12 votes

Replace-by-Fee vs Child-pays-for-Parent?

Replace-by-fee means transactions spending the same coin to the same addresses are not considered double-spends by the network and are still relayed, as long as they pay a higher fee than the ...
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  • 971
7 votes

Do unconfirmed transactions expire after some time?

In addition to Mark S.'s answer, since Bitcoin Core 0.12 there actually is an expiration in the mempool, which evicts unconfirmed transactions after N hours, where N is set by -mempoolexpiry, and ...
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6 votes
Accepted

Spending output of a low-fee transaction by following with higher-fee transaction

There are 3 cases. Case 1a: if Fee(Tx1) < Dust Fee then Tx1 gets dropped by nodes that do not offer Free Relay Policy. Then all other transaction dependent on the outputs of Tx1 will never be ...
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  • 2,378
6 votes
Accepted

Can someone outline the full pros/cons of the various Replace-By-Fee proposals?

All three proposals attempt to solve the same problem, the issue of stuck transactions. Due to the behavior of Bitcoin Core with respect to double spends (they are silently dropped, and not relayed), ...
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  • 148
5 votes

CPFP: Child Pays For Parent Clarification Needed

No, it's not a matter of sending to the same address multiple times, rather, CPFP works by spending the output of a previous transaction in a second transaction with a higher fee. Example: An ...
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  • 63.3k
5 votes
Accepted

How does first seen replace by fee work?

Right now, for the most part, Bitcoin miners follow a First-Seen-Safe rule: If 2 conflicting transactions show up in the mempool, the miner sticks with the one it saw first. Replace-By-Fee would ...
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  • 1,034
4 votes
Accepted

Why do Anchor Outputs need to enforce an nSequence of 1?

Because there must always be exactly one directly spendable output per party, in order to avoid one party to be able to "exhaust" the carve-out. With two CPFP-ble outputs, one party could ...
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4 votes
Accepted

Transaction with a high fee keeps getting skipped... Reason why?

$ src/bitcoin-cli getmempoolentry ed45c837d26c25fb6a763708376a87f1875ff57efbb0f56d1b26d00a16c1899e { "fees": { "base": 0.00012042, "modified": 0.00012042, &...
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  • 371
4 votes
Accepted

what is meant by DEFAULT_ANCESTOR_LIMIT in child pay for parent?

Bitcoin Core by default does not forward a transaction to its peers, when the full tree of its ancestor transactions contains more than 25 unconfirmed transactions or 101 kvB of unconfirmed ...
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  • 63.3k
4 votes

Spending output of a low-fee transaction by following with higher-fee transaction

To my knowledge there is not a widespread practice of miners to do this, but it certainly can be programmed. As transaction fees continue to rise and these type of stuck transaction become more of a ...
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  • 345
3 votes
Accepted

Do unconfirmed transactions expire after some time?

The newest version of bitcoin core 0.12 introduced a feature called replace by fee. This can be used to issue a transaction with a higher fee spending coins that have not yet been picked up in a block....
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  • 2,640
3 votes

Can someone outline the full pros/cons of the various Replace-By-Fee proposals?

Answer reposted from: How does first seen replace by fee work? Right now, for the most part, Bitcoin miners follow a First-Seen-Safe rule: If 2 conflicting transactions show up in the mempool, the ...
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  • 1,034
3 votes

Why are negative fees not allowed?

Very interesting brain teaser. I agree that this could be interesting in combination with CPFP. The sender could defer the transaction fees to the recipient which would probably be an interesting ...
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  • 63.3k
3 votes
Accepted

Why won't a transaction with 888/byte confirm after 11+ hours?

It won't confirm because the grandparent and parent of your child transaction aren't confirmed. The grandparent transaction was also paid with a really low fee(51.573 sat/B). I did the math for you....
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  • 1,255
3 votes
Accepted

Does miner with CPFP look through all the possible combinations of descendants to find the one with the highest fee?

