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node-feature-discovery/source/local/local.go
Markus Lehtonen a84b5c9d82 Support feature detector hooks
Implement a new feature source named 'local' whose only purpose is to
run feature source hooks found under
/etc/kubernetes/node-feature-discovery/source.d/ It tries to execute all
files found under the directory, in alphabetical order.

This feature source provides users a mechanism to implement custom
feature sources in a pluggable way, without modifying nfd source code or
Docker images.

The hooks are supposed to print all discovered features in stdout, one
feature per line. The output in stdout is used in the node label as is.
Full node label name will have the following format:
  feature.node.kubernetes.io/<hook name>-<feature name>
Stderr from the hooks is propagated to nfd log.
2018-11-30 11:51:41 +02:00

115 lines
2.6 KiB
Go

/*
Copyright 2018 The Kubernetes Authors.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package local
import (
"bytes"
"fmt"
"io/ioutil"
"log"
"os"
"os/exec"
"path/filepath"
"github.com/kubernetes-incubator/node-feature-discovery/source"
)
// Config
var (
hookDir = "/etc/kubernetes/node-feature-discovery/source.d/"
logger = log.New(os.Stderr, "", log.LstdFlags)
)
// Implement FeatureSource interface
type Source struct{}
func (s Source) Name() string { return "local" }
func (s Source) Discover() (source.Features, error) {
features := source.Features{}
files, err := ioutil.ReadDir(hookDir)
if err != nil {
if os.IsNotExist(err) {
log.Printf("ERROR: hook directory %v does not exist", hookDir)
return features, nil
}
return features, fmt.Errorf("Unable to access %v: %v", hookDir, err)
}
for _, file := range files {
hook := file.Name()
hookFeatures, err := runHook(hook)
if err != nil {
log.Printf("ERROR: source hook '%v' failed: %v", hook, err)
continue
}
for _, feature := range hookFeatures {
features[hook+"-"+feature] = true
}
}
return features, nil
}
// Run one hook
func runHook(file string) ([]string, error) {
var features []string
path := filepath.Join(hookDir, file)
filestat, err := os.Stat(path)
if err != nil {
log.Printf("ERROR: skipping %v, failed to get stat: %v", path, err)
return features, err
}
if filestat.Mode().IsRegular() {
cmd := exec.Command(path)
var stdout bytes.Buffer
var stderr bytes.Buffer
cmd.Stdout = &stdout
cmd.Stderr = &stderr
// Run hook
err = cmd.Run()
// Forward stderr to our logger
lines := bytes.Split(stderr.Bytes(), []byte("\n"))
for i, line := range lines {
if i == len(lines)-1 && len(line) == 0 {
// Don't print the last empty string
break
}
log.Printf("%v: %s", file, line)
}
// Do not return any features if an error occurred
if err != nil {
return features, err
}
// Return features printed to stdout
lines = bytes.Split(stdout.Bytes(), []byte("\n"))
for _, line := range lines {
if len(line) > 0 {
features = append(features, string(line))
}
}
}
return features, nil
}