Merge pull request #321 from arangodb/feature/scaling-limits

Added scaling limits.

Author: neunhoef

docs/Manual/Deployment/Kubernetes/DeploymentResource.md

@@ -352,6 +352,14 @@ for `spec.mode: Single` and `2` for `spec.mode: ActiveFailover`).
 For the `syncworkers` group, it is highly recommended to use the same number
 as for the `dbservers` group.
 
+### `spec.<group>.minCount: number`
+
+Specifies a minimum for the count of servers. If set, a specification is invalid if `count < minCount`.
+
+### `spec.<group>.maxCount: number`
+
+Specifies a maximum for the count of servers. If set, a specification is invalid if `count > maxCount`.
+
 ### `spec.<group>.args: []string`
 
 This setting specifies additional commandline arguments passed to all servers of this group.

pkg/apis/deployment/v1alpha/server_group_spec.go

@@ -23,6 +23,7 @@
 package v1alpha
 
 import (
+	"math"
 	"strings"
 
 	"github.com/pkg/errors"
@@ -39,6 +40,10 @@ import (
 type ServerGroupSpec struct {
 	// Count holds the requested number of servers
 	Count *int `json:"count,omitempty"`
+	// MinCount specifies a lower limit for count
+	MinCount *int `json:"minCount,omitempty"`
+	// MaxCount specifies a upper limit for count
+	MaxCount *int `json:"maxCount,omitempty"`
 	// Args holds additional commandline arguments
 	Args []string `json:"args,omitempty"`
 	// StorageClassName specifies the classname for storage of the servers.
@@ -58,6 +63,16 @@ func (s ServerGroupSpec) GetCount() int {
 	return util.IntOrDefault(s.Count)
 }
 
+// GetMinCount returns MinCount or 1 if not set
+func (s ServerGroupSpec) GetMinCount() int {
+	return util.IntOrDefault(s.MinCount, 1)
+}
+
+// GetMaxCount returns MaxCount or
+func (s ServerGroupSpec) GetMaxCount() int {
+	return util.IntOrDefault(s.MaxCount, math.MaxInt32)
+}
+
 // GetNodeSelector returns the selectors for nodes of this group
 func (s ServerGroupSpec) GetNodeSelector() map[string]string {
 	return s.NodeSelector
@@ -110,8 +125,17 @@ func (s ServerGroupSpec) Validate(group ServerGroup, used bool, mode DeploymentM
 				minCount = 2
 			}
 		}
+		if s.GetMinCount() > s.GetMaxCount() {
+			return maskAny(errors.Wrapf(ValidationError, "Invalid min/maxCount. Min (%d) bigger than Max (%d)", s.GetMinCount(), s.GetMaxCount()))
+		}
+		if s.GetCount() < s.GetMinCount() {
+			return maskAny(errors.Wrapf(ValidationError, "Invalid count value %d. Expected >= %d", s.GetCount(), s.GetMinCount()))
+		}
+		if s.GetCount() > s.GetMaxCount() {
+			return maskAny(errors.Wrapf(ValidationError, "Invalid count value %d. Expected <= %d", s.GetCount(), s.GetMaxCount()))
+		}
 		if s.GetCount() < minCount {
-			return maskAny(errors.Wrapf(ValidationError, "Invalid count value %d. Expected >= %d", s.GetCount(), minCount))
+			return maskAny(errors.Wrapf(ValidationError, "Invalid count value %d. Expected >= %d (implicit minimum; by deployment mode)", s.GetCount(), minCount))
 		}
 		if s.GetCount() > 1 && group == ServerGroupSingle && mode == DeploymentModeSingle {
 			return maskAny(errors.Wrapf(ValidationError, "Invalid count value %d. Expected 1", s.GetCount()))
@@ -160,6 +184,8 @@ func (s *ServerGroupSpec) SetDefaults(group ServerGroup, used bool, mode Deploym
 		}
 	} else if s.GetCount() > 0 && !used {
 		s.Count = nil
+		s.MinCount = nil
+		s.MaxCount = nil
 	}
 	if _, found := s.Resources.Requests[v1.ResourceStorage]; !found {
 		switch group {
@@ -189,6 +215,12 @@ func (s *ServerGroupSpec) SetDefaultsFrom(source ServerGroupSpec) {
 	if s.Count == nil {
 		s.Count = util.NewIntOrNil(source.Count)
 	}
+	if s.MinCount == nil {
+		s.MinCount = util.NewIntOrNil(source.MinCount)
+	}
+	if s.MaxCount == nil {
+		s.MaxCount = util.NewIntOrNil(source.MaxCount)
+	}
 	if s.Args == nil {
 		s.Args = source.Args
 	}

