Research logging libraries, choose one and deploy it in tofn and tofnd

[sdaveas]

No description provided.

[ggutoski]

Configurability:

• "context", which is basically a prefix string. eg. "tofn party X, round Y, event description". The "tofn", "party X", "round Y" parts should be part of the context prefix, so I need only say log("event description)
• Need the ability to direct logging output. eg. ignore, file, stdout, etc
• tofnd is the end product: it configures the logger and passes it to tofn. tofn is the library: it must use the logger received from the consumer of the library (eg. tofnd) in whatever configuration is specified by that consumer.

[sdaveas]

log is the most popular library for logs and is actively maintained the rust team. We should definitely use that.

log is a framework and isn't very useful by itself, though. It has to be combined with a logger to print outputs. simplelog is quite popular and active, and seems to support everything we need. I'll start with this and if we face any limitations it should be easy to swap into different one.

[sdaveas]

It turns out that logging in asynchronous systems is less trivial that traditional systems. tracing is a logging library we can use, that is build for sync systems like tokio and also uses log under the hood.

tracing produces log messages from spawned tasks which are then consumed by a subscriber (tracing-subscriber serves that purpose).

[ggutoski]

Yikes! Tofn does not have any async code. Is it possible to use something like log or simplelog in tofn? Can we restrict use of async logger only to where it's needed in tofnd?

[sdaveas]

Yeah, I suppose that we can do that. In terms of complexity things don't seem that bad, though.

fn foo {
    let ctx: &str = ... // creates 'keygen [key] party [A] with (t,n)=(0,2)' str
    let span = span!(Level::INFO, "keygen", ctx);
    error!("keygen failure");
}

So far, the result looks like this

Apr 07 21:41:05.523 ERROR Keygen{msg="keygen [Gus-test-key] party [A] with (t,n)=(0,2)"}: tofnd::gg20: keygen failure

[sdaveas]

@ggutoski , I recommend to use tracing for tofn logs.

Since tofn is a library and is only called externally, it doesn't have to carry a subscriber to gather logs; it just need to emit them. The only changes that are needed at tofn is to replace println!s with info! (or warn!, etc). If we do that, we get a nice combo of logs in tofnd.

The following is a tofn warning message when running tofnd's tests:

Apr 08 17:42:25.069  WARN Sign:Handle{log="sign [Gus-test-sig] party [uid:A, share:1/2]"}:Protocol{round=0}: tofn::protocol::gg20::sign::protocol: participant 1 overwrite existing R1Bcast msg from 1
                      ^    ^     ^         ---------------------------------------------      ^    --------                                        --------------------------------------------------
                      |    |     |                               |                            |      |                                                                    |
          tofn log type    |  tofnd sub-function <--------- log prefix of                     |   log prefix of                                                     tofn warning message
                           |                                                                  |      |
                           |                                                                  |      v
                      tofnd function                                                    tofnd sub-sub-function