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translate: Stub in a translation framework
Add tooling to translate higher-level configs into the basic OCI
config. On IRC, Julz floated a linux.namespaces[].fromContainer as a
higher-level version of linux.namespaces[].path for emulating exec
[1]. That makes sense to me, and Mrunal is open to something like
[2]:
$ ocitools generate --template=high-level-config.json --translate=fromContainer --runtime=runc
The interface{} -> rspec.Spec conversion happens through a JSON
serialization trick suggested by 梁辰晔 (Liang Chenye) [3] after the
translations, because before the translations the template may contain
JSON that's not represented in the OCI Spec structure
(e.g. fromContainer in namespace entries).
The /proc lookup could still be improved:
* Lookup the mount path (currently hard-coded to /proc) in
/proc/self/mounts. This would extend support to users who had
mounted proc at a different location, but it's hard to find
self/mounts unless you already know where proc is mounted ;).
* Compare /proc with the state JSON's implied PID namespace [4]. This
would extend support to users in a different PID namespace than the
one in which the state JSON's 'pid' entry applied.
But those are likely to be corner cases (and until something like [4]
lands, the latter is not possible). So I'm punting them into the
future, where they can be fixed as we discover methods to fix them.
[1]: http://ircbot.wl.linuxfoundation.org/eavesdrop/%23opencontainers/%23opencontainers.2016-04-27.log.html#t2016-04-27T20:32:09
[2]: http://ircbot.wl.linuxfoundation.org/eavesdrop/%23opencontainers/%23opencontainers.2016-04-28.log.html#t2016-04-28T16:12:48
[3]: #54 (comment)
[4]: https://groups.google.com/a/opencontainers.org/forum/#!topic/dev/ujtABQoCmgk
Subject: Linux: Adding the PID namespace inode to state JSON
Date: Wed, 30 Dec 2015 21:34:57 -0800
Message-ID: <[email protected]>
Signed-off-by: W. Trevor King <[email protected]>- Loading branch information
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,95 @@ | ||
| package translate | ||
|
|
||
| import ( | ||
| "bytes" | ||
| "encoding/json" | ||
| "fmt" | ||
| "os/exec" | ||
| "path/filepath" | ||
|
|
||
| "github.com/codegangsta/cli" | ||
| rspec "github.com/opencontainers/runtime-spec/specs-go" | ||
| ) | ||
|
|
||
| func FromContainer(data interface{}, context *cli.Context) (translated interface{}, err error) { | ||
| dataMap, ok := data.(map[string]interface{}) | ||
| if !ok { | ||
| return nil, fmt.Errorf("data is not a map[string]interface{}: %s", data) | ||
| } | ||
|
|
||
| linuxInterface, ok := dataMap["linux"] | ||
| if !ok { | ||
| return data, nil | ||
| } | ||
|
|
||
| linux, ok := linuxInterface.(map[string]interface{}) | ||
| if !ok { | ||
| return nil, fmt.Errorf("data.linux is not a map[string]interface{}: %s", linuxInterface) | ||
| } | ||
|
|
||
| namespacesInterface, ok := linux["namespaces"] | ||
| if !ok { | ||
| return data, nil | ||
| } | ||
|
|
||
| namespaces, ok := namespacesInterface.([]interface{}) | ||
| if !ok { | ||
| return nil, fmt.Errorf("data.linux.namespaces is not an array: %s", namespacesInterface) | ||
| } | ||
|
|
||
| for index, namespaceInterface := range namespaces { | ||
| namespace, ok := namespaceInterface.(map[string]interface{}) | ||
| if !ok { | ||
| return nil, fmt.Errorf("data.linux.namespaces[%d] is not a map[string]interface{}: %s", index, namespaceInterface) | ||
| } | ||
| err := namespaceFromContainer(&namespace, index, context) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| } | ||
|
|
||
| return data, nil | ||
| } | ||
|
|
||
| func namespaceFromContainer(namespace *map[string]interface{}, index int, context *cli.Context) (err error) { | ||
| fromContainerInterface, ok := (*namespace)["fromContainer"] | ||
| if ok { | ||
| fromContainer, ok := fromContainerInterface.(string) | ||
| if !ok { | ||
| return fmt.Errorf("data.linux.namespaces[%d].fromContainer is not a string: %s", index, fromContainerInterface) | ||
| } | ||
| delete(*namespace, "fromContainer") | ||
| runtime := context.String("runtime") | ||
| if (len(runtime) == 0) { | ||
| return fmt.Errorf("translating fromContainer requires a non-empty --runtime") | ||
| } | ||
| command := exec.Command(runtime, "state", fromContainer) | ||
| var out bytes.Buffer | ||
| command.Stdout = &out | ||
| err := command.Run() | ||
| if err != nil { | ||
| return err | ||
| } | ||
| var state rspec.State | ||
| err = json.Unmarshal(out.Bytes(), &state) | ||
| if err != nil { | ||
| return err | ||
| } | ||
| namespaceTypeInterface, ok := (*namespace)["type"] | ||
| if !ok { | ||
| return fmt.Errorf("data.linux.namespaces[%d].type is missing: %s", index, fromContainerInterface) | ||
| } | ||
| namespaceType, ok := namespaceTypeInterface.(string) | ||
| if !ok { | ||
| return fmt.Errorf("data.linux.namespaces[%d].type is not a string: %s", index, namespaceTypeInterface) | ||
| } | ||
| switch namespaceType { | ||
| case "network": namespaceType = "net" | ||
| case "mount": namespaceType = "mnt" | ||
| } | ||
| proc := "/proc" // FIXME: lookup in /proc/self/mounts, check right namespace | ||
| path := filepath.Join(proc, fmt.Sprint(state.Pid), "ns", namespaceType) | ||
| (*namespace)["path"] = path | ||
| } | ||
| return nil | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,20 @@ | ||
| /* | ||
| Package translate handles translation between configuration | ||
| specifications. | ||
| For example, it allows you to generate OCI-compliant config.json from | ||
| a higher-level configuration language. | ||
| */ | ||
| package translate | ||
|
|
||
| import ( | ||
| "github.com/codegangsta/cli" | ||
| ) | ||
|
|
||
| // Translate maps JSON from one specification to another. | ||
| type Translate func(data interface{}, context *cli.Context) (translated interface{}, err error) | ||
|
|
||
| // Translators is a map from translator names to Translate functions. | ||
| var Translators = map[string]Translate{ | ||
| "fromContainer": FromContainer, | ||
| } |