This actually simplifies some SPV code, as they can keep track of
a filtered block and its txn before accepting both in one step.
The previous argument was that SPV nodes should handle the txn the
same as any other free txn and then mark them as connected to a
block when they get the filtered block itself. However, it now
appears that SPV nodes will need to put in more effort to verify
loose txn than they would to verify txn in blocks, thus making it
more approriate to send the txn after the filtered block.
By specifying -txindex when initializing the database, a txid-to-diskpos
index is maintained in the blktree database. This database is used to
help answering getrawtransaction() RPC queries, when enabled.
Changing the -txindex value requires a -reindex; the client will abort
at startup if the database and the specified -txindex mismatch.
Note that the default value for fRelayTxes is false, meaning we
now no longer relay tx inv messages before receiving the remote
peer's version message.
Client (SPV) mode never got implemented entirely, and whatever part was already
working, is likely not been tested (or even executed at all) for the past two
years. This removes it entirely.
If we want an SPV implementation, I think we should first get the block chain
data structures to be encapsulated in a class implementing a standard interface,
and then writing an alternate implementation with SPV semantics.
Since block validation happens in parallel, multiple threads may be
accessing the signature cache simultaneously. To prevent contention:
* Turn the signature cache lock into a shared mutex
* Make reading from the cache only acquire a shared lock
* Let block validations not store their results in the cache
* During block verification (when parallelism is requested), script
check actions are stored instead of being executed immediately.
* After every processed transactions, its signature actions are
pushed to a CScriptCheckQueue, which maintains a queue and some
synchronization mechanism.
* Two or more threads (if enabled) start processing elements from
this queue,
* When the block connection code is finished processing transactions,
it joins the worker pool until the queue is empty.
As cs_main is held the entire time, and all verification must be
finished before the block continues processing, this does not reach
the best possible performance. It is a less drastic change than
some more advanced mechanisms (like doing verification out-of-band
entirely, and rolling back blocks when a failure is detected).
The -par=N flag controls the number of threads (1-16). 0 means auto,
and is the default.
- some users reported it as weird, that the estimated block count could be
lower than our own nodes block number (which is indeed true and not good)
- this pull adds a new default behaviour, which displays our own block
number as estimated block number, if own >= est. block count
- the pull raises space for nodes block counts in cPeerBlockCounts to 8 to
be more accurate
- also removes a reduntant setNumBlocks() call in RPCConsole and moves
initialisation of numBlocksAtStartup in ClientModel, where it belongs
-checklevel gets a new meaning:
0: verify blocks can be read from disk (like before)
1: verify (contextless) block validity (like before)
2: verify undo files can be read and have good checksums
3: verify coin database is consistent with the last few blocks
(close to level 6 before)
4: verify all validity rules of the last few blocks
Level 3 is the new default, as it's reasonably fast. As level 3 and
4 are implemented using an in-memory rollback of the database, they
are limited to as many blocks as possible without exceeding the
limits set by -dbcache. The default of -dbcache=25 allows for some
150-200 blocks to be rolled back.
In case an error is found, the application quits with a message
instructing the user to restart with -reindex. Better instructions,
and automatic recovery (when possible) or automatic reindexing are
left as future work.
When the coin database is out of date with the block database, the
best block in it is automatically switched to. This reconnection
process can take time, so allow it to be interrupted.
This also stops block connection as soon as shutdown is requested,
leading to a faster shutdown.
This problem is like earth (mostly harmless). After/during a
-reindex, it means the statistics about the last block file
reported in debug.log are always of blk00000.dat instead of the
last file. Apart from that, it means a few more database entries
need to be read when finding a file to append to the first time.
- even if we are allowed to fail pre-allocating, it's better to check
for sufficient space before calling AllocateFileRange() and if we
are out of disk space return with error()
- the above change allows us to remove the CheckDiskSpace() check
in CBlock::AcceptBlock()
In case a reorganisation fails, the internal state could become
inconsistent (memory only). Previously, a cache per block connect
or disconnect action was used, so blocks could not be applied in
a partial way. Extend this to a cache for the entire reorganisation,
making it atomic entirely. This also simplifies the code a bit.
