zap

Blazing fast, structured, leveled logging in Go.

Programming language: Go

License: MIT License

Tags: Logging     Structured Logging     Performance    

Latest version: v1.19.1

README

:zap: zap

Blazing fast, structured, leveled logging in Go.

Installation

go get -u go.uber.org/zap

Note that zap only supports the two most recent minor versions of Go.

Quick Start

In contexts where performance is nice, but not critical, use the SugaredLogger. It's 4-10x faster than other structured logging packages and includes both structured and printf-style APIs.

logger, _ := zap.NewProduction()
defer logger.Sync() // flushes buffer, if any
sugar := logger.Sugar()
sugar.Infow("failed to fetch URL",
  // Structured context as loosely typed key-value pairs.
  "url", url,
  "attempt", 3,
  "backoff", time.Second,
)
sugar.Infof("Failed to fetch URL: %s", url)

When performance and type safety are critical, use the Logger. It's even faster than the SugaredLogger and allocates far less, but it only supports structured logging.

logger, _ := zap.NewProduction()
defer logger.Sync()
logger.Info("failed to fetch URL",
  // Structured context as strongly typed Field values.
  zap.String("url", url),
  zap.Int("attempt", 3),
  zap.Duration("backoff", time.Second),
)

See the documentation and [FAQ](FAQ.md) for more details.

Performance

For applications that log in the hot path, reflection-based serialization and string formatting are prohibitively expensive — they're CPU-intensive and make many small allocations. Put differently, using encoding/json and fmt.Fprintf to log tons of interface{}s makes your application slow.

Zap takes a different approach. It includes a reflection-free, zero-allocation JSON encoder, and the base Logger strives to avoid serialization overhead and allocations wherever possible. By building the high-level SugaredLogger on that foundation, zap lets users choose when they need to count every allocation and when they'd prefer a more familiar, loosely typed API.

As measured by its own benchmarking suite, not only is zap more performant than comparable structured logging packages — it's also faster than the standard library. Like all benchmarks, take these with a grain of salt.1

Log a message and 10 fields:

Package	Time	Time % to zap	Objects Allocated
:zap: zap	862 ns/op	+0%	5 allocs/op
:zap: zap (sugared)	1250 ns/op	+45%	11 allocs/op
zerolog	4021 ns/op	+366%	76 allocs/op
go-kit	4542 ns/op	+427%	105 allocs/op
apex/log	26785 ns/op	+3007%	115 allocs/op
logrus	29501 ns/op	+3322%	125 allocs/op
log15	29906 ns/op	+3369%	122 allocs/op

Log a message with a logger that already has 10 fields of context:

Package	Time	Time % to zap	Objects Allocated
:zap: zap	126 ns/op	+0%	0 allocs/op
:zap: zap (sugared)	187 ns/op	+48%	2 allocs/op
zerolog	88 ns/op	-30%	0 allocs/op
go-kit	5087 ns/op	+3937%	103 allocs/op
log15	18548 ns/op	+14621%	73 allocs/op
apex/log	26012 ns/op	+20544%	104 allocs/op
logrus	27236 ns/op	+21516%	113 allocs/op

Log a static string, without any context or printf-style templating:

Package	Time	Time % to zap	Objects Allocated
:zap: zap	118 ns/op	+0%	0 allocs/op
:zap: zap (sugared)	191 ns/op	+62%	2 allocs/op
zerolog	93 ns/op	-21%	0 allocs/op
go-kit	280 ns/op	+137%	11 allocs/op
standard library	499 ns/op	+323%	2 allocs/op
apex/log	1990 ns/op	+1586%	10 allocs/op
logrus	3129 ns/op	+2552%	24 allocs/op
log15	3887 ns/op	+3194%	23 allocs/op

Development Status: Stable

All APIs are finalized, and no breaking changes will be made in the 1.x series of releases. Users of semver-aware dependency management systems should pin zap to ^1.

Contributing

We encourage and support an active, healthy community of contributors — including you! Details are in the [contribution guide](CONTRIBUTING.md) and the [code of conduct](CODE_OF_CONDUCT.md). The zap maintainers keep an eye on issues and pull requests, but you can also report any negative conduct to [email protected]. That email list is a private, safe space; even the zap maintainers don't have access, so don't hesitate to hold us to a high standard.

Released under the [MIT License](LICENSE.txt).

1 In particular, keep in mind that we may be benchmarking against slightly older versions of other packages. Versions are pinned in the benchmarks/go.mod file. ↩