// Copyright 2017 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package log
import (
"errors"
"fmt"
"regexp"
"runtime"
"strconv"
"strings"
"sync"
"sync/atomic"
)
// errVmoduleSyntax is returned when a user vmodule pattern is invalid.
var errVmoduleSyntax = errors.New("expect comma-separated list of filename=N")
// errTraceSyntax is returned when a user backtrace pattern is invalid.
var errTraceSyntax = errors.New("expect file.go:234")
// GlogHandler is a log handler that mimics the filtering features of Google's
// glog logger: setting global log levels; overriding with callsite pattern
// matches; and requesting backtraces at certain positions.
type GlogHandler struct {
origin Handler // The origin handler this wraps
level uint32 // Current log level, atomically accessible
override uint32 // Flag whether overrides are used, atomically accessible
backtrace uint32 // Flag whether backtrace location is set
patterns []pattern // Current list of patterns to override with
siteCache map[uintptr]Lvl // Cache of callsite pattern evaluations
location string // file:line location where to do a stackdump at
lock sync.RWMutex // Lock protecting the override pattern list
}
// NewGlogHandler creates a new log handler with filtering functionality similar
// to Google's glog logger. The returned handler implements Handler.
func NewGlogHandler(h Handler) *GlogHandler {
return &GlogHandler{
origin: h,
}
}
// SetHandler updates the handler to write records to the specified sub-handler.
func (h *GlogHandler) SetHandler(nh Handler) {
h.origin = nh
}
// pattern contains a filter for the Vmodule option, holding a verbosity level
// and a file pattern to match.
type pattern struct {
pattern *regexp.Regexp
level Lvl
}
// Verbosity sets the glog verbosity ceiling. The verbosity of individual packages
// and source files can be raised using Vmodule.
func (h *GlogHandler) Verbosity(level Lvl) {
atomic.StoreUint32(&h.level, uint32(level))
}
// Vmodule sets the glog verbosity pattern.
//
// The syntax of the argument is a comma-separated list of pattern=N, where the
// pattern is a literal file name or "glob" pattern matching and N is a V level.
//
// For instance:
//
// pattern="gopher.go=3"
// sets the V level to 3 in all Go files named "gopher.go"
//
// pattern="foo=3"
// sets V to 3 in all files of any packages whose import path ends in "foo"
//
// pattern="foo/*=3"
// sets V to 3 in all files of any packages whose import path contains "foo"
func (h *GlogHandler) Vmodule(ruleset string) error {
var filter []pattern
for _, rule := range strings.Split(ruleset, ",") {
// Empty strings such as from a trailing comma can be ignored
if len(rule) == 0 {
continue
}
// Ensure we have a pattern = level filter rule
parts := strings.Split(rule, "=")
if len(parts) != 2 {
return errVmoduleSyntax
}
parts[0] = strings.TrimSpace(parts[0])
parts[1] = strings.TrimSpace(parts[1])
if len(parts[0]) == 0 || len(parts[1]) == 0 {
return errVmoduleSyntax
}
// Parse the level and if correct, assemble the filter rule
level, err := strconv.Atoi(parts[1])
if err != nil {
return errVmoduleSyntax
}
if level <= 0 {
continue // Ignore. It's harmless but no point in paying the overhead.
}
// Compile the rule pattern into a regular expression
matcher := ".*"
for _, comp := range strings.Split(parts[0], "/") {
if comp == "*" {
matcher += "(/.*)?"
} else if comp != "" {
matcher += "/" + regexp.QuoteMeta(comp)
}
}
if !strings.HasSuffix(parts[0], ".go") {
matcher += "/[^/]+\\.go"
}
matcher = matcher + "$"
re, _ := regexp.Compile(matcher)
filter = append(filter, pattern{re, Lvl(level)})
}
// Swap out the vmodule pattern for the new filter system
h.lock.Lock()
defer h.lock.Unlock()
h.patterns = filter
h.siteCache = make(map[uintptr]Lvl)
atomic.StoreUint32(&h.override, uint32(len(filter)))
return nil
}
// BacktraceAt sets the glog backtrace location. When set to a file and line
// number holding a logging statement, a stack trace will be written to the Info
// log whenever execution hits that statement.
//
// Unlike with Vmodule, the ".go" must be present.
func (h *GlogHandler) BacktraceAt(location string) error {
// Ensure the backtrace location contains two non-empty elements
parts := strings.Split(location, ":")
if len(parts) != 2 {
return errTraceSyntax
}
parts[0] = strings.TrimSpace(parts[0])
parts[1] = strings.TrimSpace(parts[1])
if len(parts[0]) == 0 || len(parts[1]) == 0 {
return errTraceSyntax
}
// Ensure the .go prefix is present and the line is valid
if !strings.HasSuffix(parts[0], ".go") {
return errTraceSyntax
}
if _, err := strconv.Atoi(parts[1]); err != nil {
return errTraceSyntax
}
// All seems valid
h.lock.Lock()
defer h.lock.Unlock()
h.location = location
atomic.StoreUint32(&h.backtrace, uint32(len(location)))
return nil
}
// Log implements Handler.Log, filtering a log record through the global, local
// and backtrace filters, finally emitting it if either allow it through.
func (h *GlogHandler) Log(r *Record) error {
// If backtracing is requested, check whether this is the callsite
if atomic.LoadUint32(&h.backtrace) > 0 {
// Everything below here is slow. Although we could cache the call sites the
// same way as for vmodule, backtracing is so rare it's not worth the extra
// complexity.
h.lock.RLock()
match := h.location == r.Call.String()
h.lock.RUnlock()
if match {
// Callsite matched, raise the log level to info and gather the stacks
r.Lvl = LvlInfo
buf := make([]byte, 1024*1024)
buf = buf[:runtime.Stack(buf, true)]
r.Msg += "\n\n" + string(buf)
}
}
// If the global log level allows, fast track logging
if atomic.LoadUint32(&h.level) >= uint32(r.Lvl) {
return h.origin.Log(r)
}
// If no local overrides are present, fast track skipping
if atomic.LoadUint32(&h.override) == 0 {
return nil
}
// Check callsite cache for previously calculated log levels
h.lock.RLock()
lvl, ok := h.siteCache[r.Call.PC()]
h.lock.RUnlock()
// If we didn't cache the callsite yet, calculate it
if !ok {
h.lock.Lock()
for _, rule := range h.patterns {
if rule.pattern.MatchString(fmt.Sprintf("%+s", r.Call)) {
h.siteCache[r.Call.PC()], lvl, ok = rule.level, rule.level, true
break
}
}
// If no rule matched, remember to drop log the next time
if !ok {
h.siteCache[r.Call.PC()] = 0
}
h.lock.Unlock()
}
if lvl >= r.Lvl {
return h.origin.Log(r)
}
return nil
}
