78 lines
3.2 KiB
Markdown
78 lines
3.2 KiB
Markdown
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# log15 [](https://godoc.org/github.com/inconshreveable/log15) [](https://travis-ci.org/inconshreveable/log15)
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Package log15 provides an opinionated, simple toolkit for best-practice logging in Go (golang) that is both human and machine readable. It is modeled after the Go standard library's [`io`](https://golang.org/pkg/io/) and [`net/http`](https://golang.org/pkg/net/http/) packages and is an alternative to the standard library's [`log`](https://golang.org/pkg/log/) package.
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## Features
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- A simple, easy-to-understand API
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- Promotes structured logging by encouraging use of key/value pairs
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- Child loggers which inherit and add their own private context
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- Lazy evaluation of expensive operations
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- Simple Handler interface allowing for construction of flexible, custom logging configurations with a tiny API.
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- Color terminal support
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- Built-in support for logging to files, streams, syslog, and the network
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- Support for forking records to multiple handlers, buffering records for output, failing over from failed handler writes, + more
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## Versioning
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The API of the master branch of log15 should always be considered unstable. If you want to rely on a stable API,
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you must vendor the library.
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## Importing
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```go
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import log "github.com/inconshreveable/log15"
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```
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## Examples
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```go
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// all loggers can have key/value context
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srvlog := log.New("module", "app/server")
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// all log messages can have key/value context
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srvlog.Warn("abnormal conn rate", "rate", curRate, "low", lowRate, "high", highRate)
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// child loggers with inherited context
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connlog := srvlog.New("raddr", c.RemoteAddr())
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connlog.Info("connection open")
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// lazy evaluation
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connlog.Debug("ping remote", "latency", log.Lazy{pingRemote})
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// flexible configuration
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srvlog.SetHandler(log.MultiHandler(
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log.StreamHandler(os.Stderr, log.LogfmtFormat()),
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log.LvlFilterHandler(
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log.LvlError,
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log.Must.FileHandler("errors.json", log.JSONFormat()))))
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```
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Will result in output that looks like this:
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```
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WARN[06-17|21:58:10] abnormal conn rate module=app/server rate=0.500 low=0.100 high=0.800
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INFO[06-17|21:58:10] connection open module=app/server raddr=10.0.0.1
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```
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## Breaking API Changes
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The following commits broke API stability. This reference is intended to help you understand the consequences of updating to a newer version
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of log15.
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- 57a084d014d4150152b19e4e531399a7145d1540 - Added a `Get()` method to the `Logger` interface to retrieve the current handler
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- 93404652ee366648fa622b64d1e2b67d75a3094a - `Record` field `Call` changed to `stack.Call` with switch to `github.com/go-stack/stack`
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- a5e7613673c73281f58e15a87d2cf0cf111e8152 - Restored `syslog.Priority` argument to the `SyslogXxx` handler constructors
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## FAQ
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### The varargs style is brittle and error prone! Can I have type safety please?
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Yes. Use `log.Ctx`:
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```go
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srvlog := log.New(log.Ctx{"module": "app/server"})
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srvlog.Warn("abnormal conn rate", log.Ctx{"rate": curRate, "low": lowRate, "high": highRate})
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```
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## License
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Apache
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