1 // Copyright (c) 2016 Uber Technologies, Inc.
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:
10 // The above copyright notice and this permission notice shall be included in
11 // all copies or substantial portions of the Software.
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
21 // Package zap provides fast, structured, leveled logging.
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.
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,
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
44 // sugar := zap.NewExample().Sugar()
46 // sugar.Infow("failed to fetch URL",
47 // "url", "http://example.com",
49 // "backoff", time.Second,
51 // sugar.Infof("failed to fetch URL: %s", "http://example.com")
53 // By default, loggers are unbuffered. However, since zap's low-level APIs
54 // allow buffering, calling Sync before letting your process exit is a good
57 // In the rare contexts where every microsecond and every allocation matter,
58 // use the Logger. It's even faster than the SugaredLogger and allocates far
59 // less, but it only supports strongly-typed, structured logging.
60 // logger := zap.NewExample()
61 // defer logger.Sync()
62 // logger.Info("failed to fetch URL",
63 // zap.String("url", "http://example.com"),
64 // zap.Int("attempt", 3),
65 // zap.Duration("backoff", time.Second),
68 // Choosing between the Logger and SugaredLogger doesn't need to be an
69 // application-wide decision: converting between the two is simple and
71 // logger := zap.NewExample()
72 // defer logger.Sync()
73 // sugar := logger.Sugar()
74 // plain := sugar.Desugar()
78 // The simplest way to build a Logger is to use zap's opinionated presets:
79 // NewExample, NewProduction, and NewDevelopment. These presets build a logger
80 // with a single function call:
81 // logger, err := zap.NewProduction()
83 // log.Fatalf("can't initialize zap logger: %v", err)
85 // defer logger.Sync()
87 // Presets are fine for small projects, but larger projects and organizations
88 // naturally require a bit more customization. For most users, zap's Config
89 // struct strikes the right balance between flexibility and convenience. See
90 // the package-level BasicConfiguration example for sample code.
92 // More unusual configurations (splitting output between files, sending logs
93 // to a message queue, etc.) are possible, but require direct use of
94 // go.uber.org/zap/zapcore. See the package-level AdvancedConfiguration
95 // example for sample code.
99 // The zap package itself is a relatively thin wrapper around the interfaces
100 // in go.uber.org/zap/zapcore. Extending zap to support a new encoding (e.g.,
101 // BSON), a new log sink (e.g., Kafka), or something more exotic (perhaps an
102 // exception aggregation service, like Sentry or Rollbar) typically requires
103 // implementing the zapcore.Encoder, zapcore.WriteSyncer, or zapcore.Core
104 // interfaces. See the zapcore documentation for details.
106 // Similarly, package authors can use the high-performance Encoder and Core
107 // implementations in the zapcore package to build their own loggers.
109 // Frequently Asked Questions
111 // An FAQ covering everything from installation errors to design decisions is
112 // available at https://github.com/uber-go/zap/blob/master/FAQ.md.
113 package zap // import "go.uber.org/zap"