[3][sschiessl-bcp][.5][svk31] Exchange not loading for new, zero-balance accounts

[sschiessl-bcp]

When a new account is created via cloud login, the exchange tab doesnt load anymore for some markets.

prominent example:

does not load
https://wallet.bitshares.org/#/market/USD_BTS

does load
https://wallet.bitshares.org/#/market/BTS_USD

The issue is in

bitshares-ui/app/components/Exchange/Exchange.jsx

Line 288 in c69f297

let feeStatus = {};

that the feeStatus does not get loaded, which causes a return null in the render method.

[sschiessl-bcp]

So far I think it's due to the promise

bitshares-ui/app/lib/common/trxHelper.js

Line 150 in c69f297

asyncCache[key].queue.forEach(promise => {

not being resolved properly

[sschiessl-bcp]

So I probably was digging around for three hours now, learned quite some of the exchange mechanics, still no clue though.

Anyways, it seems that the issue was that there were multiple fee loading promises for BTS in the above case.

Adding this above

bitshares-ui/app/components/Exchange/Exchange.jsx

Line 288 in c69f297

let feeStatus = {};

did resolve it for me

        if (assets[0] === assets[1]) {
            assets.splice(1, 1);
        }

Any insights form anyone as to why this is connected to zero balance accounts? It feels like this is treating the symptom, not the cause.

[svk31]

That does fix the issue, I'm guessing the reason is that checkFeePoolAsync fails silently at some point because it tries to fetch and use balance objects, but the concerned accounts do not have any balances to fetch.

[svk31]

Ok found it: c6cdd4a

[sschiessl-bcp]

@svk31

do you think my initial fix with

assets[0] === assets[1]

is also necessary (I think it could be, because I often hear "my exchange is not loading" in telegram")? The code removes double entries if they occur on index 0,2 or 1,2. Is there a reason double entries occuring on 0,1 should be kept?

[svk31]

I seem to recall that the original reason for removing duplicate assets was simply to make sure the asset info was not fetched twice in parallel. With my recent changes to trxHelper adding request queueing and caching, that's no longer a concern so we can actually just remove that duplicate check in Exchange.jsx.

[svk31]

@wmbutler Not sure how to handle hours on this issue, @sschiessl-bcp's investigations allowed me to find the root cause quite quickly, and it took me about 30 minutes to fix the issue. Stefan should also be assigned some time for his investigations imo.