68 lines
2.2 KiB
Go
68 lines
2.2 KiB
Go
package mlog
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import (
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"github.com/mediocregopher/mediocre-go-lib/mcmp"
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"github.com/mediocregopher/mediocre-go-lib/mctx"
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)
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type cmpKey int
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// SetLogger sets the given logger onto the Component. The logger can later be
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// retrieved from the Component, or any of its children, using From.
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//
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// NOTE that if a Logger is set onto a Component and then changed, even though
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// the Logger is a pointer and so is changed within the Component, SetLogger
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// should still be called. This is due to some caching that From does for
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// performance.
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func SetLogger(cmp *mcmp.Component, l *Logger) {
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cmp.SetValue(cmpKey(0), l)
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// If the base Logger on this Component gets changed, then the cached Logger
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// from From on this Component, and all of its Children, ought to be reset,
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// so that any changes can be reflected in their loggers.
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var resetFromLogger func(*mcmp.Component)
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resetFromLogger = func(cmp *mcmp.Component) {
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cmp.SetValue(cmpKey(1), nil)
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for _, childCmp := range cmp.Children() {
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resetFromLogger(childCmp)
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}
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}
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resetFromLogger(cmp)
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}
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// DefaultLogger is an instance of Logger which is returned by From when a
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// Logger hasn't been previously set with SetLogger on the passed in Component.
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var DefaultLogger = NewLogger()
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// GetLogger returns the Logger which was set on the Component, or on of its
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// ancestors, using SetLogger. If no Logger was ever set then DefaultLogger is
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// returned.
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func GetLogger(cmp *mcmp.Component) *Logger {
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if l, ok := cmp.InheritedValue(cmpKey(0)); ok {
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return l.(*Logger)
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}
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return DefaultLogger
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}
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// From returns the result from GetLogger, modified so as to automatically add
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// some annotations related to the Component itself to all Messages being
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// logged.
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func From(cmp *mcmp.Component) *Logger {
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if l, _ := cmp.Value(cmpKey(1)).(*Logger); l != nil {
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return l
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}
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// if we're here it means a modified Logger wasn't set on this particular
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// Component, and therefore the current one must be modified.
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l := GetLogger(cmp).Clone()
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oldHandler := l.Handler()
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l.SetHandler(func(msg Message) error {
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ctx := mctx.MergeAnnotationsInto(cmp.Context(), msg.Contexts...)
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msg.Contexts = append(msg.Contexts[:0], ctx)
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return oldHandler(msg)
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})
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cmp.SetValue(cmpKey(1), l)
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return l
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}
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