mempool: turn on replace by fee by default

[tynes]

This matches Bitcoin Core's policy of allowing transactions to be replaced via replace by fee in the mempool by default. Turning off this policy results in many transactions being rejected from the mempool. bitcoind refers to this setting as -mempoolreplacement. See bitcoind v0.12.0 release notes:

https://github.com/bitcoin/bitcoin/blob/master/doc/release-notes/release-notes-0.12.0.md

See https://github.com/bitcoin/bitcoin/blob/master/src/validation.h#L125-L126

/** Default for -mempoolreplacement */
static const bool DEFAULT_ENABLE_REPLACEMENT = true;

Thanks to @pinheadmz for finding the code snippet in bitcoind

[codecov-io]

Codecov Report

Merging #737 into master will decrease coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #737      +/-   ##
==========================================
- Coverage   55.46%   55.45%   -0.02%     
==========================================
  Files         104      104              
  Lines       27724    27724              
  Branches     4749     4749              
==========================================
- Hits        15377    15373       -4     
- Misses      12347    12351       +4

Impacted Files	Coverage Δ
lib/mempool/mempool.js	47.64% <100%> (-0.09%)	⬇️
lib/primitives/tx.js	82.95% <0%> (-0.48%)	⬇️
lib/coins/compress.js	56.32% <0%> (+1.26%)	⬆️

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[pinheadmz]

utACK - I think electrum wallet also does RBF by default. And since all CSV transactions are RBF, we are rejecting a good amount of traffic.

[tynes]

According to @BluSyn, defaulting to false was an intentional design decision and the wallet may act differently depending on its setting. Need to investigate more deeply to prevent any regressions in behavior

[braydonf]

Also, as indication of lack of testing around it, the value was changed, and zero tests needed to be changed. This is also an option for the node, not the wallet, it's not clear how that is related. For the wallet, a "bump the fee" option for a transaction may be an improvement to clear a stuck transaction.

[pinheadmz]

It sounds like before enabling RBF on the node, we should prepare the wallet for RBF as well. I think it would be great to support RBF features similar to Core and Electrum:

• Indicate to user if a received tx is flagged as non-final. (should also be indicated in UI like bterm)
• Avoid spending from non-final UTXO (?)
• Allow user to send RBF transactions
• Allow user to bump fees and replace transactions on the network before confirmation.

[tynes]

It looks like increaseFee exists on the Wallet, but is not exposed anywhere:

bcoin/lib/wallet/wallet.js

Line 1360 in 01a7156

async increaseFee(hash, rate, passphrase) {

Hey @turbomaze, this could be useful for you for getting transactions unstuck