Add shim for collecting logs

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

vendor/github.com/coreos/go-systemd/journal/journal.go

@@ -0,0 +1,225 @@
+// 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))
+}