Failover scenarios
In this page we will explore flow and fallback techniques which allows xApp to run smoothly. Keep in mind this might be a bit technical.
Firstly xApp needs active internet connection on your device. This xApp uses combination of JS events and promises to deliver smooth experience for end-user. Lets explore fail scenarios outlined below.
Access
Read-only XRP accounts in Xaman can view NFT list and details, but can not continue to Payment. Full access accounts are allowed to use Full xApp.
XRPLWin CDN goes offline
xApp Functionality
Functional
Display
Impaired
Overall status
Functional
If CDN goes offline, user can see list of NFTs, user can see NFT IDs but not Image or Title. Filtering won't work.
XRPLWin xApp server goes down
xApp Functionality
Offline
Display
Offline
Overall status
Critical
This scenario only applies to initially loading xApp, when xApp loads fully it does not communicate anymore with xApp server.
Connection error upon opening xApp
Reload button displayed, to reload list of NFTs. User can re-open xApp.
Slow internet connection
This might show as delayed rendering of NFT metadata. User actions are not blocked.
Connection error after signing Escrow transaction
Promise will be pending until reconnect. Delay in showing next step.
Connection error after signing Burn transaction
At this point NFT is burned and user fulfilled its intent, no additional action is required of user, but xApp will try to display confirmation information.
Promise will be pending until reconnect. Delay in starting XRPL transaction verification. On connection error, "Retry action" button will be shown which user can press to retry verification.
User signs Escrow with different account
Memo field contains reference session ID which will be checked against burn transaction in background. User can continue to next step.
User signs Burn transaction with different account
tecNO_PERMISSION code will be thrown in Xaman, xApp handles this by unlocking burn button so user can try again or cancel.
User signs Burn transaction on unexisting NFTokenID
tecNO_ENTRY code will be thrown in Xaman, xApp handles this by unlocking burn button so user can try again or cancel.
Viewing account has very large amount of NFTs
There is hard-coded limit of 10 pages of max 400 NFTs per page which can be loaded with this xApp. Potential max upper limit of NFTs that can be pulled is 4000.
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