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swarm: Add note about placement preferences 

Docker 1.14 is adding a new feature called "placement preferences". This
adds a note about them, and a pointer to the "service create" reference
that explains them in detail.

Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>
This commit is contained in:
Aaron Lehmann 2017-02-13 17:00:30 -08:00 committed by Misty Stanley-Jones
parent 5d225d3c63
commit a73be0d5a6
1 changed files with 14 additions and 4 deletions
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18
engine/swarm/services.md
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@ -289,7 +289,18 @@ $ docker service create \
Service constraints let you set criteria for a node to meet before the scheduler
deploys a service to the node. You can apply constraints to the
service based upon node attributes and metadata or engine metadata. For more
information on constraints, refer to the `docker service create` [CLI reference](/engine/reference/commandline/service_create.md).
information on constraints, refer to the `docker service create`
[CLI reference](/engine/reference/commandline/service_create.md).
Use placement preferences to divide tasks evenly over different categories of
nodes. An example of where this may be useful is balancing tasks between
multiple datacenters or availability zones. In this case, you can use a
placement preference to spread out tasks to multiple datacenters and make the
service more resilient in the face of a localized outage. You can use
additional placement preferences to further divide tasks over groups of nodes.
For example, you can balance them over multiple racks within each datacenter.
For more information on constraints, refer to the `docker service create`
[CLI reference](/engine/reference/commandline/service_create.md).
### Reserving memory or number of CPUs for a service
@ -553,15 +564,14 @@ $ docker service create \
--name myservice \
<IMAGE>
```
> **Important:** If your volume driver accepts a comma-separated list as an option,
> you must escape the value from the outer CSV parser. To escape a `volume-opt`,
> surround it with double quotes (`"`) and surround the entire mount parameter
> with single quotes (`'`).
>
>
> For example, the `local` driver accepts mount options as a comma-separated
> list in the `o` parameter. This example shows the correctly to escape the list.
>
> $ docker service create \
> --mount 'type=volume,src=<VOLUME-NAME>,dst=<CONTAINER-PATH>,volume-driver=local,volume-opt=type=nfs,volume-opt=device=<nfs-server>:<nfs-path>,"volume-opt=o=addr=<nfs-address>,vers=4,soft,timeo=180,bg,tcp,rw"'
> --name myservice \