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Retrieving CryptoCompare data using Chainlink

Introduction​

CryptoCompare is a digital platform that offers an extensive API tailored to the world of cryptocurrencies. The CryptoCompare API provides users with a wealth of information, including real-time and historical cryptocurrency price data, market analysis, and other vital metrics across a multitude of exchanges. This comprehensive data set is invaluable for traders, investors, researchers, and developers aiming to integrate cryptocurrency data into their applications or platforms. By offering a combination of accuracy, breadth, and ease of use, CryptoCompare has solidified its position as a go-to resource for those seeking reliable insights into the ever-evolving cryptocurrency market.

The following guide illustrates an easy example of how to retrieve a uint256 value from the CryptoCompare API, and write it to your blockchain smart contract using our highly-resilient Chainlink oracle infrastructure.

Writing coin prices from CryptoCompare to your blockchain smart contract​

Accessing CryptoCompare data from within your blockchain contract or Web3 application is as simple as:

  1. Creating an CryptoCompare API key through the CryptoCompare website.
  2. Deploying the following Chainlink consumer contract onto the ERC-20 blockchain network of your choice.

Below we'll walk you through the steps necessary to implement such a solution.

1. Create a CryptoCompare API key​

In order to retrieve data from the CryptoCompare API, you'll need an API key.

You may request a free API key from CryptoCompare here: CryptoCompare Pricing Plans

Some CryptoCompare API requests such as this example don't require an API key, however.

2. Design your consumer contract​

Add the following sample code to your consumer contract.

2a. Add the constructor:​

The constructor specifies important information about the request destination and payment for your request. Important: This information varies by chain, oracle, and job:

docs/services/direct-request-jobs/examples/coin-price-data/CryptoCompare.sol
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You'll need to replace ADD_CHAINLINK_TOKEN_ADDRESS_HERE, ADD_ORACLE_ADDRESS_HERE, and ADD_JOB_ID_HERE with the values appropriate to the specific blockchain network and job that you'll be using. You can find these values within our Direct Request Job Documentation. Chainlink token addresses can be found here.

2b. Add your request function (example):​

The 'request' function defines the request parameters and sends the request to the Chainlink oracle. For detailed information on each required parameter, reference the above 'Request parameters' section:

docs/services/direct-request-jobs/examples/coin-price-data/CryptoCompare.sol
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2c. Retrieve the response (example):​

docs/services/direct-request-jobs/examples/coin-price-data/CryptoCompare.sol
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Need to protect your API key?​

danger

Data entered into a smart contract is visible to the general public.

If you'd like to protect your API key from being broadcast on-chain, you can instead store this information off-chain on our secure infrastructure. Please fill out our Request Survey to get started - once we receive your information, we'll provide you with a custom job ID that will send your API key safely along with your request.

Simulating the above request logic​

Let's walk through each step of the above sample request, to better understand how it all works together:

1. Send the HTTP request:​

The following curl command simulates the same HTTP request that our Chainlink node makes shortly after you trigger the request() function within your consumer contract:

curl -k -X 'GET' 'https://min-api.cryptocompare.com/data/pricemulti?fsyms=BTC,ETH&tsyms=USD,EUR' -H 'accept: application/json'

2. Analyze the response:​

The following is a sample response body returned to our Chainlink node by the above HTTP request (abbreviated for clarity):

{
  "BTC": {
    "USD": 26034.14,
    "EUR": 24082.32
  },
  "ETH": {
    "USD": 1650.14,
    "EUR": 1526.23
  }
}

3. Apply the JSON path:​

After receiving the above sample response, our Chainlink node will attempt to filter the result by the provided path parameter value (ETH,USD). After applying the provided path, we get the following result:

1650.14

4. Apply the multiplier:​

After filtering the sample response by the provided JSON path, our Chainlink node will multiply the result by the provided multiplier parameter value (10 ** 18). After applying this multiplier, we get the following value, which is ultimately written to your smart contract as a uint256 object by our Chainlink oracle:

1650140000000000000000

Troubleshooting​

Having trouble with your request? Check our Chainlink Direct Requests FAQ.

caution

This job has a configured gas limit of 1,000,000 for writing your result on-chain. If your transaction isn't returning any value after more than 60 seconds of waiting, use the appropriate block explorer to navigate to the 'Oracle Address' you entered into your consumer contract for this job to see if any recent transaction(s) have failed due to an 'out of gas' error. If so, you'll need to either A) Return a smaller response, B) Split your request into multiple oracle transactions, or C) Contact us to request a higher gas allowance for your specific use case (may result in higher job pricing).

Still need more help?​

Please reach out to us in Discord if you require additional assistance with this request.