feat: Min commission upgrade 0.44 (#10529)

<!--
The default pull request template is for types feat, fix, or refactor.
For other templates, add one of the following parameters to the url:
- template=docs.md
- template=other.md
-->

## Description

Added the ability to set a minimum commission rate that all validators cannot set their commission rate below.

replaces https://github.com/cosmos/cosmos-sdk/pull/10422

---

### Author Checklist

*All items are required. Please add a note to the item if the item is not applicable and
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

*All items are required. Please add a note if the item is not applicable and please add
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

@@ -168,6 +168,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 * (x/bank) [\#9832] (https://github.com/cosmos/cosmos-sdk/pull/9832) Account balance is stored as `sdk.Int` rather than `sdk.Coin`.
 * (x/bank) [\#9890] (https://github.com/cosmos/cosmos-sdk/pull/9890) Remove duplicate denom from denom metadata key.
 * (x/upgrade) [\#10189](https://github.com/cosmos/cosmos-sdk/issues/10189) Removed potential sources of non-determinism in upgrades
+* [\#10393](https://github.com/cosmos/cosmos-sdk/pull/10422) Add `MinCommissionRate` param to `x/staking` module.
 
  ### Deprecated
 

docs/core/proto-docs.md

@@ -8405,6 +8405,7 @@ Params defines the parameters for the staking module.
 | `max_entries` | [uint32](#uint32) |  | max_entries is the max entries for either unbonding delegation or redelegation (per pair/trio). |
 | `historical_entries` | [uint32](#uint32) |  | historical_entries is the number of historical entries to persist. |
 | `bond_denom` | [string](#string) |  | bond_denom defines the bondable coin denomination. |
+| `min_commission_rate` | [string](#string) |  | min_commission_rate is the chain-wide minimum commission rate that a validator can charge their delegators |
 
 
 

proto/cosmos/staking/v1beta1/staking.proto

@@ -282,6 +282,12 @@ message Params {
   uint32 historical_entries = 4;
   // bond_denom defines the bondable coin denomination.
   string bond_denom = 5;
+  // min_commission_rate is the chain-wide minimum commission rate that a validator can charge their delegators
+  string min_commission_rate = 6 [
+    (gogoproto.moretags)   = "yaml:\"min_commission_rate\"",
+    (gogoproto.customtype) = "github.com/cosmos/cosmos-sdk/types.Dec",
+    (gogoproto.nullable)   = false
+  ];
 }
 
 // DelegationResponse is equivalent to Delegation except that it contains a

x/staking/client/testutil/suite.go

@@ -885,12 +885,13 @@ func (s *IntegrationTestSuite) TestGetCmdQueryParams() {
 historical_entries: 10000
 max_entries: 7
 max_validators: 100
+min_commission_rate: "0.000000000000000000"
 unbonding_time: 1814400s`,
 		},
 		{
 			"with json output",
 			[]string{fmt.Sprintf("--%s=json", tmcli.OutputFlag)},
-			`{"unbonding_time":"1814400s","max_validators":100,"max_entries":7,"historical_entries":10000,"bond_denom":"stake"}`,
+			`{"unbonding_time":"1814400s","max_validators":100,"max_entries":7,"historical_entries":10000,"bond_denom":"stake","min_commission_rate":"0.000000000000000000"}`,
 		},
 	}
 	for _, tc := range testCases {

x/staking/keeper/migrations.go

@@ -25,5 +25,5 @@ func (m Migrator) Migrate1to2(ctx sdk.Context) error {
 
 // Migrate2to3 migrates x/staking state from consensus version 2 to 3.
 func (m Migrator) Migrate2to3(ctx sdk.Context) error {
-	return v045.MigrateStore(ctx, m.keeper.storeKey, m.keeper.cdc)
+	return v045.MigrateStore(ctx, m.keeper.storeKey, m.keeper.cdc, m.keeper.paramstore)
 }

x/staking/keeper/msg_server.go

@@ -35,6 +35,10 @@ func (k msgServer) CreateValidator(goCtx context.Context, msg *types.MsgCreateVa
 		return nil, err
 	}
 
