LIGHTNING-GETROUTE(7)
=====================
:doctype: manpage

NAME
----
lightning-getroute - Command for routing a payment (low-level).


SYNOPSIS
--------
*getroute* 'id' 'msatoshi' 'riskfactor' ['cltv'] ['fromid'] ['fuzzpercent']

DESCRIPTION
-----------
The *getroute* RPC command attempts to find the best route for the payment
of 'msatoshi' to lightning node 'id', such that the payment will arrive
at 'id' with 'cltv'-blocks to spare (default 9).

'msatoshi' is in millisatoshi precision; it can be a whole number, or
a whole number ending in 'msat' or 'sat', or a number with three
decimal places ending in 'sat', or a number with 1 to 11 decimal
places ending in 'btc'.

There are two considerations for how good a route is: how low the
fees are, and how long your payment will get stuck in a delayed output if a node goes down
during the process.  The 'riskfactor' floating-point field controls
this tradeoff; it is the annual cost of your funds being stuck (as a
percentage).

For example, if you thought the convenience of keeping your funds liquid
(not stuck) was worth 20% per annum interest, 'riskfactor' would be 20.

If you didn't care about risk, 'riskfactor' would be zero.

'fromid' is the node to start the route from: default is this node.

The 'fuzzpercent' is a positive floating-point number, representing a percentage of the actual fee.
The 'fuzzpercent' is used to distort computed fees along each channel,
to provide some randomization to the route generated.
0.0 means the exact fee of that channel is used,
while 100.0 means the fee used might be from 0 to twice the actual fee.
The default is 5.0, or up to 5% fee distortion.


RISKFACTOR EFFECT ON ROUTING
----------------------------
The risk factor is treated as if it were an additional fee on the route,
for the purposes of comparing routes.

The formula used is the following approximation:
----
risk-fee = amount x blocks-timeout x per-block-cost
----

We are given a 'riskfactor' expressed as a percentage.  There are 52596 blocks
per year, thus 'per-block-cost' is 'riskfactor' divided by 5,259,600.

The final result is:
----
risk-fee = amount x blocks-timeout x riskfactor / 5259600
----

Here are the risk fees in millisatoshis, using various parameters.  I
assume a channel charges the default of 1000 millisatoshis plus 1
part-per-million.  Common to_self_delay values on the network at 14 and 144 blocks.

[options="header"]
|=======================
|Amount (msat)	|Riskfactor	| Delay		|Risk Fee	|Route fee
|10,000		|1		| 14		|0		|1001
|10,000		|10		| 14		|0		|1001
|10,000		|100		| 14		|2		|1001
|10,000		|1000		| 14		|26		|1001

|1,000,000	|1		| 14		|2		|1001
|1,000,000	|10		| 14		|26		|1001
|1,000,000	|100		| 14		|266		|1001
|1,000,000	|1000		| 14		|2661		|1001

|100,000,000	|1		| 14		|266		|1100
|100,000,000	|10		| 14		|2661		|1100
|100,000,000	|100		| 14		|26617		|1100
|100,000,000	|1000		| 14		|266179		|1100

|10,000		|1		| 144		|0		|1001
|10,000		|10		| 144		|2		|1001
|10,000		|100		| 144		|27		|1001
|10,000		|1000		| 144		|273		|1001

|1,000,000	|1		| 144		|27		|1001
|1,000,000	|10		| 144		|273		|1001
|1,000,000	|100		| 144		|2737		|1001
|1,000,000	|1000		| 144		|27378		|1001

|100,000,000	|1		| 144		|2737		|1100
|100,000,000	|10		| 144		|27378		|1100
|100,000,000	|100		| 144		|273785		|1100
|100,000,000	|1000		| 144		|2737850	|1100
|=======================

RECOMMENDED RISKFACTOR VALUES
-----------------------------
The default 'fuzz' factor is 5%, so as you can see from the table above,
that tends to overwhelm the effect of 'riskfactor' less than about 5.

1 is a conservative value for a stable lightning network with very few
failures.

1000 is an aggressive value for trying to minimize timeouts at all
costs.

The default for lightning-pay(7) is 10, which starts to become a major
factor for larger amounts, and is basically ignored for tiny ones.

RETURN VALUE
------------

On success, a "route" array is returned.
Each array element contains 'id' (the node being routed through), 'msatoshi'
(the millisatoshis sent), 'amount_msat' (the same, with 'msat' appended), and 'delay' (the number of blocks to timeout at this
node).

The final 'id' will be the destination 'id' given in the input.  The
difference between the first 'msatoshi' minus the 'msatoshi' given in
the input is the fee.  The first 'delay' is the very worst case
timeout for the payment failure, in blocks.

//FIXME:Enumerate errors

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

SEE ALSO
--------
lightning-pay(7), lightning-sendpay(7).

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