The total difficulty is the sum of all block difficulties from genesis
to a certain block. This value was used in PoW for deciding which chain
is heavier, and thus which chain to select. Since PoS has a different
fork selection algorithm, all blocks since the merge have a difficulty
of 0, and all total difficulties are the same for the past 2 years.
Whilst the TDs are mostly useless nowadays, there was never really a
reason to mess around removing them since they are so tiny. This
reasoning changes when we go down the path of pruned chain history. In
order to reconstruct any TD, we **must** retrieve all the headers from
chain head to genesis and then iterate all the difficulties to compute
the TD.
In a world where we completely prune past chain segments (bodies,
receipts, headers), it is not possible to reconstruct the TD at all. In
a world where we still keep chain headers and prune only the rest,
reconstructing it possible as long as we process (or download) the chain
forward from genesis, but trying to snap sync the head first and
backfill later hits the same issue, the TD becomes impossible to
calculate until genesis is backfilled.
All in all, the TD is a messy out-of-state, out-of-consensus computed
field that is overall useless nowadays, but code relying on it forces
the client into certain modes of operation and prevents other modes or
other optimizations. This PR completely nukes out the TD from the node.
It doesn't compute it, it doesn't operate on it, it's as if it didn't
even exist.
Caveats:
- Whenever we have APIs that return TD (devp2p handshake, tracer, etc.)
we return a TD of 0.
- For era files, we recompute the TD during export time (fairly quick)
to retain the format content.
- It is not possible to "verify" the merge point (i.e. with TD gone, TTD
is useless). Since we're not verifying PoW any more, just blindly trust
it, not verifying but blindly trusting the many year old merge point
seems just the same trust model.
- Our tests still need to be able to generate pre and post merge blocks,
so they need a new way to split the merge without TTD. The PR introduces
a settable ttdBlock field on the consensus object which is used by tests
as the block where originally the TTD happened. This is not needed for
live nodes, we never want to generate old blocks.
- One merge transition consensus test was disabled. With a
non-operational TD, testing how the client reacts to TTD is useless, it
cannot react.
Questions:
- Should we also drop total terminal difficulty from the genesis json?
It's a number we cannot react on any more, so maybe it would be cleaner
to get rid of even more concepts.
---------
Co-authored-by: Gary Rong <garyrong0905@gmail.com>
Here we update the eth and snap protocol test suites with a new test chain,
created by the hivechain tool. The new test chain uses proof-of-stake. As such,
tests using PoW block propagation in the eth protocol are removed. The test suite
now connects to the node under test using the engine API in order to make it
accept transactions.
The snap protocol test suite has been rewritten to output test descriptions and
log requests more verbosely.
---------
Co-authored-by: Felix Lange <fjl@twurst.com>
This PR does a few things.
It fixes a shutdown-order flaw in the chainfreezer. Previously, the chain-freezer would shutdown the freezer backend first, and then signal for the loop to exit. This can lead to a scenario where the freezer tries to fsync closed files, which is an error-conditon that could lead to exit via log.Crit.
It also makes the printout more detailed when truncating 'dangling' items, by showing the exact number instead of approximate MB.
This PR also adds calls to fsync files before closing them, and also makes the `db inspect` command slightly more robust.
This PR fixes an issue which might result in data lost in freezer.
Whenever mutation happens in freezer, all data will be written into head data file
and it will be rotated with a new one in case the size of file reaches the threshold.
Theoretically, the rotated old data file should be fsync'd to prevent data loss.
In freezer.Sync function, we only fsync: (1) index file (2) meta file and (3) head
data file. So this PR forcibly fsync the head data file if mutation happens in the
boundary of data file.
Previously freezer has only been used for storing ancient chain data, while obviously it can be used more. This PR unties the chain data and freezer, keep the minimal freezer structure and move all other logic (like incrementally freezing block data) into a separate structure called ChainFreezer.
This PR also extends the database interface by adding a new ancient store function AncientDatadir which can return the root directory of ancient store. The ancient root directory can be used when we want to open some other ancient-stores (e.g. reverse diff freezer).
Péter Szilágyi
rjl493456442
lightclient
0xbstn
s7v7nislands
Martin Holst Swende
ucwong