docs/discovery/README.md

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---
page_title: Docker Swarm discovery
page_description: Swarm discovery
page_keywords: docker, swarm, clustering, discovery
---
# Discovery
`Docker Swarm` comes with multiple Discovery backends
## Examples
### Using the hosted discovery service
```bash
# create a cluster
$ swarm create
6856663cdefdec325839a4b7e1de38e8 # <- this is your unique <cluster_id>
# on each of your nodes, start the swarm agent
# <node_ip> doesn't have to be public (eg. 192.168.0.X),
# as long as the swarm manager can access it.
$ swarm join --addr=<node_ip:2375> token://<cluster_id>
# start the manager on any machine or your laptop
$ swarm manage -H tcp://<swarm_ip:swarm_port> token://<cluster_id>
# use the regular docker cli
$ docker -H tcp://<swarm_ip:swarm_port> info
$ docker -H tcp://<swarm_ip:swarm_port> run ...
$ docker -H tcp://<swarm_ip:swarm_port> ps
$ docker -H tcp://<swarm_ip:swarm_port> logs ...
...
# list nodes in your cluster
$ swarm list token://<cluster_id>
<node_ip:2375>
```
### Using a static file describing the cluster
```bash
# for each of your nodes, add a line to a file
# <node_ip> doesn't have to be public (eg. 192.168.0.X),
# as long as the swarm manager can access it.
$ echo <node_ip1:2375> >> /tmp/my_cluster
$ echo <node_ip2:2375> >> /tmp/my_cluster
$ echo <node_ip3:2375> >> /tmp/my_cluster
# start the manager on any machine or your laptop
$ swarm manage -H tcp://<swarm_ip:swarm_port> file:///tmp/my_cluster
# use the regular docker cli
$ docker -H tcp://<swarm_ip:swarm_port> info
$ docker -H tcp://<swarm_ip:swarm_port> run ...
$ docker -H tcp://<swarm_ip:swarm_port> ps
$ docker -H tcp://<swarm_ip:swarm_port> logs ...
...
# list nodes in your cluster
$ swarm list file:///tmp/my_cluster
<node_ip1:2375>
<node_ip2:2375>
<node_ip3:2375>
```
### Using etcd
```bash
# on each of your nodes, start the swarm agent
# <node_ip> doesn't have to be public (eg. 192.168.0.X),
# as long as the swarm manager can access it.
$ swarm join --addr=<node_ip:2375> etcd://<etcd_ip>/<path>
# start the manager on any machine or your laptop
$ swarm manage -H tcp://<swarm_ip:swarm_port> etcd://<etcd_ip>/<path>
# use the regular docker cli
$ docker -H tcp://<swarm_ip:swarm_port> info
$ docker -H tcp://<swarm_ip:swarm_port> run ...
$ docker -H tcp://<swarm_ip:swarm_port> ps
$ docker -H tcp://<swarm_ip:swarm_port> logs ...
...
# list nodes in your cluster
$ swarm list etcd://<etcd_ip>/<path>
<node_ip:2375>
```
### Using consul
```bash
# on each of your nodes, start the swarm agent
# <node_ip> doesn't have to be public (eg. 192.168.0.X),
# as long as the swarm manager can access it.
$ swarm join --addr=<node_ip:2375> consul://<consul_addr>/<path>
# start the manager on any machine or your laptop
$ swarm manage -H tcp://<swarm_ip:swarm_port> consul://<consul_addr>/<path>
# use the regular docker cli
$ docker -H tcp://<swarm_ip:swarm_port> info
$ docker -H tcp://<swarm_ip:swarm_port> run ...
$ docker -H tcp://<swarm_ip:swarm_port> ps
$ docker -H tcp://<swarm_ip:swarm_port> logs ...
...
# list nodes in your cluster
$ swarm list consul://<consul_addr>/<path>
<node_ip:2375>
```
### Using zookeeper
```bash
# on each of your nodes, start the swarm agent
# <node_ip> doesn't have to be public (eg. 192.168.0.X),
# as long as the swarm manager can access it.
$ swarm join --addr=<node_ip:2375> zk://<zookeeper_addr1>,<zookeeper_addr2>/<path>
# start the manager on any machine or your laptop
$ swarm manage -H tcp://<swarm_ip:swarm_port> zk://<zookeeper_addr1>,<zookeeper_addr2>/<path>
# use the regular docker cli
$ docker -H tcp://<swarm_ip:swarm_port> info
$ docker -H tcp://<swarm_ip:swarm_port> run ...
$ docker -H tcp://<swarm_ip:swarm_port> ps
$ docker -H tcp://<swarm_ip:swarm_port> logs ...
...
# list nodes in your cluster
$ swarm list zk://<zookeeper_addr1>,<zookeeper_addr2>/<path>
<node_ip:2375>
```
### Using a static list of ips
```bash
# start the manager on any machine or your laptop
$ swarm manage -H <swarm_ip:swarm_port> nodes://<node_ip1:2375>,<node_ip2:2375>
# or
$ swarm manage -H <swarm_ip:swarm_port> <node_ip1:2375>,<node_ip2:2375>
# use the regular docker cli
$ docker -H <swarm_ip:swarm_port> info
$ docker -H <swarm_ip:swarm_port> run ...
$ docker -H <swarm_ip:swarm_port> ps
$ docker -H <swarm_ip:swarm_port> logs ...
...
```
## Contributing a new discovery backend
Contributing a new discovery backend is easy,
simply implements this interface:
```go
type DiscoveryService interface {
Initialize(string, int) error
Fetch() ([]string, error)
Watch(WatchCallback)
Register(string) error
}
```
### Initialize
The parameters are `discovery` location without the scheme and a heartbeat (in seconds)
### Fetch
Returns the list of all the nodes from the discovery
### Watch
Triggers an update (`Fetch`). This can happen either via
a timer (like `token`) or use backend specific features (like `etcd`)
### Register
Add a new node to the discovery service.
## Docker Swarm documentation index
- [User guide](./index.md)
- [Sheduler strategies](./scheduler/strategy.md)
- [Sheduler filters](./scheduler/filter.md)
- [Swarm API](./API.md)