Request polling, Investigation

[rodolfopietro97]

Connex has function pollHead to get block current block. Similar to web socket.
Can be useful to implement a similar generic function that "poll" a generic client function?

[rodolfopietro97]

Create a generic poll that input a function. Pool can be of two kind:

1. Blocking pool -> Wait the result, block execution flow until condition is not satisfied

function blockingPoll(function: (...args: TArgs) => ReturnType, exitCondition: boolean, options) => Promise<ReturnType>

2. Non blocking poll ->Similar to websocket, gives to handlerCallBack the responsibility of doing actions without block execution flow

function nonBlockingPool(function: () => ReturnType, handlerCallBack: (ReturnType) => void, options) => void

[Valazan]

Can you provide some examples in which it can be useful to apply the blocking pool and the non blocking pool?

[rodolfopietro97]

Blocking

const balanceBefore = await thorClient.getBalance(receiverAddress)
const expectedBalanceAfter = balanceBefore + 1VET

const tx = new Transaction(...) // New transaction that transfer 1 VET to receiver
await thorClient.sendTransaction(tx.id)

/*
 * Until the condition"balanceBefore < expectedBalanceAfter" will not satisfied
 * function "thorClient.getBalance(receiverAddress)" will be called every 1 second
 *
 * EXECUTION FLOW IS BLOCKED MEANWHILE
 */
const newBalance = blockingPoll(
     thorClient.getBalance(receiverAddress), 
     balanceBefore < expectedBalanceAfter, 
     {
          requestTime: 1 SECOND
     }
)

[rodolfopietro97]

NON Blocking

const balanceBefore = await thorClient.getBalance(receiverAddress)
const expectedBalanceAfter = balanceBefore + 1VET

const tx = new Transaction(...) // New transaction that transfer 1 VET to receiver
await thorClient.sendTransaction(tx.id)

/*
 * Until the condition"balanceBefore < expectedBalanceAfter" will not satisfied
 * function "thorClient.getBalance(receiverAddress)" will be called every 1 second.
 * BUT in this case each result of "thorClient.getBalance(receiverAddress)" is given as input of 
 * an 'handlerCallback'.
 *
 * EXECUTION FLOW IS NOT BLOCKED MEANWHILE
 */
const newBalance = nonBlockingPoll(
     thorClient.getBalance(receiverAddress), 
    ({ balance, ... }) => {
        console.log(`Current balance is ${balance}`)

        if(balance >= expectedBalanceAfter) console.log('You have received money and you can buy the lambo!!!')
     },
     { requestTime: 1 SECOND }
)

// ...
doOtherStuff()

[rodolfopietro97]

@Valazan added some pseudocode examples

[pierobassa]

As discussed, for non-blocking polling we'll work with the polling request-manager pattern

https://www.enterpriseintegrationpatterns.com/patterns/conversation/Polling.html