📝 [Proposal]: Add support for standard log formats

[gaby]

Feature Proposal Description

The current logger middleware is using a custom log format. We should provide 4-5 standard log formats that are industry standard for users to use. This would allow the logs generated by Fiber to be more easy to parse by standard logging/metrics tools.

We should include:

• Apache Common log format
• Apache Combined log format
• NGINX Style log format
• Fiber Default (Current)
• Common Log Format (CLF)

These should be defined in a format.go file under the middleware.

Alignment with Express API

The apache common is the default format for expressjs/morgan middleware.

HTTP RFC Standards Compliance

n/a

API Stability

Would allow fiber logs to be more easy to parse by industry standard tools.

Feature Examples

Generated log formats by `OpenAI - o1`. Need to be verified for accuracy.


// FormatCommonLog (CLF) is fully compliant with the “Common Log Format.”
var FormatCommonLog = "${ip} - - [${time}] \"${method} ${url} ${protocol}\" ${status} ${clfBytesSent}\n"

// FormatApacheCommon is basically CLF but usually doesn’t strictly require
// a dash for unknown content length. Often used by default in Apache.
var FormatApacheCommon = "${ip} - - [${time}] \"${method} ${url} ${protocol}\" ${status} ${bytesSent}\n"

// FormatApacheCombined extends the Apache Common to add referer and user-agent.
var FormatApacheCombined = "${ip} - - [${time}] \"${method} ${url} ${protocol}\" ${status} ${bytesSent} \"${referer}\" \"${ua}\"\n"

// FormatNginx is a typical Nginx-style format (like Combined).
var FormatNginx = "${ip} - - [${time}] \"${method} ${url} ${protocol}\" ${status} ${bytesSent} \"${referer}\" \"${ua}\"\n"

// FormatJSON is an example for JSON-based logging.
var FormatJSON = "{\"time\":\"${time}\",\"ip\":\"${ip}\",\"method\":\"${method}\",\"url\":\"${url}\",\"status\":${status},\"bytesSent\":${bytesSent}}\n"

Checklist:

• I agree to follow Fiber's Code of Conduct.
• I have searched for existing issues that describe my proposal before opening this one.
• I understand that a proposal that does not meet these guidelines may be closed without explanation.

[edvardsanta]

I am currently working on this and will open a PR soon.

[edvardsanta]

I am considering how best to handle log formats and would like to get some insights.

Currently, i am thinking of two options:

1. Using Enum-like:

const (
    FormatDefault Format = iota
    FormatCommonLog
    FormatApacheCommon
    FormatApacheCombined
    FormatNginx
    FormatJSON
)

var formatStrings = map[Format]string{
    FormatDefault:        "${time}] ${ip} ${status} - ${latency} ${method} ${path} ${error}",
    FormatCommonLog:      "${ip} - - [${time}] \"${method} ${url} ${protocol}\" ${status} ${clfBytesSent}\n",
    FormatApacheCommon:   "${ip} - - [${time}] \"${method} ${url} ${protocol}\" ${status} ${bytesSent}\n",
    FormatApacheCombined: "${ip} - - [${time}] \"${method} ${url} ${protocol}\" ${status} ${bytesSent} \"${referer}\" \"${ua}\"\n",
    FormatNginx:          "${ip} - - [${time}] \"${method} ${url} ${protocol}\" ${status} ${bytesSent} \"${referer}\" \"${ua}\"\n",
    FormatJSON:           "{\"time\":\"${time}\",\"ip\":\"${ip}\",\"method\":\"${method}\",\"url\":\"${url}\",\"status\":${status},\"bytesSent\":${bytesSent}}\n",
}

2. Using Strings Directly

var formatStrings = map[string]string{
    "default":  "${time}] ${ip} ${status} - ${latency} ${method} ${path} ${error}",
    "common":   "${ip} - - [${time}] \"${method} ${url} ${protocol}\" ${status} ${clfBytesSent}\n",
    "apache":   "${ip} - - [${time}] \"${method} ${url} ${protocol}\" ${status} ${bytesSent}\n",
    "combined": "${ip} - - [${time}] \"${method} ${url} ${protocol}\" ${status} ${bytesSent} \"${referer}\" \"${ua}\"\n",
    "nginx":    "${ip} - - [${time}] \"${method} ${url} ${protocol}\" ${status} ${bytesSent} \"${referer}\" \"${ua}\"\n",
    "json":     "{\"time\":\"${time}\",\"ip\":\"${ip}\",\"method\":\"${method}\",\"url\":\"${url}\",\"status\":${status},\"bytesSent\":${bytesSent}}\n",
}

Since this is my first contribution to Fiber, I would really appreciate feedback from the community. Which approach fits Fiber’s logger best?

[edvardsanta]

I am considering how best to handle log formats and would like to get some insights.

Currently, i am thinking of two options:

1. Using Enum-like:

const (
FormatDefault Format = iota
FormatCommonLog
FormatApacheCommon
FormatApacheCombined
FormatNginx
FormatJSON
)

var formatStrings = map[Format]string{
FormatDefault: "${time}] ${ip} ${status} - ${latency} ${method} ${path} ${error}",
FormatCommonLog: "${ip} - - [${time}] "${method} ${url} ${protocol}" ${status} ${clfBytesSent}\n",
FormatApacheCommon: "${ip} - - [${time}] "${method} ${url} ${protocol}" ${status} ${bytesSent}\n",
FormatApacheCombined: "${ip} - - [${time}] "${method} ${url} ${protocol}" ${status} ${bytesSent} "${referer}" "${ua}"\n",
FormatNginx: "${ip} - - [${time}] "${method} ${url} ${protocol}" ${status} ${bytesSent} "${referer}" "${ua}"\n",
FormatJSON: "{"time":"${time}","ip":"${ip}","method":"${method}","url":"${url}","status":${status},"bytesSent":${bytesSent}}\n",
}
2. Using Strings Directly

var formatStrings = map[string]string{
"default": "${time}] ${ip} ${status} - ${latency} ${method} ${path} ${error}",
"common": "${ip} - - [${time}] "${method} ${url} ${protocol}" ${status} ${clfBytesSent}\n",
"apache": "${ip} - - [${time}] "${method} ${url} ${protocol}" ${status} ${bytesSent}\n",
"combined": "${ip} - - [${time}] "${method} ${url} ${protocol}" ${status} ${bytesSent} "${referer}" "${ua}"\n",
"nginx": "${ip} - - [${time}] "${method} ${url} ${protocol}" ${status} ${bytesSent} "${referer}" "${ua}"\n",
"json": "{"time":"${time}","ip":"${ip}","method":"${method}","url":"${url}","status":${status},"bytesSent":${bytesSent}}\n",
}
Since this is my first contribution to Fiber, I would really appreciate feedback from the community. Which approach fits Fiber’s logger best?

I will open the PR with the second approach, but we can keep the discussion

[gaby]

@edvardsanta Thank you, will comment in a bit

[gaby]

@edvardsanta We can remove this format

app.Use(logger.New(logger.Config{Format: "common"}))

and only do like you did in the PR with predefined const values. The names could use some work, but getting the tests passing first then we can talk about naming