DaemonSets On K8s
On the one hand
In the distant future, in a world governed by advanced technology, a group of brilliant scientists and engineers developed a revolutionary system called DaemonSets, taking the concept of Kubernetes to unimaginable heights.
In this future, humanity has expanded into the vast expanse of space, colonizing different planets and moons. Transportation and logistics between these celestial bodies have become routine, thanks to the advent of hyperdrive technology. However, managing and maintaining the complex fleet of space vessels presented a challenge that required a solution.
DaemonSets emerged as the perfect solution. These intelligent, self-aware entities were capable of seamlessly integrating with the spaceships’ navigation systems and machinery. Created as virtual entities within a networked infrastructure, DaemonSets embodied specialized algorithms and advanced artificial intelligence.
Represented by intricate holographic forms, DaemonSets were assigned to each spaceship that traversed the cosmos. Their primary objective was to ensure the smooth operation of various critical systems on board, constantly monitoring and analyzing data to optimize efficiency and safety. DaemonSets were programmed to detect any anomalies or malfunctions instantly and implement real-time solutions.
Within the realm of space travel, where unforeseen dangers could lurk at every corner, DaemonSets became the silent protectors of the crew. Their advanced capabilities extended beyond mere maintenance. They had the ability to instantly analyze volatile solar winds and space debris that threatened to damage the spacecraft. By calculating the ideal course of action, DaemonSets would manipulate the vessel’s propulsion systems to navigate away from hazards, allowing the crew to focus on other crucial tasks.
DaemonSets were even programmed to anticipate the crew’s needs. They could recognize patterns and adapt to user preferences, whether it was automating routine tasks, regulating the ship’s temperature, or adjusting gravity levels to mimic home-like conditions. Their advanced algorithms enabled them to learn from each mission, constantly improving their decision-making processes.
Furthermore, DaemonSets formed an interconnected network with other ships within their fleet. Through this network, they shared vital information, allowing each DaemonSet to learn from the experiences of its counterparts. They exchanged maintenance techniques, improved navigation strategies, and shared knowledge of encountered challenges. This collaborative effort ensured that each ship’s DaemonSet was continuously updated with the latest information to make informed decisions.
As time passed, DaemonSets became an integral part of space travel, instilling a sense of security among crews and enabling missions that were once considered too perilous. Their presence became synonymous with efficiency, dependability, and cutting-edge technology.
DaemonSets
DaemonSets in Kubernetes are a type of workload controller that ensures that a specific pod is running on all or some of the nodes within a cluster. It ensures that each node has an instance of the desired pod and automatically creates or destroys pods as needed when nodes are added or removed from the cluster.
The key characteristics of DaemonSets are as follows:
- One pod per node: Each node in the cluster is scheduled to run exactly one instance of the specified pod. If a new node is added to the cluster, a new pod is automatically created. Likewise, if a node is removed or becomes unavailable, the corresponding pod is automatically terminated.
- Automatic scheduling: When a DaemonSet is created, the Kubernetes scheduler automatically selects eligible nodes and deploys the pod to them. The scheduling process takes into account factors like resource availability, node constraints, and taints/tolerations.
- Pod updates and rollouts: DaemonSets provide mechanisms to update and rollout new versions of pods across the cluster. By updating the DaemonSet specification, new pods are created with updated configurations or images, and old pods are terminated gracefully.
DaemonSets are commonly used for running system-level services such as log collectors, monitoring agents, or network proxies on every node in the cluster. They ensure that essential services are deployed and running consistently across all nodes, even as the cluster scales up or down.
Overall, DaemonSets are a powerful feature in Kubernetes that enables the management of specific pods across the cluster, ensuring high availability and consistency of services on each node.
摘要
K8s上的daemonsets说明
DaemonSets是Kubernetes中一种特殊类型的控制器，用于确保在集群中的每个节点上运行相同的Pod副本。与ReplicaSets和Deployment控制器不同，DaemonSets不关心集群中的节点数目，而是关注在每个节点上运行的Pod实例。这意味着每当有新节点添加到集群中，DaemonSets会自动在新节点上创建一个新的Pod实例。
下面是DaemonSets资源的关键设计和说明点：
- Pod部署：DaemonSets资源在集群中的每个节点上都运行一个Pod实例。Pod实例通常用于运行后台任务、监控代理或各种系统守护进程等。
- 节点扩缩：DaemonSets会自动在新加入或移除节点的时候在新的节点上启动或停止相应的Pod副本。这种动态性使得DaemonSets资源非常适合在长期运行的集群中维护系统进程。
- 节点选择：DaemonSets通过使用NodeSelector、NodeAffinity和Taints/Tolerations等标签和节点选择器来选择运行Pod实例的节点。这样可以根据需求将Pod分布在集群中的特定节点或节点组中。
- 竞争冲突：当多个DaemonSets同时选择同一个节点时会引发竞争冲突。为了解决这个问题，可以使用Tolerations和PriorityClassName等方式来设置Pod的调度优先级。
- 更新策略：当DaemonSet更新时，可以使用RollingUpdate策略来控制Pod的更新过程。该策略在每个节点上逐步替换旧的Pod实例，确保在替换过程中不会中断服务。
- 容器化：DaemonSets资源的Pod中可以包含一个或多个容器。这样可以在单个节点上运行多个相关的进程，例如一个应用程序进程和一个日志收集代理。
- 监控和日志收集：DaemonSets资源通常与其他工具和服务（如Prometheus、Grafana等）集成，用于监控、日志收集和分析集群中所有节点上的Pod实例。
通过使用DaemonSets资源，可以轻松地在整个集群中运行系统进程和微服务，确保每个节点都有所需的Pod副本运行。这种资源的设计和使用方式为集群的可靠性和可扩展性提供了很大的便利
示例说明
假设我们有一个具有分布式架构的应用程序，其中有一个后台服务需要在每个节点上运行，以便处理本地数据。在这种情况下，我们可以使用DaemonSets来在每个节点上部署并运行这个后台服务。
首先，我们需要创建一个DaemonSet的YAML文件，例如 daemonset.yaml，其中包含我们的配置信息。以下示例展示了一个简单的DaemonSet配置文件：
apiVersion: apps/v1
kind: DaemonSet
metadata:
name: my-daemonset
spec:
selector:
matchLabels:
app: my-app
template:
metadata:
labels:
app: my-app
spec:
containers:
- name: my-service
image: my-service-image
# 其他配置
在这个示例中，我们定义了一个DaemonSet对象，其中：
metadata：指定了DaemonSet的名称。spec.selector.matchLabels：用于选择将在哪些节点上运行该DaemonSet的Pods。在这个示例中，我们使用app: my-app标签来选择节点。spec.template.metadata.labels：用于给创建的Pods打上标签，以便让选择器选择它们。spec.template.spec.containers：描述了要在每个节点上运行的容器的详细信息。在这个示例中，我们使用了一个名为my-service的容器，并指定了一个镜像和其他配置。
保存并应用上述配置文件：
kubectl apply -f daemonset.yaml
Kubernetes将根据我们的配置文件创建DaemonSet，并自动在每个节点上调度Pods运行我们的服务。
使用以下命令可以查看DaemonSet及其相关Pods的状态：
kubectl get daemonset
kubectl get pods -l app=my-app
当我们在集群中添加或删除节点时，Kubernetes将自动调整DaemonSet，以确保在每个节点上都有一个正在运行的Pod。
这就是使用DaemonSets在Kubernetes上部署和运行一个后台服务的简单例子。通过使用DaemonSets，我们可以方便地在集群中的每个节点上运行特定的Pod，并实现分布式应用程序的部署和管理。