nix-bitcoin/modules/charge-lnd.nix

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{ config, lib, pkgs, ... }:
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with lib;
let
options.services.charge-lnd = with types; {
enable = mkEnableOption "charge-lnd, policy-based fee manager";
extraFlags = mkOption {
type = listOf str;
default = [];
example = [ "--verbose" "--dry-run" ];
description = "Extra flags to pass to the charge-lnd command.";
};
interval = mkOption {
type = str;
default = "*-*-* 04:00:00";
example = "hourly";
description = ''
Systemd calendar expression when to adjust fees.
See <citerefentry><refentrytitle>systemd.time</refentrytitle>
<manvolnum>7</manvolnum></citerefentry> for possible values.
Default is once a day.
'';
};
randomDelay = mkOption {
type = str;
default = "1h";
description = ''
Random delay to add to scheduled time.
'';
};
policies = mkOption {
type = types.lines;
default = "";
example = literalExample ''
[discourage-routing-out-of-balance]
chan.max_ratio = 0.1
chan.min_capacity = 250000
strategy = static
base_fee_msat = 10000
fee_ppm = 500
[encourage-routing-to-balance]
chan.min_ratio = 0.9
chan.min_capacity = 250000
strategy = static
base_fee_msat = 1
fee_ppm = 2
[default]
strategy = ignore
'';
description = ''
Policy definitions in INI format.
See https://github.com/accumulator/charge-lnd/blob/master/README.md#usage
for possible properties and parameters.
Policies are evaluated from top to bottom.
The first matching policy (or `default`) is applied.
'';
};
};
cfg = config.services.charge-lnd;
nbLib = config.nix-bitcoin.lib;
lnd = config.services.lnd;
electrs = if (config.services ? electrs) && config.services.electrs.enable
then config.services.electrs
else null;
user = "charge-lnd";
group = user;
dataDir = "/var/lib/charge-lnd";
configFile = builtins.toFile "charge-lnd.config" cfg.policies;
checkedConfig = pkgs.runCommandNoCC "charge-lnd-checked.config" { } ''
${config.nix-bitcoin.pkgs.charge-lnd}/bin/charge-lnd --check --config ${configFile}
cp ${configFile} $out
'';
in
{
inherit options;
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config = mkIf cfg.enable {
services.lnd = {
enable = true;
macaroons.charge-lnd = {
user = user;
permissions = ''{"entity":"info","action":"read"},{"entity":"onchain","action":"read"},{"entity":"offchain","action":"read"},{"entity":"offchain","action":"write"}'';
};
};
systemd.services.charge-lnd = {
documentation = [ "https://github.com/accumulator/charge-lnd/blob/master/README.md" ];
after = [ "lnd.service" ];
requires = [ "lnd.service" ];
# lnd's data directory (--lnddir) is not accessible to charge-lnd.
# Instead use directory "lnddir-proxy" as lnddir and link relevant files to it.
preStart = ''
macaroonDir=${dataDir}/lnddir-proxy/data/chain/bitcoin/mainnet
mkdir -p $macaroonDir
ln -sf /run/lnd/charge-lnd.macaroon $macaroonDir
ln -sf ${lnd.certPath} ${dataDir}/lnddir-proxy/tls.cert
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'';
serviceConfig = nbLib.defaultHardening // {
ExecStart = ''
${config.nix-bitcoin.pkgs.charge-lnd}/bin/charge-lnd \
--lnddir ${dataDir}/lnddir-proxy \
--grpc ${nbLib.addressWithPort lnd.rpcAddress lnd.rpcPort} \
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--config ${checkedConfig} \
${optionalString (electrs != null)
"--electrum-server ${nbLib.addressWithPort electrs.address electrs.port}"} \
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${escapeShellArgs cfg.extraFlags}
'';
Type = "oneshot";
User = user;
Group = group;
StateDirectory = "charge-lnd";
} // nbLib.allowLocalIPAddresses;
};
systemd.timers.charge-lnd = {
description = "Adjust LND routing fees";
wantedBy = [ "timers.target" ];
timerConfig = {
OnCalendar = cfg.interval;
RandomizedDelaySec = cfg.randomDelay;
};
};
users.users.${user} = {
isSystemUser = true;
group = group;
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};
users.groups.${group} = {};
};
}