Blockchain debug additions

[scorbajio]

This change adds debug logging to core parts of the blockchain package as discussed in #3671

[holgerd77]

Ah, thanks for starting, but this is not yet going as deep as I intended with the issue! We can eventually nevertheless merge when the comments are addressed, since it is for sure already consistent and useful on its own.

I meant this more than a simple work down issue though and really go one step deeper and give this some substantial thinking where debug messages are useful, what are delicate situations and so on.

Not sure, maybe I am also off here myself, wait, I will just go through the library and write down what I would identify as "interesting and/or debug-worthy events" 🙂 (might mention some which are already in the logs, won't "sync" with the changes here, then simply ignore).

Will number here, just if we want to "talk about one of them", so order has no other meaning:

1. When a genesis block is initialized (so that's in the constructors)
2. How many blocks are put with putBlocks or putHeaders
3. How many blocks are deleted with _deleteCanonicalChainReferences
4. From where to where resetCanonicalHead is setting a head
5. What common ancestor findCommonAncestor has found and how many ancestor headers
6. How many staleHeads have been found (also citing header) in _rebuildCanonical

Ok. That's what I could identify. 🙂

I guess that's not too much! Can you therefore directly in this PR?

[holgerd77]

Can we really please keep these logger names short (and not over-namespacify 😂 )? We do not need to be 100% consistent here and not sure if you have used loggers a lot in the past but it really becomes annoying quickly if these logger names are long.

(also this :core addition is a bit inconsistent, since we are not doing/using this on any other logger for the core class)

So let's please simply do blockchain, blockchain:clique and blockchain:ethash. This is mostly for our internal usage and we can make "breaking" changes here anytime.

[scorbajio]

Changed this back to what it was before for now. Will create an issue on rethinking namespaces to allow wildcards like DEBUG=ethjs,blockchain:* work for all namespaces in blockchain and not unexpectedly exclude the core namespace, as is happening currently.

[holgerd77]

Some of these debug messages can need a bit more content. Will push an update, then we can merge! 🙂

[holgerd77]

Ok, pushed some updates, not so easy admittedly. Guess it's still worthy to clean-up blockchain, there some room for small improvements and clarifications on a lot of fronts and it's generally still somewhat hard to grasp the context of things and follow the code.

Anyhow: Debug logging now looks like this (taken from test run), definitely a start. We can go from there everytime we work with blockchain. Guess there is still some adjustments to be made (some logs too verbose, some missing):

[holgerd77]

LGTM