feat: make the minimum signal threshold configurable

Author: abarmat

contracts/rewards/IRewardsManager.sol

@@ -13,10 +13,12 @@ interface IRewardsManager {
         uint256 accRewardsPerAllocatedToken;
     }
 
-    // -- Params --
+    // -- Config --
 
     function setIssuanceRate(uint256 _issuanceRate) external;
 
+    function setMinimumSubgraphSignal(uint256 _minimumSubgraphSignal) external;
+
     // -- Denylist --
 
     function setSubgraphAvailabilityOracle(address _subgraphAvailabilityOracle) external;

contracts/rewards/RewardsManager.sol

@@ -18,12 +18,11 @@ import "./IRewardsManager.sol";
  * total rewards for the Subgraph are split up for each Indexer based on much they have Staked on
  * that Subgraph.
  */
-contract RewardsManager is RewardsManagerV1Storage, GraphUpgradeable, IRewardsManager {
+contract RewardsManager is RewardsManagerV2Storage, GraphUpgradeable, IRewardsManager {
     using SafeMath for uint256;
 
     uint256 private constant TOKEN_DECIMALS = 1e18;
     uint256 private constant MIN_ISSUANCE_RATE = 1e18;
-    uint256 private constant REWARDS_ACCRUAL_SIGNALLED_THRESHOLD = 100e18;
 
     // -- Events --
 
@@ -67,6 +66,8 @@ contract RewardsManager is RewardsManagerV1Storage, GraphUpgradeable, IRewardsMa
         _setIssuanceRate(_issuanceRate);
     }
 
+    // -- Config --
+
     /**
      * @dev Sets the issuance rate.
      * The issuance rate is defined as a percentage increase of the total supply per block.
@@ -106,6 +107,24 @@ contract RewardsManager is RewardsManagerV1Storage, GraphUpgradeable, IRewardsMa
         emit ParameterUpdated("subgraphAvailabilityOracle");
     }
 
+    /**
+     * @dev Sets the minimum signaled tokens on a subgraph to start accruing rewards.
+     * @dev Can be set to zero which means that this feature is not being used.
+     * @param _minimumSubgraphSignal Minimum signaled tokens
+     */
+    function setMinimumSubgraphSignal(uint256 _minimumSubgraphSignal) external override {
+        // Caller can be the SAO or the governor
+        require(
+            msg.sender == address(subgraphAvailabilityOracle) ||
+                msg.sender == controller.getGovernor(),
+            "Not authorized"
+        );
+        minimumSubgraphSignal = _minimumSubgraphSignal;
+        emit ParameterUpdated("minimumSubgraphSignal");
+    }
+
+    // -- Denylist --
+
     /**
      * @dev Denies to claim rewards for a subgraph.
      * NOTE: Can only be called by the subgraph availability oracle
@@ -156,6 +175,8 @@ contract RewardsManager is RewardsManagerV1Storage, GraphUpgradeable, IRewardsMa
         return denylist[_subgraphDeploymentID] > 0;
     }
 
+    // -- Getters --
+
     /**
      * @dev Gets the issuance of rewards per signal since last updated.
      *
@@ -228,7 +249,7 @@ contract RewardsManager is RewardsManagerV1Storage, GraphUpgradeable, IRewardsMa
         uint256 subgraphSignalledTokens = curation().getCurationPoolTokens(_subgraphDeploymentID);
 
         // Only accrue rewards if over a threshold
-        uint256 newRewards = (subgraphSignalledTokens > REWARDS_ACCRUAL_SIGNALLED_THRESHOLD) // Accrue new rewards since last snapshot
+        uint256 newRewards = (subgraphSignalledTokens > minimumSubgraphSignal) // Accrue new rewards since last snapshot
             ? getAccRewardsPerSignal()
                 .sub(subgraph.accRewardsPerSignalSnapshot)
                 .mul(subgraphSignalledTokens)
@@ -272,6 +293,8 @@ contract RewardsManager is RewardsManagerV1Storage, GraphUpgradeable, IRewardsMa
         );
     }
 
+    // -- Updates --
+
     /**
      * @dev Updates the accumulated rewards per signal and save checkpoint block number.
      * Must be called before `issuanceRate` or `total signalled GRT` changes

contracts/rewards/RewardsManagerStorage.sol

@@ -21,3 +21,8 @@ contract RewardsManagerV1Storage is Managed {
     // Subgraph denylist : subgraph deployment ID => block when added or zero (if not denied)
     mapping(bytes32 => uint256) public denylist;
 }
+
+contract RewardsManagerV2Storage is RewardsManagerV1Storage {
+    // Minimum amount of signaled tokens on a subgraph required to accrue rewards
+    uint256 public minimumSubgraphSignal;
+}