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Signed-off-by: Charles Smith <charles.smith@docker.com>
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Charles Smith 2016-09-08 12:10:04 -07:00
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111
docs/reference/commandline/service_create.md
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@ -48,8 +48,8 @@ Options:
-w, --workdir string Working directory inside the container
```
Creates a service as described by the specified parameters. This command has to
be run targeting a manager node.
Creates a service as described by the specified parameters. You must run this
command on a manager node.
## Examples
@ -64,10 +64,10 @@ ID NAME REPLICAS IMAGE COMMAND
dmu1ept4cxcf redis 1/1 redis:3.0.6
```
### Create a service with 5 tasks
### Create a service with 5 replica tasks (--replicas)
You can set the number of tasks for a service using the `--replicas` option. The
following command creates a `redis` service with `5` tasks:
Use the `--replicas` flag to set the number of replica tasks for a replicated
service. The following command creates a `redis` service with `5` replica tasks:
```bash
$ docker service create --name redis --replicas=5 redis:3.0.6
@ -75,12 +75,12 @@ $ docker service create --name redis --replicas=5 redis:3.0.6
```
The above command sets the *desired* number of tasks for the service. Even
though the command returns directly, actual scaling of the service may take
though the command returns immediately, actual scaling of the service may take
some time. The `REPLICAS` column shows both the *actual* and *desired* number
of tasks for the service.
of replica tasks for the service.
In the following example, the desired number of tasks is set to `5`, but the
*actual* number is `3`
In the following example the desired state is `5` replicas, but the current
number of `RUNNING` tasks is `3`:
```bash
$ docker service ls
@ -88,8 +88,8 @@ ID NAME REPLICAS IMAGE COMMAND
4cdgfyky7ozw redis 3/5 redis:3.0.7
```
Once all the tasks are created, the actual number of tasks is equal to the
desired number:
Once all the tasks are created and `RUNNING`, the actual number of tasks is
equal to the desired number:
```bash
$ docker service ls
@ -97,10 +97,8 @@ ID NAME REPLICAS IMAGE COMMAND
4cdgfyky7ozw redis 5/5 redis:3.0.7
```
### Create a service with a rolling update policy
```bash
$ docker service create \
--replicas 10 \
@ -110,10 +108,12 @@ $ docker service create \
redis:3.0.6
```
When this service is [updated](service_update.md), a rolling update will update
tasks in batches of `2`, with `10s` between batches.
When you run a [service update](service_update.md), the scheduler updates a
maximum of 2 tasks at a time, with `10s` between updates. For more information,
refer to the [rolling updates
tutorial](../../swarm/swarm-tutorial/rolling-update.md).
### Setting environment variables (-e --env)
### Set environment variables (-e, --env)
This sets environmental variables for all tasks in a service. For example:
@ -121,7 +121,7 @@ This sets environmental variables for all tasks in a service. For example:
$ docker service create --name redis_2 --replicas 5 --env MYVAR=foo redis:3.0.6
```
### Set metadata on a service (-l --label)
### Set metadata on a service (-l, --label)
A label is a `key=value` pair that applies metadata to a service. To label a
service with two labels:
@ -137,19 +137,22 @@ $ docker service create \
For more information about labels, refer to [apply custom
metadata](../../userguide/labels-custom-metadata.md).
### Set service mode
### Set service mode (--mode)
You can set the service mode to "replicated" (default) or to "global". A
replicated service runs as many tasks as specified, while a global service
runs on each active node in the swarm.
You can set the service mode to "replicated" (default) or to "global". A
replicated service runs the number of replica tasks you specify. A global
service runs on each active node in the swarm.
The following command creates a "global" service:
```bash
$ docker service create --name redis_2 --mode global redis:3.0.6
$ docker service create \
--name redis_2 \
--mode global \
redis:3.0.6
```
### Specify service constraints
### Specify service constraints (--constraint)
You can limit the set of nodes where a task can be scheduled by defining
constraint expressions. Multiple constraints find nodes that satisfy every
@ -178,45 +181,57 @@ $ docker service create \
redis:3.0.6
```
### Container networking
The containers provisioned in docker swarm mode can be accessed in service discovery either via a Virtual IP (VIP) and routed through the docker swarm ingress overlay network. Or via a DNS round robbin (DNSRR). This configuration is set using the `--endpoint-mode [vip|dnsrr]` setting. Note that dnsrr is incompatible with `--published` ports.
### Attach a service to an existing network (--network)
### Service discovery
You can use overlay networks to connect one or more services within the swarm.
Discovering other service from within a container can be ac hived via DNS lookup, but you will get different results depending on whether you want the actual service IPs, or the VIP's.
First, create an overlay network on a manager node the docker network create
command:
```bash
$ docker network create --driver overlay my-network
etjpu59cykrptrgw0z0hk5snf
```
~> nslookup service
Address: 10.255.0.7 # this is the VIP on the ingress network
After you create an overlay network in swarm mode, all manager nodes have
access to the network.
~> nslookup tasks.service
When you create a service and pass the --network flag to attach the service to
the overlay network:
Non-authoritative answer:
Name: tasks.service
Address: 10.255.0.26 # this is the real IP of a service on the ingress network
Name: tasks.service
Address: 10.255.0.27
Name: tasks.service
Address: 10.255.0.24
$ docker service create \
--replicas 3 \
--network my-network \
--name my-web \
nginx
~> nslookup tasks.service.your_net
716thylsndqma81j6kkkb5aus
The swarm extends my-network to each node running the service.
Name: tasks.service.your_net
Address: 10.0.0.29 # service 1 IP on your net
Name: tasks.service.your_net
Address: 10.0.0.26 # service 2 IP on your net
Name: tasks.service.your_net
Address: 10.0.0.28 # service 3 IP on your net
Containers on the same network can access each other using
[service discovery](../../swarm/networking.md#use-swarm-mode-service-discovery).
### Publish service ports externally to the swarm (-p, --publish)
~> nslookup service.your_net
You can publish service ports to make them available externally to the swarm
using the `--publish` flag:
Non-authoritative answer:
Name: service.your_net
Address: 10.0.0.25 # VIP on your net
```bash
docker service create --publish <TARGET-PORT>:<SERVICE-PORT> nginx
```
For example:
```bash
docker service create --name my_web --replicas 3 --publish 8080:80 nginx
```
When you publish a service port, the swarm routing mesh makes the service
accessible at the target port on every node regardless if there is a task for
the service running on the node. For more information refer to
[Use swarm mode routing mesh](../../swarm/ingress.md).
## Related information
* [service inspect](service_inspect.md)