I know that the "internal transactions" are not included in the blockchain and can only be retrieved by replaying the transactions and listening to CALL, CALLCODE and other similar opcodes. Both Parity and Geth provide means to do that.
However I am having trouble performing a full sync of Geth / Parity. Geth took over a month to sync, uses ~800 GB and as of yesterday doesn't want to run anymore, failing with Fatal: Error starting protocol stack: missing block number for head header hash. I was not able to find a solution since resync is not really an option for me. On the other hand I have started syncing Parity about a week ago and the process, fast at first, slowed to a crawl at around block #2393000.
As far as I know I can't use warp / fast sync if I want to get internal transactions. Also, I can't use Infura because it doesn't offer appropriate JSON RPC interface. I could use Etherscan, but that seems like cheating – what is the point of having a decentralized system if you fetch your data from a central endpoint? I might have to use it if everything else fails though, but I would appreciate some pointers. I am sure I am not the only one attempting to do this.
TL;DR: what is the fastest way to synchronize nodes so I can fetch the internal transactions from them? Failing that, what are other options to get this data?
Best Answer
It turns out that Parity on SSD disk is syncing much faster.
EDIT: ...it is, but fetching internal transactions is very slow. Recently Geth 1.8.0 came out which seems to be syncing faster (though still very slow on HDD) and which supports tracers. We'll see how that goes.