package log
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import "fmt"
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type level byte
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const (
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levelDebug level = 1 << iota
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levelInfo
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levelError
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)
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type filter struct {
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next Logger
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allowed level // XOR'd levels for default case
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initiallyAllowed level // XOR'd levels for initial case
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allowedKeyvals map[keyval]level // When key-value match, use this level
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}
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type keyval struct {
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key interface{}
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value interface{}
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}
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// NewFilter wraps next and implements filtering. See the commentary on the
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// Option functions for a detailed description of how to configure levels. If
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// no options are provided, all leveled log events created with Debug, Info or
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// Error helper methods are squelched.
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func NewFilter(next Logger, options ...Option) Logger {
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l := &filter{
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next: next,
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allowedKeyvals: make(map[keyval]level),
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}
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for _, option := range options {
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option(l)
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}
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l.initiallyAllowed = l.allowed
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return l
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}
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func (l *filter) Info(msg string, keyvals ...interface{}) {
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levelAllowed := l.allowed&levelInfo != 0
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if !levelAllowed {
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return
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}
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l.next.Info(msg, keyvals...)
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}
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func (l *filter) Debug(msg string, keyvals ...interface{}) {
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levelAllowed := l.allowed&levelDebug != 0
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if !levelAllowed {
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return
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}
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l.next.Debug(msg, keyvals...)
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}
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func (l *filter) Error(msg string, keyvals ...interface{}) {
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levelAllowed := l.allowed&levelError != 0
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if !levelAllowed {
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return
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}
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l.next.Error(msg, keyvals...)
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}
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// With implements Logger by constructing a new filter with a keyvals appended
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// to the logger.
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//
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// If custom level was set for a keyval pair using one of the
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// Allow*With methods, it is used as the logger's level.
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//
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// Examples:
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// logger = log.NewFilter(logger, log.AllowError(), log.AllowInfoWith("module", "crypto"))
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// logger.With("module", "crypto").Info("Hello") # produces "I... Hello module=crypto"
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//
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// logger = log.NewFilter(logger, log.AllowError(),
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// log.AllowInfoWith("module", "crypto"),
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// log.AllowNoneWith("user", "Sam"))
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// logger.With("module", "crypto", "user", "Sam").Info("Hello") # returns nil
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//
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// logger = log.NewFilter(logger,
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// log.AllowError(),
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// log.AllowInfoWith("module", "crypto"), log.AllowNoneWith("user", "Sam"))
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// logger.With("user", "Sam").With("module", "crypto").Info("Hello") # produces "I... Hello module=crypto user=Sam"
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func (l *filter) With(keyvals ...interface{}) Logger {
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keyInAllowedKeyvals := false
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for i := len(keyvals) - 2; i >= 0; i -= 2 {
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for kv, allowed := range l.allowedKeyvals {
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if keyvals[i] == kv.key {
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keyInAllowedKeyvals = true
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// Example:
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// logger = log.NewFilter(logger, log.AllowError(), log.AllowInfoWith("module", "crypto"))
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// logger.With("module", "crypto")
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if keyvals[i+1] == kv.value {
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return &filter{
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next: l.next.With(keyvals...),
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allowed: allowed, // set the desired level
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allowedKeyvals: l.allowedKeyvals,
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initiallyAllowed: l.initiallyAllowed,
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}
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}
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}
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}
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}
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// Example:
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// logger = log.NewFilter(logger, log.AllowError(), log.AllowInfoWith("module", "crypto"))
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// logger.With("module", "main")
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if keyInAllowedKeyvals {
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return &filter{
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next: l.next.With(keyvals...),
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allowed: l.initiallyAllowed, // return back to initially allowed
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allowedKeyvals: l.allowedKeyvals,
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initiallyAllowed: l.initiallyAllowed,
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}
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}
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return &filter{
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next: l.next.With(keyvals...),
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allowed: l.allowed, // simply continue with the current level
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allowedKeyvals: l.allowedKeyvals,
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initiallyAllowed: l.initiallyAllowed,
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}
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}
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//--------------------------------------------------------------------------------
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// Option sets a parameter for the filter.
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type Option func(*filter)
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// AllowLevel returns an option for the given level or error if no option exist
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// for such level.
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func AllowLevel(lvl string) (Option, error) {
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switch lvl {
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case "debug":
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return AllowDebug(), nil
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case "info":
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return AllowInfo(), nil
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case "error":
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return AllowError(), nil
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case "none":
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return AllowNone(), nil
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default:
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return nil, fmt.Errorf("expected either \"info\", \"debug\", \"error\" or \"none\" level, given %s", lvl)
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}
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}
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// AllowAll is an alias for AllowDebug.
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func AllowAll() Option {
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return AllowDebug()
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}
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// AllowDebug allows error, info and debug level log events to pass.
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func AllowDebug() Option {
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return allowed(levelError | levelInfo | levelDebug)
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}
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// AllowInfo allows error and info level log events to pass.
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func AllowInfo() Option {
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return allowed(levelError | levelInfo)
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}
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// AllowError allows only error level log events to pass.
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func AllowError() Option {
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return allowed(levelError)
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}
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// AllowNone allows no leveled log events to pass.
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func AllowNone() Option {
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return allowed(0)
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}
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func allowed(allowed level) Option {
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return func(l *filter) { l.allowed = allowed }
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}
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// AllowDebugWith allows error, info and debug level log events to pass for a specific key value pair.
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func AllowDebugWith(key interface{}, value interface{}) Option {
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return func(l *filter) { l.allowedKeyvals[keyval{key, value}] = levelError | levelInfo | levelDebug }
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}
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// AllowInfoWith allows error and info level log events to pass for a specific key value pair.
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func AllowInfoWith(key interface{}, value interface{}) Option {
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return func(l *filter) { l.allowedKeyvals[keyval{key, value}] = levelError | levelInfo }
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}
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// AllowErrorWith allows only error level log events to pass for a specific key value pair.
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func AllowErrorWith(key interface{}, value interface{}) Option {
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return func(l *filter) { l.allowedKeyvals[keyval{key, value}] = levelError }
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}
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// AllowNoneWith allows no leveled log events to pass for a specific key value pair.
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func AllowNoneWith(key interface{}, value interface{}) Option {
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return func(l *filter) { l.allowedKeyvals[keyval{key, value}] = 0 }
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}
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