Disable mpp until LND race condition is resolved

[TrezorHannes]

I'm running non-MPP for 48h on my main node and it's working fine.
This proposed change intends to reduce the number of HTLC shards LNDg fires to rebalance.

• mitigates the risk for this LND bug: [bug]: commitment transaction dips peer below chan reserve: internal error causing eclair to FC lightningnetwork/lnd#7657
• additional benefit might be a reduction in base-fees

Up for review, thanks

[BhaagBoseDK]

Ideally it should be linked to a settings with default = allow mpp. This way it is non breaking and allows user to disable MPP if they desire.

[BhaagBoseDK]

make it
if disable_mpp = True:
// set max_parts=1
else:
// keep existing functionality

you can set disable_mpp based on LocalSettings object at the top.

[TrezorHannes]

Please correct me if I'm wrong, but how would that look like in detail?
I would set LND_MPP_DISABLED = False in lndg.settings.py and

if settings.LOGIN_REQUIRED.LND_MPP_DISABLED = True:
    async for payment_response in routerstub.SendPaymentV2(lnr.SendPaymentRequest(payment_request=str(invoice_response.payment_request), fee_limit_msat=int(rebalance.fee_limit*1000), outgoing_chan_ids=chan_ids, last_hop_pubkey=bytes.fromhex(rebalance.last_hop_pubkey), timeout_seconds=(timeout-5), allow_self_payment=True, max_parts=1), timeout=(timeout+60)):
        # Add max_parts=1 for disable_mpp=True
else:
    async for payment_response in routerstub.SendPaymentV2(lnr.SendPaymentRequest(payment_request=str(invoice_response.payment_request), fee_limit_msat=int(rebalance.fee_limit*1000), outgoing_chan_ids=chan_ids, last_hop_pubkey=bytes.fromhex(rebalance.last_hop_pubkey), timeout_seconds=(timeout-5), allow_self_payment=True), timeout=(timeout+60)):
        # no max_parts=1 for disable_mpp=False

?

[TrezorHannes]

@BhaagBoseDK I'm not sure I got the LocalSettings Header part right, would you mind a review and adjust based on how you usually do it in the LNDg codebase, please?

# Define LocalSettings
class LocalSettings:
    def __init__(self):
        self.enable_mpp = True  # Default value is True

# Check if LocalSetting LND-EnableMPP exists and set enable_mpp accordingly
if LocalSettings.objects.filter(key='LND-EnableMpp').exists():
    if int(LocalSettings.objects.filter(key='LND-EnableMpp')[0].value) > 0:
        enable_mpp = True
    else:
        LocalSettings(key='LND-EnableMpp', value='0').save()  # Set with 0 value for the future
        enable_mpp = False
else:
    enable_mpp = True  # Default value is True. Not sure we need it again

if not enable_mpp:
    async for payment_response in routerstub.SendPaymentV2(
        lnr.SendPaymentRequest(
            payment_request=str(invoice_response.payment_request),
            fee_limit_msat=int(rebalance.fee_limit * 1000),
            outgoing_chan_ids=chan_ids,
            last_hop_pubkey=bytes.fromhex(rebalance.last_hop_pubkey),
            timeout_seconds=(timeout - 5),
            allow_self_payment=True,
            max_parts=1
        ),
        timeout=(timeout + 60)
    ):
        # enable_mpp=False
else:
    async for payment_response in routerstub.SendPaymentV2(
        lnr.SendPaymentRequest(
            payment_request=str(invoice_response.payment_request),
            fee_limit_msat=int(rebalance.fee_limit * 1000),
            outgoing_chan_ids=chan_ids,
            last_hop_pubkey=bytes.fromhex(rebalance.last_hop_pubkey),
            timeout_seconds=(timeout - 5),
            allow_self_payment=True
        ),
        timeout=(timeout + 60)
    ):
        # enable_mpp=True

[TrezorHannes]

Bumping this for your kind review @BhaagBoseDK

[cryptosharks131]

This looks good. I would try to condense this to a single SendPaymentRequest by making max_parts=None when MPP is not disabled. This seems to still send payments when set to None but I wasn't able to verify that MPP payments were still being made yet.

