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// Go support for leveled logs, analogous to https://github.com/google/glog.
//
// Copyright 2023 Google Inc. All Rights Reserved.
//
// 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 glog
import (
"bytes"
"errors"
"flag"
"fmt"
"path/filepath"
"runtime"
"strconv"
"strings"
"sync"
"sync/atomic"
"github.com/golang/glog/internal/logsink"
)
// modulePat contains a filter for the -vmodule flag.
// It holds a verbosity level and a file pattern to match.
type modulePat struct {
pattern string
literal bool // The pattern is a literal string
full bool // The pattern wants to match the full path
level Level
}
// match reports whether the file matches the pattern. It uses a string
// comparison if the pattern contains no metacharacters.
func (m *modulePat) match(full, file string) bool {
if m.literal {
if m.full {
return full == m.pattern
}
return file == m.pattern
}
if m.full {
match, _ := filepath.Match(m.pattern, full)
return match
}
match, _ := filepath.Match(m.pattern, file)
return match
}
// isLiteral reports whether the pattern is a literal string, that is, has no metacharacters
// that require filepath.Match to be called to match the pattern.
func isLiteral(pattern string) bool {
return !strings.ContainsAny(pattern, `\*?[]`)
}
// isFull reports whether the pattern matches the full file path, that is,
// whether it contains /.
func isFull(pattern string) bool {
return strings.ContainsRune(pattern, '/')
}
// verboseFlags represents the setting of the -v and -vmodule flags.
type verboseFlags struct {
// moduleLevelCache is a sync.Map storing the -vmodule Level for each V()
// call site, identified by PC. If there is no matching -vmodule filter,
// the cached value is exactly v. moduleLevelCache is replaced with a new
// Map whenever the -vmodule or -v flag changes state.
moduleLevelCache atomic.Value
// mu guards all fields below.
mu sync.Mutex
// v stores the value of the -v flag. It may be read safely using
// sync.LoadInt32, but is only modified under mu.
v Level
// module stores the parsed -vmodule flag.
module []modulePat
// moduleLength caches len(module). If greater than zero, it
// means vmodule is enabled. It may be read safely using sync.LoadInt32, but
// is only modified under mu.
moduleLength int32
}
// NOTE: For compatibility with the open-sourced v1 version of this
// package (github.com/golang/glog) we need to retain that flag.Level
// implements the flag.Value interface. See also go/log-vs-glog.
// String is part of the flag.Value interface.
func (l *Level) String() string {
return strconv.FormatInt(int64(l.Get().(Level)), 10)
}
// Get is part of the flag.Value interface.
func (l *Level) Get() any {
if l == &vflags.v {
// l is the value registered for the -v flag.
return Level(atomic.LoadInt32((*int32)(l)))
}
return *l
}
// Set is part of the flag.Value interface.
func (l *Level) Set(value string) error {
v, err := strconv.Atoi(value)
if err != nil {
return err
}
if l == &vflags.v {
// l is the value registered for the -v flag.
vflags.mu.Lock()
defer vflags.mu.Unlock()
vflags.moduleLevelCache.Store(&sync.Map{})
atomic.StoreInt32((*int32)(l), int32(v))
return nil
}
*l = Level(v)
return nil
}
// vModuleFlag is the flag.Value for the --vmodule flag.
type vModuleFlag struct{ *verboseFlags }
func (f vModuleFlag) String() string {
// Do not panic on the zero value.
