R4R: CDP types and methods #275

karzak · 2019-12-09T23:14:21Z

TODO

msgs
rebase and re-integrate tests using new testing pattern

denalimarsh

Looks good! Review comments are mostly focused on general cleaning and limiting code duplication. Are there any specific Golang styles we're using? I'm pretty sure Cosmos has been using Uber's Go style guide.

denalimarsh · 2020-01-07T15:09:00Z

x/cdp/keeper/deposit.go

+	// deposits blocked if cdp is in liquidation, have to check all deposits
+	deposits := k.GetDeposits(ctx, cdp.ID)
+	for _, d := range deposits {
+		if d.InLiquidation {
+			return types.ErrCdpNotAvailable(k.codespace, cdp.ID)
+		}
+	}


Duplicated below on lines 73-79 and in draw.go on lines 17-22 and 95-100. Could be potentially cleaned up by moving this block into a new method such as func (k Keeper) ValidateAvailableCDP().

denalimarsh · 2020-01-07T15:19:04Z

x/cdp/keeper/deposit.go

+	if !found {
+		return types.ErrCdpNotFound(k.codespace, owner, collateral[0].Denom)
+	}
+	// withdrawals blocked if cdp is in liquidation


See above comment

Not clear we reduce duplication here, as the GetCdpByOwnerAndDenom call is necessary, so to replace it was a ValidateCdpFound() method wouldn't do much.

Was referring to lines 73-79. It appears that my single line selection during reviews is buggy and automatically selects a 4 line block with the single selected line at the bottom, noticed it over in #276 as well. That seems to be the source of the confusion here.

denalimarsh · 2020-01-07T15:33:03Z

x/cdp/keeper/deposit.go

+	collateralizationRatio, err := k.CalculateCollateralizationRatio(ctx, cdp.Collateral.Sub(collateral), cdp.Principal, cdp.AccumulatedFees.Add(fees))
+	if err != nil {
+		return err
+	}
+	liquidationRatio := k.getLiquidationRatio(ctx, collateral[0].Denom)
+	if collateralizationRatio.LT(liquidationRatio) {
+		return types.ErrInvalidCollateralRatio(k.codespace, collateral[0].Denom, collateralizationRatio, liquidationRatio)
+	}


Similar to draw.go lines 32-40 and cdp.go lines 27-34. Can we move this to a ValidateCollateralizationRatio() helper function which checks for ErrInvalidCollateralRatio?

denalimarsh · 2020-01-07T15:37:50Z

x/cdp/keeper/draw.go

+	}
+
+	// fee calculation
+	periods := sdk.NewInt(ctx.BlockTime().Unix() - cdp.FeesUpdated.Unix())


Update to use ...Sub(sdk.NewInt(cdp.FeesUpdated.Unix())), as done in deposit.go lines 49 and 91.

denalimarsh · 2020-01-07T15:38:11Z

x/cdp/keeper/draw.go

+	}
+
+	// calculate fees
+	periods := sdk.NewInt(ctx.BlockTime().Unix() - cdp.FeesUpdated.Unix())


See above comment

denalimarsh · 2020-01-07T15:45:04Z

x/cdp/keeper/deposit.go

+	if deposit.InLiquidation {
+		return types.ErrDepositNotAvailable(k.codespace, cdp.ID, depositor)
+	}


Due to the liquidation status check on line 76, will this condition ever be true?

denalimarsh · 2020-01-07T15:47:14Z

x/cdp/keeper/cdp.go

+	collateralRatio, err := k.CalculateCollateralizationRatio(ctx, collateral, principal, sdk.NewCoins())
+	if err != nil {
+		return err
+	}
+	liquidationRatio := k.getLiquidationRatio(ctx, collateral[0].Denom)
+	if collateralRatio.LT(liquidationRatio) {
+		return types.ErrInvalidCollateralRatio(k.codespace, collateral[0].Denom, collateralRatio, liquidationRatio)
+	}


See #275 (comment)

denalimarsh · 2020-01-07T16:04:16Z

x/cdp/keeper/cdp.go

+		if dc.Amount.LT(dp.DebtFloor) {
+			return types.ErrBelowDebtFloor(k.codespace, sdk.NewCoins(dc), dp.DebtFloor)
+		}


Should a DebtFloor check also be added somewhere in DepositCollateral()/ValidatePrincipalDraw() to prevent dust with additional principal coin types? May allow us to combine this function with ValidatePrincipalDraw(), but I'm not sure I fully understand all the potential implications of such an addition.

rhuairahrighairidh · 2020-01-07T17:31:44Z

x/cdp/types/keys.go

+// - 0x07<denom>:feeRate
+// - 0x08:previousBlockTime
+// - 0x20 - 0xff are reserved for collaterals


Remove this comment? Correct me if I'm wrong but collateral types are assigned byte ids, which as used in store keys, but their namespace doesn't conflict with the other store keys. So they can start at 0x00.

rhuairahrighairidh · 2020-01-07T17:49:42Z

x/cdp/keeper/cdp.go

+func (k Keeper) IndexCdpByCollateralRatio(ctx sdk.Context, denom string, id uint64, collateralRatio sdk.Dec) {
+	store := prefix.NewStore(ctx.KVStore(k.key), types.CollateralRatioIndexPrefix)
+	db, _ := k.GetDenomPrefix(ctx, denom)
+	store.Set(types.CollateralRatioKey(db, id, collateralRatio), types.GetCdpIDBytes(id))
+}
+
+// RemoveCdpCollateralRatioIndex deletes the cdp id from the store's index of cdps by collateral type and collateral to debt ratio
+func (k Keeper) RemoveCdpCollateralRatioIndex(ctx sdk.Context, denom string, id uint64, collateralRatio sdk.Dec) {
+	store := prefix.NewStore(ctx.KVStore(k.key), types.CollateralRatioIndexPrefix)
+	db, _ := k.GetDenomPrefix(ctx, denom)
+	store.Delete(types.CollateralRatioKey(db, id, collateralRatio))
+}


In the staking module, any index updates are written into the Get/Set methods. I kind of like that approach - reduces code repitition in higher level keeper methods, and avoids the posibility that indexes are not updated when they should be.
Do you think it's worth doing for CDP indexes?

