blockchain.transaction.relayable / status?

[monsterbitar]

I had a talk with shammah about how he uses electrum for stamp, and we identified a feature that might be good to have: checking if a transaction is relayable or not.

For the case not, it could be due to it being a double-spend, or not matching standardness, or too low fee etc.

The call would take a hex-encoded raw transaction, or an array of such, and then return information about the transactions validity / relayability. It would be particulary useful in places that works with off-line transactions where part of the check for validity is that it's unspent and valid according to the network itself.

Input: Array of raw transactions, and optional broadcast flag.
Output: Boolean for total outcome, array of txid:bool, and optional broadcast txid.

It might be possible to include this functionality as part of #86 (both as a standalone blockchain.transaction.status and as a subscription), rather than making a separate feature.

[cculianu]

Note that the corresponding discussion in Fulcrum here is also relevant: cculianu/Fulcrum#44

In particular we may want to not specify an array of tx's, but have it just be 1-tx-per-call.

The usefulness of the array is limited considering bitcoind's testrawtransaction API can only accept 1 tx-per-call anyway, so it's not like you can test the tx's together as a set or anything, and Fulcrum's internals would be very grateful if it were 1-tx-per-call because it makes it easier to ensure no DoS attacks here (due to the way Fulcrum's internals work).

Anyway @monsterbitar agrees to my 1-tx-per call suggestion here... so. Just writing here to inform the discussion of that fact.

[cculianu]

Note that testmempoolaccept returns the following information:

 {
  "txid"           (string) The transaction hash in hex
  "allowed"        (boolean) If the mempool allows this tx to be inserted
  "reject-reason"  (string) Rejection string (only present when 'allowed' is false)
 }

[rnbrady]

Thanks @monsterbitar for linking here from Twitter thread re DSPs and Electrum Cash Protocol. I have opened dagurval/electrum-cash-protocol#22 to discuss DSPs specifically.