First commit

third_party/github.com/coreos/go-systemd/journal/send.go

@@ -0,0 +1,168 @@
+/*
+Copyright 2013 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 systemd journal
+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 iff the systemd journal is available for logging
+func Enabled() bool {
+	return conn != nil
+}
+
+// Send a message to the 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())
+		}
+		_, 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")
+		}
+		unixConn.WriteMsgUnix([]byte{}, rights, nil)
+	} else if err != nil {
+		return journalError(err.Error())
+	}
+	return 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
+	}
+	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)
+}