小白学 docker「docker-swarm 服务管理 （一）」-腾讯云开发者社区-腾讯云

The “leader” is the node with overall responsibility for the cluster. When we create a cluster of one or more Docker Engines its called a swarm mode. A swarm consists of one or more nodes physical or virtual machines running Docker Engine. When you run a service, it compels the manager node to sync with its configurations. The manager node then runs the rest of the worker nodes based on the specified settings in the service.

Docker Swarm enables enterprises to create small, self-contained code components that demand little resources. When an application deploys to a swarm, we submit a service definition to a manager node. The manager node then dispatches units of work or tasks to worker nodes.

Step 1: Update Software Repositories

Prior to Docker version 1.12 it was the only native Docker option for clustering hosts, and it needed a lot of additional setup for distributed state, service discovery and security. So, instead of installing the JRE onto your computer, you could simply download a portable JRE as an image and include it in the container with your application code. When launching the application from the container, all of the resources necessary for the application to run smoothly will be present in the isolated containerized environment.

However, the platform is faster in deploying containers than what K8s can offer as there’s no complex framework slowing scaling down. If you’re unable to meet customer demands due to slow development time, then Kubernetes might help. The Docker Containers overcome a lot of problems faced by the virtual machines. Hence, the Docker Container wins the game of Docker Container vs. Virtual Machines any day! To enumerate, Docker Containers are faster, portable, provide isolation, use less memory, etc. Docker swarm installation is quite easier, by using fewer commands you can install Docker in your virtual machine or even on the cloud.

Docker Swarm vs Kubernetes: Definitions

IT admins and developers may use swarm to create and manage a cluster of Docker nodes as a single virtual system. Docker Engine, the layer between the OS and container images, also has a native swarm managed docker swarm mode. Swarm mode adds docker swarm’s orchestration features into Docker Engine 1.12 and newer releases. A task carries a Docker container as well as the commands to run inside this container.

You can also deploy
the plugin in a similar way as a global service using the Docker API, by specifying
a PluginSpec instead of a ContainerSpec. This is useful when a
manager node becomes unavailable or if you want to take a manager offline for
maintenance. Therefore, node labels can be used to limit critical tasks to nodes that meet
certain requirements.

Docker Swarm vs Kubernetes: What are the Differences?

Swarm never creates individual containers like we did in the previous step of this tutorial. Instead, all Swarm workloads are scheduled as services, which are scalable groups of containers with added networking features maintained automatically by Swarm. Furthermore, all Swarm objects can and should be described in manifests called stack files. These YAML files describe all the components and configurations of your Swarm app, and can be used to easily create and destroy your app in any Swarm environment.

You simply interact with the swarm and it takes care of the network routing. Inside the docker swarm that contains a vast number of hosts, every worker node performs the received tasks/operations. Also, it executes each task allocated by the leader node(or manager node). Kubernetes is a portable, open-source, cloud-native infrastructure tool initially designed by Google to manage their clusters. Being a container orchestration tool, it automates the scaling, deployment, and management of containerized applications. We may orchestrate by generating tasks for each service using the API that we connect in our Swarm environment.

Creating Your Own Swarm

The swarm manager will update each container instance individually. You can adjust the number of tasks updated in a single operation with the –update-parallelism flag. The docker application’s main focus is on the utilization of the containers and management of the software development process.

As you see below diagram the manager node is responsible for the allocation of the task, dispatch the tasks, and schedule the tasks. API in the manager is the medium between the manager node and the worker node to communicate with each other by using the HTTP protocol. In a docker swarm with numerous hosts, each worker node functions by receiving and executing the tasks that are allocated to it by manager nodes. By default, all manager modes are also worker nodes and are capable of executing tasks when they have the resources available to do so. As the number of clients to serve increases, we increase the cluster by commissioning additional application servers. Mostly we do it manually, but some servers have built-in cluster features to help speed up and automate the commissioning of additional nodes in the cluster.

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You probably know how to spin up a Docker container or even run a Docker Compose for multiple containers in one host. But Docker Swarm is handier for deploying apps with complex architecture. It breaks up processes into units, improves runtime access, and reduces or even eliminates the chances of downtime.

These are services performed by using the swarm manager to schedule a single task to every available Node that meets the resource requirement and service constraints. It is a kind of software platform that enables the developers to integrate the use of containers seamlessly into software applications’ development process. Atatus is delivered as a fully managed cloud service with minimal setup at any scale that requires no maintenance. It monitors logs from all of your systems and applications into a centralized and easy-to-navigate user interface, allowing you to troubleshoot faster. Service discovery is handled differently in Docker Swarm and Kubernetes. Containers must be explicitly defined as services in Kubernetes.

The Docker Swarm Architecture

See the
run command for more details on
publish options used with docker run. Mail us on h[email protected], to get more information about given services. One of the significant advantages of swarm’s operations is the significant level of availability for the Applications. If somehow the leader node becomes unavailable due to some fatal error or hardware failure, another node is against chosen from the available nodes.

• It is a kind of software platform that enables the developers to integrate the use of containers seamlessly into software applications’ development process.
• The Swarm manager then uses the internal load balancing to distribute the requests among services within the cluster based on the DNS name of the service.
• One can access the service on the PublishedPort of any node in the cluster by external components.
• Then we have tried to understand the working and also learned a couple of Docker commands that are used in swarm mode.
• You need to integrate Docker Swarm with a third-party tool to get a GUI.
• This may include the application itself, any external components it needs such as databases, and network and storage definitions.
• You can prevent task scheduling on the manager by switching its state from active to drain.