Improve cluster instance placement

cmd/incusd/api_cluster_evacuation.go

@@ -607,20 +607,12 @@ func evacuateClusterSelectTarget(ctx context.Context, s *state.State, inst insta
 
 	// If target member not specified yet, then find the least loaded cluster member which
 	// supports the instance's architecture.
-	if targetMemberInfo == nil {
-		var err error
-
-		err = s.DB.Cluster.Transaction(ctx, func(ctx context.Context, tx *db.ClusterTx) error {
-			targetMemberInfo, err = tx.GetNodeWithLeastInstances(ctx, candidateMembers)
-			if err != nil {
-				return err
-			}
+	if targetMemberInfo == nil && len(candidateMembers) > 0 {
+		targetMemberInfo = &candidateMembers[0]
+	}
 
-			return nil
-		})
-		if err != nil {
-			return nil, nil, err
-		}
+	if targetMemberInfo == nil {
+		return nil, nil, fmt.Errorf("Couldn't find a cluster member for the instance")
 	}
 
 	return sourceMemberInfo, targetMemberInfo, nil

cmd/incusd/instance_post.go

@@ -367,13 +367,11 @@ func instancePost(d *Daemon, r *http.Request) response.Response {
 				}
 			}
 
-			err := s.DB.Cluster.Transaction(r.Context(), func(ctx context.Context, tx *db.ClusterTx) error {
-				targetMemberInfo, err = tx.GetNodeWithLeastInstances(ctx, filteredCandidateMembers)
-				return err
-			})
-			if err != nil {
-				return response.SmartError(err)
+			if len(filteredCandidateMembers) == 0 {
+				return response.InternalError(fmt.Errorf("Couldn't find a cluster member for the instance"))
 			}
+
+			targetMemberInfo = &filteredCandidateMembers[0]
 		}
 
 		if targetMemberInfo.IsOffline(s.GlobalConfig.OfflineThreshold()) {

cmd/incusd/instances_post.go

@@ -1130,14 +1130,12 @@ func instancesPost(d *Daemon, r *http.Request) response.Response {
 		}
 
 		// If no target member was selected yet, pick the member with the least number of instances.
+		if targetMemberInfo == nil && len(candidateMembers) > 0 {
+			targetMemberInfo = &candidateMembers[0]
+		}
+
 		if targetMemberInfo == nil {
-			err = s.DB.Cluster.Transaction(r.Context(), func(ctx context.Context, tx *db.ClusterTx) error {
-				targetMemberInfo, err = tx.GetNodeWithLeastInstances(ctx, candidateMembers)
-				return err
-			})
-			if err != nil {
-				return response.SmartError(err)
-			}
+			return response.InternalError(fmt.Errorf("Couldn't find a cluster member for the instance"))
 		}
 	}
 

doc/api-extensions.md

@@ -2627,3 +2627,7 @@ Allow for creating new LVM cluster pools by setting the `source` to the shared b
 ## `network_ovn_external_interfaces`
 
 This adds support for `bridge.external_interfaces` on OVN networks.
+
+## `instances_scriptlet_get_instances_count`
+
+This allows the instance scriptlet to fetch the count instances given an optional Project or Location filter as well as including pending instances.

doc/explanation/clustering.md

@@ -202,6 +202,7 @@ The following functions are available to the scriptlet (in addition to those pro
 - `get_cluster_member_state(member_name)`: Get the cluster member's state. Returns an object with the cluster member's state in the form of [`api.ClusterMemberState`](https://pkg.go.dev/github.com/lxc/incus/shared/api#ClusterMemberState). `member_name` is the name of the cluster member to get the state for.
 - `get_instance_resources()`: Get information about the resources the instance will require. Returns an object with the resource information in the form of [`scriptlet.InstanceResources`](https://pkg.go.dev/github.com/lxc/incus/shared/api/scriptlet/#InstanceResources).
 - `get_instances(location, project)`: Get a list of instances based on project and/or location filters. Returns the list of instances in the form of [`[]api.Instance`](https://pkg.go.dev/github.com/lxc/incus/shared/api#Instance).
+- `get_instances_count(location, project, pending)`: Get a count of the instances based on project and/or location filters. The count may include instances currently being created for which no database record exists yet..
 - `get_cluster_members(group)`: Get a list of cluster members based on the cluster group. Returns the list of cluster members in the form of [`[]api.ClusterMember`](https://pkg.go.dev/github.com/lxc/incus/shared/api#ClusterMember).
 - `get_project(name)`: Get a project object based on the project name. Returns a project object in the form of [`api.Project`](https://pkg.go.dev/github.com/lxc/incus/shared/api#Project).
 

