Add SchedulerAlgorithm to SchedulerConfig

api/operator.go

@@ -112,7 +112,11 @@ func (op *Operator) RaftRemovePeerByID(id string, q *WriteOptions) error {
 	return nil
 }
 
+// SchedulerConfiguration is the config for controlling scheduler behavior
 type SchedulerConfiguration struct {
+	// SchedulerAlgorithm lets you select between available scheduling algorithms.
+	SchedulerAlgorithm string
+
 	// PreemptionConfig specifies whether to enable eviction of lower
 	// priority jobs to place higher priority jobs.
 	PreemptionConfig PreemptionConfig
@@ -140,6 +144,11 @@ type SchedulerSetConfigurationResponse struct {
 	WriteMeta
 }
 
+// SchedulerAlgorithm is an enum string that encapsulates the valid options for a
+// SchedulerConfiguration stanza's SchedulerAlgorithm. These modes will allow the
+// scheduler to be user-selectable.
+type SchedulerAlgorithm string
+
 // PreemptionConfig specifies whether preemption is enabled based on scheduler type
 type PreemptionConfig struct {
 	SystemSchedulerEnabled  bool

command/agent/operator_endpoint.go

@@ -14,6 +14,8 @@ import (
 	"github.com/hashicorp/raft"
 )
 
+// OperatorRequest is used route operator/raft API requests to the implementing
+// functions.
 func (s *HTTPServer) OperatorRequest(resp http.ResponseWriter, req *http.Request) (interface{}, error) {
 	path := strings.TrimPrefix(req.URL.Path, "/v1/operator/raft/")
 	switch {
@@ -251,7 +253,12 @@ func (s *HTTPServer) schedulerUpdateConfig(resp http.ResponseWriter, req *http.R
 		return nil, CodedError(http.StatusBadRequest, fmt.Sprintf("Error parsing scheduler config: %v", err))
 	}
 
+	if !structs.SchedulerAlgorithmIsValid(conf.SchedulerAlgorithm) {
+		return nil, CodedError(http.StatusBadRequest, fmt.Sprintf("Invalid scheduler algorithm selected."))
+	}
+
 	args.Config = structs.SchedulerConfiguration{
+		SchedulerAlgorithm: conf.SchedulerAlgorithm,
 		PreemptionConfig: structs.PreemptionConfig{
 			SystemSchedulerEnabled:  conf.PreemptionConfig.SystemSchedulerEnabled,
 			BatchSchedulerEnabled:   conf.PreemptionConfig.BatchSchedulerEnabled,

nomad/config.go

@@ -403,6 +403,7 @@ func DefaultConfig() *Config {
 		ServerHealthInterval: 2 * time.Second,
 		AutopilotInterval:    10 * time.Second,
 		DefaultSchedulerConfig: structs.SchedulerConfiguration{
+			SchedulerAlgorithm: structs.SchedulerAlgorithmBinpack,
 			PreemptionConfig: structs.PreemptionConfig{
 				SystemSchedulerEnabled:  true,
 				BatchSchedulerEnabled:   false,

nomad/structs/operator.go

@@ -124,8 +124,37 @@ type AutopilotConfig struct {
 	ModifyIndex uint64
 }
 
+// SchedulerAlgorithm is an enum string that encapsulates the valid options for a
+// SchedulerConfiguration stanza's SchedulerAlgorithm. These modes will allow the
+// scheduler to be user-selectable.
+type SchedulerAlgorithm string
+
+const (
+	// SchedulerAlgorithmBinpack indicates that the scheduler should spread
+	// allocations as evenly as possible over the available hardware.
+	SchedulerAlgorithmBinpack string = "binpack"
+
+	// SchedulerAlgorithmSpread indicates that the scheduler should spread
+	// allocations as evenly as possible over the available hardware.
+	SchedulerAlgorithmSpread string = "spread"
+)
+
+// SchedulerAlgorithmIsValid validates the given SchedulerAlgorithm string and
+// returns true only when a correct algorithm is specified.
+func SchedulerAlgorithmIsValid(alg string) bool {
+	switch alg {
+	case SchedulerAlgorithmBinpack, SchedulerAlgorithmSpread:
+		return true
+	default:
+		return false
+	}
+}
+
 // SchedulerConfiguration is the config for controlling scheduler behavior
 type SchedulerConfiguration struct {
+	// SchedulerAlgorithm lets you select between available scheduling algorithms.
+	SchedulerAlgorithm string `hcl:"scheduler_algorithm"`
+
 	// PreemptionConfig specifies whether to enable eviction of lower
 	// priority jobs to place higher priority jobs.
 	PreemptionConfig PreemptionConfig `hcl:"preemption_config"`