Is it possible to call a payable function within __callback of Oraclize?

Question

I want to run an Oracle query periodically and my idea was to call getUTCTimestamp(0) for the first query where getUTCTimestamp is:

function getUTCTimestamp(uint256 delay) payable {
   oraclize_query(delay,"WolframAlpha", "Timestamp now");
}

and then inside the callback call getUTCTimestamp(60) to have a call every 60 seconds. The thing is that the call inside callback is never executed and I imagine that happens because no ether is supplied. Is this correct? Is there any way to achieve what I want?

Answer 1

Is there any way to achieve what I want?

Yes, recursive queries are very possible using Oraclize.

From the Oraclize documentation at recursive queries:

Smart contracts using Oraclize can be effectively autonomous by implementing a new call to Oraclize into their __callback method. This can be useful for implementing periodic updates of some on-chain reference data, as with price feeds, or to periodically check for some off-chain conditions.

Oraclize recommend to use this kind of queries with particular attention.

The thing is that the call inside callback is never executed and I imagine that happens because no ether is supplied. Is this correct?

Correct. Remember that with Oraclize only the first query is free. After the first you need to pay.You can find at this link more information about the prices: Oraclize pricing.

What you need to do perform recursive queries is just provide your smart contract enough ether to pay for the Oraclize Query multiple times.