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Data Feed: Stream a data feed on-chain at regular intervals

Overview
A Data Feed utilizes a cron job, which is a time-based job scheduler in Unix-like operating systems, to automatically trigger the submission of transactions to a smart contract on a blockchain. This means that the program will execute the transaction submission at regular intervals without requiring any manual intervention.
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CronJobTriggered Source: 
1.Time-based job scheduler defined in the CronJobTriggered Source definition.
MakeHttpRequest Task:  
1.Makes an API request to the coinbase domain in a secure manner
2.Extracts the ethPrice from the API response
3.Sends the price to the Transact To EVM Function task
TransactToEvmFunction task:
1.Sends back the ethPrice to the contract via function defined by the user in the next block
Midpoint
$ npm install -g midpoint-cli
$ midpoint init blank my-data-feed
1 . Cron Job Triggered 
$ midpoint add-source cronJobTriggeredSource cron-job-source
We define the Cron Job Triggered source so that contract can make a midpoint request. 
{
    "cronJobTriggeredSource": {
        "crontab": "* * * * *",
        "excludeLogs": [],
        "extracts": [
            {
                "name": "Midpoint_ID",
                "from": "Midpoint_ID"
            }
        ]
    }
}
2.  Make Http Request
$ midpoint add-task makeHttpRequest get-eth-price
We define the Make HTTP Request Task to get the ethPrice from the coinbase endpoint.  
{
    "makeHttpRequest": {
        "urlRaw": "https://api.coinbase.com/v2/prices/ETH-USD/spot",
        "method": "GET",
        "urlType": "raw",
        "extracts": [
            {
                "name": "ethPrice",
                "from": "body.data.amount"
            }
        ]
    }
}
3. Shift Decimal
$ midpoint add-task makeHttpRequest shift-eth-price
We define the Shift Decimal Task to return a usable price on-chain. 
{
    "shiftDecimal": {
        "inputValue": "{{ethPrice}}",
        "decimalPlaces": "5",
        "outputName": "ethPriceScaled",
        "round": "false",
        "excludeLogs": []
    }
}
4.  Transact To EVM Function
$ midpoint add-task transactToEvmFunctionTestnet post-eth-price-on-blockchain
We define the Transact to EVM Function Task to send the summary back to the contract. 
{
    "transactToEvmFunctionTestnet": {
        "chainId": "80001",
        "contractAddress": "0xC05f817a17bC0c505E48AC9CC52b5cb556F7B296",
        "arguments": [
            {
                "name": "Midpoint_ID",
                "datatype": "uint64",
                "value": "{{Midpoint_ID}}"
            },
            {
                "name": "EthPrice",
                "datatype": "uint64",
                "value": "{{ethPriceScaled}}"
            }
        ],
        "functionName": "latestEthPrice"
    }
}
5.  Define Path
We define our path file. 
cron-job-source => get-eth-price
get-eth-price => shift-eth-price
shift-eth-price => post-eth-price-to-blockchain
6.  Publish Midpoint
$ midpoint publish
Listener: Subscribe an internal service to any event
Data Bridge: Pass arbitrary messages between chains
Last modified 8mo ago