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DelphiOracle

The DelphiOracle contract acts as a multi-party source of truth, designed to provide the near-realtime price of the asset pairs to other smart contracts or to external users.

The contract allows the current top 105 block producers to push rates for various assets, at a maximum frequency of 1 minute per asset.

When a new datapoint is pushed to the contract, the contract will use the median from the last 21 datapoints.

This provides strong DPOS byzantine fault tolerance guarantees, ensuring a reliable pricefeed even if up to 10 block producers are colluding or corrupt (once a sufficient number of BPs are pushing rates).

Consumer contracts or external applications can retrieve the last price and use it for their needs.

As more block producers and oracles will begin pushing the value at a 1 minute interval, confidence and accuracy of the value will increase.

This repository provides the code to the contract, as well as an updating script written in node.js for oracles and block producers to use.

Ideally, block producers acting as oracles should use their own mechanism to retrieve and aggregate the data, using multiple sources.

A sample updating script using cryptocompare.com's api to retrieve the EOSUSD, EOSBTC and EOSCNY prices is provided as an example.

View live rates on EOS Mainnet:

https://labs.eostitan.com/#/pricefeed-oracle

Incentive mechanisms for BPs to push rates

Each time a BP pushes a datapoint, a counter for this BP is incremented. The contract supports an EOS transfer notification handler which splits any EOS reward sent to the contract between BPs that are pushing rates, proportionally to the number of datapoints they have pushed.

This allows for anyone relying on this pricefeed to incentivize BPs to join and to push rates, simply by transferring any amount of EOS to the contract.

BPs can claim these rewards by calling the claim function.

cleos push action delphioracle claim '{"owner":"<account>"}' -p <account>

In addition, the contract act as a proxy, and automatically revotes every 10,000 datapoints for up to 30 BPs, ranking them by total number of datapoints contributed since inception.

https://www.alohaeos.com/vote/proxy/delphioracle

Users and dApps relying on DelphiOracle are invited to delegate their votes to it, and support contributing BPs.

Push values to the contract

Qualified block producers can call the contract up to once every minute to provide the current price of an asset pair.

Note:

for EOS/USD (eosusd) and EOS/CNY (eoscny), price must be pushed as integer, using the last 4 digits to represent the value after the decimal separator (10,000th of a dollar / yuan precision)

for EOS/BTC (eosbtc), price must be pushed as integer, using the last 8 digits to represent the value after the decimal separator (100,000,000th of a bitcoin precision)

Example: a value for EOS/USD of $5.85 pushed by block producer acryptotitan to delphioracle contract would look like this:

cleos push action delphioracle write '{"owner":"acryptotitan", "quotes": [{"value":58500, "pair":"eosusd"}]}' -p acryptotitan@active

Set up and run updater.js

Updater.js is a nodejs module meant to retrieve the EOS/USD price using cryptocompare.com's API, and push the result to the DelphiOracle smart contract automatically and continuously, with the help of CRON.

cd scripts
npm install

Required: Copy sample.env to .env and update values

Example file for CryptoKylin:

EOS_PROTOCOL='http'
EOS_HOST='api.kylin.alohaeos.com'
EOS_PORT='80'
EOS_KEY='5... <replace with private key>'
EOS_CHAIN='5fff1dae8dc8e2fc4d5b23b2c7665c97f9e9d8edf2b6485a86ba311c25639191'
ORACLE="acryptotitan"
CONTRACT="delphioracle"
FREQ=15000
ORACLE_PERMISSION="active"

Run script (once):

node updater.js

Run script every minute via CRON:

crontab -e

And add the following entry:

* * * * * /path/to/contract/folder/scripts/update.sh

Optional: Create a custom permission for oracle write action. Custom oracle permission can be supplied in the .env file under ORACLE_PERMISSION (defaults to active).

cleos set account permission <eosaccount> <permissionname> <eoskey> <permissionparent>
cleos set action permission <eosaccount> <eoscontract> <action> <permissionname>

