kr / logfmt Goto Github PK

values := map[string]string{}
logfmt.Unmarshal(log_content, &values)

The code will crash; must I use a specified struct?

I adopted the code in the example into a main package and expected the program to produce no errors. However, when I ran the program, I received this:

$ go version
go version go1.0.3

$ go run x.go
2013/04/30 18:22:30 err="invalid syntax"

Here is x.go:

package main

import (
    "bytes"
    "fmt"
    "github.com/kr/logfmt"
    "log"
    "strconv"
)

type Measurement struct {
    Key  string
    Val  float64
    Unit string // (e.g. ms, MB, etc)
}

type Measurements []*Measurement

var measurePrefix = []byte("measure.")

func (mm *Measurements) HandleLogfmt(key, val []byte) error {
    if !bytes.HasPrefix(key, measurePrefix) {
        return nil
    }
    i := bytes.LastIndexFunc(val, isDigit)
    v, err := strconv.ParseFloat(string(val[:i+1]), 10)
    if err != nil {
        return err
    }
    m := &Measurement{
        Key:  string(key[len(measurePrefix):]),
        Val:  v,
        Unit: string(val[i+1:]),
    }
    *mm = append(*mm, m)
    return nil
}

// return true if r is an ASCII digit only, as opposed to unicode.IsDigit.
func isDigit(r rune) bool {
    return '0' <= r && r <= '9'
}

func main() {
    var data = []byte("measure.a=1ms measure.b=10 measure.c=100MB measure.d=1s garbage")

    mm := make(Measurements, 0)
    if err := logfmt.Unmarshal(data, &mm); err != nil {
        log.Fatalf("err=%q", err)
    }
    for _, m := range mm {
        fmt.Printf("%v\n", *m)
    }

}

The spec specifies that values containing bytes less than or equal to " " (\x20) must be quoted but not escaped.
Specifically with regards to newlines this is rather problematic when parsing incomplete logstreams. Take this example:

...
msg=" level=info time=2021-07-30T08:24:01.604Z
msg="
...

Apologies for the rather contrived scenario, but it shows the ambiguity when parsing a logstream rather well. The point here is you don't know whether a newline is the beginning, middle, or end of a log entry. The complete output for the above record(s) could look like this:

msg=" level=info time=2021-07-30T08:24:01.604Z
msg="

So: {msg: " level=info time=2021-07-30T08:24:01.604Z\nmsg="}
Or this:

out="
msg=" level=info time=2021-07-30T08:24:01.604Z
msg="
" level=error time=2021-07-30T08:24:05.004Z

So: {out: "\nmsg=", level: "info", time: "2021-07-30T08:24:01.604Z"} and {msg: "\n", level: "error", time: "2021-07-30T08:24:05.004Z"}

The bigger issue here is that there is no way to get back to a "clean slate". The second version could have variations that never cause a parsing error and the parser would keep on having an off-by-one error:

...
moreLines x=1 f="
out="
msg=" level=info time=2021-07-30T08:24:01.604Z
msg="
" level=error time=2021-07-30T08:24:05.004Z
x="is this quoted, who knows
" it might be. It all depends on the first line.

The above could be a long string value, or it could be a bunch of keys with the value true

Before I raise a PR, any thoughts as to why not?

A follow-up on https://gist.github.com/kr/0e8d5ee4b954ce604bb2 really. I would be interested in helping out and make logfmt more official and supported. Is there some interest in this ?

At this point there is an EBNFish syntax and a reference implementation. I think there are still clarifications to be made, for example the encoding of the content (I would say binary), if there is a limit on the length of the line (I would say it depends on the transport but 4k should be a safe bet). Ideally there would exist a test suite to help other languages implement the parsing and production of this format and an official website.

Let me know if I can help with any of these (except the website, I suck at design). Cheers !

The README says:

Go package for parsing (and, eventually, generating) log lines in the logfmt style.

Is there still interest in working on the generating part?

I've been contributing to both log15 and gokit/log. log15 already supports a logfmt flavor of output, and gokit/log would like to. In go-kit/kit#34 I suggested it would be nice to have an encoding/json or encoding/xml style package that supports marshaling and unmarshaling logfmt data with support for the encoding.TextMarshaler and encoding.TextUnmarshaller interfaces.

Is there interest in doing that work here? If not, would @kr and @bmizerany object to a new project attempting to create such an API for logfmt, possibly starting as a fork of this repo? Would you be willing to help with feedback if questions arise regarding logfmt specifics?

It seems that the default delimiter used is (space).
I'm using the logfmt parser in fluent-bit, but have a use case where i need the delimiter to be , (comma space).
Is this a built-in functionality of the logfmt package?

Below is a sample log file which contains a message field inside the json array

{"timestamp":"2021-05-26T20:45:08.751Z","sequence":568,"loggerClassName":"org.jboss.logging.Logger","loggerName":"org.keycloak.events","level":"WARN","message":"type=LOGIN_ERROR, realmId=master, clientId=ui, userId=92cdda0b-28b4-46df-8f81-48458708eb48, ipAddress=1.1.1.1, error=invalid_user_credentials, auth_method=openid-connect, auth_type=code, redirect_uri=https://centralus-v2.mydomain.com/signin, code_id=f8d8be37-eb0e-40cc-a507-db5862cd0719, username=[email protected], authSessionParentId=f8d8be37-eb0e-40cc-a507-db5862cd0719, authSessionTabId=pvMeYvDFhU4","threadName":"default task-2","threadId":147,"mdc":{},"ndc":"","hostName":"keycloak-b9576f6db-np5dx","processName":"jboss-modules.jar","processId":617}

It would help with distribution integration.
Thanks.