Lnd: rpc: REST endpoint for CloseChannel hangs

[jamaljsr]

Background

When sending an HTTP request to DELETE /v1/channels/{channel_point.funding_txid_str}/{channel_point.output_index}, the response hangs until the next block is mined. When the response is returned it contains two JSON objects instead of a single one.

{"result":{"close_pending":{"txid":"3F8yolDdkh8OEVmdnK8lHlQaNG7a+qtHbw3WLHITGeU="}}}
{"result":{"chan_close":{"closing_txid":"3F8yolDdkh8OEVmdnK8lHlQaNG7a+qtHbw3WLHITGeU="}}}

i skimmed through the rpc.proto file and noticed that the SendPayment and OpenChannel have *Sync versions for the REST proxy but CloseChannel does not. It returns a stream instead of a response object, which I believe may be the reason why it hangs until the async operation completes.

There is also no way to pass in the --force parameter via the REST API. Currently the two parameters for funding_txid and output_index are supplied in the URL. The endpoint does not have a way to provide the additional options, such as force, time_limit, block, conf_target, sat_per_byte.

Your environment

• version of lnd: tested 0.5.2-beta and master branch as of 2a65245
• which operating system (uname -a on *Nix): Ubuntu 16.04.5 LTS and Windows 10 Pro 1803
• version of btcd, bitcoind, or other backend: btcd version 0.12.0-beta (using --simnet)

Steps to reproduce

Try to close a channel via the REST API using Postman or curl

curl -X DELETE \ 
 https://localhost:8001/v1/channels/1c1cc3d7fb9c5a94628186a376d0c832dced9951968733db745c66aa9ba4cd2d/1 \
  -H 'Content-Type: application/json' \
  -H 'grpc-metadata-macaroon: 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'

Here's a screen cap of the issue in action on simnet
https://imgur.com/a/kGc3mzy

Expected behaviour

The HTTP response should return synchronously with the closing_txid

Actual behaviour

The HTTP response hangs until the next block is mined, which will be in minutes on mainnet/testnet

[wpaulino]

i skimmed through the rpc.proto file and noticed that the SendPayment and OpenChannel have *Sync versions for the REST proxy but CloseChannel does not. It returns a stream instead of a response object, which I believe may be the reason why it hangs until the async operation completes.

This is the problem indeed.

There is also no way to pass in the --force parameter via the REST API. Currently the two parameters for funding_txid and output_index are supplied in the URL. The endpoint does not have a way to provide the additional options, such as force, time_limit, block, conf_target, sat_per_byte.

You should be able to pass these in the URL itself, e.g. https://localhost:8001/v1/channels/1c1cc3d7fb9c5a94628186a376d0c832dced9951968733db745c66aa9ba4cd2d/1?force=true&sat_per_byte=1

[infiniteannant]

{channel_point.funding_txid_str}/{channel_point.output_index}
where can i get these parameters. I got only channel point. Where can i get funding_txid_str and output_index

[jamaljsr]

@infiniteannant the funding_txid_str and output_index are combined to create the channel point, separated by a colon. So given the following channel point returned from lncli listchannels:

{
    ...
    "channel_point": "1c1cc3d7fb9c5a94628186a376d0c832dced9951968733db745c66aa9ba4cd2d:1"
    ...
}

funding_id_str = 1c1cc3d7fb9c5a94628186a376d0c832dced9951968733db745c66aa9ba4cd2d
output_index = 1

[jamaljsr]

Hey @Roasbeef, I know this is a pretty old issue. Is the problem fixed or are you closing because it will not be fixed in the future?

[halseth]

something something websockets?

[sako0938]

So it seems websockets are the only way to close a channel nicely with the rest API?

[guggero]

Yes. There is no "sync" variant of this RPC at the moment.

[sako0938]

If anyone wants some example websocket code for this:

async def closeChannelStream():
    channel_point = ""
    output_index = 0
    force = False
    fee_rate = 3
    url = f'/v1/channels/{channel_point}/{output_index}?force={force}&sat_per_byte={fee_rate}'
    ws = await websockets.connect(f"wss://192.168.1.123:8080{url}&method=DELETE", ping_timeout=None, ping_interval=1, ssl=ssl_context, extra_headers=headers, max_size=1000000000)
    close_data = {}
    await ws.send(json.dumps({}).encode('UTF-8'))
    hi = await ws.recv()
    print(hi)
    async for message in ws:
        print('receiving')
        try:
            hi = await asyncio.wait_for(ws.recv(), timeout=5)
            hi = json.loads(hi)
            # hi = hi['result']
            pprint(hi)
        except asyncio.TimeoutError:
            print('timeout!')
        except asyncio.CancelledError:
            print("cancelled?")