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logf
logf is a high-performance, zero-alloc logging library for Go applications with a minimal API overhead. It's also the fastest logfmt logging library for Go.
logf emits structured logs in logfmt style. logfmt is a flexible format that involves key=value pairs to emit structured log lines. logfmt achieves the goal of generating logs that are not just machine-friendly but also readable by humans, unlike the clunky JSON lines.
Example
package main
import (
"time"
"github.com/zerodha/logf"
)
func main() {
logger := logf.New(logf.Opts{
EnableColor: true,
Level: logf.DebugLevel,
CallerSkipFrameCount: 3,
EnableCaller: true,
TimestampFormat: time.RFC3339Nano,
DefaultFields: []any{"scope", "example"},
})
// Basic logs.
logger.Info("starting app")
logger.Debug("meant for debugging app")
// Add extra keys to the log.
logger.Info("logging with some extra metadata", "component", "api", "user", "karan")
// Log with error key.
logger.Error("error fetching details", "error", "this is a dummy error")
// Log the error and set exit code as 1.
logger.Fatal("goodbye world")
}
Text Output
timestamp=2022-07-07T12:09:10.221+05:30 level=info message="starting app"
timestamp=2022-07-07T12:09:10.221+05:30 level=info message="logging with some extra metadata" component=api user=karan
timestamp=2022-07-07T12:09:10.221+05:30 level=error message="error fetching details" error="this is a dummy error"
timestamp=2022-07-07T12:09:10.221+05:30 level=fatal message="goodbye world"
Console Output
Why another lib
There are several logging libraries, but the available options didn't meet our use case.
logf meets our constraints of:
- Clean API
- Minimal dependencies
- Structured logging but human-readable (
logfmt!) - Sane defaults out of the box
Benchmarks
You can run benchmarks with make bench.
No Colors (Default)
BenchmarkNoField-8 7884771 144.2 ns/op 0 B/op 0 allocs/op
BenchmarkOneField-8 6251565 186.7 ns/op 0 B/op 0 allocs/op
BenchmarkThreeFields-8 6273717 188.2 ns/op 0 B/op 0 allocs/op
BenchmarkErrorField-8 6687260 174.8 ns/op 0 B/op 0 allocs/op
BenchmarkHugePayload-8 3395139 360.3 ns/op 0 B/op 0 allocs/op
BenchmarkThreeFields_WithCaller-8 2764860 437.9 ns/op 216 B/op 2 allocs/op
With Colors
BenchmarkNoField_WithColor-8 6501867 186.6 ns/op 0 B/op 0 allocs/op
BenchmarkOneField_WithColor-8 5938155 205.7 ns/op 0 B/op 0 allocs/op
BenchmarkThreeFields_WithColor-8 4613145 379.4 ns/op 0 B/op 0 allocs/op
BenchmarkErrorField_WithColor-8 3512522 353.6 ns/op 0 B/op 0 allocs/op
BenchmarkHugePayload_WithColor-8 1520659 799.5 ns/op 0 B/op 0 allocs/op
For a comparison with existing popular libs, visit uber-go/zap#performance.
fix: remove pointer receiver
Bench stat:
Infof helpers
Hi,
logf looks awesome. What do you think to provide a
Infof(format, args...)variant ? I known this API won't allow to add fields, but that may be handy to format message.Regards,
draft: new field input format
Benchstat:
feat: Improve performance by writing directly to a buffer.
This also removes intermediary map & slices and writes directly to the buffer.
Benchmarks before this PR:
Benchmarks after this PR:
This makes this atleast 4x faster.
feat: Change any to interface{} to support Go 1.17.
Currently
logffails to compile on Go 1.17 due to usinganyin place ofinterface{}. I think there's no technical reason to not support 1.17 until it reaches end of life.We can change this to
anyonce1.17reaches end of life.fix: more tests, improve codecov, broken caller
Improves code coverage and adds + fixes while writing a few tests.
fix: avoid alloc using strings.IndexFunc instead
Uses strings.IndexFunc to avoid allocs.
After patching:
Before patching:
Benchstat:
More performance fixes
This is the new benchmarks: