7 +869,7 @@ The Pod `template` for the `zk` StatefulSet specifies a liveness probe.
|
|||
```
|
||||
|
||||
|
||||
The probe calls a simple bash script that uses the ZooKeeper `ruok` four letter
|
||||
The probe calls a simple bash script that uses the ZooKeeper `ruok` four letter
|
||||
word to test the server's health.
|
||||
|
||||
|
||||
|
|
@ -900,7 +900,7 @@ kubectl exec zk-0 -- rm /opt/zookeeper/bin/zkOk.sh
|
|||
```
|
||||
|
||||
|
||||
When the liveness probe for the ZooKeeper process fails, Kubernetes will
|
||||
When the liveness probe for the ZooKeeper process fails, Kubernetes will
|
||||
automatically restart the process for you, ensuring that unhealthy processes in
|
||||
the ensemble are restarted.
|
||||
|
||||
|
|
@ -921,10 +921,10 @@ zk-0 1/1 Running 1 1h
|
|||
#### Testing for Readiness
|
||||
|
||||
|
||||
Readiness is not the same as liveness. If a process is alive, it is scheduled
|
||||
and healthy. If a process is ready, it is able to process input. Liveness is
|
||||
Readiness is not the same as liveness. If a process is alive, it is scheduled
|
||||
and healthy. If a process is ready, it is able to process input. Liveness is
|
||||
a necessary, but not sufficient, condition for readiness. There are many cases,
|
||||
particularly during initialization and termination, when a process can be
|
||||
particularly during initialization and termination, when a process can be
|
||||
alive but not ready.
|
||||
|
||||
|
||||
|
|
@ -932,8 +932,8 @@ If you specify a readiness probe, Kubernetes will ensure that your application's
|
|||
processes will not receive network traffic until their readiness checks pass.
|
||||
|
||||
|
||||
For a ZooKeeper server, liveness implies readiness. Therefore, the readiness
|
||||
probe from the `zookeeper.yaml` manifest is identical to the liveness probe.
|
||||
For a ZooKeeper server, liveness implies readiness. Therefore, the readiness
|
||||
probe from the `zookeeper.yaml` manifest is identical to the liveness probe.
|
||||
|
||||
|
||||
```yaml
|
||||
|
|
@ -946,28 +946,28 @@ probe from the `zookeeper.yaml` manifest is identical to the liveness probe.
|
|||
```
|
||||
|
||||
|
||||
Even though the liveness and readiness probes are identical, it is important
|
||||
to specify both. This ensures that only healthy servers in the ZooKeeper
|
||||
Even though the liveness and readiness probes are identical, it is important
|
||||
to specify both. This ensures that only healthy servers in the ZooKeeper
|
||||
ensemble receive network traffic.
|
||||
|
||||
|
||||
### Tolerating Node Failure
|
||||
|
||||
ZooKeeper needs a quorum of servers in order to successfully commit mutations
|
||||
to data. For a three server ensemble, two servers must be healthy in order for
|
||||
writes to succeed. In quorum based systems, members are deployed across failure
|
||||
domains to ensure availability. In order to avoid an outage, due to the loss of an
|
||||
individual machine, best practices preclude co-locating multiple instances of the
|
||||
ZooKeeper needs a quorum of servers in order to successfully commit mutations
|
||||
to data. For a three server ensemble, two servers must be healthy in order for
|
||||
writes to succeed. In quorum based systems, members are deployed across failure
|
||||
domains to ensure availability. In order to avoid an outage, due to the loss of an
|
||||
individual machine, best practices preclude co-locating multiple instances of the
|
||||
application on the same machine.
|
||||
|
||||
By default, Kubernetes may co-locate Pods in a StatefulSet on the same node.
|
||||
By default, Kubernetes may co-locate Pods in a StatefulSet on the same node.
|
||||
For the three server ensemble you created, if two servers reside on the same
|
||||
node, and that node fails, the clients of your ZooKeeper service will experience
|
||||
an outage until at least one of the Pods can be rescheduled.
|
||||
an outage until at least one of the Pods can be rescheduled.
|
||||
|
||||
You should always provision additional capacity to allow the processes of critical
|
||||
systems to be rescheduled in the event of node failures. If you do so, then the
|
||||
outage will only last until the Kubernetes scheduler reschedules one of the ZooKeeper
|
||||
systems to be rescheduled in the event of node failures. If you do so, then the
|
||||
outage will only last until the Kubernetes scheduler reschedules one of the ZooKeeper
|
||||
servers. However, if you want your service to tolerate node failures with no downtime,
|
||||
you should use a `PodAntiAffinity` annotation.
