cmd,core,eth,logger: prettify logging

[whilei]

problem

Normal logging is kind of "noisy," as @splix complains in #410. With that in mind, making logs "pretty" also removes important debugging information.

solution

Makes pretty logs when a single flag --pretty is used. The reason I used opt-in prettiness in 199652e is because I believe geth should use defaults that are most useful for developers. While indeed it's important for beginners and laymen to have access to an approachable interface, I t hink we'd be shooting ourselves in the foot (it's hard enough getting issue contributors to include any logs) and moving away from a "technology first" principle by establishing a default prioritizing the 💄 before the 🔧 .

With that said, there's very little I love more than a good interface. There's still a long way to go IMO with formatting the STATUS logs, adding possible other STATUS logs besides SYNC, and improving the design of the non-textual visual interface (eg. domino effect); but this is a start.

note here that I'm overriding --log-status interval manually; the default for --pretty is sync=15 [seconds]

solve specs

• only verbosity=error lines are shown
• geth still logs normal configuration stuff on startup
• file traces will be excluded unless debug.verbosity(5) is used to set verbosity on the fly (like if user is experiencing some weirdness or just wants a closer look for whatever reason) OR if debug.verbosityTraceFloor(1) is used to set the minimum global verbosity threshold determining if file traces should be included
• status logs will be dispatched every 15 seconds, including a new block progress display I call the domino effect 🃏

All of these defaults can be overridden manually with their respective flags.

Further, in case of severity=error or severity=fatal, the calling file trace will always be shown.

As explained in geth help:

  --pretty							Use pretty defaults for logging (verbosity=1,vmodule='cmd/geth/*=3',verbosity-trace-floor=5,log-status='sync=15')

how it works

As-is, there are two "dimensions" of logging: verbosity and severity.

• Verbosity means "how much to say." It scales the granularity and detail of reporting.
• Severity means "how to say it." It scales the importance, relative to verbosity.

• TODO: explain this more

The domino effect uses the number of dominos to represent the number of blocks imported since last log, and the domino dot-number to represent number of transactions per block (eg 🁣 = 0 txs, 🂓 = 12+ txs). Representing blocks imported and txs are currently simply 1:1 with actual blocks/txs, but eventually should be scaled dynamically (with a log function... get it?) based on maximums and the limits of reasonable display units, eg. show no more than 20 dominoes, and if tx count increases a lot lately, use domino 3-dots to represent 9 txs or whatever

changes

• Implement flag --verbosity-trace-floor and JSON-API:debug.verbosityTraceFloor to set the minimum global verbosity level at which to include file name traces in log line headers, eg.

I1127 13:10:19.130503  imported 1 block(s) (0 queued 0 ignored) including 89 txs in 118.756888ms. #4912033 [024edb99 / 024edb99]

vs.

I1127 13:09:59.359355 core/blockchain.go:1514] imported 1 block(s) (0 queued 0 ignored) including 2 txs in 8.742389ms. #4912032 [66839ff4 / 66839ff4]

• Enable glog.formatHeader to use verbosity and severity thresholds for including file traces in the headers
• Implement flag --pretty to toggle pretty default log settings, all of which can be overridden manually with their own flags.
• Implement missing glog.Verbosity#Warn[|ln|f] and glog.Verbosity#Error[|ln|f] methods for using severity with verbosity in logging.
• Establish default of >= severity.error for including file traces. Important for debugging and reporting bugs.

---

• update tests

[whilei]

The reason I used opt-in prettiness in 199652e is because I believe geth should use defaults that are most useful for developers.

This is an arguable point. I might be dead wrong. In which case we could just use --:neckbeard: instead.

[whilei]

Closing. Have taken lessons learned here and expanded on them in forthcoming PR from (a very messy) https://github.com/whilei/go-ethereum/tree/feat/log-display-separation