internal/server/db/instances.go

@@ -13,6 +13,7 @@ import (
 
 	internalInstance "github.com/lxc/incus/v6/internal/instance"
 	"github.com/lxc/incus/v6/internal/server/db/cluster"
+	"github.com/lxc/incus/v6/internal/server/db/operationtype"
 	"github.com/lxc/incus/v6/internal/server/db/query"
 	deviceConfig "github.com/lxc/incus/v6/internal/server/device/config"
 	"github.com/lxc/incus/v6/internal/server/instance/instancetype"
@@ -1103,3 +1104,102 @@ func UpdateInstance(tx *sql.Tx, id int, description string, architecture int, ep
 
 	return nil
 }
+
+// GetInstancesCount returns the number of instances with possible filtering for project or location.
+// It also supports looking for instances currently being created.
+func (c *ClusterTx) GetInstancesCount(ctx context.Context, projectName string, locationName string, includePending bool) (int, error) {
+	var err error
+
+	// Load the project ID if needed.
+	projectID := int64(-1)
+	if projectName != "" {
+		projectID, err = cluster.GetProjectID(ctx, c.Tx(), projectName)
+		if err != nil {
+			return -1, err
+		}
+	}
+
+	// Load the cluster member ID if needed.
+	nodeID := int64(-1)
+	if locationName != "" {
+		nodeID, err = cluster.GetNodeID(ctx, c.Tx(), locationName)
+		if err != nil {
+			return -1, err
+		}
+	}
+
+	// Count the instances.
+	var count int
+
+	if projectID != -1 && nodeID != -1 {
+		// Count for specified project and cluster member.
+		created, err := query.Count(ctx, c.tx, "instances", "project_id=? AND node_id=?", projectID, nodeID)
+		if err != nil {
+			return -1, fmt.Errorf("Failed to get instances count: %w", err)
+		}
+
+		count += created
+
+		if includePending {
+			pending, err := query.Count(ctx, c.tx, "operations", "project_id=? AND node_id=? AND type=?", projectID, nodeID, operationtype.InstanceCreate)
+			if err != nil {
+				return -1, fmt.Errorf("Failed to get pending instances count: %w", err)
+			}
+
+			count += pending
+		}
+	} else if projectID != -1 {
+		// Count for specified project.
+		created, err := query.Count(ctx, c.tx, "instances", "project_id=?", projectID)
+		if err != nil {
+			return -1, fmt.Errorf("Failed to get instances count: %w", err)
+		}
+
+		count += created
+
+		if includePending {
+			pending, err := query.Count(ctx, c.tx, "operations", "project_id=? AND type=?", projectID, operationtype.InstanceCreate)
+			if err != nil {
+				return -1, fmt.Errorf("Failed to get pending instances count: %w", err)
+			}
+
+			count += pending
+		}
+	} else if nodeID != -1 {
+		// Count for specified cluster member.
+		created, err := query.Count(ctx, c.tx, "instances", "node_id=?", nodeID)
+		if err != nil {
+			return -1, fmt.Errorf("Failed to get instances count: %w", err)
+		}
+
+		count += created
+
+		if includePending {
+			pending, err := query.Count(ctx, c.tx, "operations", "node_id=? AND type=?", nodeID, operationtype.InstanceCreate)
+			if err != nil {
+				return -1, fmt.Errorf("Failed to get pending instances count: %w", err)
+			}
+
+			count += pending
+		}
+	} else {
+		// Count everything.
+		created, err := query.Count(ctx, c.tx, "instances", "")
+		if err != nil {
+			return -1, fmt.Errorf("Failed to get instances count: %w", err)
+		}
+
+		count += created
+
+		if includePending {
+			pending, err := query.Count(ctx, c.tx, "operations", "type=?", operationtype.InstanceCreate)
+			if err != nil {
+				return -1, fmt.Errorf("Failed to get pending instances count: %w", err)
+			}
+
+			count += pending
+		}
+	}
+
+	return count, nil
+}

internal/server/db/node.go

@@ -8,12 +8,12 @@ import (
 	"fmt"
 	"net/http"
 	"slices"
+	"sort"
 	"strconv"
 	"strings"
 	"time"
 
 	"github.com/lxc/incus/v6/internal/server/db/cluster"
-	"github.com/lxc/incus/v6/internal/server/db/operationtype"
 	"github.com/lxc/incus/v6/internal/server/db/query"
 	localUtil "github.com/lxc/incus/v6/internal/server/util"
 	"github.com/lxc/incus/v6/internal/version"
@@ -1135,40 +1135,14 @@ func (c *ClusterTx) GetCandidateMembers(ctx context.Context, allMembers []NodeIn
 		}
 	}
 
-	return candidateMembers, nil
-}
-
-// GetNodeWithLeastInstances returns the name of the member with the least number of instances that are either
-// already created or being created with an operation.
-func (c *ClusterTx) GetNodeWithLeastInstances(ctx context.Context, members []NodeInfo) (*NodeInfo, error) {
-	var member *NodeInfo
-	var lowestInstanceCount = -1
-
-	for i := range members {
-		// Fetch the number of instances already created on this member.
-		created, err := query.Count(ctx, c.tx, "instances", "node_id=?", members[i].ID)
-		if err != nil {
-			return nil, fmt.Errorf("Failed to get instances count: %w", err)
-		}
+	sort.Slice(candidateMembers, func(i int, j int) bool {
+		iCount, _ := c.GetInstancesCount(ctx, "", candidateMembers[i].Name, true)
+		jCount, _ := c.GetInstancesCount(ctx, "", candidateMembers[j].Name, true)
 
