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reader.go
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/
reader.go
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// Copyright 2015 Google Inc. All Rights Reserved.
//
// 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 netlink
import (
"fmt"
"os"
info "github.com/google/cadvisor/info/v1"
"github.com/golang/glog"
)
type NetlinkReader struct {
familyId uint16
conn *Connection
}
func New() (*NetlinkReader, error) {
conn, err := newConnection()
if err != nil {
return nil, fmt.Errorf("failed to create a new connection: %s", err)
}
id, err := getFamilyId(conn)
if err != nil {
return nil, fmt.Errorf("failed to get netlink family id for task stats: %s", err)
}
glog.V(4).Infof("Family id for taskstats: %d", id)
return &NetlinkReader{
familyId: id,
conn: conn,
}, nil
}
func (self *NetlinkReader) Stop() {
if self.conn != nil {
self.conn.Close()
}
}
func (self *NetlinkReader) Start() error {
// We do the start setup for netlink in New(). Nothing to do here.
return nil
}
// Returns instantaneous number of running tasks in a group.
// Caller can use historical data to calculate cpu load.
// path is an absolute filesystem path for a container under the CPU cgroup hierarchy.
// NOTE: non-hierarchical load is returned. It does not include load for subcontainers.
func (self *NetlinkReader) GetCpuLoad(name string, path string) (info.LoadStats, error) {
if len(path) == 0 {
return info.LoadStats{}, fmt.Errorf("cgroup path can not be empty!")
}
cfd, err := os.Open(path)
if err != nil {
return info.LoadStats{}, fmt.Errorf("failed to open cgroup path %s: %q", path, err)
}
stats, err := getLoadStats(self.familyId, cfd.Fd(), self.conn)
if err != nil {
return info.LoadStats{}, err
}
glog.V(4).Infof("Task stats for %q: %+v", path, stats)
return stats, nil
}