Add "Cancel" button to the trades in the Exchange view

[Erlix322]

Could you add a cancel Button in the Exchange view?
Would be great to cancel a pending order directly in there.

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HyperDEX 0.1.0-alpha.1
Electron 2.0.0
win32 10.0.16299
Locale: de

[sindresorhus]

Thanks for the suggestion. We plan to add this.

[lukechilds]

Currently this functionality isn't very useful due to the fact that you can only cancel pending swaps. Normally a swap will either be matched fairly quickly or never match.

• Cancelling swaps that never match obviously doesn't add any real usability.
• Cancelling a swap before it's matched is difficult as it gets matched so fast.
• Cancelling a swap after it's matched would be useful for the user and is probably what most users expect to be able to do but isn't allowed by marketmaker.

I raised this before with James and asked if we could cancel matched swaps but he was strongly opposed to it. Is there any chance you would reconsider @jl777?

[jl777]

we could slow the ordermatch down a lot, but that seems not so good.

alternatively, changing the protocol would be required. What do you suggest to be done? Alice would need to force bob to reclaim the payment and deposit. I am not against it, it just seems quite impractical

[lukechilds]

we could slow the ordermatch down a lot, but that seems not so good.

No, fast matching is good.

alternatively, changing the protocol would be required. What do you suggest to be done? Alice would need to force bob to reclaim the payment and deposit. I am not against it, it just seems quite impractical

@jl777 couldn't you just stop Alice from responding to Bob anymore? So as far as Bob's concerned the swap failed due to network/communication issues. Then the swap will unwind/reclaim using the normal procedure.

Obviously id there's any way to instantly cancel and reclaim funds that's great, but I'm guessing that's not possible due to the timelock.

If so we will display a clear message to the user when they click cancel. We'll let them know that they'll lose their dexfee and it may take up to 4 hours for their funds to be reclaimed. We'll require them to confirm they're ok with that before actually cancelling.

[jl777]

user can effectively do this just by exiting, but I see how it is good to do it your way. I would need to add external signalling to the main swap threads. If we can limit to one cancel at a time, that would enable a global variable based method, it would then generate a "swapcancelled" message so you would know when you can cancel another one

[lukechilds]

If we can limit to one cancel at a time

Aren't we already limited to this because marketmaker requests are serial?

it would then generate a "swapcancelled" message so you would know when you can cancel another one

I think there is already a specific error code in a swap fail message for user cancellation. Not sure which it is but I think it might be one of the ones listed here without a description:

https://docs.google.com/spreadsheets/d/1blgmrJCZ-SfYaJdTTVdk717kZ43R4yzm9YIW2Bt--EM/edit#gid=0

[jl777]

but you want to cancel swaps that are already in progress, dont you?
there is no limit to the number of those, other than the practical limit of how many you can get going before they start completing

[lukechilds]

but you want to cancel swaps that are already in progress, dont you?

Yeah. I was assuming the mm would respond with a success after it's cancelled. So mm wouldn't process a new cancel until the first one finished.

But after re-reading your message with regards to the socket message. It sounds like mm would respond to the request before it's finished cancelling and then we get a message later notifying us when it's successfully cancelled.

If we can limit to one cancel at a time, that would enable a global variable based method, it would then generate a "swapcancelled" message so you would know when you can cancel another one

If I understand this correctly you want to have a single global variable that signals if a swap is cancelling so issuing multiple calls would overwrite the variable and mess things up.

Is there a reason it needs to be implemented like that? Could you add something like an isCancelling property to the specific trade that is cancelling? Or have list of cancelling trades rather than a single value? That way we could cancel multiple trades at once.

Or is that not possible?

[jl777]

once an atomic swap starts, it launches a dedicated thread for that swap
to send messages to a specific swap, then I need to implement a messaging system from the main mm process to all the threads. Not impossible, but:

UUID_being_cancelled = uuid;

above is a much simpler way to implement it. if you update the UUID_being_cancelled before it actually is noticed and cancelled by the dedicated thread, it just wouldnt be cancelled