Shulou(Shulou.com)06/01 Report--

Main functions of Kubernetes 1. Data Volume

Data is shared between containers in    Pod, and data volumes can be used.

2. Application health check

The service in the    container may be blocked and unable to process requests. You can set a monitoring and checking policy to ensure application robustness.

3. Copy the application instance

The    controller maintains the number of Pod copies, ensuring that a Pod or a set of similar Pod quantities are always available.

4. Elastic expansion

   automatically scales the number of Pod copies according to the set indicator (CPU utilization).

5. Service discovery

   uses environment variables or DNS service plug-ins to ensure that the program in the container discovers the Pod entry access address.

6. Load balancing

A group of Pod replicas of    are assigned a private ClusterIP address, and the cloud load balancer forwards the request to the backend container. Other Pod within the cluster can access the application through this ClusterIP.

7. Rolling updates

The    update service is uninterrupted, updating one Pod at a time, rather than deleting the entire service at the same time.

8. Service arrangement

   makes application deployment more efficient by describing deployment services in a file.

9. Resource monitoring

The    Node node component integrates the cAdvisor resource collection tool, which can summarize the resource data of the entire cluster node through Heapster, then store it in the InfluxDB timing database, and then display it by Grafana.

10. Provide authentication and authorization

   supports attribute access control (ABAC) and role access control (RBAC) authentication and authorization policies.

2. Kubernetes basic object concept (resource object) 1. Basic object: 1. Pod

   Pod is the smallest deployment unit. A Pod consists of one or more containers that share storage and network in Pod and run on the same Docker host.

2 、 Service

   Service is an application service abstraction that defines the Pod logical collection and the policy to access the Pod collection.

The    Service proxy Pod collection is externally represented as an access entry, assigning a cluster IP address, and the request from this IP forwards the load balancer to the container in the backend Pod.

   Service selects a set of Pod to provide services through LableSelector.

​, one pod with multiple tags.

​ can call multiple pod with one tag.

3 、 Volume

   data volumes that share the data used by containers in Pod.

4 、 Namespace

   namespaces logically assign objects to different Namespace, which can be managed differently by different projects, users, etc., and set control policies to achieve multi-tenancy.

The    namespace is also known as a virtual cluster.

5 、 Lable

   tags are used to distinguish between objects (such as Pod, Service), key / value pairs exist; each object can have multiple tags, associated with objects through tags.

2. Kubernetes is abstracted at a higher level based on basic objects. 1. ReplicaSet

   next generation ReplicationController. Ensures the number of Pod copies specified at any given time and provides features such as declarative updates.

The only difference between    RC and RS is that lableselector supports new set-based tags, RS supports new set-based tags, and RC only supports equality-based tags.

2 、 Deployment

   Deployment is a higher-level API object that manages ReplicaSets and Pod and provides features such as declarative updates.

   officially recommends using Deployment to manage ReplicaSets instead of using ReplicaSets directly, which means that you may never need to manipulate ReplicaSet objects directly.

3 、 StatefulSet

   StatefulSet is suitable for persistent applications, with unique network identifiers (IP), persistent storage, and orderly deployment, extension, deletion, and rolling updates.

4 、 DaemonSet

   demonSet ensures that all (or some) nodes are running the same Pod. When a node joins the Kubernetes cluster, the Pod is scheduled to run on the node, and when the node is removed from the cluster, the Pod of the DaemonSet is deleted. Deleting a DaemonSet cleans up all the Pod it creates.

5 、 Job

   one-time task. After the completion of the run, the Pod is destroyed and the new container is not restarted. Tasks can also be run regularly.

3. Understanding and definition of Kubernetes resource objects 1. Pod

Kubernetes assigns a unique IP address to each Pod, called Pod IP, and multiple containers in a Pod share Pod IP addresses. Kubernetes requires the underlying network to support direct TCP/IP communication between any two Pod in the cluster, which is usually realized by virtual layer 2 network technology, such as Flannel, Open vSwitch and so on. Therefore, in Kubernetes, a container in one Pod can communicate directly with a Pod container on another host.

There are two types of Pod: normal Pod and static Pod (Static Pod). Static Pod is not stored in etcd storage, but in a specific file on a specific Node, and only starts running on this Node. Once a normal Pod is created, it is stored in etcd, and then dispatched by Kubernetes Master to a specific Node and Binding, the kubelet process on that Node instantiates it into a set of related Docker containers and starts it. When a container in the Pod stops, Kubernetes automatically detects the problem and restarts the Pod (restart all containers in the Pod); if the Node where the Pod is located is down, all Pod on this Node will be rescheduled to run on other nodes.

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