Not quite sure what the suggestion is here. Looking through staking, the Set methods are pretty small and there are separate methods for indexes (ie SetValidatorByPowerIndex). The main difference appears to be that there is only one key prefix, which I'm not sure I can accomplish. I thought about the various indexes and iterators that were desirable for CDPs and couldn't come up with an approach that had fewer keys.

ah yeah looking at staking again it's only the SetUnbondingDelegations and SetRedelegations methods that update their indexes. Didn't see validator indexes are not updated in SetValidator.

The idea was that I couldn't think of any reason you would want to set a CDP in the store, but not update the CDP indexes. Having this happen by accident could be bad. Therefore it seems safer to combine SetCDP and IndexCdpByCollateralRatio into one function.

rhuairahrighairidh · 2020-01-07T17:56:39Z

x/cdp/keeper/deposit.go

+	deposit.Amount = deposit.Amount.Sub(collateral)
+	k.SetDeposit(ctx, deposit)


ifdeposit.Amount is reduced down to zero, the deposit is never removed from state. Think this could be exploited to add arbitrary numbers of zero size deposits.

rhuairahrighairidh · 2020-01-07T18:15:26Z

x/cdp/types/keys.go

+// - 0x01<collateralDenomPrefix>:<cdpID_Bytes>: CDP
+//    - cdps are prefix by denom prefix so we can iterate over cdps of one type
+//    - uses : as separator, otherwise the cdp with ID 11 would be selected when iterating over denom with prefix 1


Pretty sure separators aren't needed. If each part of a key is a known fixed length so there's no need to rely on a special : byte to seprate them. The collateralDenomPrefix is fixed at one byte right?
Maybe just update comment, can't see any harm in leaving separators in.

denalimarsh

Review changes look good. Willing to merge this into develop now, as branch kd-update-liquidator will be adding more functionality into the CDP module given the restructuring.

* wip: tpyes and keeper methods * wip: iterators * wip: types and keeper methods * wip: add msgs * wip: client methods * wip: rebase develop * wip: types tests * wip: keeper tests, small fixes * wip: add cdp tests * wip: deposit tests * wip: keeper tests * wip: tests and module methods * feat: error when fetching expired price * feat: conversion factor for external assets * feat: debt floor for new cdps * feat: save deposits on export genesis * feat: ensure messages implement msg * feat: index deposits by status * fix: stray comment * wip: address review comments * address review comments

karzak added the WIP PR is a work in progress and not ready for review label Dec 9, 2019

karzak added 6 commits December 12, 2019 14:27

wip: tpyes and keeper methods

ac471e0

wip: iterators

e2d5797

wip: types and keeper methods

9f8b733

wip: add msgs

a4293be

wip: client methods

dce5687

wip: rebase develop

9e8d857

karzak force-pushed the kd-propose-cdp branch from 4752bba to 9e8d857 Compare December 12, 2019 19:32

karzak added 9 commits December 13, 2019 16:02

wip: types tests

d548ff6

wip: keeper tests, small fixes

b8cbb54

wip: add cdp tests

f3ee33d

wip: deposit tests

5a36f9f

wip: keeper tests

f4b7869

wip: tests and module methods

03320ae

feat: error when fetching expired price

153ff5f

feat: conversion factor for external assets

8786042

feat: debt floor for new cdps

3bbc4f7

karzak added R4R When a PR is ready for review and removed WIP PR is a work in progress and not ready for review labels Dec 26, 2019

karzak changed the title ~~WIP: CDP types and methods~~ R4R: CDP types and methods Dec 26, 2019

karzak added 3 commits December 27, 2019 15:00

feat: save deposits on export genesis

4791b4d

feat: ensure messages implement msg

dc9e103

feat: index deposits by status

4cb344a

denalimarsh self-requested a review January 7, 2020 14:49

denalimarsh reviewed Jan 7, 2020

View reviewed changes

fix: stray comment

0a65454

rhuairahrighairidh reviewed Jan 7, 2020

View reviewed changes

wip: address review comments

5a31fe2

denalimarsh mentioned this pull request Jan 8, 2020

Update Auction Module #276

Merged

11 tasks

address review comments

039e142

denalimarsh approved these changes Jan 11, 2020

View reviewed changes

rebase develop, remove liquidator

5d7cf93

karzak merged commit d849d69 into develop Jan 12, 2020

karzak deleted the kd-propose-cdp branch January 15, 2020 10:40

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R4R: CDP types and methods #275

R4R: CDP types and methods #275

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		deposit.Amount = deposit.Amount.Sub(collateral)
		k.SetDeposit(ctx, deposit)

R4R: CDP types and methods #275

R4R: CDP types and methods #275

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karzak commented Dec 9, 2019 •

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