feat: add autoscaling configuration for prebuilds

Author: evgeniy-scherbina

docs/data-sources/workspace_preset.md

@@ -54,8 +54,27 @@ Required:
 
 Optional:
 
+- `autoscaling` (Block List, Max: 1) Configuration block that defines autoscaling behavior for prebuilds. Use this to automatically adjust the number of prebuild instances based on a schedule. (see [below for nested schema](#nestedblock--prebuilds--autoscaling))
 - `expiration_policy` (Block Set, Max: 1) Configuration block that defines TTL (time-to-live) behavior for prebuilds. Use this to automatically invalidate and delete prebuilds after a certain period, ensuring they stay up-to-date. (see [below for nested schema](#nestedblock--prebuilds--expiration_policy))
 
+<a id="nestedblock--prebuilds--autoscaling"></a>
+### Nested Schema for `prebuilds.autoscaling`
+
+Required:
+
+- `schedule` (Block List, Min: 1) One or more schedule blocks that define when to scale the number of prebuild instances. (see [below for nested schema](#nestedblock--prebuilds--autoscaling--schedule))
+- `timezone` (String) The timezone to use for the autoscaling schedule (e.g., "UTC", "America/New_York").
+
+<a id="nestedblock--prebuilds--autoscaling--schedule"></a>
+### Nested Schema for `prebuilds.autoscaling.schedule`
+
+Required:
+
+- `cron` (String) A cron expression that defines when this schedule should be active. The cron expression must be in the format "* HOUR * * DAY-OF-WEEK" where HOUR is 0-23 and DAY-OF-WEEK is 0-6 (Sunday-Saturday). The minute, day-of-month, and month fields must be "*".
+- `instances` (Number) The number of prebuild instances to maintain during this schedule period.
+
+
+
 <a id="nestedblock--prebuilds--expiration_policy"></a>
 ### Nested Schema for `prebuilds.expiration_policy`
 

integration/integration_test.go

@@ -90,12 +90,17 @@ func TestIntegration(t *testing.T) {
 				// TODO (sasswart): the cli doesn't support presets yet.
 				// once it does, the value for workspace_parameter.value
 				// will be the preset value.
-				"workspace_parameter.value":                        `param value`,
-				"workspace_parameter.icon":                         `param icon`,
-				"workspace_preset.name":                            `preset`,
-				"workspace_preset.parameters.param":                `preset param value`,
-				"workspace_preset.prebuilds.instances":             `1`,
-				"workspace_preset.prebuilds.expiration_policy.ttl": `86400`,
+				"workspace_parameter.value":                                  `param value`,
+				"workspace_parameter.icon":                                   `param icon`,
+				"workspace_preset.name":                                      `preset`,
+				"workspace_preset.parameters.param":                          `preset param value`,
+				"workspace_preset.prebuilds.instances":                       `1`,
+				"workspace_preset.prebuilds.expiration_policy.ttl":           `86400`,
+				"workspace_preset.prebuilds.autoscaling.timezone":            `UTC`,
+				"workspace_preset.prebuilds.autoscaling.schedule0.cron":      `\* 8-18 \* \* 1-5`,
+				"workspace_preset.prebuilds.autoscaling.schedule0.instances": `3`,
+				"workspace_preset.prebuilds.autoscaling.schedule1.cron":      `\* 8-14 \* \* 6`,
+				"workspace_preset.prebuilds.autoscaling.schedule1.instances": `1`,
 			},
 		},
 		{

integration/test-data-source/main.tf

@@ -30,6 +30,17 @@ data "coder_workspace_preset" "preset" {
     expiration_policy {
       ttl = 86400
     }
+    autoscaling {
+      timezone = "UTC"
+      schedule {
+        cron      = "* 8-18 * * 1-5"
+        instances = 3
+      }
+      schedule {
+        cron      = "* 8-14 * * 6"
+        instances = 1
+      }
+    }
   }
 }
 
@@ -56,6 +67,11 @@ locals {
     "workspace_preset.parameters.param" : data.coder_workspace_preset.preset.parameters.param,
     "workspace_preset.prebuilds.instances" : tostring(one(data.coder_workspace_preset.preset.prebuilds).instances),
     "workspace_preset.prebuilds.expiration_policy.ttl" : tostring(one(one(data.coder_workspace_preset.preset.prebuilds).expiration_policy).ttl),
+    "workspace_preset.prebuilds.autoscaling.timezone" : tostring(one(one(data.coder_workspace_preset.preset.prebuilds).autoscaling).timezone),
+    "workspace_preset.prebuilds.autoscaling.schedule0.cron" : tostring(one(one(data.coder_workspace_preset.preset.prebuilds).autoscaling).schedule[0].cron),
+    "workspace_preset.prebuilds.autoscaling.schedule0.instances" : tostring(one(one(data.coder_workspace_preset.preset.prebuilds).autoscaling).schedule[0].instances),
+    "workspace_preset.prebuilds.autoscaling.schedule1.cron" : tostring(one(one(data.coder_workspace_preset.preset.prebuilds).autoscaling).schedule[1].cron),
+    "workspace_preset.prebuilds.autoscaling.schedule1.instances" : tostring(one(one(data.coder_workspace_preset.preset.prebuilds).autoscaling).schedule[1].instances),
   }
 }
 

provider/workspace_preset.go

@@ -3,13 +3,18 @@ package provider
 import (
 	"context"
 	"fmt"
+	"strings"
+	"time"
 
