lightning-feerates – Command for querying recommended onchain feerates¶
The feerates command returns the feerates that C-lightning will use. The feerates will be based on the recommended feerates from the backend. The backend may fail to provide estimates, but if it was able to provide estimates in the past, C-lightning will continue to use those for a while. C-lightning will also smoothen feerate estimations from the backend.
style is either of the two strings:
- perkw - provide feerate in units of satoshis per 1000 weight.
- perkb - provide feerate in units of satoshis per 1000 virtual bytes.
Bitcoin transactions have non-witness and witness bytes:
- Non-witness bytes count as 4 weight, 1 virtual byte. All bytes other than SegWit witness count as non-witness bytes.
- Witness bytes count as 1 weight, 0.25 virtual bytes.
Thus, all perkb feerates will be exactly 4 times perkw feerates.
To compute the fee for a transaction, multiply its weight or virtual bytes by the appropriate perkw or perkw feerate returned by this command, then divide by 1000.
There is currently no way to change these feerates from the RPC.
If you need custom control over onchain feerates,
you will need to provide your own plugin
that replaces the
bcli plugin backend.
For commands like lightning-withdraw(7) or lightning-fundchannel(7) you
can provide a preferred feerate directly as a parameter,
which will override the recommended feerates returned by feerates.
The feerates command returns the feerates in an object named perkw or perkb, depending on your style parameter.
Some of these estimations may be missing, except for min_acceptable and max_acceptable, which are always present.
The perkw or perkb object may have fields containing the estimates:
- opening - feerate used for channel opening by lightning-fundchannel(7), as well as normal onchain-to-onchain spends by lightning-withdraw(7). In general, for all normal onchain-to-onchain spends, this is the feerate you should also use.
- mutual_close - the starting feerate used in mutual close negotiation. Note that since mutual close is a negotiation, the actual feerate used in mutual close will be somewhere between this and the corresponding mutual close feerate of the peer.
- unilateral_close - the feerate we will pay for when a unilateral close is done on a channel we originally funded. When anchor commitments are implemented, this will be the feerate we will use for a unilateral close we initiated.
- delayed_to_us - the feerate we will use when claiming our output from a unilateral close we initiated.
- htlc_resolution - the feerate we will use to claim HTLCs from a unilateral close we initiated.
- penalty - the feerate we will use to revoke old state, if the counterparty attempts to cheat us.
The following fields are always present in the perkw or perkb object:
- min_acceptable - the smallest feerate that you can use, usually the minimum relayed feerate of the backend.
- max_acceptable - the largest feerate we will accept from remote negotiations. If a peer attempts to open a channel to us but wants a unilateral close feerate larger than max_acceptable, we reject the open attempt. If the peer attempts to change the unilateral close feerate of a channel it opened to us, such that the new feerate exceeds max_acceptable, we unilaterally close the channel (at the current unilateral close feerate instead of the new one).
The feerates command will never error, however some fields may be missing in the result if feerate estimates for that kind of transaction are unavailable.
Many other commands have a feerate parameter, which can be the strings urgent, normal, or slow. These are mapped to the feerates outputs as:
- urgent - equal to unilateral_close
- normal - equal to opening
- slow - equal to min_acceptable.
In C-lightning we like to call the weight unit “sipa” in honor of Pieter Wuille, who uses the name “sipa” on IRC and elsewhere. Internally we call the perkw style as “feerate per kilosipa”.
lightning-fundchannel(7), lightning-withdraw(7), lightning-txprepare(7), lightning-fundchannel_start(7).