78 lines
2.2 KiB
Go
78 lines
2.2 KiB
Go
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package mlog
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import (
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"path"
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"github.com/mediocregopher/mediocre-go-lib/mctx"
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)
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type ctxKey int
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// CtxSet caches the Logger in the Context, overwriting any previous one which
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// might have been cached there. From is the corresponding function which
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// retrieves the Logger back out when needed.
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//
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// This function can be used to premptively set a preconfigured Logger on a root
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// Context so that the default (NewLogger) isn't used when From is called for
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// the first time.
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func CtxSet(ctx mctx.Context, l *Logger) {
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mctx.GetSetMutableValue(ctx, false, ctxKey(0), func(interface{}) interface{} {
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return l
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})
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}
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type ctxPathStringer struct {
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str Stringer
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pathStr string
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}
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func (cp ctxPathStringer) String() string {
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return "(" + cp.pathStr + ") " + cp.str.String()
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}
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// From returns an instance of Logger which has been customized for this
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// Context, primarily by adding a prefix describing the Context's path to all
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// Message descriptions the Logger receives.
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//
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// The Context caches within it the generated Logger, so a new one isn't created
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// everytime. When From is first called on a Context the Logger inherits the
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// Context parent's Logger. If the parent hasn't had From called on it its
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// parent will be queried instead, and so on.
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func From(ctx mctx.Context) *Logger {
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var from func(mctx.Context) *Logger
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from = func(ctx mctx.Context) *Logger {
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return mctx.GetSetMutableValue(ctx, true, ctxKey(0), func(interface{}) interface{} {
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ctxPath := mctx.Path(ctx)
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if len(ctxPath) == 0 {
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// we're at the root node and it doesn't have a Logger set, use
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// the default
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return NewLogger()
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}
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// set up child's logger
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pathStr := "/"
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if len(ctxPath) > 0 {
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pathStr += path.Join(ctxPath...)
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}
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parentL := from(mctx.Parent(ctx))
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prevH := parentL.Handler()
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return parentL.WithHandler(func(msg Message) error {
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// if the Description is already a ctxPathStringer it can be
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// assumed this Message was passed in from a child Logger.
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if _, ok := msg.Description.(ctxPathStringer); !ok {
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msg.Description = ctxPathStringer{
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str: msg.Description,
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pathStr: pathStr,
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}
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}
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return prevH(msg)
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})
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}).(*Logger)
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}
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return from(ctx)
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}
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