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| 1 | +// Copyright 2022 Intel Corporation. All Rights Reserved. |
| 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 pidfile |
| 16 | + |
| 17 | +import ( |
| 18 | + "fmt" |
| 19 | + "os" |
| 20 | + "path/filepath" |
| 21 | + "strconv" |
| 22 | + "strings" |
| 23 | + "syscall" |
| 24 | + |
| 25 | + "github.com/pkg/errors" |
| 26 | +) |
| 27 | + |
| 28 | +var ( |
| 29 | + pidFilePath = defaultPath() |
| 30 | + pidFile *os.File |
| 31 | +) |
| 32 | + |
| 33 | +// GetPath returns the current pidfile path. |
| 34 | +func GetPath() string { |
| 35 | + return pidFilePath |
| 36 | +} |
| 37 | + |
| 38 | +// SetPath sets the pidfile path to the given one. |
| 39 | +func SetPath(path string) { |
| 40 | + close() |
| 41 | + pidFilePath = path |
| 42 | +} |
| 43 | + |
| 44 | +// Write opens the PID file and writes os.Getpid() to it. If the PID file already |
| 45 | +// exists Write() fails with an error. On successful completion, Write keeps the |
| 46 | +// PID file open. |
| 47 | +func Write() error { |
| 48 | + if pidFile != nil { |
| 49 | + return nil |
| 50 | + } |
| 51 | + |
| 52 | + err := os.MkdirAll(filepath.Dir(pidFilePath), 0755) |
| 53 | + if err != nil { |
| 54 | + return errors.Wrap(err, "failed to create PID file") |
| 55 | + } |
| 56 | + |
| 57 | + pidFile, err = os.OpenFile(pidFilePath, os.O_CREATE|os.O_EXCL|os.O_WRONLY, 0644) |
| 58 | + if err != nil { |
| 59 | + return errors.Wrap(err, "failed to create PID file") |
| 60 | + } |
| 61 | + |
| 62 | + _, err = pidFile.Write([]byte(fmt.Sprintf("%d\n", os.Getpid()))) |
| 63 | + if err != nil { |
| 64 | + close() |
| 65 | + return errors.Wrap(err, "failed to write PID file") |
| 66 | + } |
| 67 | + |
| 68 | + return nil |
| 69 | +} |
| 70 | + |
| 71 | +// Read reads the content of the PID file. It returns the process ID found |
| 72 | +// in the file. If opening the file or reading an integer process ID fails |
| 73 | +// Read() returns -1 and an error. |
| 74 | +func Read() (int, error) { |
| 75 | + var ( |
| 76 | + pid int |
| 77 | + buf []byte |
| 78 | + err error |
| 79 | + ) |
| 80 | + |
| 81 | + if buf, err = os.ReadFile(pidFilePath); err != nil { |
| 82 | + if os.IsNotExist(err) { |
| 83 | + return 0, nil |
| 84 | + } |
| 85 | + return -1, errors.Wrap(err, "failed to read PID file") |
| 86 | + } |
| 87 | + |
| 88 | + if pid, err = strconv.Atoi(strings.TrimRight(string(buf), "\n")); err != nil { |
| 89 | + return -1, errors.Wrapf(err, "invalid PID (%q) in PID file", string(buf)) |
| 90 | + } |
| 91 | + |
| 92 | + return pid, nil |
| 93 | +} |
| 94 | + |
| 95 | +// close closes the PID file and truncates it to zero length. |
| 96 | +func close() { |
| 97 | + if pidFile != nil { |
| 98 | + pidFile.Truncate(0) |
| 99 | + pidFile.Close() |
| 100 | + pidFile = nil |
| 101 | + } |
| 102 | +} |
| 103 | + |
| 104 | +// Remove removes the PID file for the process unconditionally, regardless if |
| 105 | +// the current process had created the PID file or not. |
| 106 | +func Remove() error { |
| 107 | + close() |
| 108 | + err := os.Remove(pidFilePath) |
| 109 | + if err != nil { |
| 110 | + if os.IsNotExist(err) { |
| 111 | + return nil |
| 112 | + } |
| 113 | + } |
| 114 | + return err |
| 115 | +} |
| 116 | + |
| 117 | +// OwnerPid returns the ID of the process owning the PID file. 0 is returned |
| 118 | +// if it is known that no process owns the file. -1 and an error is returned |
| 119 | +// if the owner or its existence could not be determined. |
| 120 | +func OwnerPid() (int, error) { |
| 121 | + var ( |
| 122 | + pid int |
| 123 | + p *os.Process |
| 124 | + err error |
| 125 | + ) |
| 126 | + |
| 127 | + pid, err = Read() |
| 128 | + if err != nil { |
| 129 | + return -1, err |
| 130 | + } |
| 131 | + if pid == 0 { |
| 132 | + return 0, nil |
| 133 | + } |
| 134 | + |
| 135 | + p, err = os.FindProcess(pid) |
| 136 | + if err != nil { |
| 137 | + return -1, errors.Wrapf(err, "FindProcess() failed for PID %d", pid) |
| 138 | + } |
| 139 | + |
| 140 | + err = p.Signal(syscall.Signal(0)) |
| 141 | + if err == os.ErrProcessDone { |
| 142 | + return 0, nil |
| 143 | + } |
| 144 | + if err == nil { |
| 145 | + return pid, nil |
| 146 | + } |
| 147 | + |
| 148 | + return -1, errors.Wrapf(err, "failed to check process %d", pid) |
| 149 | +} |
| 150 | + |
| 151 | +// defaultPath returns the default pidfile path. |
| 152 | +func defaultPath() string { |
| 153 | + var path string |
| 154 | + |
| 155 | + if len(os.Args) > 0 { |
| 156 | + name := filepath.Base(os.Args[0]) |
| 157 | + if euid := os.Geteuid(); euid > 0 { |
| 158 | + path = filepath.Join("/tmp", name+".pid") |
| 159 | + } else { |
| 160 | + path = filepath.Join("/", "var", "run", name+".pid") |
| 161 | + } |
| 162 | + } |
| 163 | + |
| 164 | + return path |
| 165 | +} |
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