93 lines
2.6 KiB
Go
93 lines
2.6 KiB
Go
// Copyright 2016 Google Inc. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package devicemapper
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import (
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"bufio"
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"bytes"
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"fmt"
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"os/exec"
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"strconv"
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"strings"
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"github.com/golang/glog"
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)
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// thinLsClient knows how to run a thin_ls very specific to CoW usage for
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// containers.
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type thinLsClient interface {
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// ThinLs runs a thin ls on the given device, which is expected to be a
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// metadata device. The caller must hold the metadata snapshot for the
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// device.
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ThinLs(deviceName string) (map[string]uint64, error)
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}
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// newThinLsClient returns a thinLsClient or an error if the thin_ls binary
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// couldn't be located.
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func newThinLsClient() (thinLsClient, error) {
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thinLsPath, err := ThinLsBinaryPresent()
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if err != nil {
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return nil, fmt.Errorf("error creating thin_ls client: %v", err)
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}
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return &defaultThinLsClient{thinLsPath}, nil
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}
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// defaultThinLsClient is a functional thinLsClient
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type defaultThinLsClient struct {
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thinLsPath string
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}
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var _ thinLsClient = &defaultThinLsClient{}
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func (c *defaultThinLsClient) ThinLs(deviceName string) (map[string]uint64, error) {
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args := []string{"--no-headers", "-m", "-o", "DEV,EXCLUSIVE_BYTES", deviceName}
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glog.V(4).Infof("running command: thin_ls %v", strings.Join(args, " "))
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output, err := exec.Command(c.thinLsPath, args...).Output()
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if err != nil {
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return nil, fmt.Errorf("Error running command `thin_ls %v`: %v\noutput:\n\n%v", strings.Join(args, " "), err, string(output))
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}
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return parseThinLsOutput(output), nil
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}
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// parseThinLsOutput parses the output returned by thin_ls to build a map of
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// device id -> usage.
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func parseThinLsOutput(output []byte) map[string]uint64 {
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cache := map[string]uint64{}
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// parse output
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scanner := bufio.NewScanner(bytes.NewReader(output))
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for scanner.Scan() {
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output := scanner.Text()
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fields := strings.Fields(output)
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if len(fields) != 2 {
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continue
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}
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deviceID := fields[0]
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usage, err := strconv.ParseUint(fields[1], 10, 64)
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if err != nil {
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glog.Warning("unexpected error parsing thin_ls output: %v", err)
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continue
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}
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cache[deviceID] = usage
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}
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return cache
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}
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