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https://github.com/uber-go/zap

Blazing fast, structured, leveled logging in Go.
https://github.com/uber-go/zap

golang logging structured-logging zap

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Blazing fast, structured, leveled logging in Go.

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# :zap: zap






Blazing fast, structured, leveled logging in Go.



![Zap logo](assets/logo.png)



[![GoDoc][doc-img]][doc] [![Build Status][ci-img]][ci] [![Coverage Status][cov-img]][cov]






## 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.



```go

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.



```go

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][doc] 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](#footnote-versions)



Log a message and 10 fields:



| Package | Time | Time % to zap | Objects Allocated |

| :------ | :--: | :-----------: | :---------------: |

| :zap: zap | 656 ns/op | +0% | 5 allocs/op

| :zap: zap (sugared) | 935 ns/op | +43% | 10 allocs/op

| zerolog | 380 ns/op | -42% | 1 allocs/op

| go-kit | 2249 ns/op | +243% | 57 allocs/op

| slog (LogAttrs) | 2479 ns/op | +278% | 40 allocs/op

| slog | 2481 ns/op | +278% | 42 allocs/op

| apex/log | 9591 ns/op | +1362% | 63 allocs/op

| log15 | 11393 ns/op | +1637% | 75 allocs/op

| logrus | 11654 ns/op | +1677% | 79 allocs/op



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



| Package | Time | Time % to zap | Objects Allocated |

| :------ | :--: | :-----------: | :---------------: |

| :zap: zap | 67 ns/op | +0% | 0 allocs/op

| :zap: zap (sugared) | 84 ns/op | +25% | 1 allocs/op

| zerolog | 35 ns/op | -48% | 0 allocs/op

| slog | 193 ns/op | +188% | 0 allocs/op

| slog (LogAttrs) | 200 ns/op | +199% | 0 allocs/op

| go-kit | 2460 ns/op | +3572% | 56 allocs/op

| log15 | 9038 ns/op | +13390% | 70 allocs/op

| apex/log | 9068 ns/op | +13434% | 53 allocs/op

| logrus | 10521 ns/op | +15603% | 68 allocs/op



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



| Package | Time | Time % to zap | Objects Allocated |

| :------ | :--: | :-----------: | :---------------: |

| :zap: zap | 63 ns/op | +0% | 0 allocs/op

| :zap: zap (sugared) | 81 ns/op | +29% | 1 allocs/op

| zerolog | 32 ns/op | -49% | 0 allocs/op

| standard library | 124 ns/op | +97% | 1 allocs/op

| slog | 196 ns/op | +211% | 0 allocs/op

| slog (LogAttrs) | 200 ns/op | +217% | 0 allocs/op

| go-kit | 213 ns/op | +238% | 9 allocs/op

| apex/log | 771 ns/op | +1124% | 5 allocs/op

| logrus | 1439 ns/op | +2184% | 23 allocs/op

| log15 | 2069 ns/op | +3184% | 20 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).



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. [↩](#anchor-versions)



[doc-img]: https://pkg.go.dev/badge/go.uber.org/zap

[doc]: https://pkg.go.dev/go.uber.org/zap

[ci-img]: https://github.com/uber-go/zap/actions/workflows/go.yml/badge.svg

[ci]: https://github.com/uber-go/zap/actions/workflows/go.yml

[cov-img]: https://codecov.io/gh/uber-go/zap/branch/master/graph/badge.svg

[cov]: https://codecov.io/gh/uber-go/zap

[benchmarking suite]: https://github.com/uber-go/zap/tree/master/benchmarks

[benchmarks/go.mod]: https://github.com/uber-go/zap/blob/master/benchmarks/go.mod