+	if msg.Commission.Rate.LT(k.MinCommissionRate(ctx)) {
+		return nil, sdkerrors.Wrapf(types.ErrCommissionLTMinRate, "cannot set validator commission to less than minimum rate of %s", k.MinCommissionRate(ctx))
+	}
+
 	// check to see if the pubkey or sender has been registered before
 	if _, found := k.GetValidator(ctx, valAddr); found {
 		return nil, types.ErrValidatorOwnerExists
@@ -74,6 +78,7 @@ func (k msgServer) CreateValidator(goCtx context.Context, msg *types.MsgCreateVa
 	if err != nil {
 		return nil, err
 	}
+
 	commission := types.NewCommissionWithTime(
 		msg.Commission.Rate, msg.Commission.MaxRate,
 		msg.Commission.MaxChangeRate, ctx.BlockHeader().Time,

x/staking/keeper/params.go

@@ -47,7 +47,13 @@ func (k Keeper) PowerReduction(ctx sdk.Context) sdk.Int {
 	return sdk.DefaultPowerReduction
 }
 
-// Get all parameteras as types.Params
+// MinCommissionRate - Minimum validator commission rate
+func (k Keeper) MinCommissionRate(ctx sdk.Context) (res sdk.Dec) {
+	k.paramstore.Get(ctx, types.KeyMinCommissionRate, &res)
+	return
+}
+
+// Get all parameters as types.Params
 func (k Keeper) GetParams(ctx sdk.Context) types.Params {
 	return types.NewParams(
 		k.UnbondingTime(ctx),
@@ -55,6 +61,7 @@ func (k Keeper) GetParams(ctx sdk.Context) types.Params {
 		k.MaxEntries(ctx),
 		k.HistoricalEntries(ctx),
 		k.BondDenom(ctx),
+		k.MinCommissionRate(ctx),
 	)
 }
 

x/staking/keeper/validator.go

@@ -138,6 +138,10 @@ func (k Keeper) UpdateValidatorCommission(ctx sdk.Context,
 		return commission, err
 	}
 
+	if newRate.LT(k.MinCommissionRate(ctx)) {
+		return commission, fmt.Errorf("cannot set validator commission to less than minimum rate of %s", k.MinCommissionRate(ctx))
+	}
+
 	commission.Rate = newRate
 	commission.UpdateTime = blockTime
 

x/staking/keeper/validator_test.go

@@ -1052,6 +1052,11 @@ func TestUpdateValidatorCommission(t *testing.T) {
 	app, ctx, _, addrVals := bootstrapValidatorTest(t, 1000, 20)
 	ctx = ctx.WithBlockHeader(tmproto.Header{Time: time.Now().UTC()})
 
+	// Set MinCommissionRate to 0.05
+	params := app.StakingKeeper.GetParams(ctx)
+	params.MinCommissionRate = sdk.NewDecWithPrec(5, 2)
+	app.StakingKeeper.SetParams(ctx, params)
+
 	commission1 := types.NewCommissionWithTime(
 		sdk.NewDecWithPrec(1, 1), sdk.NewDecWithPrec(3, 1),
 		sdk.NewDecWithPrec(1, 1), time.Now().UTC().Add(time.Duration(-1)*time.Hour),
@@ -1076,6 +1081,7 @@ func TestUpdateValidatorCommission(t *testing.T) {
 		{val2, sdk.NewDecWithPrec(-1, 1), true},
 		{val2, sdk.NewDecWithPrec(4, 1), true},
 		{val2, sdk.NewDecWithPrec(3, 1), true},
+		{val2, sdk.NewDecWithPrec(1, 2), true},
 		{val2, sdk.NewDecWithPrec(2, 1), false},
 	}
 

x/staking/migrations/v045/store.go

@@ -5,19 +5,29 @@ import (
 	"github.com/cosmos/cosmos-sdk/store/prefix"
 	storetypes "github.com/cosmos/cosmos-sdk/store/types"
 	sdk "github.com/cosmos/cosmos-sdk/types"
+	paramtypes "github.com/cosmos/cosmos-sdk/x/params/types"
 	v040staking "github.com/cosmos/cosmos-sdk/x/staking/migrations/v040"
+	"github.com/cosmos/cosmos-sdk/x/staking/types"
 )
 
 // MigrateStore performs in-place store migrations from v0.43/v0.44 to v0.45.
 // The migration includes:
 //
 // - Removing delegations that have a zero share or token amount.
-func MigrateStore(ctx sdk.Context, storeKey storetypes.StoreKey, cdc codec.BinaryCodec) error {
+// - Setting the MinCommissionRate param in the paramstore
+func MigrateStore(ctx sdk.Context, storeKey storetypes.StoreKey, cdc codec.BinaryCodec, paramstore paramtypes.Subspace) error {
 	store := ctx.KVStore(storeKey)
 
