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Add prioritization of conflicting constraints #293

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Add prioritization of conflicting constraints #293

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8eb4990
Add prioritization of conflicting constraints
Varsius Oct 22, 2024
003a27e
Remove pointless constraint unit tests
Varsius Nov 1, 2024
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41 changes: 26 additions & 15 deletions internal/core/logic.go
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Original file line number Diff line number Diff line change
Expand Up @@ -121,17 +121,6 @@ func GetEligibleOperations(res ResourceLogic, asset AssetStatus) map[castellum.O
func checkReason(res ResourceLogic, asset AssetStatus, reason castellum.OperationReason) *uint64 {
// phase 1: generate global constraints
//
//NOTE: We only add MinimumSize as a constraint for downsizing. For upsizing,
// it's okay if the target is below MinimumSize. It just means we're inching
// closer *towards* the happy area. (And vice versa for MaximumSize.)
c := emptyConstraints()
if reason == castellum.OperationReasonLow && res.MinimumSize != nil {
c.forbidBelow(*res.MinimumSize)
}
if reason != castellum.OperationReasonLow && res.MaximumSize != nil {
c.forbidAbove(*res.MaximumSize)
}

// We have a bunch of constraints that can cause action if they are crossed:
//- On the Asset, StrictMinimumSize and StrictMaximumSize values describe
// technical constraints that the raw usage numbers cannot represent.
Expand All @@ -140,10 +129,23 @@ func checkReason(res ResourceLogic, asset AssetStatus, reason castellum.Operatio
//
// Because the logic for all of these is identical, we start out by merging
// them (strongest constraint wins).
// Priority 0: StrictMinimumSize, StrictMaximumSize
// Priority 1: MinimumFreeSize, MinimumSize, MaximumSize
c := emptyConstraints()

enforceableMaxSize := asset.StrictMaximumSize
if reason != castellum.OperationReasonLow && enforceableMaxSize != nil {
c.forbidAbove(*enforceableMaxSize)
}

enforceableMinSize := asset.StrictMinimumSize
if res.MinimumFreeSize != nil {
for _, metric := range res.UsageMetrics {
minSize := *res.MinimumFreeSize + uint64(math.Ceil(asset.Usage[metric]))
// Only apply MinimumFreeSize constraint if there is no conflict with strict constraints
if enforceableMaxSize != nil && *enforceableMaxSize < minSize {
continue
}
if enforceableMinSize == nil || *enforceableMinSize < minSize {
enforceableMinSize = &minSize
}
Expand All @@ -153,9 +155,18 @@ func checkReason(res ResourceLogic, asset AssetStatus, reason castellum.Operatio
c.forbidBelow(*enforceableMinSize)
}

enforceableMaxSize := asset.StrictMaximumSize
if reason != castellum.OperationReasonLow && enforceableMaxSize != nil {
c.forbidAbove(*enforceableMaxSize)
//NOTE: We only add MinimumSize as a constraint for downsizing. For upsizing,
// it's okay if the target is below MinimumSize. It just means we're inching
// closer *towards* the happy area. (And vice versa for MaximumSize.)
if reason == castellum.OperationReasonLow && res.MinimumSize != nil {
if asset.StrictMaximumSize == nil || *res.MinimumSize < *asset.StrictMaximumSize {
c.forbidBelow(*res.MinimumSize)
}
}
if reason != castellum.OperationReasonLow && res.MaximumSize != nil {
if asset.StrictMinimumSize == nil || *asset.StrictMinimumSize < *res.MaximumSize {
c.forbidAbove(*res.MaximumSize)
}
}

