feat: new grpc call for subscribing alerts and low balance alert (#864)

[rsercano]

Resolves #864

This adds a new middleware between alerts that are being thrown during xud flows and grpc level as we discussed @sangaman But I haven't created two separate PRs, it doesn't make sense since we add a single alert instead of two as in the previous PR (#1984)

• Created a new middleware Alerts class.
• I added time to alert message let me know if want me to remove it or put it to json output.
• Minimum balance alert threshold to re-throw is 10 seconds, let me know if you want to change.
• I added a TODO to Alerts class, it's because we need a clear mechanism there for the map.

This requires a full re-test sorry @raladev

[erkarl]

Thanks for the PR.

Created a new middleware Alerts class.

Why do we need a a new class Alerts? Currently, the class has no public methods and it's just a wrapper event emitter for swap client. Would it make sense to move this to SwapClientManager? Thoughts @sangaman @rsercano?

[rsercano]

Thanks for the PR.

Created a new middleware Alerts class.

Why do we need a a new class Alerts? Currently, the class has no public methods and it's just a wrapper event emitter for swap client. Would it make sense to move this to SwapClientManager? Thoughts @sangaman @rsercano?

Since alerts are not specific to swaps/swapclients actually it was @sangaman's idea to create a new class, which I think makes more sense because in a further time we can add more alerts to xud flow's different places.

[raladev]

@rsercano can u please rebase it ? (need to get connext changes for vector from master).

[rsercano]

@rsercano can u please rebase it ? (need to get connext changes for vector from master).

rebased @raladev

[kilrau]

* we need to decide how it will look for connext or we just should support this alert only for lnd (looks correct for me) @rsercano @sangaman @kilrau

The user will be able to influence this. At the moment the requestCollateral is hidden from the user, but once users need to pay for collateral we will have to show it to the user. We can keep this alert imo.

[rsercano]

@raladev added date to json output as Unix time and formatted in formatted output :)

[kilrau]

Let's give this another round of review @sangaman @raladev

[sangaman]

I pushed a commit to do some refactoring and to preserve type checking. As a general rule I really think we ought to preserve types whenever possible, which are lost with declaring emit: Function.

My last concern is in regards to the proto file field naming & comments/description for purposes of API documentation. See my comments on the unresolved issues above.

[kilrau]

also keep an eye on the failing builds

[sangaman]

also keep an eye on the failing builds

Thanks, just a linting issue. Fixed.

[rsercano]

I guess @sangaman already pushed a commit for this review: https://github.com/ExchangeUnion/xud/pull/2023#discussion_r547105133 Is there anything to do for me here? @raladev @sangaman

[raladev]

I guess @sangaman already pushed a commit for this review: #2023 (comment) Is there anything to do for me here? @raladev @sangaman

• [x] Resolve conflicts
• [x] Check tests, they contain JS errors

[rsercano]

https://github.com/ExchangeUnion/xud/pull/2023#discussion_r551751553 @kilrau @raladev

[kilrau]

I synced with @michael1011 about this and we will not use this information for a channel rebalancer any time soon, the UI will rather use it to display a notification about a general imbalance on a certain asset (not even a specific channel). I think the fields in this PR deliver this, so if if passed your review with that in mind, we can merge as is @sangaman