Do the notifications from walletnotify and blocknotify are sent during the wallet synchronization or at the end? Say the wallet was offline for 100 blocks and when started: will it send the notifications after the each block it downloads and verifies and so all the relevant transactions in them or will it send them at the end? I would assume it sends them as it gets them, so then how would I resolve these properly if all the incoming request at that time are blocked?
Refers to Bitcoin Core 0.17:
Will be executed at the time when a transaction gets added to the wallet. If your wallet is 100 blocks behind and in those 100 blocks you have 2 transaction in each block, the wallet notify script will be called twice per block (== 200 executions during the 100 block catch up).
Only valid blocks (valid transaction) will result in a wallet-notify call.
Will also be called when a mempool transactions (unconfirmed transaction) was added to the wallet (and therefore relevant to the wallet)
Will be executed when a block gets connected to the active chain and before
Consider taking a closer look at Bitcoin Cores ZMQ API that allows more efficient process interaction (wallet/block notify spawn a process on each call).