feat: adds pruning for feegrant (#10830)

Closes: #10685 



---

### Author Checklist

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please add links to any relevant follow up issues.*

I have...

- [ ] included the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] added `!` to the type prefix if API or client breaking change
- [ ] targeted the correct branch (see [PR Targeting](https://github.com/cosmos/cosmos-sdk/blob/master/CONTRIBUTING.md#pr-targeting))
- [ ] provided a link to the relevant issue or specification
- [ ] followed the guidelines for [building modules](https://github.com/cosmos/cosmos-sdk/blob/master/docs/building-modules)
- [ ] included the necessary unit and integration [tests](https://github.com/cosmos/cosmos-sdk/blob/master/CONTRIBUTING.md#testing)
- [ ] added a changelog entry to `CHANGELOG.md`
- [ ] included comments for [documenting Go code](https://blog.golang.org/godoc)
- [ ] updated the relevant documentation or specification
- [ ] reviewed "Files changed" and left comments if necessary
- [ ] confirmed all CI checks have passed

### Reviewers Checklist

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your handle next to the items reviewed if you only reviewed selected items.*

I have...

- [ ] confirmed the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] confirmed `!` in the type prefix if API or client breaking change
- [ ] confirmed all author checklist items have been addressed 
- [ ] reviewed state machine logic
- [ ] reviewed API design and naming
- [ ] reviewed documentation is accurate
- [ ] reviewed tests and test coverage
- [ ] manually tested (if applicable)

CHANGELOG.md

@@ -202,6 +202,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 * [\#10868](https://github.com/cosmos/cosmos-sdk/pull/10868) Bump gov to v1beta2. Both v1beta1 and v1beta2 queries and Msgs are accepted.
 * [\#11011](https://github.com/cosmos/cosmos-sdk/pull/11011) Remove burning of deposits when qourum is not reached on a governance proposal and when the deposit is not fully met. 
 * [\#11019](https://github.com/cosmos/cosmos-sdk/pull/11019) Add `MsgCreatePermanentLockedAccount` and CLI method for creating permanent locked account
+* (x/feegrant) [\#10830](https://github.com/cosmos/cosmos-sdk/pull/10830) Expired allowances will be pruned from state.
 
 ### Deprecated
 

x/feegrant/basic_fee.go

@@ -1,6 +1,8 @@
 package feegrant
 
 import (
+	time "time"
+
 	sdk "github.com/cosmos/cosmos-sdk/types"
 	sdkerrors "github.com/cosmos/cosmos-sdk/types/errors"
 )
@@ -52,3 +54,7 @@ func (a BasicAllowance) ValidateBasic() error {
 
 	return nil
 }
+
+func (a BasicAllowance) ExpiresAt() (*time.Time, error) {
+	return a.Expiration, nil
+}

x/feegrant/events.go

@@ -5,6 +5,7 @@ const (
 	EventTypeUseFeeGrant    = "use_feegrant"
 	EventTypeRevokeFeeGrant = "revoke_feegrant"
 	EventTypeSetFeeGrant    = "set_feegrant"
+	EventTypeUpdateFeeGrant = "update_feegrant"
 
 	AttributeKeyGranter = "granter"
 	AttributeKeyGrantee = "grantee"

x/feegrant/fees.go

@@ -1,6 +1,8 @@
 package feegrant
 
 import (
+	"time"
+
 	sdk "github.com/cosmos/cosmos-sdk/types"
 )
 
@@ -22,4 +24,7 @@ type FeeAllowanceI interface {
 	// ValidateBasic should evaluate this FeeAllowance for internal consistency.
 	// Don't allow negative amounts, or negative periods for example.
 	ValidateBasic() error
+
+	// ExpiresAt returns the expiry time of the allowance.
+	ExpiresAt() (*time.Time, error)
 }

x/feegrant/filtered_fee.go

@@ -1,6 +1,8 @@
 package feegrant
 
 import (
+	"time"
+
 	"github.com/gogo/protobuf/proto"
 
