Use prod logger's user context to read logging level

impl/prod/logger.go

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package prod
 
 import (
         "fmt"
 
         "github.com/luci/luci-go/common/logging"
         "golang.org/x/net/context"
         "google.golang.org/appengine/log"
 )
 
 // useLogging adds a logging.Logger implementation to the context which logs to
 // appengine's log handler.
 func useLogging(c context.Context) context.Context {
         return logging.SetFactory(c, func(ic context.Context) logging.Logger {
                 return &loggerImpl{AEContext(ic), ic}
         })
 }
 
 type loggerImpl struct {
         aeCtx context.Context
         ic    context.Context

[estaab, 2015/12/23 16:50:46]

what does the i in ic stand for?

 }
 
 func (gl *loggerImpl) Debugf(format string, args ...interface{}) {
         gl.LogCall(logging.Debug, 1, format, args)
 }
 func (gl *loggerImpl) Infof(format string, args ...interface{}) {
         gl.LogCall(logging.Info, 1, format, args)
 }
 func (gl *loggerImpl) Warningf(format string, args ...interface{}) {
         gl.LogCall(logging.Warning, 1, format, args)
 }
 func (gl *loggerImpl) Errorf(format string, args ...interface{}) {
         gl.LogCall(logging.Error, 1, format, args)
 }
 
 // TODO(riannucci): prefix with caller's code location.
 func (gl *loggerImpl) LogCall(l logging.Level, calldepth int, format string, args []interface{}) {
-        if gl.aeCtx == nil || !logging.IsLogging(gl.aeCtx, l) {
+        if gl.aeCtx == nil || !logging.IsLogging(gl.ic, l) {

[iannucci, 2015/12/23 16:34:43]

If you look below (line 62), we use the ic context to pull fields for logging.
When the logging lib changes the level, it's changing it on ic, not aeCtx.

                 return
         }
 
         var logf func(context.Context, string, ...interface{})
         switch l {
         case logging.Debug:
                 logf = log.Debugf
         case logging.Info:
                 logf = log.Infof
         case logging.Warning:
                 logf = log.Warningf
 
         case logging.Error:
                 fallthrough
         default:
                 logf = log.Errorf
         }
 
         fields := logging.GetFields(gl.ic)
         if len(fields) > 0 {
                 logf(gl.aeCtx, "%s :: %s", fmt.Sprintf(format, args...), fields.FieldString(true))
         } else {
                 logf(gl.aeCtx, format, args...)
         }
 }