Add CPFP endpoint

[dabura667]

Dependent on PR bitpay/bitcoind-rpc#24

Also, not sure whether it makes a difference with bitcore's bindings performance wise, but also related: bitcoin/bitcoin#10300

Feature: Adds access to an endpoint that will let the user know how much additional fee to add to their transaction to ensure that unconfirmed parent transactions are confirmed along with it at the same fee rate.

This can be utilized by bitcore-wallet-service when deciding a fee if a user specifies to use CPFP.

[dabura667]

Note: Starting with bitcoin core 0.13.0, a new RPC call was added called getmempoolentry

If bitcore would support >=0.13.0 bitcoin Core, then we could add support for that to bitcoind-rpc repo make this better.

bitcoin-cli getmempoolentry ebf88e8aede968e8bd70e91f2e9400523157b42af06a96a207bfeb1b18866495
{
  "size": 225,
  "fee": 0.00027120,
  "modifiedfee": 0.00027120,
  "time": 1493777210,
  "height": 464590,
  "startingpriority": 0,
  "currentpriority": 0,
  "descendantcount": 1,
  "descendantsize": 225,
  "descendantfees": 27120,
  "ancestorcount": 4,
  "ancestorsize": 902,
  "ancestorfees": 108480,
  "depends": [
    "ee466a87cd2447cd0564a1f703a145e376ab32cffd6562e19bb610b980f7d7e8"
  ]
}

[isocolsky]

utACK, nicely done, very straight forward

[isocolsky]

Regarding the getmempoolentry API. Do you think it is an absolute requirement given that the mempool is huge nowadays? Or maybe we can move forward with the less performant version and then upgrade?

[dabura667]

Looking back on this:

1. We should probably cut off after 8 decimal places
2. If we could cache the getrawmempool true results and clear the cache after every new block it shouldn't be too bad... but yeah, I piped getrawmempool into a file the other day and it took my quad core gaming PC 2 seconds. getmempoolentry was a couple milliseconds.

Slush seems to be pushing for bitcoin Core to include the Bitcore patches into Core. (Mainly all the indexes)

Satoshilabs might be able to help bump bitcore up to support segwit and later versions of Core.

[karelbilek]

Hello, thanks for this work, we will be adding this to satoshilabs fork :)

[dabura667]

@Runn1ng just FYI getmempoolentry is more efficient than getrawmempool and parsing in nodeJS.

bitcoin/bitcoin#10300 (comment)