-		// Fetch the number of instances currently being created on this member.
-		pending, err := query.Count(ctx, c.tx, "operations", "node_id=? AND type=?", members[i].ID, operationtype.InstanceCreate)
-		if err != nil {
-			return nil, fmt.Errorf("Failed to get pending instances count: %w", err)
-		}
-
-		memberInstanceCount := created + pending
-		if lowestInstanceCount == -1 || memberInstanceCount < lowestInstanceCount {
-			lowestInstanceCount = memberInstanceCount
-			member = &members[i]
-		}
-	}
-
-	if member == nil {
-		return nil, api.StatusErrorf(http.StatusNotFound, "No suitable cluster member could be found")
-	}
+		return iCount < jCount
+	})
 
-	return member, nil
+	return candidateMembers, nil
 }
 
 // SetNodeVersion updates the schema and API version of the node with the

internal/server/db/node_test.go

@@ -305,7 +305,7 @@ INSERT INTO storage_volumes(name, storage_pool_id, node_id, type, project_id, de
 
 // If there are 2 online nodes, return the address of the one with the least
 // number of instances.
-func TestGetNodeWithLeastInstances(t *testing.T) {
+func TestGetCandidateMembers(t *testing.T) {
 	tx, cleanup := db.NewTestClusterTx(t)
 	defer cleanup()
 
@@ -325,14 +325,12 @@ INSERT INTO instances (id, node_id, name, architecture, type, project_id, descri
 	require.NoError(t, err)
 	require.Len(t, members, 2)
 
-	member, err := tx.GetNodeWithLeastInstances(context.Background(), members)
-	require.NoError(t, err)
-	assert.Equal(t, "buzz", member.Name)
+	assert.Equal(t, "buzz", members[0].Name)
 }
 
 // If there are nodes, and one of them is offline, return the name of the
 // online node, even if the offline one has more instances.
-func TestGetNodeWithLeastInstances_OfflineNode(t *testing.T) {
+func TestGetCandidateMembers_OfflineNode(t *testing.T) {
 	tx, cleanup := db.NewTestClusterTx(t)
 	defer cleanup()
 
@@ -356,14 +354,12 @@ INSERT INTO instances (id, node_id, name, architecture, type, project_id, descri
 	require.NoError(t, err)
 	require.Len(t, members, 1)
 
-	member, err := tx.GetNodeWithLeastInstances(context.Background(), members)
-	require.NoError(t, err)
-	assert.Equal(t, "buzz", member.Name)
+	assert.Equal(t, "buzz", members[0].Name)
 }
 
 // If there are 2 online nodes, and an instance is pending on one of them,
 // return the address of the other one number of instances.
-func TestGetNodeWithLeastInstances_Pending(t *testing.T) {
+func TestGetCandidateMembers_Pending(t *testing.T) {
 	tx, cleanup := db.NewTestClusterTx(t)
 	defer cleanup()
 
@@ -383,14 +379,12 @@ INSERT INTO operations (id, uuid, node_id, type, project_id) VALUES (1, 'abc', 1
 	require.NoError(t, err)
 	require.Len(t, members, 2)
 
-	member, err := tx.GetNodeWithLeastInstances(context.Background(), members)
-	require.NoError(t, err)
-	assert.Equal(t, "buzz", member.Name)
+	assert.Equal(t, "buzz", members[0].Name)
 }
 
 // If specific architectures were selected, return only nodes with those
 // architectures.
-func TestGetNodeWithLeastInstances_Architecture(t *testing.T) {
+func TestGetCandidateMembers_Architecture(t *testing.T) {
 	tx, cleanup := db.NewTestClusterTx(t)
 	defer cleanup()
 
@@ -419,9 +413,7 @@ INSERT INTO instances (id, node_id, name, architecture, type, project_id, descri
 	require.Len(t, members, 1)
 
 	// The local member is returned despite it has more instances.
-	member, err := tx.GetNodeWithLeastInstances(context.Background(), members)
-	require.NoError(t, err)
-	assert.Equal(t, "none", member.Name)
+	assert.Equal(t, "none", members[0].Name)
 }
 
 func TestUpdateNodeFailureDomain(t *testing.T) {
@@ -452,7 +444,7 @@ func TestUpdateNodeFailureDomain(t *testing.T) {
 	assert.Equal(t, map[string]uint64{"0.0.0.0": 0, "1.2.3.4:666": 0}, domains)
 }
 
-func TestGetNodeWithLeastInstances_DefaultArch(t *testing.T) {
+func TestGetCandidateMembers_DefaultArch(t *testing.T) {
 	tx, cleanup := db.NewTestClusterTx(t)
 	defer cleanup()
 
@@ -480,7 +472,5 @@ INSERT INTO instances (id, node_id, name, architecture, type, project_id, descri
 	require.NoError(t, err)
 	require.Len(t, members, 1)
 
-	member, err := tx.GetNodeWithLeastInstances(context.Background(), members)
-	require.NoError(t, err)
-	assert.Equal(t, "buzz", member.Name)
+	assert.Equal(t, "buzz", members[0].Name)
 }