Cache jobs in pool manager

This change caches jobs meant for an entity in the pool manager. This
allows us to avoid querying the db as much and allows us to better determine
when we should scale down.

Signed-off-by: Gabriel Adrian Samfira <gsamfira@cloudbasesolutions.com>

database/sql/instances.go

@@ -20,6 +20,7 @@ import (
 	"errors"
 	"fmt"
 	"log/slog"
+	"math"
 
 	"github.com/google/uuid"
 	"gorm.io/datatypes"
@@ -31,54 +32,74 @@ import (
 	"github.com/cloudbase/garm/params"
 )
 
-func (s *sqlDatabase) CreateInstance(_ context.Context, poolID string, param params.CreateInstanceParams) (instance params.Instance, err error) {
-	pool, err := s.getPoolByID(s.conn, poolID)
-	if err != nil {
-		return params.Instance{}, fmt.Errorf("error fetching pool: %w", err)
-	}
-
+func (s *sqlDatabase) CreateInstance(ctx context.Context, poolID string, param params.CreateInstanceParams) (instance params.Instance, err error) {
 	defer func() {
 		if err == nil {
 			s.sendNotify(common.InstanceEntityType, common.CreateOperation, instance)
 		}
 	}()
 
-	var labels datatypes.JSON
-	if len(param.AditionalLabels) > 0 {
-		labels, err = json.Marshal(param.AditionalLabels)
+	err = s.conn.Transaction(func(tx *gorm.DB) error {
+		pool, err := s.getPoolByID(tx, poolID)
 		if err != nil {
-			return params.Instance{}, fmt.Errorf("error marshalling labels: %w", err)
+			return fmt.Errorf("error fetching pool: %w", err)
 		}
-	}
-
-	var secret []byte
-	if len(param.JitConfiguration) > 0 {
-		secret, err = s.marshalAndSeal(param.JitConfiguration)
-		if err != nil {
-			return params.Instance{}, fmt.Errorf("error marshalling jit config: %w", err)
+		var cnt int64
+		q := s.conn.Model(&Instance{}).Where("pool_id = ?", pool.ID).Count(&cnt)
+		if q.Error != nil {
+			return fmt.Errorf("error fetching instance count: %w", q.Error)
 		}
+		var maxRunners int64
+		if pool.MaxRunners > math.MaxInt64 {
+			maxRunners = math.MaxInt64
+		} else {
+			maxRunners = int64(pool.MaxRunners)
+		}
+		if cnt >= maxRunners {
+			return runnerErrors.NewConflictError("max runners reached for pool %s", pool.ID)
+		}
+
+		var labels datatypes.JSON
+		if len(param.AditionalLabels) > 0 {
+			labels, err = json.Marshal(param.AditionalLabels)
+			if err != nil {
+				return fmt.Errorf("error marshalling labels: %w", err)
+			}
+		}
+
+		var secret []byte
+		if len(param.JitConfiguration) > 0 {
+			secret, err = s.marshalAndSeal(param.JitConfiguration)
+			if err != nil {
+				return fmt.Errorf("error marshalling jit config: %w", err)
+			}
+		}
+
+		newInstance := Instance{
+			Pool:              pool,
+			Name:              param.Name,
+			Status:            param.Status,
+			RunnerStatus:      param.RunnerStatus,
+			OSType:            param.OSType,
+			OSArch:            param.OSArch,
+			CallbackURL:       param.CallbackURL,
+			MetadataURL:       param.MetadataURL,
+			GitHubRunnerGroup: param.GitHubRunnerGroup,
+			JitConfiguration:  secret,
+			AditionalLabels:   labels,
+			AgentID:           param.AgentID,
+		}
+		q = tx.Create(&newInstance)
+		if q.Error != nil {
+			return fmt.Errorf("error creating instance: %w", q.Error)
+		}
+		return nil
+	})
+	if err != nil {
+		return params.Instance{}, fmt.Errorf("error creating instance: %w", err)
 	}
 
-	newInstance := Instance{
-		Pool:              pool,
-		Name:              param.Name,
-		Status:            param.Status,
-		RunnerStatus:      param.RunnerStatus,
-		OSType:            param.OSType,
-		OSArch:            param.OSArch,
-		CallbackURL:       param.CallbackURL,
-		MetadataURL:       param.MetadataURL,
-		GitHubRunnerGroup: param.GitHubRunnerGroup,
-		JitConfiguration:  secret,
-		AditionalLabels:   labels,
-		AgentID:           param.AgentID,
-	}
-	q := s.conn.Create(&newInstance)
-	if q.Error != nil {
-		return params.Instance{}, fmt.Errorf("error creating instance: %w", q.Error)
-	}
-
-	return s.sqlToParamsInstance(newInstance)
+	return s.GetInstance(ctx, param.Name)
 }
 
 func (s *sqlDatabase) getPoolInstanceByName(poolID string, instanceName string) (Instance, error) {