1 // Copyright 2022 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
4 5 //go:build !go1.21
6 7 package slog
8 9 import (
10 "golang.org/x/exp/slog"
11 )
12 13 // A Level is the importance or severity of a log event.
14 // The higher the level, the more important or severe the event.
15 type Level = slog.Level
16 17 // Level numbers are inherently arbitrary,
18 // but we picked them to satisfy three constraints.
19 // Any system can map them to another numbering scheme if it wishes.
20 //
21 // First, we wanted the default level to be Info, Since Levels are ints, Info is
22 // the default value for int, zero.
23 //
24 // Second, we wanted to make it easy to use levels to specify logger verbosity.
25 // Since a larger level means a more severe event, a logger that accepts events
26 // with smaller (or more negative) level means a more verbose logger. Logger
27 // verbosity is thus the negation of event severity, and the default verbosity
28 // of 0 accepts all events at least as severe as INFO.
29 //
30 // Third, we wanted some room between levels to accommodate schemes with named
31 // levels between ours. For example, Google Cloud Logging defines a Notice level
32 // between Info and Warn. Since there are only a few of these intermediate
33 // levels, the gap between the numbers need not be large. Our gap of 4 matches
34 // OpenTelemetry's mapping. Subtracting 9 from an OpenTelemetry level in the
35 // DEBUG, INFO, WARN and ERROR ranges converts it to the corresponding slog
36 // Level range. OpenTelemetry also has the names TRACE and FATAL, which slog
37 // does not. But those OpenTelemetry levels can still be represented as slog
38 // Levels by using the appropriate integers.
39 //
40 // Names for common levels.
41 const (
42 LevelDebug Level = slog.LevelDebug
43 LevelInfo Level = slog.LevelInfo
44 LevelWarn Level = slog.LevelWarn
45 LevelError Level = slog.LevelError
46 )
47 48 // A LevelVar is a Level variable, to allow a Handler level to change
49 // dynamically.
50 // It implements Leveler as well as a Set method,
51 // and it is safe for use by multiple goroutines.
52 // The zero LevelVar corresponds to LevelInfo.
53 type LevelVar = slog.LevelVar
54 55 // A Leveler provides a Level value.
56 //
57 // As Level itself implements Leveler, clients typically supply
58 // a Level value wherever a Leveler is needed, such as in HandlerOptions.
59 // Clients who need to vary the level dynamically can provide a more complex
60 // Leveler implementation such as *LevelVar.
61 type Leveler = slog.Leveler
62