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// Copyright 2015 CoreOS, Inc.
//
// 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 journal provides write bindings to the local systemd journal.
// It is implemented in pure Go and connects to the journal directly over its
// unix socket.
//
// To read from the journal, see the "sdjournal" package, which wraps the
// sd-journal a C API.
//
// http://www.freedesktop.org/software/systemd/man/systemd-journald.service.html
package journal
import (
"bytes"
"encoding/binary"
"errors"
"fmt"
"io"
"io/ioutil"
"net"
"os"
"strconv"
"strings"
"syscall"
)
// Priority of a journal message
type Priority int
const (
PriEmerg Priority = iota
PriAlert
PriCrit
PriErr
PriWarning
PriNotice
PriInfo
PriDebug
)
var conn net.Conn
func init() {
var err error
conn, err = net.Dial("unixgram", "/run/systemd/journal/socket")
if err != nil {
conn = nil
}
}
// Enabled returns true if the local systemd journal is available for logging
func Enabled() bool {
return conn != nil
}
// Send a message to the local systemd journal. vars is a map of journald
// fields to values. Fields must be composed of uppercase letters, numbers,
// and underscores, but must not start with an underscore. Within these
// restrictions, any arbitrary field name may be used. Some names have special
// significance: see the journalctl documentation
// (http://www.freedesktop.org/software/systemd/man/systemd.journal-fields.html)
// for more details. vars may be nil.
func Send(message string, priority Priority, vars map[string]string) error {
if conn == nil {
return journalError("could not connect to journald socket")
}
data := new(bytes.Buffer)
appendVariable(data, "PRIORITY", strconv.Itoa(int(priority)))
appendVariable(data, "MESSAGE", message)
for k, v := range vars {
appendVariable(data, k, v)
}
_, err := io.Copy(conn, data)
if err != nil && isSocketSpaceError(err) {
file, err := tempFd()
if err != nil {
return journalError(err.Error())
}
defer file.Close()
_, err = io.Copy(file, data)
if err != nil {
return journalError(err.Error())
}
rights := syscall.UnixRights(int(file.Fd()))
/* this connection should always be a UnixConn, but better safe than sorry */
unixConn, ok := conn.(*net.UnixConn)
if !ok {
return journalError("can't send file through non-Unix connection")
}
_, _, err = unixConn.WriteMsgUnix([]byte{}, rights, nil)
if err != nil {
return journalError(err.Error())
}
} else if err != nil {
return journalError(err.Error())
}
return nil
}
// Print prints a message to the local systemd journal using Send().
func Print(priority Priority, format string, a ...interface{}) error {
return Send(fmt.Sprintf(format, a...), priority, nil)
}
func appendVariable(w io.Writer, name, value string) {
if !validVarName(name) {
journalError("variable name contains invalid character, ignoring")
}
if strings.ContainsRune(value, '\n') {
/* When the value contains a newline, we write:
* - the variable name, followed by a newline
* - the size (in 64bit little endian format)
* - the data, followed by a newline
*/
fmt.Fprintln(w, name)
binary.Write(w, binary.LittleEndian, uint64(len(value)))
fmt.Fprintln(w, value)
} else {
/* just write the variable and value all on one line */
fmt.Fprintf(w, "%s=%s\n", name, value)
}
}
func validVarName(name string) bool {
/* The variable name must be in uppercase and consist only of characters,
* numbers and underscores, and may not begin with an underscore. (from the docs)
*/
valid := name[0] != '_'
for _, c := range name {
valid = valid && ('A' <= c && c <= 'Z') || ('0' <= c && c <= '9') || c == '_'
}
return valid
}
func isSocketSpaceError(err error) bool {
opErr, ok := err.(*net.OpError)
if !ok {
return false
}
sysErr, ok := opErr.Err.(syscall.Errno)
if !ok {
return false
}
return sysErr == syscall.EMSGSIZE || sysErr == syscall.ENOBUFS
}
func tempFd() (*os.File, error) {
file, err := ioutil.TempFile("/dev/shm/", "journal.XXXXX")
if err != nil {
return nil, err
}
err = syscall.Unlink(file.Name())
if err != nil {
return nil, err
}
return file, nil
}
func journalError(s string) error {
s = "journal error: " + s
fmt.Fprintln(os.Stderr, s)
return errors.New(s)
}
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