Recent btcd versions only allow one rescan to run at any given time
per websocket client. To better handle this, a new set of goroutines
are started by the account manager which batch and serialize rescan
jobs.
If no rescans are currently running, a new rescan starts. If a rescan
is already being processed, the request is queued and runs after the
current rescan finishes. For any additional incoming requests before
the current rescan finishes, the requests are merged with the
currently-waiting request so both can be handled with a single rescan.
This change also prepares for rescan progress notifications from btcd,
but are still unhandled until the necessary details for
partially-synced addresses are added to the wallet file format.
Notifications ariving from btcd were being reordered (each handled by
its own goroutine, rather then being always sent in the order they
originated). This was breaking the new transaction store by inserting
transaction records in an 'impossible' manner, that is, inserting txs
without block info after the store already held records of the same tx
with block info, without first performing a rollback.
This is handled by the transaction store insert methods by checking
for identical transactions (double spends with the same tx sha), but
where the block heights mismatch and the new record does not have a
block set. The error is returned all the way up to the goroutine
running each rpc request/notification handler, and if hit, the btcd
connection is closed and all accounts are reopened from disk. This is
not optimal, but it allows us to use the connect logic to correctly
catch us up to the best chain with the last good state of all accounts
while only rescanning a few blocks.
Fixes#72.
This change replaces the old transaction store file format and
implementation. The most important change is how the full backing
transactions for any received or sent transaction are now saved,
rather than simply saving parsed-out details of the tx (tx shas, block
height/hash, pkScripts, etc.).
To support the change, notifications for received transaction outputs
and txs spending watched outpoints have been updated to use the new
redeemingtx and recvtx notifications as these contain the full tx,
which is deserializead and inserted into the store.
The old transaction store serialization code is completely removed, as
updating to the new format automatically cannot be done. Old wallets
first running past this change will error reading the file and start a
full rescan to rebuild the data. Unlike previous rescan code,
transactions spending outpoint managed by wallet are also included.
This results in recovering not just received history, but history for
sent transactions as well.
The disk syncer now maintains its own countdown timer, creating a new
timer only when necessary (when there is no timer running, and
something is scheduled to be written). When the timer expires, the
select loop begins selecting on a grab of the account manager's binary
semaphore, and if read, performs the sync and nils the select channel
to prevent a future grab until a new timer has expired.
Tested with a race-enabled build on Windows. No lockups or races
related to the disk syncing experienced with constant client requests
and incoming btcd notifications, and scheduled writes run as expected
once the countdown timer expires, locking out all server request and
notifiation handling.
This change removes the three separate mutexes which used to lock an
account's wallet, tx store, and utxo store. Accounts no longer
contain any locking mechanism and rely on go's other synchronization
constructs (goroutines and channels) for correct access.
All accounts are now managed as a collection through the new
AccountManager, rather than the old AccountStore. AccountManager runs
as its own goroutine to provide access to accounts.
RPC requests are now queued for handling, being denied if the queue
buffer is exhausted. Notifications are also queued (instead of being
sent from their own goroutine after being received, in which order is
undefined), however, notifications are never dropped and will
potentially grow a queue of infinite size if unhandled.