If we run the getrawmempool true RPC, we can look at the data Bitcoin Core has for each of its mempool transactions. Here's an example: "...
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3 votes
Accepted

Do miners have an incentive to confirm various transactions from same address?

It sounds like you have rediscovered a mechanism called child pays for parent. Generally, no, two independent transactions could get included in any order even when they were sent from the same wallet ...
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  • 63.3k
3 votes

A question about CPFP relaying policy

Correct. tx0 is removed, and tx0child is "invalid" because it spends a UTXO that does not exist in the current chain or mempool. This could change in the future with package RBF and package ...
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  • 83
2 votes
Accepted

Does parent also pay for child?

Does it also work the other way - that is, does transaction with high fee pays for child transaction that has low fees, given that they are both in the mempool? Or is the policy only "one way", from ...
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  • 7,479
2 votes
Accepted

Is it possible to get CPFP information from full node, without requesting full mempool dump?

The answer is getmempoolentry. https://chainquery.com/bitcoin-api/help/getmempoolentry
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  • 2,545
2 votes
Accepted

Does bitcoin core node relay those child-pay-for-parent transactions?

(updated based on Pieter's comments below) There are (essentially) two sets of UTXOs at play. One is constructed from the blockchain itself, by reading the blocks on disk and updating with any new ...
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  • 16.5k
2 votes
Accepted

How does one create another transaction when all funds are tied up in an unconfirmed previous transaction?

It depends on your wallet software. Some may simply refuse to create the transaction. Others will spend the change output of the unconfirmed transaction. CPFP and RBF typically only occur when you ...
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  • 61.3k
2 votes
Accepted

What happens if the commitment tx fee is too low?

Only if the state changes fees are negotiated (and for mutual closing the channel) so in case the onchain fees change and the channel is not used for a long time just send a fake payment hash to adapt ...
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2 votes

Bitcoin.conf setting for CPFP - how can I enable longer 'chains' of unconfirmed transactions?

The maximum unconfirmed descendant count is a mempool setting, not a wallet one. Assuming most of the network run with the default of 25, even if you changed your own mempool to accept a longer chain ...
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1 vote

LND funding transaction stuck in mempool due to low fees

I got a sweep TX (from a force closed channel) stuck, also due to low fees. This answer is inspired by OPs answer. I got it working with: lncli openchannel \ --sat_per_byte=${fees per byte for the ...
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  • 111
1 vote

LND funding transaction stuck in mempool due to low fees

I solved the problem whit CPFP (children pay for parent). I used the unconfirmed change of the fund TX stuck in mempool to open a new channel. At the time of broadcasting TX the median fee is ...
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  • 31
1 vote

Bump zero fee transaction with CPFP

In order for a node to relay a transaction, the transaction must satisfy the node's minRelayTxFee. This fee rate cut off is by default set to 1000 satoshi per kvB (= 1 satoshi per vbyte). Your first ...
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  • 63.3k
1 vote

From multibit to electrum : low fee and unconfirmed parent

Seems like your 589 Sat/Byte went through now, however that transaction is not a double-spend of your 1st transaction because the total output Total Input amount is different. Transaction ...
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  • 1,255
1 vote

Where do I find my Blockchain wallet's change address?

The best way to get the change address is to check the transaction corresponding to the "known" address from your wallet from where the transaction was originated. Blockchain does not keep a track of ...
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1 vote

Where do I find my Blockchain wallet's change address?

Go to https://iancoleman.io/bip39/ and download the page to use it offline (you should never enter private keys into a website). Scroll down and choose the BIP 44 tab. In the text box next to "...
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  • 61.3k
1 vote
Accepted

Why is CPFP (Child pay for parent) immune to double spend?

If you're doing CPFP right, The two transactions you sent are both originating from the same UTXO, but one spends the output of the older transaction with a higher fee. If the miners want to get the ...
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