container.go

Documentation: go.opentelemetry.io/otel/sdk/resource

     1  // Copyright The OpenTelemetry Authors
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package resource // import "go.opentelemetry.io/otel/sdk/resource"
    16  
    17  import (
    18  	"bufio"
    19  	"context"
    20  	"errors"
    21  	"io"
    22  	"os"
    23  	"regexp"
    24  
    25  	semconv "go.opentelemetry.io/otel/semconv/v1.21.0"
    26  )
    27  
    28  type containerIDProvider func() (string, error)
    29  
    30  var (
    31  	containerID         containerIDProvider = getContainerIDFromCGroup
    32  	cgroupContainerIDRe                     = regexp.MustCompile(`^.*/(?:.*-)?([0-9a-f]+)(?:\.|\s*$)`)
    33  )
    34  
    35  type cgroupContainerIDDetector struct{}
    36  
    37  const cgroupPath = "/proc/self/cgroup"
    38  
    39  // Detect returns a *Resource that describes the id of the container.
    40  // If no container id found, an empty resource will be returned.
    41  func (cgroupContainerIDDetector) Detect(ctx context.Context) (*Resource, error) {
    42  	containerID, err := containerID()
    43  	if err != nil {
    44  		return nil, err
    45  	}
    46  
    47  	if containerID == "" {
    48  		return Empty(), nil
    49  	}
    50  	return NewWithAttributes(semconv.SchemaURL, semconv.ContainerID(containerID)), nil
    51  }
    52  
    53  var (
    54  	defaultOSStat = os.Stat
    55  	osStat        = defaultOSStat
    56  
    57  	defaultOSOpen = func(name string) (io.ReadCloser, error) {
    58  		return os.Open(name)
    59  	}
    60  	osOpen = defaultOSOpen
    61  )
    62  
    63  // getContainerIDFromCGroup returns the id of the container from the cgroup file.
    64  // If no container id found, an empty string will be returned.
    65  func getContainerIDFromCGroup() (string, error) {
    66  	if _, err := osStat(cgroupPath); errors.Is(err, os.ErrNotExist) {
    67  		// File does not exist, skip
    68  		return "", nil
    69  	}
    70  
    71  	file, err := osOpen(cgroupPath)
    72  	if err != nil {
    73  		return "", err
    74  	}
    75  	defer file.Close()
    76  
    77  	return getContainerIDFromReader(file), nil
    78  }
    79  
    80  // getContainerIDFromReader returns the id of the container from reader.
    81  func getContainerIDFromReader(reader io.Reader) string {
    82  	scanner := bufio.NewScanner(reader)
    83  	for scanner.Scan() {
    84  		line := scanner.Text()
    85  
    86  		if id := getContainerIDFromLine(line); id != "" {
    87  			return id
    88  		}
    89  	}
    90  	return ""
    91  }
    92  
    93  // getContainerIDFromLine returns the id of the container from one string line.
    94  func getContainerIDFromLine(line string) string {
    95  	matches := cgroupContainerIDRe.FindStringSubmatch(line)
    96  	if len(matches) <= 1 {
    97  		return ""
    98  	}
    99  	return matches[1]
   100  }
   101
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