This commit is the result of inspecting the results of both cpu and
memory profiling, to improve areas where wallet can be more efficient
on transaction inserts.
One problem that's very evident by profiling is how much waiting there
is for file (txstore, wallet) writes. This commit does not attempt to
fix this yet, but focuses on the easier-to-fix memory allocation
issues which can slow down the rest of wallet due to excessive garbage
collection scanning.
While here, fix a race where a closure run as a goroutine was closing
over a range iterator.
This change "reverses" the mapping used by the transaction store to
reference and lookup unspent credits. Rather than mapping slice
indexes of a block, and then another block map for slice indexes of
transactions with unspent credits, and requiring a lookup through each
credit for whether it is spent or unspent, keep a simple map of
outpoints to a lookup key to find the transaction in a block.
This has a positive effect on performance when searching for previous
transaction outputs that have been spent by a newly-inserted
transaction. Rather than iterating through every block with an
unspent credit, and then every transaction with unspent credits, a
simple map lookup can be done to check whether a transaction input's
previous outpoint is marked as unspent by wallet, and then access the
transaction record itself by the lookup key. While transactions
created by wallet with the sendfrom/many RPCs may mark debits with the
previous credits already known, the previous outputs may still not be
known if a debiting transaction was added by rescan, or notified as a
result of a create+sendrawtransaction.
This change is the result of using the errcheck tool
(https://github.com/kisielk/errcheck) to find all unchecked errors,
both unassigned and those assigned to the blank identifier.
Every returned error is now handled in some manner. These include:
- Logging errors that would otherwise be missed
- Returning errors to the caller for further processing
- Checking error values to determine what to do next
- Panicking for truely exceptional "impossible" errors
On the subject of panics, they are a sharp tool and should be used
sparingly. That being said, I have added them to check errors that
were previously explicitly ignored, because they were expected to
always return without failure. This could be due to fake error paths
(i.e. writing to a bytes.Buffer panics for OOM and should never return
an error) or previous logic asserts that an error case is impossible.
Rather than leaving these unhandled and letting code fail later,
either with incorrect results or a nil pointer dereference, it now
produces a stack trace at the error emit site, which I find far more
useful when debugging.
While here, a bunch of dead code was removed, including code to move
pre-0.1.1 uxto and transaction history account files to the new
directory (as they would be unreadable anyways) and a big chunk of
commented out rpcclient code.
