LIGHTNING-PAY(7)

NAME
lightning-pay - Command for sending a payment to a BOLT11 invoice

SYNOPSIS

pay bolt11 [msatoshi] [label] [riskfactor] [maxfeepercent] [retry_for] [maxdelay] [exemptfee]

DESCRIPTION

The pay RPC command attempts to find a route to the given destination, and send the funds it asks for. If the bolt11 does not contain an amount, msatoshi is required, otherwise if it is specified it must be null. msatoshi is in millisatoshi precision; it can be a whole number, or a whole number with suffix msat or sat, or a three decimal point number with suffix sat, or an 1 to 11 decimal point number suffixed by btc.

The label field is used to attach a label to payments, and is returned in lightning-listpays(7) and lightning-listsendpays(7). The riskfactor is described in detail in lightning-getroute(7), and defaults to 10. The maxfeepercent limits the money paid in fees, and defaults to 0.5. The maxfeepercent' is a percentage of the amount that is to be paid. The `exemptfee option can be used for tiny payments which would be dominated by the fee leveraged by forwarding nodes. Setting exemptfee allows the maxfeepercent check to be skipped on fees that are smaller than exemptfee (default: 5000 millisatoshi).

The response will occur when the payment fails or succeeds. Once a payment has succeeded, calls to pay with the same bolt11 will succeed immediately.

Until retry_for seconds passes (default: 60), the command will keep finding routes and retrying the payment. However, a payment may be delayed for up to maxdelay blocks by another node; clients should be prepared for this worst case.

When using lightning-cli, you may skip optional parameters by using null. Alternatively, use -k option to provide parameters by name.

RANDOMIZATION

To protect user privacy, the payment algorithm performs some randomization.

    1. Route Randomization

    2. Shadow Route

Route randomization means the payment algorithm does not always use the lowest-fee or shortest route. This prevents some highly-connected node from learning all of the user payments by reducing their fees below the network average.

Shadow route means the payment algorithm will virtually extend the time delays along the route, making it appear to intermediate nodes that the route is longer than it actually is. This prevents intermediate nodes from reliably guessing their distance from the payee.

Route randomization will never exceed maxfeepercent of the payment. Route randomization and shadow routing will not take routes that would exceed maxdelay.

RETURN VALUE

On success, this returns the payment_preimage which hashes to the payment_hash to prove that the payment was successful. It will also return, a getroute_tries and a sendpay_tries statistics for the number of times it internally called getroute and sendpay.

You can monitor the progress and retries of a payment using the lightning-paystatus(7) command.

The following error codes may occur:

    • -1. Catchall nonspecific error.

    • 201. Already paid with this hash using different amount or destination.

    • 203. Permanent failure at destination. The data field of the error will be routing failure object.

    • 205. Unable to find a route.

    • 206. Route too expensive. Either the fee or the needed total locktime for the route exceeds your maxfeepercent or maxdelay settings, respectively. The data field of the error will indicate the actual fee as well as the feepercent percentage that the fee has of the destination payment amount. It will also indicate the actual delay along the route.

    • 207. Invoice expired. Payment took too long before expiration, or already expired at the time you initiated payment. The data field of the error indicates now (the current time) and expiry (the invoice expiration) as UNIX epoch time in seconds.

    • 210. Payment timed out without a payment in progress.

Error codes 202 and 204 will only get reported at sendpay; in pay we will keep retrying if we would have gotten those errors.

A routing failure object has the fields below:

    • erring_index. The index of the node along the route that reported the error. 0 for the local node, 1 for the first hop, and so on.

    • erring_node. The hex string of the pubkey id of the node that reported the error.

    • erring_channel. The short channel ID of the channel that has the error, or 0:0:0 if the destination node raised the error.

    • failcode. The failure code, as per BOLT #4.

    • channel_update. The hex string of the channel_update message received from the remote node. Only present if error is from the remote node and the failcode has the UPDATE bit set, as per BOLT #4.

The data field of errors will include statistics getroute_tries and sendpay_tries. It will also contain a failures field with detailed data about routing errors.

AUTHOR

Rusty Russell <rusty@rustcorp.com.au> is mainly responsible.

SEE ALSO

lightning-listpays(7), lightning-decodepay(7), lightning-listinvoice(7), lightning-delinvoice(7), lightning-getroute(7), lightning-invoice(7).

RESOURCES

Main web site: https://github.com/ElementsProject/lightning