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.
32 package internal
33 34 import (
35 "context"
36 "io"
37 "log/slog"
38 "os"
39 "strings"
40 "time"
41 )
42 43 const (
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.
55 func 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.
65 func 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.
86 func 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.
95 func 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.
118 type noOpHandler struct{}
119 120 func (h noOpHandler) Enabled(_ context.Context, _ slog.Level) bool {
121 return false
122 }
123 124 func (h noOpHandler) Handle(_ context.Context, _ slog.Record) error {
125 return nil
126 }
127 128 func (h noOpHandler) WithAttrs(_ []slog.Attr) slog.Handler {
129 return h
130 }
131 132 func (h noOpHandler) WithGroup(_ string) slog.Handler {
133 return h
134 }
135