1// Copyright 2024, Google Inc.
2// All rights reserved.
3//
4// Redistribution and use in source and binary forms, with or without
5// modification, are permitted provided that the following conditions are
6// met:
7//
8// * Redistributions of source code must retain the above copyright
9// notice, this list of conditions and the following disclaimer.
10// * Redistributions in binary form must reproduce the above
11// copyright notice, this list of conditions and the following disclaimer
12// in the documentation and/or other materials provided with the
13// distribution.
14// * Neither the name of Google Inc. nor the names of its
15// contributors may be used to endorse or promote products derived from
16// this software without specific prior written permission.
17//
18// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
21// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
22// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
23// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
24// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
28// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29
30// Package internal provides some common logic and types to other logging
31// sub-packages.
32package internal
33
34import (
35 "context"
36 "io"
37 "log/slog"
38 "os"
39 "strings"
40 "time"
41)
42
43const (
44 // LoggingLevelEnvVar is the environment variable used to enable logging
45 // at a particular level.
46 LoggingLevelEnvVar = "GOOGLE_SDK_GO_LOGGING_LEVEL"
47
48 googLvlKey = "severity"
49 googMsgKey = "message"
50 googSourceKey = "sourceLocation"
51 googTimeKey = "timestamp"
52)
53
54// NewLoggerWithWriter is exposed for testing.
55func NewLoggerWithWriter(w io.Writer) *slog.Logger {
56 lvl, loggingEnabled := checkLoggingLevel()
57 if !loggingEnabled {
58 return slog.New(noOpHandler{})
59 }
60 return slog.New(newGCPSlogHandler(lvl, w))
61}
62
63// checkLoggingLevel returned the configured logging level and whether or not
64// logging is enabled.
65func checkLoggingLevel() (slog.Leveler, bool) {
66 sLevel := strings.ToLower(os.Getenv(LoggingLevelEnvVar))
67 var level slog.Level
68 switch sLevel {
69 case "debug":
70 level = slog.LevelDebug
71 case "info":
72 level = slog.LevelInfo
73 case "warn":
74 level = slog.LevelWarn
75 case "error":
76 level = slog.LevelError
77 default:
78 return nil, false
79 }
80 return level, true
81}
82
83// newGCPSlogHandler returns a Handler that is configured to output in a JSON
84// format with well-known keys. For more information on this format see
85// https://cloud.google.com/logging/docs/agent/logging/configuration#special-fields.
86func newGCPSlogHandler(lvl slog.Leveler, w io.Writer) slog.Handler {
87 return slog.NewJSONHandler(w, &slog.HandlerOptions{
88 Level: lvl,
89 ReplaceAttr: replaceAttr,
90 })
91}
92
93// replaceAttr remaps default Go logging keys to match what is expected in
94// cloud logging.
95func replaceAttr(groups []string, a slog.Attr) slog.Attr {
96 if groups == nil {
97 if a.Key == slog.LevelKey {
98 a.Key = googLvlKey
99 return a
100 } else if a.Key == slog.MessageKey {
101 a.Key = googMsgKey
102 return a
103 } else if a.Key == slog.SourceKey {
104 a.Key = googSourceKey
105 return a
106 } else if a.Key == slog.TimeKey {
107 a.Key = googTimeKey
108 if a.Value.Kind() == slog.KindTime {
109 a.Value = slog.StringValue(a.Value.Time().Format(time.RFC3339))
110 }
111 return a
112 }
113 }
114 return a
115}
116
117// The handler returned if logging is not enabled.
118type noOpHandler struct{}
119
120func (h noOpHandler) Enabled(_ context.Context, _ slog.Level) bool {
121 return false
122}
123
124func (h noOpHandler) Handle(_ context.Context, _ slog.Record) error {
125 return nil
126}
127
128func (h noOpHandler) WithAttrs(_ []slog.Attr) slog.Handler {
129 return h
130}
131
132func (h noOpHandler) WithGroup(_ string) slog.Handler {
133 return h
134}