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Merge pull request #30802 from anusha-ragunathan/debug_docs

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Add plugin debug docs.
(cherry picked from commit d4be5a2f67)

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
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Sebastiaan van Stijn 2017-02-08 11:49:11 -08:00 committed by Sebastiaan van Stijn
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docs/extend/index.md
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@ -17,10 +17,10 @@ title: Managed plugin system
* [Installing and using a plugin](index.md#installing-and-using-a-plugin)
* [Developing a plugin](index.md#developing-a-plugin)
* [Debugging plugins](index.md#debugging-plugins)
Docker Engine's plugins system allows you to install, start, stop, and remove
plugins using Docker Engine. This mechanism is currently only available for
volume drivers, but more plugin driver types will be available in future releases.
plugins using Docker Engine.
For information about the legacy plugin system available in Docker Engine 1.12
and earlier, see [Understand legacy Docker Engine plugins](legacy_plugins.md).
@ -212,7 +212,9 @@ Consider the following `config.json` file.
"types": ["docker.volumedriver/1.0"],
"socket": "sshfs.sock"
},
"capabilities": ["CAP_SYS_ADMIN"]
"linux": {
"capabilities": ["CAP_SYS_ADMIN"]
}
}
```
@ -231,3 +233,59 @@ in subdirectory `rootfs`.
After that the plugin `<plugin-name>` will show up in `docker plugin ls`.
Plugins can be pushed to remote registries with
`docker plugin push <plugin-name>`.
## Debugging plugins
Stdout of a plugin is redirected to dockerd logs. Such entries have a
`plugin=<ID>` suffix. Here are a few examples of commands for pluginID
`f52a3df433b9aceee436eaada0752f5797aab1de47e5485f1690a073b860ff62` and their
corresponding log entries in the docker daemon logs.
```bash
$ docker plugin install tiborvass/sample-volume-plugins
INFO[0036] Starting... Found 0 volumes on startup plugin=f52a3df433b9aceee436eaada0752f5797aab1de47e5485f1690a073b860ff62
```
```bash
$ docker volume create -d tiborvass/sample-volume-plugins samplevol
INFO[0193] Create Called... Ensuring directory /data/samplevol exists on host... plugin=f52a3df433b9aceee436eaada0752f5797aab1de47e5485f1690a073b860ff62
INFO[0193] open /var/lib/docker/plugin-data/local-persist.json: no such file or directory plugin=f52a3df433b9aceee436eaada0752f5797aab1de47e5485f1690a073b860ff62
INFO[0193] Created volume samplevol with mountpoint /data/samplevol plugin=f52a3df433b9aceee436eaada0752f5797aab1de47e5485f1690a073b860ff62
INFO[0193] Path Called... Returned path /data/samplevol plugin=f52a3df433b9aceee436eaada0752f5797aab1de47e5485f1690a073b860ff62
```
```bash
$ docker run -v samplevol:/tmp busybox sh
INFO[0421] Get Called... Found samplevol plugin=f52a3df433b9aceee436eaada0752f5797aab1de47e5485f1690a073b860ff62
INFO[0421] Mount Called... Mounted samplevol plugin=f52a3df433b9aceee436eaada0752f5797aab1de47e5485f1690a073b860ff62
INFO[0421] Path Called... Returned path /data/samplevol plugin=f52a3df433b9aceee436eaada0752f5797aab1de47e5485f1690a073b860ff62
INFO[0421] Unmount Called... Unmounted samplevol plugin=f52a3df433b9aceee436eaada0752f5797aab1de47e5485f1690a073b860ff62
```
#### Using docker-runc to obtain logfiles and shell into the plugin.
`docker-runc`, the default docker container runtime can be used for debugging
plugins. This is specifically useful to collect plugin logs if they are
redirected to a file.
```bash
$ docker-runc list
ID PID STATUS BUNDLE CREATED
f52a3df433b9aceee436eaada0752f5797aab1de47e5485f1690a073b860ff62 2679 running /run/docker/libcontainerd/f52a3df433b9aceee436eaada0752f5797aab1de47e5485f1690a073b860ff62 2017-02-06T21:53:03.031537592Z
r
```
```bash
$ docker-runc exec f52a3df433b9aceee436eaada0752f5797aab1de47e5485f1690a073b860ff62 cat /var/log/plugin.log
```
If the plugin has a built-in shell, then exec into the plugin can be done as
follows:
```bash
$ docker-runc exec -t f52a3df433b9aceee436eaada0752f5797aab1de47e5485f1690a073b860ff62 sh
```