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Update documentation for links

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Signed-off-by: Aanand Prasad <aanand.prasad@gmail.com>
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Aanand Prasad 2016-01-21 13:55:54 +00:00
commit 18a1829db0
3 changed files with 53 additions and 26 deletions
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docs/compose-file.md
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@ -318,6 +318,10 @@ container name and the link alias (`CONTAINER:ALIAS`).
- project_db_1:mysql
- project_db_1:postgresql
> **Note:** If you're using the [version 2 file format](#version-2), the
> externally-created containers must be connected to at least one of the same
> networks as the service which is linking to them.
### extra_hosts
Add hostname mappings. Use the same values as the docker client `--add-host` parameter.
@ -358,27 +362,24 @@ It's recommended that you use reverse-DNS notation to prevent your labels from c
### links
> [Version 1 file format](#version-1) only. In version 2 files, use
> [networking](networking.md) for communication between containers.
Link to containers in another service. Either specify both the service name and
the link alias (`SERVICE:ALIAS`), or just the service name (which will also be
used for the alias).
a link alias (`SERVICE:ALIAS`), or just the service name.
links:
- db
- db:database
- redis
web:
links:
- db
- db:database
- redis
An entry with the alias' name will be created in `/etc/hosts` inside containers
for this service, e.g:
Containers for the linked service will be reachable at a hostname identical to
the alias, or the service name if no alias was specified.
172.17.2.186 db
172.17.2.186 database
172.17.2.187 redis
Links also express dependency between services in the same way as
[depends_on](#depends-on), so they determine the order of service startup.
Environment variables will also be created - see the [environment variable
reference](env.md) for details.
> **Note:** If you define both links and [networks](#networks), services with
> links between them must share at least one network in common in order to
> communicate.
### logging
@ -862,7 +863,6 @@ In the majority of cases, moving from version 1 to 2 is a very simple process:
1. Indent the whole file by one level and put a `services:` key at the top.
2. Add a `version: 2` line at the top of the file.
3. Delete all `links` entries.
It's more complicated if you're using particular configuration features:
@ -879,14 +879,28 @@ It's more complicated if you're using particular configuration features:
options:
syslog-address: "tcp://192.168.0.42:123"
- `links` with aliases: If you've defined a link with an alias such as
`myservice:db`, there's currently no equivalent to this in version 2. You
will have to refer to the service using its name (in this example,
`myservice`).
- `links` with environment variables: As documented in the
[environment variables reference](env.md), environment variables created by
links have been deprecated for some time. In the new Docker network system,
they have been removed. You should either connect directly to the
appropriate hostname or set the relevant environment variable yourself,
using the link hostname:
- `external_links`: Links are deprecated, so you should use
[external networks](networking.md#using-externally-created-networks) to
communicate with containers outside the app.
web:
links:
- db
environment:
- DB_PORT=tcp://db:5432
- `external_links`: Compose uses Docker networks when running version 2
projects, so links behave slightly differently. In particular, two
containers must be connected to at least one network in common in order to
communicate, even if explicitly linked together.
Either connect the external container to your app's
[default network](networking.md), or connect both the external container and
your service's containers to an
[external network](networking.md#using-a-pre-existing-network).
- `net`: If you're using `host`, `bridge` or `none`, this is now replaced by
`networks`: