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91 lines
4.2 KiB
Markdown
91 lines
4.2 KiB
Markdown
<!--[metadata]>
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+++
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title = "Swarm mode overview"
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description = "Docker Engine swarm mode overview"
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keywords = ["docker, container, cluster, swarm"]
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[menu.main]
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identifier="swarm_overview"
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parent="engine_swarm"
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weight="1"
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+++
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<![end-metadata]-->
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# Swarm mode overview
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To use Docker Engine in swarm mode, install the Docker Engine `v1.12.0` or
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later from the [Docker releases GitHub
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repository](https://github.com/docker/docker/releases). Alternatively, install
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the latest Docker for Mac or Docker for Windows Beta.
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Docker Engine 1.12 includes swarm mode for natively managing a cluster of
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Docker Engines called a *swarm*. Use the Docker CLI to create a swarm, deploy
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application services to a swarm, and manage swarm behavior.
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If you’re using a Docker version prior to `v1.12.0`, see [Docker
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Swarm](https://docs.docker.com/swarm).
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## Feature highlights
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* **Cluster management integrated with Docker Engine:** Use the Docker Engine
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CLI to create a swarm of Docker Engines where you can deploy application
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services. You don't need additional orchestration software to create or manage
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a swarm.
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* **Decentralized design:** Instead of handling differentiation between node
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roles at deployment time, the Docker Engine handles any specialization at
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runtime. You can deploy both kinds of nodes, managers and workers, using the
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Docker Engine. This means you can build an entire swarm from a single disk
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image.
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* **Declarative service model:** Docker Engine uses a declarative approach to
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let you define the desired state of the various services in your application
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stack. For example, you might describe an application comprised of a web front
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end service with message queueing services and a database backend.
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* **Scaling:** For each service, you can declare the number of tasks you want to
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run. When you scale up or down, the swarm manager automatically adapts by
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adding or removing tasks to maintain the desired state.
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* **Desired state reconciliation:** The swarm manager node constantly monitors
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the cluster state and reconciles any differences between the actual state your
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expressed desired state. For example, if you set up a service to run 10
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replicas of a container, and a worker machine hosting two of those replicas
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crashes, the manager will create two new replicas to replace the replicas that
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crashed. The swarm manager assigns the new replicas to workers that are
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running and available.
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* **Multi-host networking:** You can specify an overlay network for your
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services. The swarm manager automatically assigns addresses to the containers
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on the overlay network when it initializes or updates the application.
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* **Service discovery:** Swarm manager nodes assign each service in the swarm a
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unique DNS name and load balances running containers. You can query every
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container running in the swarm through a DNS server embedded in the swarm.
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* **Load balancing:** You can expose the ports for services to an
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external load balancer. Internally, the swarm lets you specify how to distribute
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service containers between nodes.
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* **Secure by default:** Each node in the swarm enforces TLS mutual
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authentication and encryption to secure communications between itself and all
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other nodes. You have the option to use self-signed root certificates or
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certificates from a custom root CA.
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* **Rolling updates:** At rollout time you can apply service updates to nodes
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incrementally. The swarm manager lets you control the delay between service
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deployment to different sets of nodes. If anything goes wrong, you can
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roll-back a task to a previous version of the service.
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## What's next?
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* Learn swarm mode [key concepts](key-concepts.md).
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* Get started with the [swarm mode tutorial](swarm-tutorial/index.md).
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* Explore swarm mode CLI commands:
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* [swarm init](../reference/commandline/swarm_init.md)
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* [swarm join](../reference/commandline/swarm_join.md)
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* [service create](../reference/commandline/service_create.md)
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* [service inspect](../reference/commandline/service_inspect.md)
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* [service ls](../reference/commandline/service_ls.md)
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* [service rm](../reference/commandline/service_rm.md)
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* [service scale](../reference/commandline/service_scale.md)
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* [service ps](../reference/commandline/service_ps.md)
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* [service update](../reference/commandline/service_update.md)
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