[TrezorHannes]

Thanks @cryptosharks131
How about this consolidating the SendPaymentRequest.

@ziggie1984 would you know whether we still send it when max_parts=None?

# Define LocalSettings
class LocalSettings:
    def __init__(self):
        self.enable_mpp = True  # Default value is True

# Check if LocalSetting LND-EnableMPP exists and set enable_mpp accordingly
if LocalSettings.objects.filter(key='LND-EnableMpp').exists():
    if int(LocalSettings.objects.filter(key='LND-EnableMpp')[0].value) > 0:
        enable_mpp = True
    else:
        LocalSettings(key='LND-EnableMpp', value='0').save()  # Set with 0 value for the future
        enable_mpp = False
else:
    enable_mpp = True  # Default value is True. Not sure we need it again

max_parts = 1 if enable_mpp else None  # Adjust max_parts based on the enable_mpp value

async for payment_response in routerstub.SendPaymentV2(
    lnr.SendPaymentRequest(
        payment_request=str(invoice_response.payment_request),
        fee_limit_msat=int(rebalance.fee_limit * 1000),
        outgoing_chan_ids=chan_ids,
        last_hop_pubkey=bytes.fromhex(rebalance.last_hop_pubkey),
        timeout_seconds=(timeout - 5),
        allow_self_payment=True,
        max_parts=max_parts  # Set max_parts based on the enable_mpp value
    ),
    timeout=(timeout + 60)
):

[ziggie1984]

Maybe a bit of background:

The lightning network has either MPP Payment or AMP payments (lnd only). An MPP payment can also be of size 1. So when selecting None here, this will trigger the default behaviour of 16 shards (default) on the lnd side.

I would rather name this setting MaxShards and default it to 1, and allow the user to set it to the default value if he likes?

Btw, value none works but ChatGPT said it won't, never trust an AI !

[TrezorHannes]

I think it's safer to adhere to the standard-payment algo LND already uses, and not define MaxShards arbitrarily.

So we either set it to 1 (which effectively is MPP deactivated nonetheless), or none by default to follow the LND standards. In case LND changes it to another number than 16, we have code tax which needs to be manually adjusted.

I think I had a typo in the max_parts = algo, it should be None if allow_multishards = True, not the other way around as stated above.

Please review

# Define LocalSettings
class LocalSettings:
    def __init__(self):
        self.allow_multishards = True  # Default value is True

# Check if LocalSetting LND-EnableMPP exists and set allow_mpp accordingly
if LocalSettings.objects.filter(key='LND-MaxShards').exists():
    if int(LocalSettings.objects.filter(key='LND-MaxShards')[0].value) > 0:
        allow_multishards = True
    else:
        LocalSettings(key='LND-MaxShards', value='0').save()  # Set with 0 value for the future
        allow_multishards = False
else:
    allow_multishards = True  # Default value is True. Not sure we need it again

max_parts = None if allow_multishards else 1  # Adjust max_parts based on the allow_multishards value

async for payment_response in routerstub.SendPaymentV2(
    lnr.SendPaymentRequest(
        payment_request=str(invoice_response.payment_request),
        fee_limit_msat=int(rebalance.fee_limit * 1000),
        outgoing_chan_ids=chan_ids,
        last_hop_pubkey=bytes.fromhex(rebalance.last_hop_pubkey),
        timeout_seconds=(timeout - 5),
        allow_self_payment=True,
        max_parts=max_parts  # Set max_parts based on the allow_multishards value
    ),
    timeout=(timeout + 60)
):

[ziggie1984]

sounds reasonable let's do it like this

[cryptosharks131]

Looks good, the self declarations are not needed at the top. Maybe we could rename the variable since its more of an on/off here than a max shards setting. I think something like LND-DisableMPP makes sense, since the user is deviating from default LND behavior.