 	"github.com/cosmos/cosmos-sdk/codec/types"
@@ -120,3 +122,11 @@ func (a *AllowedMsgAllowance) ValidateBasic() error {
 
 	return allowance.ValidateBasic()
 }
+
+func (a *AllowedMsgAllowance) ExpiresAt() (*time.Time, error) {
+	allowance, err := a.GetAllowance()
+	if err != nil {
+		return nil, err
+	}
+	return allowance.ExpiresAt()
+}

x/feegrant/keeper/grpc_query.go

@@ -110,10 +110,12 @@ func (q Keeper) AllowancesByGranter(c context.Context, req *feegrant.QueryAllowa
 	var grants []*feegrant.Grant
 
 	store := ctx.KVStore(q.storeKey)
-	pageRes, err := query.Paginate(store, req.Pagination, func(key []byte, value []byte) error {
+	prefixStore := prefix.NewStore(store, feegrant.FeeAllowanceKeyPrefix)
+	pageRes, err := query.Paginate(prefixStore, req.Pagination, func(key []byte, value []byte) error {
 		var grant feegrant.Grant
 
-		granter, _ := feegrant.ParseAddressesFromFeeAllowanceKey(key)
+		// ParseAddressesFromFeeAllowanceKey expects the full key including the prefix.
+		granter, _ := feegrant.ParseAddressesFromFeeAllowanceKey(append(feegrant.FeeAllowanceKeyPrefix, key...))
 		if !granter.Equals(granterAddr) {
 			return nil
 		}

x/feegrant/keeper/keeper.go

@@ -2,6 +2,7 @@ package keeper
 
 import (
 	"fmt"
+	"time"
 
 	storetypes "github.com/cosmos/cosmos-sdk/store/types"
 	"github.com/tendermint/tendermint/libs/log"
@@ -49,6 +50,45 @@ func (k Keeper) GrantAllowance(ctx sdk.Context, granter, grantee sdk.AccAddress,
 
 	store := ctx.KVStore(k.storeKey)
 	key := feegrant.FeeAllowanceKey(granter, grantee)
+
+	var oldExp *time.Time
+	existingGrant, err := k.getGrant(ctx, grantee, granter)
+	if err != nil && existingGrant != nil && existingGrant.GetAllowance() != nil {
+		grantInfo, err := existingGrant.GetGrant()
+		if err != nil {
+			return err
+		}
+
+		oldExp, err = grantInfo.ExpiresAt()
+		if err != nil {
+			return err
+		}
+	}
+
+	newExp, err := feeAllowance.ExpiresAt()
+	if err != nil {
+		return err
+	} else if newExp != nil && newExp.Before(ctx.BlockTime()) {
+		return sdkerrors.Wrap(sdkerrors.ErrInvalidRequest, "expiration is before current block time")
+	} else if oldExp == nil && newExp != nil {
+		// when old oldExp is nil there won't be any key added before to queue.
+		// add the new key to queue directly.
+		k.addToFeeAllowanceQueue(ctx, key[1:], newExp)
+	} else if oldExp != nil && newExp == nil {
+		// when newExp is nil no need of adding the key to the pruning queue
+		// remove the old key from queue.
+		k.removeFromGrantQueue(ctx, oldExp, key[1:])
+	} else if oldExp != nil && newExp != nil && !oldExp.Equal(*newExp) {
+		// `key` formed here with the prefix of `FeeAllowanceKeyPrefix` (which is `0x00`)
+		// remove the 1st byte and reuse the remaining key as it is.
+
+		// remove the old key from queue.
+		k.removeFromGrantQueue(ctx, oldExp, key[1:])
+
+		// add the new key to queue.
+		k.addToFeeAllowanceQueue(ctx, key[1:], newExp)
+	}
+
 	grant, err := feegrant.NewGrant(granter, grantee, feeAllowance)
 	if err != nil {
 		return err
@@ -72,6 +112,39 @@ func (k Keeper) GrantAllowance(ctx sdk.Context, granter, grantee sdk.AccAddress,
 	return nil
 }
 
