epoching: simulation infra for integration testing #68
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SebastianElvis
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x/epoching/simulation/operations.go
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| func(_ *rand.Rand) { | ||
| weightMsgDelegate = simappparams.DefaultWeightMsgDelegate | ||
| }, |
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I don't really understand what's happening with this callback. The address of an weightMsgDelegate is passed to GetOrGenerate, and we're setting the value as well to a default... Why not just set it to that default?
I should read the docs you linked to, but perhaps some comments would help anyone coming across this.
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You are right, weightMsgDelegate is always the default value in this case and is not randomised w.r.t. *rand.Rand. This is also taken from the staking module. Sometimes Cosmos SDK uses randomised weights, e.g., https://github.com/cosmos/cosmos-sdk/blob/v0.45.5/x/staking/simulation/genesis.go#L48-L61
In fact I think it's good to randomise its value and the other two weights, in order to simulate all possible distributions of delegation/undelegation/redelegation. Not sure why Cosmos SDK does not do this. Added some TODOs here and will consider randomising these weights in the future.
x/epoching/simulation/operations.go
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| if val.InvalidExRate() { | ||
| return simtypes.NoOpMsg(types.ModuleName, types.TypeMsgWrappedDelegate, "validator's invalid echange rate"), nil, nil | ||
| } |
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| if val.InvalidExRate() { | |
| return simtypes.NoOpMsg(types.ModuleName, types.TypeMsgWrappedDelegate, "validator's invalid echange rate"), nil, nil | |
| } | |
| if val.InvalidExRate() { | |
| return simtypes.NoOpMsg(types.ModuleName, types.TypeMsgWrappedDelegate, "validator's invalid exchange rate"), nil, nil | |
| } |
Not sure, just see ExRate.
What does this mean?
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Judging from https://github.com/cosmos/cosmos-sdk/blob/v0.45.5/x/staking/types/validator.go#L296-L301 it means that the validator has zero token but has delegations with positive token amount, which is impossible and thus invalid.
| srcAddr := srcVal.GetOperator() | ||
| delegations := stk.GetValidatorDelegations(ctx, srcAddr) | ||
| if delegations == nil { | ||
| return simtypes.NoOpMsg(types.ModuleName, types.TypeMsgWrappedBeginRedelegate, "keeper does have any delegation entries"), nil, nil |
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| return simtypes.NoOpMsg(types.ModuleName, types.TypeMsgWrappedBeginRedelegate, "keeper does have any delegation entries"), nil, nil | |
| return simtypes.NoOpMsg(types.ModuleName, types.TypeMsgWrappedBeginRedelegate, "keeper does not have any delegation entries"), nil, nil |
x/epoching/simulation/operations.go
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| delAddr := delegation.GetDelegatorAddr() | ||
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| if stk.HasReceivingRedelegation(ctx, delAddr, srcAddr) { | ||
| return simtypes.NoOpMsg(types.ModuleName, types.TypeMsgWrappedBeginRedelegate, "receveing redelegation is not allowed"), nil, nil // skip |
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| return simtypes.NoOpMsg(types.ModuleName, types.TypeMsgWrappedBeginRedelegate, "receveing redelegation is not allowed"), nil, nil // skip | |
| return simtypes.NoOpMsg(types.ModuleName, types.TypeMsgWrappedBeginRedelegate, "receiving redelegation is not allowed"), nil, nil // skip |
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Wow, there are many typos in the original staking module's implementation 😢 Thanks for catching all of them
| for i, p := range paramChanges { | ||
| require.Equal(t, expected[i].composedKey, p.ComposedKey()) | ||
| require.Equal(t, expected[i].key, p.Key()) | ||
| require.Equal(t, expected[i].simValue, p.SimValue()(r)) |
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Is "82" the random value it changed to with that seed?
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Exactly. If we change rand.NewSource(1) to rand.NewSource(2) then simValue will no longer be 82.
| // NewDecodeStore returns a decoder function closure that unmarshals the KVPair's | ||
| // Value to the corresponding epoching type. | ||
| func NewDecodeStore(cdc codec.Codec) func(kvA, kvB kv.Pair) string { |
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Where is this used? What are these newline separated strings for?
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The decoder function returned by NewDecodeStore will be a part of the module (via RegisterStoreDecoder at https://github.com/cosmos/cosmos-sdk/blob/v0.45.5/x/staking/module.go#L194-L197 for staking module). The decoder function allows the simulation program to test importing/exporting the entire app, which includes parameters, genesis states, and DB (in the GetSimulationLog function at https://github.com/cosmos/cosmos-sdk/blob/v0.45.5/simapp/sim_test.go#L180-L189).
Fixes BM-83
This PR adds the simulation support for the epoching module. It also makes minor modifications on some DB schemas for serialisation and simulation support.
Most of the code is adapted from https://github.com/cosmos/cosmos-sdk/blob/v0.45.5/x/staking/simulation and is based on my understanding below.
Background of Cosmos SDK simulation and integration testing
Cosmos SDK supports integration tests by using the "simulation" technique, in which the simulator program generates the Cosmos-SDK-based application with randomised parameters and genesis states, sends random messages to the application, and verifies the system's correctness properties specified by the developers. See https://docs.cosmos.network/master/core/simulation.html for more details on Cosmos blockchain simulator.
To support simulation, the Cosmo-SDK-based blockchain has to implement a
simulationsubmodule for each module. For each module, itssimulationsubmodule allows to generate random parameters, genesis states and messages of this module. See https://docs.cosmos.network/master/building-modules/simulator.html for details on the module simulation.As an example, Osmosis has submodule
simulationfor each of its module, and implements the simulation program by themselves https://github.com/osmosis-labs/osmosis/tree/main/simulation.