| // 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" |
| "sync" |
| "sync/atomic" |
| "syscall" |
| "unsafe" |
| ) |
| |
| // Priority of a journal message |
| type Priority int |
| |
| const ( |
| PriEmerg Priority = iota |
| PriAlert |
| PriCrit |
| PriErr |
| PriWarning |
| PriNotice |
| PriInfo |
| PriDebug |
| ) |
| |
| var ( |
| // This can be overridden at build-time: |
| // https://github.com/golang/go/wiki/GcToolchainTricks#including-build-information-in-the-executable |
| journalSocket = "/run/systemd/journal/socket" |
| |
| // unixConnPtr atomically holds the local unconnected Unix-domain socket. |
| // Concrete safe pointer type: *net.UnixConn |
| unixConnPtr unsafe.Pointer |
| // onceConn ensures that unixConnPtr is initialized exactly once. |
| onceConn sync.Once |
| ) |
| |
| func init() { |
| onceConn.Do(initConn) |
| } |
| |
| // Enabled checks whether the local systemd journal is available for logging. |
| func Enabled() bool { |
| onceConn.Do(initConn) |
| |
| if (*net.UnixConn)(atomic.LoadPointer(&unixConnPtr)) == nil { |
| return false |
| } |
| |
| if _, err := net.Dial("unixgram", journalSocket); err != nil { |
| return false |
| } |
| |
| return true |
| } |
| |
| // 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 { |
| conn := (*net.UnixConn)(atomic.LoadPointer(&unixConnPtr)) |
| if conn == nil { |
| return errors.New("could not initialize socket to journald") |
| } |
| |
| socketAddr := &net.UnixAddr{ |
| Name: journalSocket, |
| Net: "unixgram", |
| } |
| |
| 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 := conn.WriteMsgUnix(data.Bytes(), nil, socketAddr) |
| if err == nil { |
| return nil |
| } |
| if !isSocketSpaceError(err) { |
| return err |
| } |
| |
| // Large log entry, send it via tempfile and ancillary-fd. |
| file, err := tempFd() |
| if err != nil { |
| return err |
| } |
| defer file.Close() |
| _, err = io.Copy(file, data) |
| if err != nil { |
| return err |
| } |
| rights := syscall.UnixRights(int(file.Fd())) |
| _, _, err = conn.WriteMsgUnix([]byte{}, rights, socketAddr) |
| if err != nil { |
| return err |
| } |
| |
| 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 err := validVarName(name); err != nil { |
| fmt.Fprintf(os.Stderr, "variable name %s contains invalid character, ignoring\n", name) |
| } |
| 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) |
| } |
| } |
| |
| // validVarName validates a variable name to make sure journald will accept it. |
| // The variable name must be in uppercase and consist only of characters, |
| // numbers and underscores, and may not begin with an underscore: |
| // https://www.freedesktop.org/software/systemd/man/sd_journal_print.html |
| func validVarName(name string) error { |
| if name == "" { |
| return errors.New("Empty variable name") |
| } else if name[0] == '_' { |
| return errors.New("Variable name begins with an underscore") |
| } |
| |
| for _, c := range name { |
| if !(('A' <= c && c <= 'Z') || ('0' <= c && c <= '9') || c == '_') { |
| return errors.New("Variable name contains invalid characters") |
| } |
| } |
| return nil |
| } |
| |
| // isSocketSpaceError checks whether the error is signaling |
| // an "overlarge message" condition. |
| func isSocketSpaceError(err error) bool { |
| opErr, ok := err.(*net.OpError) |
| if !ok || opErr == nil { |
| return false |
| } |
| |
| sysErr, ok := opErr.Err.(*os.SyscallError) |
| if !ok || sysErr == nil { |
| return false |
| } |
| |
| return sysErr.Err == syscall.EMSGSIZE || sysErr.Err == syscall.ENOBUFS |
| } |
| |
| // tempFd creates a temporary, unlinked file under `/dev/shm`. |
| 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 |
| } |
| |
| // initConn initializes the global `unixConnPtr` socket. |
| // It is meant to be called exactly once, at program startup. |
| func initConn() { |
| autobind, err := net.ResolveUnixAddr("unixgram", "") |
| if err != nil { |
| return |
| } |
| |
| sock, err := net.ListenUnixgram("unixgram", autobind) |
| if err != nil { |
| return |
| } |
| |
| atomic.StorePointer(&unixConnPtr, unsafe.Pointer(sock)) |
| } |