+// UpdateAllowance updates the existing grant.
+func (k Keeper) UpdateAllowance(ctx sdk.Context, granter, grantee sdk.AccAddress, feeAllowance feegrant.FeeAllowanceI) error {
+	store := ctx.KVStore(k.storeKey)
+	key := feegrant.FeeAllowanceKey(granter, grantee)
+
+	_, err := k.getGrant(ctx, granter, grantee)
+	if err != nil {
+		return err
+	}
+
+	grant, err := feegrant.NewGrant(granter, grantee, feeAllowance)
+	if err != nil {
+		return err
+	}
+
+	bz, err := k.cdc.Marshal(&grant)
+	if err != nil {
+		return err
+	}
+
+	store.Set(key, bz)
+
+	ctx.EventManager().EmitEvent(
+		sdk.NewEvent(
+			feegrant.EventTypeUpdateFeeGrant,
+			sdk.NewAttribute(feegrant.AttributeKeyGranter, grant.Granter),
+			sdk.NewAttribute(feegrant.AttributeKeyGrantee, grant.Grantee),
+		),
+	)
+
+	return nil
+}
+
 // revokeAllowance removes an existing grant
 func (k Keeper) revokeAllowance(ctx sdk.Context, granter, grantee sdk.AccAddress) error {
 	_, err := k.getGrant(ctx, granter, grantee)
@@ -177,7 +250,7 @@ func (k Keeper) UseGrantedFees(ctx sdk.Context, granter, grantee sdk.AccAddress,
 	emitUseGrantEvent(ctx, granter.String(), grantee.String())
 
 	// if fee allowance is accepted, store the updated state of the allowance
-	return k.GrantAllowance(ctx, granter, grantee, grant)
+	return k.UpdateAllowance(ctx, granter, grantee, grant)
 }
 
 func emitUseGrantEvent(ctx sdk.Context, granter, grantee string) {
@@ -228,3 +301,30 @@ func (k Keeper) ExportGenesis(ctx sdk.Context) (*feegrant.GenesisState, error) {
 		Allowances: grants,
 	}, err
 }
+
+func (k Keeper) removeFromGrantQueue(ctx sdk.Context, exp *time.Time, allowanceKey []byte) {
+	key := feegrant.FeeAllowancePrefixQueue(exp, allowanceKey)
+	store := ctx.KVStore(k.storeKey)
+	store.Delete(key)
+}
+
+func (k Keeper) addToFeeAllowanceQueue(ctx sdk.Context, grantKey []byte, exp *time.Time) {
+	store := ctx.KVStore(k.storeKey)
+	store.Set(feegrant.FeeAllowancePrefixQueue(exp, grantKey), []byte{})
+}
+
+// RemoveExpiredAllowances iterates grantsByExpiryQueue and deletes the expired grants.
+func (k Keeper) RemoveExpiredAllowances(ctx sdk.Context) {
+	exp := ctx.BlockTime()
+	store := ctx.KVStore(k.storeKey)
+	iterator := store.Iterator(feegrant.FeeAllowanceQueueKeyPrefix, sdk.InclusiveEndBytes(feegrant.AllowanceByExpTimeKey(&exp)))
+	defer iterator.Close()
+
+	for ; iterator.Valid(); iterator.Next() {
+		store.Delete(iterator.Key())
+		expLen := len(sdk.FormatTimeBytes(ctx.BlockTime()))
+
+		// extract the fee allowance key by removing the allowance queue prefix length, expiration length from key.
+		store.Delete(append(feegrant.FeeAllowanceKeyPrefix, iterator.Key()[1+expLen:]...))
+	}
+}

x/feegrant/keeper/keeper_test.go

@@ -214,15 +214,18 @@ func (suite *KeeperTestSuite) TestUseGrantedFee() {
 		})
 	}
 
-	expired := &feegrant.BasicAllowance{
+	basicAllowance := &feegrant.BasicAllowance{
 		SpendLimit: eth,
 		Expiration: &blockTime,
 	}
-	// creating expired feegrant
-	ctx := suite.sdkCtx.WithBlockTime(oneYear)
-	err := suite.keeper.GrantAllowance(ctx, suite.addrs[0], suite.addrs[2], expired)
+
+	// create basic fee allowance
+	err := suite.keeper.GrantAllowance(suite.sdkCtx, suite.addrs[0], suite.addrs[2], basicAllowance)
 	suite.Require().NoError(err)
 
