forked from scionproto/scion
-
Notifications
You must be signed in to change notification settings - Fork 0
/
context.go
47 lines (41 loc) · 1.49 KB
/
context.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
// Copyright 2018 ETH Zurich
// Copyright 2019 ETH Zurich, Anapaya Systems
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package log
import (
"context"
)
type loggerContextKey string
const loggerKey loggerContextKey = "logger"
// CtxWith returns a new context, based on ctx, that embeds argument
// logger. The logger can be recovered using GetLogger. Attaching a logger to a
// context which already contains one will overwrite the existing value.
func CtxWith(ctx context.Context, logger Logger) context.Context {
return context.WithValue(ctx, loggerKey, logger)
}
// FromCtx returns the logger embedded in ctx if one exists, or the root
// logger otherwise. FromCtx is guaranteed to never return nil.
func FromCtx(ctx context.Context) Logger {
if ctx == nil {
return Root()
}
if logger := ctx.Value(loggerKey); logger != nil {
return logger.(Logger)
}
// Logger not found in ctx, make sure we never return a nil root
if Root() == nil {
panic("unable to find non-nil logger")
}
return Root()
}