|
||||
|
||||
|
|
@ -985,7 +985,7 @@ kubernetes-minion-group-a5aq
|
|||
kubernetes-minion-group-2g2d
|
||||
```
|
||||
|
||||
This is because the Pods in the `zk` StatefulSet contain a
|
||||
This is because the Pods in the `zk` StatefulSet contain a
|
||||
[PodAntiAffinity](/docs/user-guide/node-selection/) annotation.
|
||||
|
||||
```yaml
|
||||
|
|
@ -1006,11 +1006,11 @@ scheduler.alpha.kubernetes.io/affinity: >
|
|||
}
|
||||
```
|
||||
|
||||
The `requiredDuringSchedulingRequiredDuringExecution` field tells the
|
||||
The `requiredDuringSchedulingRequiredDuringExecution` field tells the
|
||||
Kubernetes Scheduler that it should never co-locate two Pods from the `zk-headless`
|
||||
Service in the domain defined by the `topologyKey`. The `topologyKey`
|
||||
`kubernetes.io/hostname` indicates that the domain is an individual node. Using
|
||||
different rules, labels, and selectors, you can extend this technique to spread
|
||||
`kubernetes.io/hostname` indicates that the domain is an individual node. Using
|
||||
different rules, labels, and selectors, you can extend this technique to spread
|
||||
your ensemble across physical, network, and power failure domains.
|
||||
|
||||
### Surviving Maintenance
|
||||
|
|
@ -1018,8 +1018,8 @@ your ensemble across physical, network, and power failure domains.
|
|||
**In this section you will cordon and drain nodes. If you are using this tutorial
|
||||
on a shared cluster, be sure that this will not adversely affect other tenants.**
|
||||
|
||||
The previous section showed you how to spread your Pods across nodes to survive
|
||||
unplanned node failures, but you also need to plan for temporary node failures
|
||||
The previous section showed you how to spread your Pods across nodes to survive
|
||||
unplanned node failures, but you also need to plan for temporary node failures
|
||||
that occur due to planned maintenance.
|
||||
|
||||
Get the nodes in your cluster.
|
||||
|
|
@ -1028,7 +1028,7 @@ Get the nodes in your cluster.
|
|||
kubectl get nodes
|
||||
```
|
||||
|
||||
Use [`kubectl cordon`](/docs/user-guide/kubectl/kubectl_cordon/) to
|
||||
Use [`kubectl cordon`](/docs/user-guide/kubectl/kubectl_cordon/) to
|
||||
cordon all but four of the nodes in your cluster.
|
||||
|
||||
```shell{% raw %}
|
||||
|
|
@ -1041,8 +1041,8 @@ Get the `zk-budget` PodDisruptionBudget.
|
|||
kubectl get poddisruptionbudget zk-budget
|
||||
```
|
||||
|
||||
The `min-available` field indicates to Kubernetes that at least two Pods from
|
||||
`zk` StatefulSet must be available at any time.
|
||||
The `min-available` field indicates to Kubernetes that at least two Pods from
|
||||
`zk` StatefulSet must be available at any time.
|
||||
|
||||
```yaml
|
||||
NAME MIN-AVAILABLE ALLOWED-DISRUPTIONS AGE
|
||||
|
|
@ -1065,7 +1065,7 @@ kubernetes-minion-group-ixsl
|
|||
kubernetes-minion-group-i4c4
|
||||
{% endraw %}```
|
||||
|
||||
Use [`kubectl drain`](/docs/user-guide/kubectl/kubectl_drain/) to cordon and
|
||||
Use [`kubectl drain`](/docs/user-guide/kubectl/kubectl_drain/) to cordon and
|
||||
drain the node on which the `zk-0` Pod is scheduled.
|
||||
|
||||
```shell {% raw %}
|
||||
|
|
@ -1075,7 +1075,7 @@ pod "zk-0" deleted
|
|||
node "kubernetes-minion-group-pb41" drained
|
||||
{% endraw %}```
|
||||
|
||||
As there are four nodes in your cluster, `kubectl drain`, succeeds and the
|
||||
As there are four nodes in your cluster, `kubectl drain`, succeeds and the
|
||||
`zk-0` is rescheduled to another node.
|
||||
|
||||
```
|
||||
|
|
@ -1095,7 +1095,7 @@ zk-0 0/1 Running 0 51s
|
|||
zk-0 1/1 Running 0 1m
|
||||
```
|
||||
|
||||
Keep watching the StatefulSet's Pods in the first terminal and drain the node on which
|
||||
Keep watching the StatefulSet's Pods in the first terminal and drain the node on which
|
||||
`zk-1` is scheduled.