+	// waiting for future blocks, allowance to be pruned.
+	ctx := suite.sdkCtx.WithBlockTime(oneYear)
+
 	// expect error: feegrant expired
 	err = suite.keeper.UseGrantedFees(ctx, suite.addrs[0], suite.addrs[2], eth, []sdk.Msg{})
 	suite.Error(err)
@@ -232,7 +235,6 @@ func (suite *KeeperTestSuite) TestUseGrantedFee() {
 	_, err = suite.keeper.GetAllowance(ctx, suite.addrs[0], suite.addrs[2])
 	suite.Error(err)
 	suite.Contains(err.Error(), "fee-grant not found")
-
 }
 
 func (suite *KeeperTestSuite) TestIterateGrants() {
@@ -257,5 +259,87 @@ func (suite *KeeperTestSuite) TestIterateGrants() {
 		suite.Require().Contains([]string{suite.addrs[0].String(), suite.addrs[2].String()}, grant.Granter)
 		return true
 	})
+}
+
+func (suite *KeeperTestSuite) TestPruneGrants() {
+	eth := sdk.NewCoins(sdk.NewInt64Coin("eth", 123))
+	now := suite.sdkCtx.BlockTime()
+	oneYearExpiry := now.AddDate(1, 0, 0)
 
+	testCases := []struct {
+		name      string
+		ctx       sdk.Context
+		granter   sdk.AccAddress
+		grantee   sdk.AccAddress
+		allowance feegrant.FeeAllowanceI
+		expErrMsg string
+	}{
+		{
+			name:    "grant not pruned from state",
+			ctx:     suite.sdkCtx,
+			granter: suite.addrs[0],
+			grantee: suite.addrs[1],
+			allowance: &feegrant.BasicAllowance{
+				SpendLimit: suite.atom,
+				Expiration: &now,
+			},
+		},
+		{
+			name:      "grant pruned from state after a block: error",
+			ctx:       suite.sdkCtx.WithBlockTime(now.AddDate(0, 0, 1)),
+			granter:   suite.addrs[2],
+			grantee:   suite.addrs[1],
+			expErrMsg: "not found",
+			allowance: &feegrant.BasicAllowance{
+				SpendLimit: eth,
+				Expiration: &now,
+			},
+		},
+		{
+			name:    "grant not pruned from state after a day: no error",
+			ctx:     suite.sdkCtx.WithBlockTime(now.AddDate(0, 0, 1)),
+			granter: suite.addrs[1],
+			grantee: suite.addrs[0],
+			allowance: &feegrant.BasicAllowance{
+				SpendLimit: eth,
+				Expiration: &oneYearExpiry,
+			},
+		},
+		{
+			name:      "grant pruned from state after a year: error",
+			ctx:       suite.sdkCtx.WithBlockTime(now.AddDate(1, 0, 1)),
+			granter:   suite.addrs[1],
+			grantee:   suite.addrs[2],
+			expErrMsg: "not found",
+			allowance: &feegrant.BasicAllowance{
+				SpendLimit: eth,
+				Expiration: &oneYearExpiry,
+			},
+		},
+		{
+			name:    "no expiry: no error",
+			ctx:     suite.sdkCtx.WithBlockTime(now.AddDate(1, 0, 0)),
+			granter: suite.addrs[1],
+			grantee: suite.addrs[2],
+			allowance: &feegrant.BasicAllowance{
+				SpendLimit: eth,
+				Expiration: &oneYearExpiry,
+			},
+		},
+	}
+
+	for _, tc := range testCases {
+		tc := tc
+		suite.Run(tc.name, func() {
+			suite.keeper.GrantAllowance(suite.sdkCtx, tc.granter, tc.grantee, tc.allowance)
+			suite.app.FeeGrantKeeper.RemoveExpiredAllowances(tc.ctx)
+			grant, err := suite.keeper.GetAllowance(tc.ctx, tc.granter, tc.grantee)
+			if tc.expErrMsg != "" {
+				suite.Error(err)
+				suite.Contains(err.Error(), tc.expErrMsg)
+			} else {
+				suite.NotNil(grant)
+			}
+		})
+	}
 }

x/feegrant/keeper/migrations.go

@@ -0,0 +1,21 @@
+package keeper
+
+import (
+	sdk "github.com/cosmos/cosmos-sdk/types"
+	v046 "github.com/cosmos/cosmos-sdk/x/feegrant/migrations/v046"
+)
+
+// Migrator is a struct for handling in-place store migrations.
+type Migrator struct {
+	keeper Keeper
+}
+
+// NewMigrator returns a new Migrator.
+func NewMigrator(keeper Keeper) Migrator {
+	return Migrator{keeper: keeper}
+}
+
+// Migrate1to2 migrates from version 1 to 2.
+func (m Migrator) Migrate1to2(ctx sdk.Context) error {
+	return v046.MigrateStore(ctx, m.keeper.storeKey, m.keeper.cdc)
+}