log: implement a glog style pattern matching handler
This commit is contained in:
Péter Szilágyi
227
log/handler_glog.go
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227
log/handler_glog.go
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// Copyright 2017 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package log
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import (
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"errors"
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"fmt"
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"regexp"
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"runtime"
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"strconv"
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"strings"
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"sync"
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"sync/atomic"
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)
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// errVmoduleSyntax is returned when a user vmodule pattern is invalid.
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var errVmoduleSyntax = errors.New("expect comma-separated list of filename=N")
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// errTraceSyntax is returned when a user backtrace pattern is invalid.
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var errTraceSyntax = errors.New("expect file.go:234")
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// GlogHandler is a log handler that mimics the filtering features of Google's
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// glog logger: setting global log levels; overriding with callsite pattern
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// matches; and requesting backtraces at certain positions.
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type GlogHandler struct {
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origin Handler // The origin handler this wraps
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level uint32 // Current log level, atomically accessible
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override uint32 // Flag whether overrides are used, atomically accessible
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backtrace uint32 // Flag whether backtrace location is set
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patterns []pattern // Current list of patterns to override with
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siteCache map[uintptr]Lvl // Cache of callsite pattern evaluations
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location string // file:line location where to do a stackdump at
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lock sync.RWMutex // Lock protecting the override pattern list
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}
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// NewGlogHandler creates a new log handler with filtering functionality similar
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// to Google's glog logger. The returned handler implements Handler.
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func NewGlogHandler(h Handler) *GlogHandler {
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return &GlogHandler{
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origin: h,
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}
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}
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// pattern contains a filter for the Vmodule option, holding a verbosity level
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// and a file pattern to match.
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type pattern struct {
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pattern *regexp.Regexp
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level Lvl
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}
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// Verbosity sets the glog verbosity ceiling. The verbosity of individual packages
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// and source files can be raised using Vmodule.
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func (h *GlogHandler) Verbosity(level Lvl) {
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atomic.StoreUint32(&h.level, uint32(level))
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}
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// Vmodule sets the glog verbosity pattern.
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//
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// The syntax of the argument is a comma-separated list of pattern=N, where the
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// pattern is a literal file name or "glob" pattern matching and N is a V level.
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//
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// For instance:
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//
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// pattern="gopher.go=3"
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// sets the V level to 3 in all Go files named "gopher.go"
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//
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// pattern="foo=3"
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// sets V to 3 in all files of any packages whose import path ends in "foo"
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//
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// pattern="foo/*=3"
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// sets V to 3 in all files of any packages whose import path contains "foo"
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func (h *GlogHandler) Vmodule(ruleset string) error {
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var filter []pattern
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for _, rule := range strings.Split(ruleset, ",") {
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// Empty strings such as from a trailing comma can be ignored
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if len(rule) == 0 {
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continue
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}
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// Ensure we have a pattern = level filter rule
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parts := strings.Split(rule, "=")
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if len(parts) != 2 {
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return errVmoduleSyntax
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}
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parts[0] = strings.TrimSpace(parts[0])
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parts[1] = strings.TrimSpace(parts[1])
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if len(parts[0]) == 0 || len(parts[1]) == 0 {
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return errVmoduleSyntax
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}
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// Parse the level and if correct, assemble the filter rule
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level, err := strconv.Atoi(parts[1])
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if err != nil {
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return errVmoduleSyntax
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}
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if level <= 0 {
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continue // Ignore. It's harmless but no point in paying the overhead.
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}
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// Compile the rule pattern into a regular expression
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matcher := ".*"
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for _, comp := range strings.Split(parts[0], "/") {
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if comp == "*" {
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matcher += "(/.*)?"
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} else if comp != "" {
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matcher += "/" + regexp.QuoteMeta(comp)
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}
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}
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if !strings.HasSuffix(parts[0], ".go") {
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matcher += "/[^/]+\\.go"
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}
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matcher = matcher + "$"
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re, _ := regexp.Compile(matcher)
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filter = append(filter, pattern{re, Lvl(level)})
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}
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// Swap out the vmodule pattern for the new filter system
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h.lock.Lock()
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defer h.lock.Unlock()
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h.patterns = filter
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h.siteCache = make(map[uintptr]Lvl)
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atomic.StoreUint32(&h.override, uint32(len(filter)))
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return nil
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}
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// BacktraceAt sets the glog backtrace location. When set to a file and line
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// number holding a logging statement, a stack trace will be written to the Info
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// log whenever execution hits that statement.
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//
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// Unlike with Vmodule, the ".go" must be present.
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func (h *GlogHandler) BacktraceAt(location string) error {
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// Ensure the backtrace location contains two non-empty elements
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parts := strings.Split(location, ":")
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if len(parts) != 2 {
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return errTraceSyntax
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}
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parts[0] = strings.TrimSpace(parts[0])
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parts[1] = strings.TrimSpace(parts[1])
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if len(parts[0]) == 0 || len(parts[1]) == 0 {
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return errTraceSyntax
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}
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// Ensure the .go prefix is present and the line is valid
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if !strings.HasSuffix(parts[0], ".go") {
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return errTraceSyntax
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}
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if _, err := strconv.Atoi(parts[1]); err != nil {
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return errTraceSyntax
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}
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// All seems valid
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h.lock.Lock()
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defer h.lock.Unlock()
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h.location = location
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atomic.StoreUint32(&h.backtrace, uint32(len(location)))
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return nil
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}
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// Log implements Handler.Log, filtering a log record through the global, local
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// and backtrace filters, finally emitting it if either allow it through.
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func (h *GlogHandler) Log(r *Record) error {
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// If backtracing is requested, check whether this is the callsite
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if atomic.LoadUint32(&h.backtrace) > 0 {
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// Everything below here is slow. Although we could cache the call sites the
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// same way as for vmodule, backtracing is so rare it's not worth the extra
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// complexity.
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h.lock.RLock()
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match := h.location == r.Call.String()
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h.lock.RUnlock()
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if match {
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// Callsite matched, raise the log level to info and gather the stacks
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r.Lvl = LvlInfo
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buf := make([]byte, 1024*1024)
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buf = buf[:runtime.Stack(buf, true)]
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r.Msg += "\n\n" + string(buf)
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}
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}
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// If the global log level allows, fast track logging
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if atomic.LoadUint32(&h.level) >= uint32(r.Lvl) {
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return h.origin.Log(r)
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}
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// If no local overrides are present, fast track skipping
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if atomic.LoadUint32(&h.override) == 0 {
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return nil
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}
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// Check callsite cache for previously calculated log levels
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h.lock.RLock()
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lvl, ok := h.siteCache[r.Call.PC()]
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h.lock.RUnlock()
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// If we didn't cache the callsite yet, calculate it
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if !ok {
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h.lock.Lock()
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for _, rule := range h.patterns {
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if rule.pattern.MatchString(fmt.Sprintf("%+s", r.Call)) {
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h.siteCache[r.Call.PC()], lvl, ok = rule.level, rule.level, true
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break
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}
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}
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// If no rule matched, remember to drop log the next time
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if !ok {
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h.siteCache[r.Call.PC()] = 0
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}
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h.lock.Unlock()
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}
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if lvl >= r.Lvl {
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return h.origin.Log(r)
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}
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return nil
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}
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