|
||||
|
||||
```shell{% raw %}
|
||||
|
|
@ -1105,8 +1105,8 @@ pod "zk-1" deleted
|
|||
node "kubernetes-minion-group-ixsl" drained
|
||||
{% endraw %}```
|
||||
|
||||
The `zk-1` Pod can not be scheduled. As the `zk` StatefulSet contains a
|
||||
`PodAntiAffinity` annotation preventing co-location of the Pods, and as only
|
||||
The `zk-1` Pod can not be scheduled. As the `zk` StatefulSet contains a
|
||||
`PodAntiAffinity` annotation preventing co-location of the Pods, and as only
|
||||
two nodes are schedulable, the Pod will remain in a Pending state.
|
||||
|
||||
```shell
|
||||
|
|
@ -1133,7 +1133,7 @@ zk-1 0/1 Pending 0 0s
|
|||
zk-1 0/1 Pending 0 0s
|
||||
```
|
||||
|
||||
Continue to watch the Pods of the stateful set, and drain the node on which
|
||||
Continue to watch the Pods of the stateful set, and drain the node on which
|
||||
`zk-2` is scheduled.
|
||||
|
||||
```shell{% raw %}
|
||||
|
|
@ -1145,9 +1145,9 @@ There are pending pods when an error occurred: Cannot evict pod as it would viol
|
|||
pod/zk-2
|
||||
{% endraw %}```
|
||||
|
||||
Use `CRTL-C` to terminate to kubectl.
|
||||
Use `CRTL-C` to terminate to kubectl.
|
||||
|
||||
You can not drain the third node because evicting `zk-2` would violate `zk-budget`. However,
|
||||
You can not drain the third node because evicting `zk-2` would violate `zk-budget`. However,
|
||||
the node will remain cordoned.
|
||||
|
||||
Use `zkCli.sh` to retrieve the value you entered during the sanity test from `zk-0`.
|
||||
|
|
@ -1232,9 +1232,9 @@ node "kubernetes-minion-group-ixsl" uncordoned
|
|||
```
|
||||
|
||||
You can use `kubectl drain` in conjunction with PodDisruptionBudgets to ensure that your service
|
||||
remains available during maintenance. If drain is used to cordon nodes and evict pods prior to
|
||||
taking the node offline for maintenance, services that express a disruption budget will have that
|
||||
budget respected. You should always allocate additional capacity for critical services so that
|
||||
remains available during maintenance. If drain is used to cordon nodes and evict pods prior to
|
||||
taking the node offline for maintenance, services that express a disruption budget will have that
|
||||
budget respected. You should always allocate additional capacity for critical services so that
|
||||
their Pods can be immediately rescheduled.
|
||||
|
||||
{% endcapture %}
|
||||
|
|
@ -1242,8 +1242,8 @@ their Pods can be immediately rescheduled.
|
|||
{% capture cleanup %}
|
||||
* Use `kubectl uncordon` to uncordon all the nodes in your cluster.
|
||||
* You will need to delete the persistent storage media for the PersistentVolumes
|
||||
used in this tutorial. Follow the necessary steps, based on your environment,
|
||||
storage configuration, and provisioning method, to ensure that all storage is
|
||||
used in this tutorial. Follow the necessary steps, based on your environment,
|
||||
storage configuration, and provisioning method, to ensure that all storage is
|
||||
reclaimed.
|
||||
{% endcapture %}
|
||||
{% include templates/tutorial.md %}
|
||||
|
|
|
|||
|
|
@ -85,8 +85,8 @@ NAME CLUSTER-IP EXTERNAL-IP PORT(S) AGE
|
|||
my-nginx-svc 10.0.0.208 80/TCP 0s
|
||||
```
|
||||
|
||||
With the above commands, we first create resources under docs/user-guide/nginx/ and print the resources created with `-o name` output format
|
||||
(print each resource as resource/name). Then we `grep` only the "service", and then print it with `kubectl get`.
|
||||
With the above commands, we first create resources under docs/user-guide/nginx/ and print the resources created with `-o name` output format
|
||||
(print each resource as resource/name). Then we `grep` only the "service", and then print it with `kubectl get`.
|
||||
|
||||
If you happen to organize your resources across several subdirectories within a particular directory, you can recursively perform the operations on the subdirectories also, by specifying `--recursive` or `-R` alongside the `--filename,-f` flag.
|
||||
|
||||
|
|
|
|||
Loading…
Reference in New Issue