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Smart contracts

Streamr can be deployed on any EVM compatible chain. Current deployments are Polygon PoS and the Polygon Amoy testnet.

Smart contract usage​

Please refer to the network incentives document for the high-level description of the tokenomics system. There you also find described two processes: delegation and staking. In delegation, node operators receive DATA tokens from delegators who then receive a share of the profits generated by the operators. In staking, node operators stake the DATA tokens into Sponsorship contracts, and withdraw earnings; sponsoring is included in the staking process as well.

The relevant transactions in the delegation process are:

  • Delegation, sending DATA tokens into the Operator contract: DATA.transferAndCall(operatorAddress, amountWei, "0x")
  • Undelegation, requesting DATA tokens back, either partially or in full: Operator.undelegate(amountWei)
    • the DATA tokens will only return immediate insofar as the Operator contract happens to hold non-staked tokens. The undelegation goes into a queue that gets resolved when DATA returns to the Operator, either via withdrawing or unstaking. The queue takes always precedence: delegators are paid their DATA before they can be re-staked.
    • in case the operator doesn't withdraw earnings and/or unstake enough tokens to pay out the queued delegators, then after 30 days, anyone can force the Operator contract to unstake from a sponsorship contract: Operator.forceUnstake(sponsorshipAddress, 0)

The relevant Operator transactions in the staking process are:

  • Staking, sending DATA tokens from Operator to Sponsorships: Operator.stake(sponsorshipAddress, amountWei)
    • this same function can be used for adding stake, so calling this 2nd time with same arguments will double the stake (not idempotent)
    • once staked, the operator must start relaying the streams associated with the Sponsorship, or risk having their stake slashed
  • Withdrawing, pulling DATA token earnings from Sponsorship: Operator.withdrawEarningsFromSponsorships(sponsorshipAddressList)
  • Reducing stake, pulling some stake back from Sponsorship: Operator.reduceStakeTo(sponsorshipAddress, targetStakeWei)
    • calling this 2nd time with same arguments will fail with Sponsorship.CannotIncreaseStakeUsingReduceStakeTo error
  • Unstaking, pulling DATA token earnings and all stake from Sponsorship: Operator.unstake(sponsorshipAddress, amountWei)
    • once unstaked, the operator may stop relaying the streams associated with the Sponsorship; they receive their stake back, so flagging and slashing can't happen anymore and thus the obligation to relay has ended

The tokens enter the staking process in a transaction from the sponsor(s):

  • Sponsoring, sending DATA tokens into the Sponsorship contract: DATA.transferAndCall(operatorAddress, amountWei, "0x")

Features for compatibility with arbitrary ERC20 token (no transferAndCall)​

This section doesn't apply to the deployed Streamr contracts that use DATA token (that supports transferAndCall). We discourage the use these functions with Streamr contracts: Sponsorship.sponsor, Operator.delegate; use DATA.transferAndCall instead as detailed above.

The tokenomics contracts have been written in such a way that transferAndCall isn't strictly required from the token, but any ERC20 token will also work. This however will require an extra approve transaction on the token before the actual smart contract call that does the sponsoring or delegating.

When sponsoring, the transferAndCall can be replaced with an IERC20.approve(operatorAddress, amountWei) followed by Sponsorship.sponsor.

When delegating, the transferAndCall can be replaced with an IERC20.approve(operatorAddress, amountWei) followed by Operator.delegate(amountWei).