track burned fee

app/app.go

@@ -713,7 +713,7 @@ func initMessageAnteDecorators(encodingConfig axelarParams.EncodingConfig, keepe
 func InitModuleAccountPermissions() map[string][]string {
 	return map[string][]string{
 		authtypes.FeeCollectorName:     nil,
-		distrtypes.ModuleName:          {authtypes.Burner},
+		distrtypes.ModuleName:          {authtypes.Minter, authtypes.Burner},
 		minttypes.ModuleName:           {authtypes.Minter},
 		stakingtypes.BondedPoolName:    {authtypes.Burner, authtypes.Staking},
 		stakingtypes.NotBondedPoolName: {authtypes.Burner, authtypes.Staking},

x/distribution/keeper/keeper.go

@@ -1,8 +1,6 @@
 package keeper
 
 import (
-	"fmt"
-
 	sdk "github.com/cosmos/cosmos-sdk/types"
 	distribution "github.com/cosmos/cosmos-sdk/x/distribution/keeper"
 	distributionTypes "github.com/cosmos/cosmos-sdk/x/distribution/types"
@@ -11,6 +9,7 @@ import (
 	"github.com/axelarnetwork/axelar-core/utils/events"
 	"github.com/axelarnetwork/axelar-core/x/distribution/types"
 	"github.com/axelarnetwork/utils/funcs"
+	"github.com/axelarnetwork/utils/slices"
 )
 
 // Keeper wraps the distribution keeper to customize fee allocation mechanism
@@ -39,12 +38,7 @@ func NewKeeper(
 // AllocateTokens modifies the fee distribution by:
 // - Allocating the community tax portion to the community pool
 // - Burning all remaining tokens instead of distributing to validators
-func (k Keeper) AllocateTokens(
-	ctx sdk.Context, _, totalPreviousPower int64,
-	previousProposer sdk.ConsAddress, _ []abci.VoteInfo,
-) {
-	logger := k.Logger(ctx)
-
+func (k Keeper) AllocateTokens(ctx sdk.Context, _, _ int64, _ sdk.ConsAddress, _ []abci.VoteInfo) {
 	// fetch and clear the collected fees for distribution, since this is
 	// called in BeginBlock, collected fees will be from the previous block
 	// (and distributed to the previous proposer)
@@ -58,22 +52,15 @@ func (k Keeper) AllocateTokens(
 		panic(err)
 	}
 
-	// temporary workaround to keep CanWithdrawInvariant happy
-	// general discussions here: https://github.com/cosmos/cosmos-sdk/issues/2906#issuecomment-441867634
 	feePool := k.GetFeePool(ctx)
-	if totalPreviousPower == 0 {
-		feePool.CommunityPool = feePool.CommunityPool.Add(feesCollected...)
-		k.SetFeePool(ctx, feePool)
-		return
-	}
 
 	communityTaxRate := k.GetCommunityTax(ctx)
 	communityPoolAmount := feesCollected.MulDecTruncate(communityTaxRate)
 	remaining := feesCollected.Sub(communityPoolAmount)
 
 	// truncate the remaining coins, return remainder to community pool
-	feeToBurn, remainder := remaining.TruncateDecimal()
-	communityPoolAmount = communityPoolAmount.Add(remainder...)
+	feeToBurn, truncationRemainder := remaining.TruncateDecimal()
+	communityPoolAmount = communityPoolAmount.Add(truncationRemainder...)
 
 	// allocate community funding
 	feePool.CommunityPool = feePool.CommunityPool.Add(communityPoolAmount...)
@@ -85,18 +72,10 @@ func (k Keeper) AllocateTokens(
 		Coins: feeToBurn,
 	})
 
-	// keep the error log from the original implementation
-	proposerValidator := k.stakingKeeper.ValidatorByConsAddr(ctx, previousProposer)
-	if proposerValidator == nil {
-		// previous proposer can be unknown if say, the unbonding period is 1 block, so
-		// e.g. a validator undelegates at block X, it's removed entirely by
-		// block X+1's endblock, then X+2 we need to refer to the previous
-		// proposer for X+1, but we've forgotten about them.
-		logger.Error(fmt.Sprintf(
-			"WARNING: Attempt to allocate proposer rewards to unknown proposer %s. "+
-				"This should happen only if the proposer unbonded completely within a single block, "+
-				"which generally should not happen except in exceptional circumstances (or fuzz testing). "+
-				"We recommend you investigate immediately.",
-			previousProposer.String()))
-	}
+	// track cumulative burned fee
+	feeBurned := slices.Map(feeToBurn, func(coin sdk.Coin) sdk.Coin {
+		return types.ToBurned(coin)
+	})
+	funcs.MustNoErr(k.bankKeeper.MintCoins(ctx, distributionTypes.ModuleName, feeBurned))
+	funcs.MustNoErr(k.bankKeeper.SendCoinsFromModuleToAccount(ctx, distributionTypes.ModuleName, types.ZeroAddress, feeBurned))
 }