Example:

cleos set account permission eostitantest oracle EOS6JhWzHJWystQmEv8VbXTHVagf5LKRVjkowwsdqCNYDFxYZQEJ9 active
cleos set action permission eostitantest delphioracle write oracle

Retrieve the last data point

Note: Use average / 10^quote_precision to get the actual value. quote_precision can be found in the pairs table

cleos get table <eoscontract> <eoscontract> pairs

cleos get table <eoscontract> eosusd datapoints --limit 1

Sample output:

{
  "rows": [{
      "id": "0",
      "owner": "acryptotitan",
      "value": 56800,
      "median": 56863,
      "timestamp": "1564096083"
    }
  ],
  "more": true
}

RNG Data Source

Qualified block producers can call the contract up to once every minute to provide a random source of data for the DelphiOracle RNG.

Example: a source of data pushed by block producer acryptotitan to delphioracle contract would look like this:

cleos push action delphioracle writehash '{"owner":"acryptotitan", "hash":"559aead08264d5795d3909718cdd05abd49572e84fe55590eef31a88a08fdffd", "reveal":""}' -p acryptotitan@active
cleos push action delphioracle writehash '{"owner":"acryptotitan", "hash":"df7e70e5021544f4834bbee64a9e3789febc4be81470df629cad6ddb03320a5c", "reveal":"A"}' -p acryptotitan@active
cleos push action delphioracle writehash '{"owner":"acryptotitan", "hash":"6b23c0d5f35d1b11f9b683f0b0a617355deb11277d91ae091d399c655b87940d", "reveal":"B"}' -p acryptotitan@active
cleos push action delphioracle writehash '{"owner":"acryptotitan", "hash":"3f39d5c348e5b79d06e842c114e6cc571583bbf44e4b0ebfda1a01ec05745d43", "reveal":"C"}' -p acryptotitan@active

• reveal parameter must be empty string on first push.

Compile and deploy delphioracle.cpp (using eosio.cdt v.1.6.x)

git clone https://github.com/eostitan/delphioracle
cd delphioracle
cd build
cmake .. && make
./deploy.sh <eoscontract>

Running the contract locally

If you're querying the contract from your own and need it to run on the local node for testing purposes, you'll need to first create the required account, compile the contract and deploy it. However, before compiling you'll need to edit the source to comment out a line that checks for your account to be a "qualified oracle". This will prevent you from posting prices. The line, in the src/delphioracle.cpp, within the delphioracle::write method is this:

check(check_oracle(owner), "account is not a qualified oracle");

comment it out by prepending the line with //. Next run the following ($PK below should contain the value of your private key):

cleos create account eosio delphioracle $PK $PK -p eosio@active
cd delphioracle
eosio-cpp  -I include/delphioracle/ src/delphioracle.cpp -o delphioracle.wasm --abigen
cleos set contract delphioracle . delphioracle.wasm delphioracle.abi -p delphioracle@active

Once running, the contract needs to be configured:

cd scripts
cleos push action delphioracle configure  "$(cat configure.json)" -p delphioracle

and finally, a price can be pushed up for the EOS/USD pair:

cleos push action delphioracle write '{"owner":"MyAccount", "quotes": [{"value":58500,"pair":"eosusd"}]}' -p MyAccount@active

However, as developers are likely to prefer the "median" field over the "value" field, the above needs to be run 20 times before median gets populated. Of course, the contract throttles traffic so only 1 write per minute is allowed. The developer can run this:

for i in {1..21}; do cleos push action delphioracle write '{"owner":"MyAccont", "quotes": [{"value":56000,"pair":"eosusd"}]}' -p MyAccount@active; sleep 60; done

You can now check the table to make sure your price is there:

cleos get table --limit 100 delphioracle eosusd datapoints

if you have jq installed, you can show the first record, which should contain your price, like this:

cleos get table --limit 100 delphioracle eosusd datapoints |jq .rows[0]