find route for ldk-swift throwing exception when trying to get fee estimate

[diegovelascommerce]

Hello,
I am currently trying to implement a function that tries to get an estimate on the fees that will be added to a bolt11.
The client just wants an idea/estimate on what the fees could be before they pay it.

I implemented the following function that tries to take apart a bolt 11 and then does a findRoute to return the fees.

the is the function I am trying to implement.
https://github.com/diegovelascommerce/VelasLightning/blob/05a7a5b73984f6e6619ed99344227e521ebdf05f/VelasLightningFramework/VelasLightningFramework/Lightning/Lightning.swift#L852

this is where it appears to be where I'm having problems.
https://github.com/diegovelascommerce/VelasLightning/blob/05a7a5b73984f6e6619ed99344227e521ebdf05f/VelasLightningFramework/VelasLightningFramework/Lightning/Lightning.swift#L902

is there something I'm doing wrong in I'm calling Bindings.findRoute or in how I'm setting up the ProbabilisticScorer?

any suggestions or tips would be appreciated.
If you need more clarification, I am more than willing to help

[jkczyz]

findRoute should return either an Ok or Err result. Is it returning an Err there? If so, what is the exact error?

I suspect you need to pass in channelManager.listUsableChannels() to firstHops. Otherwise, if your node is unannounced (i.e., only has unannounced channels) you won't be able to find a path to the payee without doing so.

[diegovelascommerce]

this is the method it tells me to overwrite in the documentation.

[arik-so]

Sorry, I'll update the docs. We now group the transactions so the method signature has changed to take an array of [UInt8]s:

open func broadcastTransactions(txs: [[UInt8]]) {

[diegovelascommerce]

okay that seemed to solve that problem

[diegovelascommerce]

but. now get these problems

[arik-so]

Yeah LDK had some renames under the hood, where Invoice has been renamed to Bolt11Invoice, and ProbabilisticScoringParameters are now ProbabilisticScoringFeeParameters.

[diegovelascommerce]

it can't find Invoice in scope or ProbablisticScoringParameters. were these object renamed to something else?

[diegovelascommerce]

I saw it. I just have not got around to making the changes yet. I will by the end of today.

[diegovelascommerce]

Okay, I renamed all the Invoices to Bolt11Invoice and ProbabilisticScoringParameters to ProbabilisticScoringFeeParameters

but now I'm getting this error.

Cannot convert value of type 'Bindings.ProbabilisticScoringFeeParameters' to expected argument type 'Bindings.ProbabilisticScoringDecayParameters'??? how do I fix this?

[jkczyz]

The parameters were divided into two structs.ProbabilisticScoringDecayParameters should be used for initialization.

[diegovelascommerce]

okay, that got ride of those errors

[diegovelascommerce]

[diegovelascommerce]

Missing argument for parameter 'allowMpp' in call

what does this do?

[jkczyz]

MPP is multi-path payments. Enabling it may cause the router to split your payment into smaller parts sent across multiple paths.

https://bitcoinops.org/en/topics/multipath-payments/

[diegovelascommerce]

wow, that seems like a really cool feature. but for right now I'm just going to keep it at false.

[diegovelascommerce]

Incorrect argument label in call (have 'params:networkGraph:logger:', expected 'decayParams:networkGraph:logger:')

is this fixed as simply as renaming the parameter???

[jkczyz]

Likewise, use ProbabilisticScoringDecayParameters.

[diegovelascommerce]

okay, that took care of it too. just two more to go

[tnull]

@diegovelascommerce Would love to learn if you had any further issues, or if this was resolved?

[diegovelascommerce]

build succeeded

[arik-so]

I was able to replicate it and create a failing unit tests that should be fixed by this PR: lightningdevkit/ldk-swift#118

[arik-so]

I hope this generated archive works for you, @diegovelascommerce: https://github.com/lightningdevkit/ldk-swift/actions/runs/6166381791

[diegovelascommerce]

okay, I will give it a try, though I will need this fix in SPM

[arik-so]

I'm happy to rerelease if it works :)

[diegovelascommerce]

Okay, it returns something now.

question, is the amount returned in Sats or MilliSats.

a total of 1333 sats routing fees seems high for me. especially since the amount for the bolt11 was only 333 sats

[diegovelascommerce]

now it's just returning 0 every time

[diegovelascommerce]

hmmmm: only this bolt11 returns a fee.

lntb3330n1pjsxdscpp58nx5s6zzu0ssazv9d0c25z3j5sxfxphprqj8unja5dwjw2jfcmqqdqqcqzzsxqyz5vqsp5azl3yf208wu0jk6cm6wju3kldw2j4jrnuy0c233cgr3w77320t4s9qyyssqaaykgz4c0sa7uwd7u2wrv8jdux529tjega7jvzlz5kprj3xkv74sqwh7jgvl3dyzpw5sy8a9agg56f2ynjrl0a2dnwernttpqf2dshcpp3eznh

the rest of the ones I made with htlc.me return zero?????

[arik-so]

We're looking into this. Thanks for the screenshots!

[arik-so]

hey @diegovelascommerce, just fyi, I'm still investigating this issue. It's currently looking like there's some underlying gossip bug that I'm running into, so I think there's a chance this bug may not even be caused by the bindings.

[diegovelascommerce]

so what your are saying is that this could be a protocol issues then a code issue?

[arik-so]

hey @diegovelascommerce, would you mind giving this another shot now that Swift 118 is out?