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ebebd41769
this change improves the instructions for
swarm join-token and swarm init;
- only print the join-token command for workers
instead of for both managers and workers, to
prevent users from copying the wrong command.
An extra line is added to explain how to obtain
the manager token.
- print a message that a token was rotated
sucesfully if '--rotate' is used.
- add some extra white-space before / after
the join commands, to make copy/pasting
easier.
this change also does some refactoring of join-token;
- move flagname-constants together with other constants
- use variables for selected role ("worker" / "manager")
to prevent checking for them multiple times, and to
keep the "worker" / "manager" sting centralized
- add an extra blank line after "join-token" instructions
this makes it easier to copy, and cleans up the
code a tiny bit
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
113 lines
4.1 KiB
Markdown
113 lines
4.1 KiB
Markdown
<!--[metadata]>
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+++
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title = "Join nodes to a swarm"
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description = "Add worker and manager nodes to a swarm"
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keywords = ["guide, swarm mode, node"]
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[menu.main]
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identifier="join-nodes-guide"
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parent="engine_swarm"
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weight=13
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+++
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<![end-metadata]-->
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# Join nodes to a swarm
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When you first create a swarm, you place a single Docker Engine (Engine) into
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swarm mode. To take full advantage of swarm mode you can add nodes to the swarm:
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* Adding worker nodes increases capacity. When you deploy a service to a swarm,
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the Engine schedules tasks on available nodes whether they are worker nodes or
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manager nodes. When you add workers to your swarm, you increase the scale of
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the swarm to handle tasks without affecting the manager raft consenus.
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* Manager nodes increase fault-tolerance. Manager nodes perform the
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orchestration and cluster management functions for the swarm. Among manager
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nodes, a single leader node conducts orchestration tasks. If a leader node
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goes down, the remaining manager nodes elect a new leader and resume
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orchestration and maintenance of the swarm state. By default, manager nodes
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also run tasks.
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Before you add nodes to a swarm you must install Docker Engine 1.12 or later on
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the host machine.
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The Docker Engine joins the swarm depending on the **join-token** you provide to
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the `docker swarm join` command. The node only uses the token at join time. If
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you subsequently rotate the token, it doesn't affect existing swarm nodes. Refer
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to [Run Docker Engine in swarm mode](swarm-mode.md#view-the-join-command-or-update-a-swarm-join-token).
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## Join as a worker node
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To retrieve the join command including the join token for worker nodes, run the
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following command on a manager node:
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```bash
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$ docker swarm join-token worker
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To add a worker to this swarm, run the following command:
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docker swarm join \
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--token SWMTKN-1-49nj1cmql0jkz5s954yi3oex3nedyz0fb0xx14ie39trti4wxv-8vxv8rssmk743ojnwacrr2e7c \
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192.168.99.100:2377
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```
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Run the command from the output on the worker to join the swarm:
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```bash
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$ docker swarm join \
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--token SWMTKN-1-49nj1cmql0jkz5s954yi3oex3nedyz0fb0xx14ie39trti4wxv-8vxv8rssmk743ojnwacrr2e7c \
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192.168.99.100:2377
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This node joined a swarm as a worker.
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```
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The `docker swarm join` command does the following:
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* switches the Docker Engine on the current node into swarm mode.
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* requests a TLS certificate from the manager.
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* names the node with the machine hostname
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* joins the current node to the swarm at the manager listen address based upon the swarm token.
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* sets the current node to `Active` availability, meaning it can receive tasks
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from the scheduler.
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* extends the `ingress` overlay network to the current node.
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### Join as a manager node
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When you run `docker swarm join` and pass the manager token, the Docker Engine
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switches into swarm mode the same as for workers. Manager nodes also participate
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in the raft consensus. The new nodes should be `Reachable`, but the existing
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manager will remain the swarm `Leader`.
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Docker recommends three or five manager nodes per cluster to implement high
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availability. Because swarm mode manager nodes share data using Raft, there
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must be an odd number of managers. The swarm can continue to function after as
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long as a quorum of more than half of the manager nodes are available.
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For more detail about swarm managers and administering a swarm, see
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[Administer and maintain a swarm of Docker Engines](admin_guide.md).
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To retrieve the join command including the join token for manager nodes, run the
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following command on a manager node:
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```bash
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$ docker swarm join-token manager
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To add a manager to this swarm, run the following command:
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docker swarm join \
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--token SWMTKN-1-61ztec5kyafptydic6jfc1i33t37flcl4nuipzcusor96k7kby-5vy9t8u35tuqm7vh67lrz9xp6 \
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192.168.99.100:2377
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```
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Run the command from the output on the manager to join the swarm:
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```bash
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$ docker swarm join \
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--token SWMTKN-1-61ztec5kyafptydic6jfc1i33t37flcl4nuipzcusor96k7kby-5vy9t8u35tuqm7vh67lrz9xp6 \
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192.168.99.100:2377
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This node joined a swarm as a manager.
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```
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## Learn More
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* `swarm join`[command line reference](../reference/commandline/swarm_join.md)
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* [Swarm mode tutorial](swarm-tutorial/index.md)
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