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update port filter document for host mode 

Signed-off-by: Chanwit Kaewkasi <chanwit@gmail.com>
This commit is contained in:
Chanwit Kaewkasi 2015-01-22 01:37:40 +07:00
parent 83848918da
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scheduler/filter/README.md
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@ -266,6 +266,48 @@ $ docker run -d -p 80:80 nginx
2014/10/29 00:33:20 Error response from daemon: no resources available to schedule container
```
### Port filter in Host Mode
Docker in the host mode, running with `--net=host`, differs from the default `bridge` mode as the `host` mode does not perform any port binding. So, it requires to explicitly expose one or more port numbers (using `EXPOSE` in the Dockerfile or `--expose` on the command line). `Swarm` makes use of this information in conjunction with the `host` mode to choose an available node for a new container.
For example, the following commands start `nginx` on 3-node cluster.
```
$ docker run -d --expose=80 --net=host nginx
640297cb29a7
$ docker run -d --expose=80 --net=host nginx
7ecf562b1b3f
$ docker run -d --expose=80 --net=host nginx
09a92f582bc2
```
Port binding information will not be available through `ps` command because they are all started in the `host` mode.
```
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
640297cb29a7 nginx:1 "nginx -g 'daemon of Less than a second ago Up 30 seconds box3/furious_heisenberg
7ecf562b1b3f nginx:1 "nginx -g 'daemon of Less than a second ago Up 28 seconds box2/ecstatic_meitner
09a92f582bc2 nginx:1 "nginx -g 'daemon of 46 seconds ago Up 27 seconds box1/mad_goldstine
```
Docker cluster will refuse the operation when trying to instantiate the 4th one.
```
$ docker run -d --expose=80 --net=host nginx
FATA[0000] Error response from daemon: unable to find a node with port 80/tcp available in the Host mode
```
However port binding to the different value, e.g. 81, is still allowed.
```
$ docker run -d -p 81:80 nginx:latest
832f42819adc
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
832f42819adc nginx:1 "nginx -g 'daemon of Less than a second ago Up Less than a second 443/tcp, 192.168.136.136:81->80/tcp box3/thirsty_hawking
640297cb29a7 nginx:1 "nginx -g 'daemon of 8 seconds ago Up About a minute box3/furious_heisenberg
7ecf562b1b3f nginx:1 "nginx -g 'daemon of 13 seconds ago Up About a minute box2/ecstatic_meitner
09a92f582bc2 nginx:1 "nginx -g 'daemon of About a minute ago Up About a minute box1/mad_goldstine
```
## Dependency Filter
This filter co-schedules dependent containers on the same node.