W3C extended log file format fromatter about log

[phuslu]

what if https://play.golang.org/p/t3SBYkF4YRl or https://play.golang.org/p/eNtrQBmUrSn ?

[syncplify]

That's a good approach. I'll toy a little bit with it on Monday, to see what I can do.

The "log header" part each time a file is rotated remains an open issue. I could add lines by logging them of course, but if lines come in at the same time from other groutines, the header may end up intertwined with those lines. Headers should be "atomically written".

But thank you for pointing me the right direction regarding writer-chaining to address the W3C log format. Much appreciated.

[phuslu]

For the "log header", this is a problem. When I implementing csv logger, I also encountered this problem.

Currently I have no good ideas to solve this problem in a pretty way.

[phuslu]

A straightforward way is, add a LogHeader callback to FileWriter

type FileWriter struct {
	// LogHeader specifies an optional log header after rotation
	LogHeader func(fileinfo os.FileInfo) []byte
}

But this a little ugly, because it tied logger and writer. Any thoughts/comments ?

[syncplify]

I agree, this is an "easy" solution but comes with a "cost" (logger and writer being tied as you mentioned). On the other hand the weight of this tie wouldn't be heavier than the Rotate callback in my humble opinion. Leaving the callback function pointer to nil would ensure the Writer works just like it does now, but would provide an option for those who need it to specify a custom behavior that only applies to this writer.

If, on the other hand, we think that a custom atomic header would be useful for other writers as well, then maybe we can come up with a dedicated additional interface{} that all Writers implement (on top of io.Writer and io.WriteCloser) although this could end up being slightly more cumbersome to implement.

One more possibility could be (consequences to be evaluated) to "derive" a descendant of FileWriter... something like:

type FileWriterWithHeaderCallback struct {
    FileWriter
    /...
}

(but this may or may not be a rabbit hole, just put it out there as food for thoughts)

[phuslu]

I create a PR based on "Header" callback idea, #42 please take a look and comment, thanks!

[syncplify]

Checked your PR #42 and it looks perfect to me. Easy, elegant, no frills, just plain effective.

[phuslu]

thanks, I merged and tagged v1.0.73