New feature gelf "raw" message processing

[131]

Description

Today,the gelf driver take a line and use it as the "short" version of a message, adding all metadata in a surrounding JSON armor.

I suggest a new gelf-raw-json option to parse every incoming log line as a JSON payload, and merge all drivers metadata in it.
That will dramaticaly increase the gelf driver capability yet, in a safe design.

This is simple enough for me to implement, here is the related PR

[cpuguy83]

to parse every incoming log line as a JSON payload, and merge all drivers metadata in it.

What does this mean? Do you have an example?

[131]

What does this mean? Do you have an example?

Let say my application output (on stderr) native JSON payload
{"message": "this is something", "source_file": "/path/to/my/exe", "severity": "WHATEVER"}

Currently, using the GELF driver, all this line will end up in a super structure

{
     "_container_id":   info.ContainerID,
    "_container_name": info.Name(),
    "_image_id":       info.ContainerImageID,
    "_image_name":     info.ContainerImageName,
    "_command":        info.Command(),
    "_tag":            tag,
    "_created":        info.ContainerCreated,
    "message" : "{\"message\":\"this is something\",\"source_file\":\"/path/to/my/exe\",\"severity\":\"WHATEVER\"}"

}

All metadata will be lost, and post processing will be required.

With gelf-json-raw = true, gelf will receive,

{
     "message": "this is something",
     "source_file": "/path/to/my/exe",
     "severity": "WHATEVER",

     "_container_id":   info.ContainerID,
    "_container_name": info.Name(),
    "_image_id":       info.ContainerImageID,
    "_image_name":     info.ContainerImageName,
    "_command":        info.Command(),
    "_tag":            tag,
    "_created":        info.ContainerCreated,
}

All metadata are preserved and usable by gralog.

Please note that all native driver field will take precedence on untrusted payload.