// https://groups.google.com/g/golang-nuts/c/Atlr8uAjn6U/m/iId17Td5BQAJ.
if f.verboseFlags == nil {
return ""
}
f.mu.Lock()
defer f.mu.Unlock()
var b bytes.Buffer
for i, f := range f.module {
if i > 0 {
b.WriteRune(',')
}
fmt.Fprintf(&b, "%s=%d", f.pattern, f.level)
}
return b.String()
}
// Get returns nil for this flag type since the struct is not exported.
func (f vModuleFlag) Get() any { return nil }
var errVmoduleSyntax = errors.New("syntax error: expect comma-separated list of filename=N")
// Syntax: -vmodule=recordio=2,foo/bar/baz=1,gfs*=3
func (f vModuleFlag) Set(value string) error {
var filter []modulePat
for _, pat := range strings.Split(value, ",") {
if len(pat) == 0 {
// Empty strings such as from a trailing comma can be ignored.
continue
}
patLev := strings.Split(pat, "=")
if len(patLev) != 2 || len(patLev[0]) == 0 || len(patLev[1]) == 0 {
return errVmoduleSyntax
}
pattern := patLev[0]
v, err := strconv.Atoi(patLev[1])
if err != nil {
return errors.New("syntax error: expect comma-separated list of filename=N")
}
// TODO: check syntax of filter?
filter = append(filter, modulePat{pattern, isLiteral(pattern), isFull(pattern), Level(v)})
}
f.mu.Lock()
defer f.mu.Unlock()
f.module = filter
atomic.StoreInt32((*int32)(&f.moduleLength), int32(len(f.module)))
f.moduleLevelCache.Store(&sync.Map{})
return nil
}
func (f *verboseFlags) levelForPC(pc uintptr) Level {
if level, ok := f.moduleLevelCache.Load().(*sync.Map).Load(pc); ok {
return level.(Level)
}
f.mu.Lock()
defer f.mu.Unlock()
level := Level(f.v)
fn := runtime.FuncForPC(pc)
file, _ := fn.FileLine(pc)
// The file is something like /a/b/c/d.go. We want just the d for
// regular matches, /a/b/c/d for full matches.
file = strings.TrimSuffix(file, ".go")
full := file
if slash := strings.LastIndex(file, "/"); slash >= 0 {
file = file[slash+1:]
}
for _, filter := range f.module {
if filter.match(full, file) {
level = filter.level
break // Use the first matching level.
}
}
f.moduleLevelCache.Load().(*sync.Map).Store(pc, level)
return level
}
func (f *verboseFlags) enabled(callerDepth int, level Level) bool {
if atomic.LoadInt32(&f.moduleLength) == 0 {
// No vmodule values specified, so compare against v level.
return Level(atomic.LoadInt32((*int32)(&f.v))) >= level
}
pcs := [1]uintptr{}
if runtime.Callers(callerDepth+2, pcs[:]) < 1 {
return false
}
frame, _ := runtime.CallersFrames(pcs[:]).Next()
return f.levelForPC(frame.Entry) >= level
}
// traceLocation represents an entry in the -log_backtrace_at flag.
type traceLocation struct {
file string
line int
}
var errTraceSyntax = errors.New("syntax error: expect file.go:234")
func parseTraceLocation(value string) (traceLocation, error) {
fields := strings.Split(value, ":")
if len(fields) != 2 {
return traceLocation{}, errTraceSyntax
}
file, lineStr := fields[0], fields[1]
if !strings.Contains(file, ".") {
return traceLocation{}, errTraceSyntax
}
line, err := strconv.Atoi(lineStr)
if err != nil {
return traceLocation{}, errTraceSyntax
}
if line < 0 {
return traceLocation{}, errors.New("negative value for line")
}
return traceLocation{file, line}, nil
}
// match reports whether the specified file and line matches the trace location.
// The argument file name is the full path, not the basename specified in the flag.
func (t traceLocation) match(file string, line int) bool {
if t.line != line {
return false
}
if i := strings.LastIndex(file, "/"); i >= 0 {
file = file[i+1:]
}
return t.file == file
}
func (t traceLocation) String() string {
return fmt.Sprintf("%s:%d", t.file, t.line)
}
// traceLocations represents the -log_backtrace_at flag.
