fluent-cat --format none added

[kawanet]

Input plugins accept format none since #182 but fluent-cat doesn't yet. The tiny patch allows fluent-cat accept it.

echo "a plain text message" | fluent-cat --none debug
echo "another plain text message" | fluent-cat --format none --message-key message debug

The structured raw logs comes here again! I rarely agree for fluent-cat to accept rest of all formats as it should be kept simple and light weighted as it were. I guess, however, that the plain text format is enough convenient for plain simple usages expected for fluent-cat.

The optional --message-key parameter could be removed to keep it simple.

It seems that -f message or -f plain could be more clear rather than -f none at this usage above, by the way. It should follow the vocabulary at format parameter at input plugins.

[sonots]

👍 LGTM

[repeatedly]

If we go with --none, next patch becomes --csv?
So I think --format none is better for the future.

In the first place, --msgpack / --json options are bad for me...

[kawanet]

Yay! Thank you both for your feedbacks!

The primary objective at the PR is that --format option accepts none value. The other options of both --none and --message-key are not necessary for me. I could agree to remove both, at first.

Usage: fluent-cat [options] <tag>
    -p, --port PORT                  fluent tcp port (default: 24224)
    -h, --host HOST                  fluent host (default: 127.0.0.1)
    -u, --unix                       use unix socket instead of tcp
    -s, --socket PATH                unix socket path (default: /var/run/fluent/fluent.sock)
    -f, --format FORMAT              input format (default: json)
        --json                       same as: -f json
        --msgpack                    same as: -f msgpack
        --none                       same as: -f none
        --message-key KEY            key field for none format (default: message)

(1) adding --csv in the future?

On a care for further extension to accept the other formats like --csv in the future, I don't think they SHOULD NOT come down to fluent-cat. Once fluent-cat accepts --format none, users could transform it via fluent-plugin-parser, etc. on a later stage of fluentd. I prefer fluent-cat stay simple but not fat.

(2) removing --none?

The only value of the independent --none option is to give the same manner of the existing --msgpack and --json options as you mentioned. To be honest, I have had a little worry about the independent --none which could misguide users to expect a wrong feature something like /dev/null blackhole. Instead of the spell of --none, --plain could be another option to make it clear. However, plain is not a vocabulary of input plugins, but none is. The help message above could guide users to understand it rather than misunderstand it. This means --none is only worth with the help message ;)

Conclusion on my view:

• --format none gives the most simple way to store logs to fluentd because none is the most plain and general format.
• The alias of --none is almost acceptable because (1) --csv should not come in the future, (2) the line of --none at the help message could show the same manner of the existing options of --json and --msgpack.
• Removing --json and --msgpack is not a business of the PR. The other PR may manage it. I don't need to remove them though.
• --message-key could be removed for fluent-cat to keep itself most simple in design. Any opinions on it?

[repeatedly]

I don't have strong counter opinions.
fluent-cat is testing tools and shorter options are useful for beginners.

If there is no concerns, I will merge this PR later.