pkg/apis/deployment/v1alpha/server_group_spec_test.go

@@ -48,6 +48,12 @@ func TestServerGroupSpecValidateCount(t *testing.T) {
 	assert.Nil(t, ServerGroupSpec{Count: util.NewInt(2)}.Validate(ServerGroupSyncMasters, true, DeploymentModeCluster, EnvironmentProduction))
 	assert.Nil(t, ServerGroupSpec{Count: util.NewInt(2)}.Validate(ServerGroupSyncWorkers, true, DeploymentModeCluster, EnvironmentProduction))
 
+	assert.Nil(t, ServerGroupSpec{Count: util.NewInt(2), MinCount: util.NewInt(2), MaxCount: util.NewInt(5)}.Validate(ServerGroupCoordinators, true, DeploymentModeCluster, EnvironmentDevelopment))
+	assert.Nil(t, ServerGroupSpec{Count: util.NewInt(1), MaxCount: util.NewInt(5)}.Validate(ServerGroupCoordinators, true, DeploymentModeCluster, EnvironmentDevelopment))
+	assert.Nil(t, ServerGroupSpec{Count: util.NewInt(6), MinCount: util.NewInt(2)}.Validate(ServerGroupCoordinators, true, DeploymentModeCluster, EnvironmentDevelopment))
+	assert.Nil(t, ServerGroupSpec{Count: util.NewInt(5), MinCount: util.NewInt(5), MaxCount: util.NewInt(5)}.Validate(ServerGroupCoordinators, true, DeploymentModeCluster, EnvironmentDevelopment))
+	assert.Nil(t, ServerGroupSpec{Count: util.NewInt(2)}.Validate(ServerGroupCoordinators, true, DeploymentModeCluster, EnvironmentDevelopment))
+
 	// Invalid
 	assert.Error(t, ServerGroupSpec{Count: util.NewInt(1)}.Validate(ServerGroupSingle, false, DeploymentModeCluster, EnvironmentDevelopment))
 	assert.Error(t, ServerGroupSpec{Count: util.NewInt(2)}.Validate(ServerGroupSingle, true, DeploymentModeSingle, EnvironmentDevelopment))
@@ -70,6 +76,11 @@ func TestServerGroupSpecValidateCount(t *testing.T) {
 	assert.Error(t, ServerGroupSpec{Count: util.NewInt(1)}.Validate(ServerGroupCoordinators, true, DeploymentModeCluster, EnvironmentProduction))
 	assert.Error(t, ServerGroupSpec{Count: util.NewInt(1)}.Validate(ServerGroupSyncMasters, true, DeploymentModeCluster, EnvironmentProduction))
 	assert.Error(t, ServerGroupSpec{Count: util.NewInt(1)}.Validate(ServerGroupSyncWorkers, true, DeploymentModeCluster, EnvironmentProduction))
+
+	assert.Error(t, ServerGroupSpec{Count: util.NewInt(2), MinCount: util.NewInt(5), MaxCount: util.NewInt(1)}.Validate(ServerGroupCoordinators, true, DeploymentModeCluster, EnvironmentDevelopment))
+	assert.Error(t, ServerGroupSpec{Count: util.NewInt(6), MaxCount: util.NewInt(5)}.Validate(ServerGroupCoordinators, true, DeploymentModeCluster, EnvironmentDevelopment))
+	assert.Error(t, ServerGroupSpec{Count: util.NewInt(1), MinCount: util.NewInt(2)}.Validate(ServerGroupCoordinators, true, DeploymentModeCluster, EnvironmentDevelopment))
+
 }
 
 func TestServerGroupSpecDefault(t *testing.T) {

pkg/apis/deployment/v1alpha/zz_generated.deepcopy.go

@@ -170,6 +170,8 @@ func (ci *clusterScalingIntegration) inspectCluster(ctx context.Context, expectS
 	if dbserversChanged {
 		newSpec.DBServers.Count = util.NewInt(req.GetDBServers())
 	}
+	// Validate will additionally check if
+	// 		min <= count <= max holds for the given server groups
 	if err := newSpec.Validate(); err != nil {
 		// Log failure & create event
 		log.Warn().Err(err).Msg("Validation of updated spec has failed")