fix: Take a snapshot of GRT supply when signal is updated

Author: pcarranzav

config/graph.mainnet.yml

@@ -103,7 +103,9 @@ contracts:
     proxy: true
     init:
       controller: "${{Controller.address}}"
-      issuanceRate: "1000000012184945188" # per block increase of total supply, blocks in a year = 365*60*60*24/13
+    calls:
+      - fn: "setIssuanceRate"
+        _issuanceRate: "1000000012184945188" # per block increase of total supply, blocks in a year = 365*60*60*24/13
   AllocationExchange:
     init:
       graphToken: "${{GraphToken.address}}"

contracts/rewards/RewardsManager.sol

@@ -27,7 +27,7 @@ import "./IRewardsManager.sol";
  * These functions may overestimate the actual rewards due to changes in the total supply
  * until the actual takeRewards function is called.
  */
-contract RewardsManager is RewardsManagerV2Storage, GraphUpgradeable, IRewardsManager {
+contract RewardsManager is RewardsManagerV3Storage, GraphUpgradeable, IRewardsManager {
     using SafeMath for uint256;
 
     uint256 private constant TOKEN_DECIMALS = 1e18;
@@ -68,11 +68,8 @@ contract RewardsManager is RewardsManagerV2Storage, GraphUpgradeable, IRewardsMa
     /**
      * @dev Initialize this contract.
      */
-    function initialize(address _controller, uint256 _issuanceRate) external onlyImpl {
+    function initialize(address _controller) external onlyImpl {
         Managed._initialize(_controller);
-
-        // Settings
-        _setIssuanceRate(_issuanceRate);
     }
 
     // -- Config --
@@ -224,7 +221,7 @@ contract RewardsManager is RewardsManagerV2Storage, GraphUpgradeable, IRewardsMa
         }
 
         uint256 r = issuanceRate;
-        uint256 p = graphToken.totalSupply();
+        uint256 p = tokenSupplySnapshot;
         uint256 a = p.mul(_pow(r, t, TOKEN_DECIMALS)).div(TOKEN_DECIMALS);
 
         // New issuance of tokens during time steps
@@ -315,6 +312,7 @@ contract RewardsManager is RewardsManagerV2Storage, GraphUpgradeable, IRewardsMa
     function updateAccRewardsPerSignal() public override returns (uint256) {
         accRewardsPerSignal = getAccRewardsPerSignal();
         accRewardsPerSignalLastBlockUpdated = block.number;
+        tokenSupplySnapshot = graphToken().totalSupply();
         return accRewardsPerSignal;
     }
 

contracts/rewards/RewardsManagerStorage.sol

@@ -26,3 +26,8 @@ contract RewardsManagerV2Storage is RewardsManagerV1Storage {
     // Minimum amount of signaled tokens on a subgraph required to accrue rewards
     uint256 public minimumSubgraphSignal;
 }
+
+contract RewardsManagerV3Storage is RewardsManagerV2Storage {
+    // Snapshot of the total supply of GRT when accRewardsPerSignal was last updated
+    uint256 public tokenSupplySnapshot;
+}

test/lib/deployment.ts

@@ -231,7 +231,7 @@ export async function deployRewardsManager(
   return network.deployContractWithProxy(
     proxyAdmin,
     'RewardsManager',
-    [controller, defaults.rewards.issuanceRate],
+    [controller],
     deployer,
   ) as unknown as RewardsManager
 }

test/lib/fixtures.ts

@@ -75,6 +75,7 @@ export class NetworkFixture {
     await staking.connect(deployer).setSlasher(slasherAddress, true)
     await grt.connect(deployer).addMinter(rewardsManager.address)
     await gns.connect(deployer).approveAll()
+    await rewardsManager.connect(deployer).setIssuanceRate(deployment.defaults.rewards.issuanceRate)
 
     // Unpause the protocol
     await controller.connect(deployer).setPaused(false)

test/staking/allocation.test.ts

@@ -17,7 +17,7 @@ import {
   Account,
 } from '../lib/testHelpers'
 
-const { AddressZero, HashZero } = constants
+const { AddressZero } = constants
 
 const MAX_PPM = toBN('1000000')