x/distribution/keeper/keeper_test.go

@@ -33,12 +33,14 @@ func TestAllocateTokens(t *testing.T) {
 		k           keeper.Keeper
 		accBalances map[string]sdk.Coins
 		bk          *mock.BankKeeperMock
+		fee         sdk.Coins
 	)
 
 	ctx := sdk.NewContext(fake.NewMultiStore(), tmproto.Header{}, false, log.TestingLogger())
 
+	fee = sdk.NewCoins(sdk.NewCoin(axelarnettypes.NativeAsset, sdk.NewInt(rand.PosI64())))
 	accBalances = map[string]sdk.Coins{
-		authtypes.NewModuleAddress(authtypes.FeeCollectorName).String(): sdk.NewCoins(sdk.NewCoin(axelarnettypes.NativeAsset, sdk.NewInt(rand.PosI64()))),
+		authtypes.NewModuleAddress(authtypes.FeeCollectorName).String(): fee,
 	}
 
 	Given("an axelar distribution keeper", func() {
@@ -65,10 +67,24 @@ func TestAllocateTokens(t *testing.T) {
 
 				return nil
 			},
+			SendCoinsFromModuleToAccountFunc: func(ctx sdk.Context, senderModule string, recipientAddr sdk.AccAddress, amt sdk.Coins) error {
+				senderModule = authtypes.NewModuleAddress(senderModule).String()
+
+				accBalances[senderModule] = accBalances[senderModule].Sub(amt)
+				accBalances[recipientAddr.String()] = accBalances[recipientAddr.String()].Add(amt...)
+
+				return nil
+			},
 			BurnCoinsFunc: func(ctx sdk.Context, name string, amt sdk.Coins) error {
 				acc := authtypes.NewModuleAddress(name).String()
 				accBalances[acc] = accBalances[acc].Sub(amt)
 
+				return nil
+			},
+			MintCoinsFunc: func(ctx sdk.Context, name string, amt sdk.Coins) error {
+				acc := authtypes.NewModuleAddress(name).String()
+				accBalances[acc] = accBalances[acc].Add(amt...)
+
 				return nil
 			},
 		}
@@ -98,6 +114,16 @@ func TestAllocateTokens(t *testing.T) {
 				return e.Type == feeBurnedType
 			}), 1)
 
+			expectedBurnedFee := sdk.NewCoins(slices.Map(expectedBurnedFee(ctx, k, fee), types.ToBurned)...)
+			assert.Equal(t, expectedBurnedFee, accBalances[types.ZeroAddress.String()])
 		}).
 		Run(t)
 }
+
+func expectedBurnedFee(ctx sdk.Context, k keeper.Keeper, fee sdk.Coins) sdk.Coins {
+	feesDec := sdk.NewDecCoinsFromCoins(fee...)
+	tax := feesDec.MulDecTruncate(k.GetCommunityTax(ctx))
+	burnAmt, _ := feesDec.Sub(tax).TruncateDecimal()
+
+	return burnAmt
+}

x/distribution/types/expected_keepers.go

@@ -13,6 +13,7 @@ import (
 type BankKeeper interface {
 	types.BankKeeper
 	BurnCoins(ctx sdk.Context, moduleName string, amt sdk.Coins) error
+	MintCoins(ctx sdk.Context, moduleName string, amt sdk.Coins) error
 }
 
 type AccountKeeper interface {

x/distribution/types/types.go

@@ -0,0 +1,16 @@
+package types
+
+import (
+	"fmt"
+
+	sdk "github.com/cosmos/cosmos-sdk/types"
+)
+
+const feeBurnedPrefix = "burned"
+
+var ZeroAddress = sdk.AccAddress(make([]byte, 32))
+
+// ToBurned converts a coin to a coin with 'burned' prefix
+func ToBurned(coin sdk.Coin) sdk.Coin {
+	return sdk.NewCoin(fmt.Sprintf("%s-%s", feeBurnedPrefix, coin.Denom), coin.Amount)
+}