// do not allow downsize operations to cross above the high/critical thresholds
Expand Down Expand Up @@ -235,7 +246,7 @@ func checkReason(res ResourceLogic, asset AssetStatus, reason castellum.Operatio
}

if reason == enforcer {
a.AddAction(action{Min: *enforceableMinSize, Desired: *enforceableMinSize}, *c)
a.AddAction(action{Desired: *enforceableMinSize}, *c)
// We also let the rest of this method behave as if the `high` threshold
// was crossed. The percentage-step resizing may generate a larger
// target size than this action right now did, in which case it will
Expand Down
59 changes: 42 additions & 17 deletions internal/core/logic_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -333,31 +333,56 @@ func TestGetEligibleOperations(t *testing.T) {

// test conflicts between constraints
//
// Entirely conflicting constraints (max < min) shall paralyze Castellum and
// suppress all actions.
// Entirely conflicting constraints of equal priority shall paralyze Castellum and
// suppress all actions. Otherwise, the stronger constraint should be enforced.
// Priority 0: StrictMinimumSize, StrictMaximumSize
// Priority 1: MinimumFreeSize, MinimumSize, MaximumSize

check(
"low=20%, high=80%, crit=95%, step=200%, min=1000",
"size=1000, usage=500, smax=900",
"", "", // MinimumSize is upheld, but StrictMaximumSize is trying to get us to break it
"low=20%, high=80%, crit=95%, step=20%, max=900",
"size=1000, usage=500, smin=1100",
"high->1200", "high->1100", // StrictMinimumSize takes precedence over maximum constraint
)
check(
"low=20%, high=80%, crit=95%, step=200%, min=1000",
"size=900, usage=500, smax=800",
"", "", // MinimumSize is already broken, and StrictMaximumSize is trying to get us to break it further
"low=10%, high=80%, crit=95%, step=20%, min_free=550",
"size=1000, usage=500, smin=1100",
"high->1200", "high->1100", // StrictMinimumSize takes precedence over minimum free constraint
)
check(
"low=20%, high=80%, crit=95%, step=200%, max=1000",
"size=1000, usage=500, smin=1100",
"", "", // MaximumSize is upheld, but StrictMinimumSize is trying to get us to break it
"low=20%, high=80%, crit=95%, step=20%, min_free=200",
"size=1000, usage=900, smax=1050",
"high->1050", "high->1050", // StrictMaximumSize takes precedence over minimum free constraint
)
check(
"low=20%, high=80%, crit=95%, step=200%, max=1000",
"size=1100, usage=500, smin=1200",
"", "", // MaximumSize is already broken, and StrictMinimumSize is trying to get us to break it further
"low=20%, high=80%, crit=95%, step=20%, min_free=200",
"size=1000, usage=800, smax=900",
"low->900", "low->900", // StrictMaximumSize enforces downsizing over minimum free constraint
)
check(
"low=20%, high=80%, crit=95%, step=20%, min=1100",
"size=1000, usage=800, smax=900",
"low->900", "low->900", // StrictMaximumSize takes precedence over minimum constraint
)
check(
"low=20%, high=80%, crit=95%, step=20%, max=1050, min_free=600",
"size=1000, usage=500",
"high->1050", "high->1050", // Upsizing due to MinimumFreeSize should not exceed maximum constraint
)
check(
"low=20%, high=80%, crit=95%, step=20%",
"size=1000, usage=500, smin=1100, smax=900",
"", "", // Conflict of strict constrains should result in no action
)
check(
"low=20%, high=80%, crit=95%, step=20%, min=1100, max=900",
"size=1000, usage=990",
"", "", // Conflict of non-strict constrains should prevent upsizing
)
check(
"low=20%, high=80%, crit=95%, step=20%, min=1100, max=900",
"size=1000, usage=100",
"", "", // Conflict of non-strict constrains should prevent downsizing
)

//TODO: change the unit tests above to enforce proper precedence between limiting and enforceable constraints
// (paralysis shall only happen when the conflicting constraints are of equal rank, e.g. `smin > smax`)
}

// Builds a ResourceLogic from a compact string representation like "low=20%, high=80%, step=single, min=200".
Expand Down
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