+	migrateParamsStore(ctx, paramstore)
+
 	return purgeDelegations(store, cdc)
 }
 
+func migrateParamsStore(ctx sdk.Context, paramstore paramtypes.Subspace) {
+	paramstore.WithKeyTable(types.ParamKeyTable())
+	paramstore.Set(ctx, types.KeyMinCommissionRate, types.DefaultMinCommissionRate)
+}
+
 func purgeDelegations(store sdk.KVStore, cdc codec.BinaryCodec) error {
 	prefixDelStore := prefix.NewStore(store, v040staking.DelegationKey)
 

x/staking/migrations/v045/store_test.go

@@ -0,0 +1,32 @@
+package v045_test
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/cosmos/cosmos-sdk/simapp"
+	"github.com/cosmos/cosmos-sdk/testutil"
+	sdk "github.com/cosmos/cosmos-sdk/types"
+	paramtypes "github.com/cosmos/cosmos-sdk/x/params/types"
+	v045staking "github.com/cosmos/cosmos-sdk/x/staking/migrations/v045"
+	"github.com/cosmos/cosmos-sdk/x/staking/types"
+)
+
+func TestStoreMigration(t *testing.T) {
+	encCfg := simapp.MakeTestEncodingConfig()
+	stakingKey := sdk.NewKVStoreKey("staking")
+	tStakingKey := sdk.NewTransientStoreKey("transient_test")
+	ctx := testutil.DefaultContext(stakingKey, tStakingKey)
+	paramstore := paramtypes.NewSubspace(encCfg.Codec, encCfg.Amino, stakingKey, tStakingKey, "staking")
+
+	// Check no params
+	require.False(t, paramstore.Has(ctx, types.KeyMinCommissionRate))
+
+	// Run migrations.
+	err := v045staking.MigrateStore(ctx, stakingKey, encCfg.Codec, paramstore)
+	require.NoError(t, err)
+
+	// Make sure the new params are set.
+	require.True(t, paramstore.Has(ctx, types.KeyMinCommissionRate))
+}

x/staking/simulation/genesis.go

@@ -40,9 +40,10 @@ func getHistEntries(r *rand.Rand) uint32 {
 func RandomizedGenState(simState *module.SimulationState) {
 	// params
 	var (
-		unbondTime  time.Duration
-		maxVals     uint32
-		histEntries uint32
+		unbondTime        time.Duration
+		maxVals           uint32
+		histEntries       uint32
+		minCommissionRate sdk.Dec
 	)
 
 	simState.AppParams.GetOrGenerate(
@@ -63,7 +64,7 @@ func RandomizedGenState(simState *module.SimulationState) {
 	// NOTE: the slashing module need to be defined after the staking module on the
 	// NewSimulationManager constructor for this to work
 	simState.UnbondTime = unbondTime
-	params := types.NewParams(simState.UnbondTime, maxVals, 7, histEntries, sdk.DefaultBondDenom)
+	params := types.NewParams(simState.UnbondTime, maxVals, 7, histEntries, sdk.DefaultBondDenom, minCommissionRate)
 
 	// validators & delegations
 	var (

x/staking/spec/08_params.md

@@ -6,11 +6,11 @@ order: 8
 
 The staking module contains the following parameters:
 
-| Key               | Type             | Example           |
-|-------------------|------------------|-------------------|
-| UnbondingTime     | string (time ns) | "259200000000000" |
-| MaxValidators     | uint16           | 100               |
-| KeyMaxEntries     | uint16           | 7                 |
-| HistoricalEntries | uint16           | 3                 |
-| BondDenom         | string           | "stake"           |
-| PowerReduction    | string           | "1000000"         |
+| Key               | Type             | Example                |
+|-------------------|------------------|------------------------|
+| UnbondingTime     | string (time ns) | "259200000000000"      |
+| MaxValidators     | uint16           | 100                    |
+| KeyMaxEntries     | uint16           | 7                      |
+| HistoricalEntries | uint16           | 3                      |
+| BondDenom         | string           | "stake"                |
+| MinCommissionRate | string           | "0.000000000000000000" |

x/staking/types/errors.go

@@ -49,4 +49,5 @@ var (
 	ErrInvalidHistoricalInfo           = sdkerrors.Register(ModuleName, 37, "invalid historical info")
 	ErrNoHistoricalInfo                = sdkerrors.Register(ModuleName, 38, "no historical info found")
 	ErrEmptyValidatorPubKey            = sdkerrors.Register(ModuleName, 39, "empty validator public key")
+	ErrCommissionLTMinRate             = sdkerrors.Register(ModuleName, 40, "commission cannot be less than min rate")
 )

x/staking/types/params.go

@@ -32,12 +32,18 @@ const (
 	DefaultHistoricalEntries uint32 = 10000
 )
 