 	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/validation"
 	"github.com/mitchellh/mapstructure"
+	rbcron "github.com/robfig/cron/v3"
 )
 
+var PrebuildsCRONParser = rbcron.NewParser(rbcron.Minute | rbcron.Hour | rbcron.Dom | rbcron.Month | rbcron.Dow)
+
 type WorkspacePreset struct {
 	Name       string            `mapstructure:"name"`
 	Parameters map[string]string `mapstructure:"parameters"`
@@ -29,12 +34,23 @@ type WorkspacePrebuild struct {
 	// for utilities that parse our terraform output using this type. To remain compatible
 	// with those cases, we use a slice here.
 	ExpirationPolicy []ExpirationPolicy `mapstructure:"expiration_policy"`
+	Autoscaling      []Autoscaling      `mapstructure:"autoscaling"`
 }
 
 type ExpirationPolicy struct {
 	TTL int `mapstructure:"ttl"`
 }
 
+type Autoscaling struct {
+	Timezone string     `mapstructure:"timezone"`
+	Schedule []Schedule `mapstructure:"schedule"`
+}
+
+type Schedule struct {
+	Cron      string `mapstructure:"cron"`
+	Instances int    `mapstructure:"instances"`
+}
+
 func workspacePresetDataSource() *schema.Resource {
 	return &schema.Resource{
 		SchemaVersion: 1,
@@ -119,9 +135,82 @@ func workspacePresetDataSource() *schema.Resource {
 								},
 							},
 						},
+						"autoscaling": {
+							Type:        schema.TypeList,
+							Description: "Configuration block that defines autoscaling behavior for prebuilds. Use this to automatically adjust the number of prebuild instances based on a schedule.",
+							Optional:    true,
+							MaxItems:    1,
+							Elem: &schema.Resource{
+								Schema: map[string]*schema.Schema{
+									"timezone": {
+										Type:        schema.TypeString,
+										Description: "The timezone to use for the autoscaling schedule (e.g., \"UTC\", \"America/New_York\").",
+										Required:    true,
+										ValidateFunc: func(val interface{}, key string) ([]string, []error) {
+											timezone := val.(string)
+
+											_, err := time.LoadLocation(timezone)
+											if err != nil {
+												return nil, []error{fmt.Errorf("failed to load location: %w", err)}
+											}
+
+											return nil, nil
+										},
+									},
+									"schedule": {
+										Type:        schema.TypeList,
+										Description: "One or more schedule blocks that define when to scale the number of prebuild instances.",
+										Required:    true,
+										MinItems:    1,
+										Elem: &schema.Resource{
+											Schema: map[string]*schema.Schema{
+												"cron": {
+													Type:        schema.TypeString,
+													Description: "A cron expression that defines when this schedule should be active. The cron expression must be in the format \"* HOUR * * DAY-OF-WEEK\" where HOUR is 0-23 and DAY-OF-WEEK is 0-6 (Sunday-Saturday). The minute, day-of-month, and month fields must be \"*\".",
+													Required:    true,
+													ValidateFunc: func(val interface{}, key string) ([]string, []error) {
+														cronSpec := val.(string)
+
+														err := validatePrebuildsCronSpec(cronSpec)
+														if err != nil {
+															return nil, []error{fmt.Errorf("cron spec failed validation: %w", err)}
+														}
+
+														_, err = PrebuildsCRONParser.Parse(cronSpec)
+														if err != nil {
+															return nil, []error{fmt.Errorf("failed to parse cron spec: %w", err)}
+														}
+
+														return nil, nil
+													},
+												},
+												"instances": {
+													Type:        schema.TypeInt,
+													Description: "The number of prebuild instances to maintain during this schedule period.",
+													Required:    true,
+												},
+											},
+										},
+									},
+								},
+							},
+						},
 					},
 				},
 			},
 		},
 	}
 }
+
+// validatePrebuildsCronSpec ensures that the minute, day-of-month and month options of spec are all set to *
+func validatePrebuildsCronSpec(spec string) error {
+	parts := strings.Fields(spec)
+	if len(parts) != 5 {
+		return fmt.Errorf("cron specification should consist of 5 fields")
+	}
+	if parts[0] != "*" || parts[2] != "*" || parts[3] != "*" {
+		return fmt.Errorf("minute, day-of-month and month should be *")
+	}
+
+	return nil
+}