1 // Copyright (c) 2016 Uber Technologies, Inc.
2 //
3 // Permission is hereby granted, free of charge, to any person obtaining a copy
4 // of this software and associated documentation files (the "Software"), to deal
5 // in the Software without restriction, including without limitation the rights
6 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
7 // copies of the Software, and to permit persons to whom the Software is
8 // furnished to do so, subject to the following conditions:
9 //
10 // The above copyright notice and this permission notice shall be included in
11 // all copies or substantial portions of the Software.
12 //
13 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
14 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
15 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
16 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
17 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
18 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
19 // THE SOFTWARE.
20 21 // Package zap provides fast, structured, leveled logging.
22 //
23 // For applications that log in the hot path, reflection-based serialization
24 // and string formatting are prohibitively expensive - they're CPU-intensive
25 // and make many small allocations. Put differently, using json.Marshal and
26 // fmt.Fprintf to log tons of interface{} makes your application slow.
27 //
28 // Zap takes a different approach. It includes a reflection-free,
29 // zero-allocation JSON encoder, and the base Logger strives to avoid
30 // serialization overhead and allocations wherever possible. By building the
31 // high-level SugaredLogger on that foundation, zap lets users choose when
32 // they need to count every allocation and when they'd prefer a more familiar,
33 // loosely typed API.
34 //
35 // # Choosing a Logger
36 //
37 // In contexts where performance is nice, but not critical, use the
38 // SugaredLogger. It's 4-10x faster than other structured logging packages and
39 // supports both structured and printf-style logging. Like log15 and go-kit,
40 // the SugaredLogger's structured logging APIs are loosely typed and accept a
41 // variadic number of key-value pairs. (For more advanced use cases, they also
42 // accept strongly typed fields - see the SugaredLogger.With documentation for
43 // details.)
44 //
45 // sugar := zap.NewExample().Sugar()
46 // defer sugar.Sync()
47 // sugar.Infow("failed to fetch URL",
48 // "url", "http://example.com",
49 // "attempt", 3,
50 // "backoff", time.Second,
51 // )
52 // sugar.Infof("failed to fetch URL: %s", "http://example.com")
53 //
54 // By default, loggers are unbuffered. However, since zap's low-level APIs
55 // allow buffering, calling Sync before letting your process exit is a good
56 // habit.
57 //
58 // In the rare contexts where every microsecond and every allocation matter,
59 // use the Logger. It's even faster than the SugaredLogger and allocates far
60 // less, but it only supports strongly-typed, structured logging.
61 //
62 // logger := zap.NewExample()
63 // defer logger.Sync()
64 // logger.Info("failed to fetch URL",
65 // zap.String("url", "http://example.com"),
66 // zap.Int("attempt", 3),
67 // zap.Duration("backoff", time.Second),
68 // )
69 //
70 // Choosing between the Logger and SugaredLogger doesn't need to be an
71 // application-wide decision: converting between the two is simple and
72 // inexpensive.
73 //
74 // logger := zap.NewExample()
75 // defer logger.Sync()
76 // sugar := logger.Sugar()
77 // plain := sugar.Desugar()
78 //
79 // # Configuring Zap
80 //
81 // The simplest way to build a Logger is to use zap's opinionated presets:
82 // NewExample, NewProduction, and NewDevelopment. These presets build a logger
83 // with a single function call:
84 //
85 // logger, err := zap.NewProduction()
86 // if err != nil {
87 // log.Fatalf("can't initialize zap logger: %v", err)
88 // }
89 // defer logger.Sync()
90 //
91 // Presets are fine for small projects, but larger projects and organizations
92 // naturally require a bit more customization. For most users, zap's Config
93 // struct strikes the right balance between flexibility and convenience. See
94 // the package-level BasicConfiguration example for sample code.
95 //
96 // More unusual configurations (splitting output between files, sending logs
97 // to a message queue, etc.) are possible, but require direct use of
98 // go.uber.org/zap/zapcore. See the package-level AdvancedConfiguration
99 // example for sample code.
100 //
101 // # Extending Zap
102 //
103 // The zap package itself is a relatively thin wrapper around the interfaces
104 // in go.uber.org/zap/zapcore. Extending zap to support a new encoding (e.g.,
105 // BSON), a new log sink (e.g., Kafka), or something more exotic (perhaps an
106 // exception aggregation service, like Sentry or Rollbar) typically requires
107 // implementing the zapcore.Encoder, zapcore.WriteSyncer, or zapcore.Core
108 // interfaces. See the zapcore documentation for details.
109 //
110 // Similarly, package authors can use the high-performance Encoder and Core
111 // implementations in the zapcore package to build their own loggers.
112 //
113 // # Frequently Asked Questions
114 //
115 // An FAQ covering everything from installation errors to design decisions is
116 // available at https://github.com/uber-go/zap/blob/master/FAQ.md.
117 package zap // import "go.uber.org/zap"
118