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