* Update sync scheduler pool mode
why:
The pool mode allows to loop over active peers one after another. This
is ideal for soft re-starting peers. As this is a two tier experience
(start/stop, setup/release) the loop must be run twice. This is
controlled by a more rigid re-definition of how to use the `poolMode`
flag.
* Mitigate RLP serialiser deficiency
why:
Currently, serialising the `BlockBody` in not conevrtible and need
to be checked in the `eth` module. Currently a local fix for the
wire protocol applies. Unit tests will stay (after this local solution
will have been removed.)
* Code cosmetics and massage
details:
Main part is `types.toStr()` as a unified function for logging block
numbers.
* Allow to use a logical genesis replacement (start of history)
why:
Snap sync will set up an arbitrary pivot at a block number different
from zero. In fact, the higher the block number the better.
details:
A non-genesis start of history will currently only affect the score
values which were derived from the difficulty.
* Provide function to store the snap pivot block header in chain db
why:
Together with the start of history facility, this allows to proceed
with full syncing once snap has finished.
details:
Snap db storage was switched from a sub-tables to the flat chain db.
* Provide database completeness and sanity checker
details:
For debugging on smaller databases, only
* Implement snap -> full sync switch
* Somewhat tighten error handling
why:
Zombie state is invoked when the current peer turns out to be useless
for further communication. While there is a chance to further talk
to a peer about another topic (aka healing) after some protocol failure,
it makes no sense to do so after a network problem.
The latter state is explained bu the `peerDegraded` flag that goes
together with the `zombie` state flag. A degraded peer is dropped
immediately.
* Remove `--sync-mode=snapCtx` option, always start snap in recovery mode
why:
No need for a snap sync option without recovery mode, can be achieved
by deleting the database.
* Code cosmetics, typos, prettify logging, debugging helper, etc.
* Split off snap sync sub-mode handler into separate modules
details:
The original `worker.nim` source has become a multiplexer for several
snap sync sub-modes `full` and `snap`. The source modules of the
incarnations of a particular sync sub-mode are places into the
`worker/play` directory.
* Update ticker for snap and full sync logging
Jordan Hrycaj