+var (
+	// DefaultMinCommissionRate is set to 0%
+	DefaultMinCommissionRate = sdk.ZeroDec()
+)
+
 var (
 	KeyUnbondingTime     = []byte("UnbondingTime")
 	KeyMaxValidators     = []byte("MaxValidators")
 	KeyMaxEntries        = []byte("MaxEntries")
 	KeyBondDenom         = []byte("BondDenom")
 	KeyHistoricalEntries = []byte("HistoricalEntries")
+	KeyMinCommissionRate = []byte("MinCommissionRate")
 )
 
 var _ paramtypes.ParamSet = (*Params)(nil)
@@ -48,13 +54,14 @@ func ParamKeyTable() paramtypes.KeyTable {
 }
 
 // NewParams creates a new Params instance
-func NewParams(unbondingTime time.Duration, maxValidators, maxEntries, historicalEntries uint32, bondDenom string) Params {
+func NewParams(unbondingTime time.Duration, maxValidators, maxEntries, historicalEntries uint32, bondDenom string, minCommissionRate sdk.Dec) Params {
 	return Params{
 		UnbondingTime:     unbondingTime,
 		MaxValidators:     maxValidators,
 		MaxEntries:        maxEntries,
 		HistoricalEntries: historicalEntries,
 		BondDenom:         bondDenom,
+		MinCommissionRate: minCommissionRate,
 	}
 }
 
@@ -66,6 +73,7 @@ func (p *Params) ParamSetPairs() paramtypes.ParamSetPairs {
 		paramtypes.NewParamSetPair(KeyMaxEntries, &p.MaxEntries, validateMaxEntries),
 		paramtypes.NewParamSetPair(KeyHistoricalEntries, &p.HistoricalEntries, validateHistoricalEntries),
 		paramtypes.NewParamSetPair(KeyBondDenom, &p.BondDenom, validateBondDenom),
+		paramtypes.NewParamSetPair(KeyMinCommissionRate, &p.MinCommissionRate, validateMinCommissionRate),
 	}
 }
 
@@ -77,6 +85,7 @@ func DefaultParams() Params {
 		DefaultMaxEntries,
 		DefaultHistoricalEntries,
 		sdk.DefaultBondDenom,
+		DefaultMinCommissionRate,
 	)
 }
 
@@ -124,6 +133,10 @@ func (p Params) Validate() error {
 		return err
 	}
 
+	if err := validateMinCommissionRate(p.MinCommissionRate); err != nil {
+		return err
+	}
+
 	return nil
 }
 
@@ -204,3 +217,19 @@ func ValidatePowerReduction(i interface{}) error {
 
 	return nil
 }
+
+func validateMinCommissionRate(i interface{}) error {
+	v, ok := i.(sdk.Dec)
+	if !ok {
+		return fmt.Errorf("invalid parameter type: %T", i)
+	}
+
+	if v.IsNegative() {
+		return fmt.Errorf("minimum commission rate cannot be negative: %s", v)
+	}
+	if v.GT(sdk.OneDec()) {
+		return fmt.Errorf("minimum commission rate cannot be greater than 100%%: %s", v)
+	}
+
+	return nil
+}

x/staking/types/params_test.go

@@ -5,6 +5,7 @@ import (
 
 	"github.com/stretchr/testify/require"
 
+	sdk "github.com/cosmos/cosmos-sdk/types"
 	"github.com/cosmos/cosmos-sdk/x/staking/types"
 )
 
@@ -21,3 +22,17 @@ func TestParamsEqual(t *testing.T) {
 	ok = p1.Equal(p2)
 	require.False(t, ok)
 }
+
+func Test_validateParams(t *testing.T) {
+	params := types.DefaultParams()
+
+	// default params have no error
+	require.NoError(t, params.Validate())
+
+	// validate mincommision
+	params.MinCommissionRate = sdk.NewDec(-1)
+	require.Error(t, params.Validate())
+
+	params.MinCommissionRate = sdk.NewDec(2)
+	require.Error(t, params.Validate())
+}