midas: A Go repository from dtgorski

midas

Fast and cheap HTTP access logger middleware for Go.

Installation

go get -u github.com/dtgorski/midas

midas.Logger

... is a fast HTTP middleware for machine-readable response logging (access.log). Special care has been taken in order to ensure marginal heap memory footprint and low garbage collector pressure. The customized output layout has been chosen due to a specific requirement. If you need a different layout, feel free to fork.

Usage with a common router software:

import "github.com/dtgorski/midas"
.
.
router.Use(
    midas.Logger(os.Stdout),
    .
    .
)

Usage with handcrafted routing:

package main

import (
    "io"
    "log"
    "net/http"
    "os"

    "github.com/dtgorski/midas"
)

func main() {
    handler := http.HandlerFunc(
        func(w http.ResponseWriter, req *http.Request) {
            io.WriteString(w, "Hello, world!\n")
        },
    )
    logger := midas.Logger(os.Stdout)
    http.Handle("/", logger(handler))

    log.Fatal(http.ListenAndServe(":8080", nil))
}

Log output could look like:

0000-00-00T00:00:00+00:00 | 127.0.0.1 | - | GET /hello HTTP/1.1 | 200 | - | - | Mozilla/5.0 (X11; Linux… | - | - | 14 | 0.000 | -
0000-00-00T00:00:00+00:00 | 127.0.0.1 | - | GET / HTTP/1.1 | 200 | - | - | Mozilla/5.0 (X11; Linux… | - | - | 14 | 0.000 | -
0000-00-00T00:00:00+00:00 | 127.0.0.1 | - | GET / HTTP/1.1 | 200 | - | - | Mozilla/5.0 (X11; Linux… | - | - | 14 | 0.000 | -

A log line consists of fields separated by a pipe and is suffixed by a newline (\n). Non-printable whitespace characters and UTF-8 runes will be replaced by a period sign (.). The fields in their order:

access time
remote address without port
remote user, if any
request method, path, protocol
response status code
referer, if any
forwarded for, if any
user agent, if any
SSL protocol, if any
SSL cipher, if any
bytes sent in response
request time in seconds, three fractional digits
request id, if any

Although targeted for machine-reading (like log aggregators), the field values are padded with spaces for better human perception.

Artificial benchmark:

$ make bench 
CGO_ENABLED=0 go test -run=^$ -bench=. -benchmem
goos: linux
goarch: amd64
pkg: github.com/dtgorski/midas

BenchmarkLoggerConcatFullLine-8   2000000   850 ns/op   48 B/op   2 allocs/op

dtgorski/midas