// Syntax: -log_backtrace_at=recordio.go:234,sstable.go:456
// Note that unlike vmodule the file extension is included here.
type traceLocations struct {
mu sync.Mutex
locsLen int32 // Safe for atomic read without mu.
locs []traceLocation
}
func (t *traceLocations) String() string {
t.mu.Lock()
defer t.mu.Unlock()
var buf bytes.Buffer
for i, tl := range t.locs {
if i > 0 {
buf.WriteString(",")
}
buf.WriteString(tl.String())
}
return buf.String()
}
// Get always returns nil for this flag type since the struct is not exported
func (t *traceLocations) Get() any { return nil }
func (t *traceLocations) Set(value string) error {
var locs []traceLocation
for _, s := range strings.Split(value, ",") {
if s == "" {
continue
}
loc, err := parseTraceLocation(s)
if err != nil {
return err
}
locs = append(locs, loc)
}
t.mu.Lock()
defer t.mu.Unlock()
atomic.StoreInt32(&t.locsLen, int32(len(locs)))
t.locs = locs
return nil
}
func (t *traceLocations) match(file string, line int) bool {
if atomic.LoadInt32(&t.locsLen) == 0 {
return false
}
t.mu.Lock()
defer t.mu.Unlock()
for _, tl := range t.locs {
if tl.match(file, line) {
return true
}
}
return false
}
// severityFlag is an atomic flag.Value implementation for logsink.Severity.
type severityFlag int32
func (s *severityFlag) get() logsink.Severity {
return logsink.Severity(atomic.LoadInt32((*int32)(s)))
}
func (s *severityFlag) String() string { return strconv.FormatInt(int64(*s), 10) }
func (s *severityFlag) Get() any { return s.get() }
func (s *severityFlag) Set(value string) error {
threshold, err := logsink.ParseSeverity(value)
if err != nil {
// Not a severity name. Try a raw number.
v, err := strconv.Atoi(value)
if err != nil {
return err
}
threshold = logsink.Severity(v)
if threshold < logsink.Info || threshold > logsink.Fatal {
return fmt.Errorf("Severity %d out of range (min %d, max %d).", v, logsink.Info, logsink.Fatal)
}
}
atomic.StoreInt32((*int32)(s), int32(threshold))
return nil
}
var (
vflags verboseFlags // The -v and -vmodule flags.
logBacktraceAt traceLocations // The -log_backtrace_at flag.
// Boolean flags. Not handled atomically because the flag.Value interface
// does not let us avoid the =true, and that shorthand is necessary for
// compatibility. TODO: does this matter enough to fix? Seems unlikely.
toStderr bool // The -logtostderr flag.
alsoToStderr bool // The -alsologtostderr flag.
stderrThreshold severityFlag // The -stderrthreshold flag.
)
// verboseEnabled returns whether the caller at the given depth should emit
// verbose logs at the given level, with depth 0 identifying the caller of
// verboseEnabled.
func verboseEnabled(callerDepth int, level Level) bool {
return vflags.enabled(callerDepth+1, level)
}
// backtraceAt returns whether the logging call at the given function and line
// should also emit a backtrace of the current call stack.
func backtraceAt(file string, line int) bool {
return logBacktraceAt.match(file, line)
}
func init() {
vflags.moduleLevelCache.Store(&sync.Map{})
flag.Var(&vflags.v, "v", "log level for V logs")
flag.Var(vModuleFlag{&vflags}, "vmodule", "comma-separated list of pattern=N settings for file-filtered logging")
flag.Var(&logBacktraceAt, "log_backtrace_at", "when logging hits line file:N, emit a stack trace")
stderrThreshold = severityFlag(logsink.Error)
flag.BoolVar(&toStderr, "logtostderr", false, "log to standard error instead of files")
flag.BoolVar(&alsoToStderr, "alsologtostderr", false, "log to standard error as well as files")
flag.Var(&stderrThreshold, "stderrthreshold", "logs at or above this threshold go to stderr")
}
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