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Refactor auto scaler logic #13

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merged 4 commits into from
Aug 12, 2024
Merged

Refactor auto scaler logic #13

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6928189
extract autoscaler logic
ilya-hontarau Aug 8, 2024
8a16206
add tests for autoscaler logic
ilya-hontarau Aug 8, 2024
644cdb7
gen mocks in test pkg
ilya-hontarau Aug 8, 2024
734f93f
rename mock
ilya-hontarau Aug 8, 2024
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111 changes: 1 addition & 110 deletions cmd/internal/handle.go
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,6 @@ package internal
import (
"context"
"fmt"
"time"

"github.com/caarlos0/env/v9"
"golang.org/x/exp/slog"
Expand All @@ -17,117 +16,9 @@ func Handle(ctx context.Context, logger *slog.Logger) error {
return fmt.Errorf("could not parse environment variables: %w", err)
}

logger = logger.With(
"asg_arn", cfg.AutoscalingGroupARN,
"worker_pool_id", cfg.SpaceliftWorkerPoolID,
)

controller, err := internal.NewController(ctx, &cfg)
if err != nil {
return fmt.Errorf("could not create controller: %w", err)
}

workerPool, err := controller.GetWorkerPool(ctx)
if err != nil {
return fmt.Errorf("could not get worker pool: %w", err)
}

asg, err := controller.GetAutoscalingGroup(ctx)
if err != nil {
return fmt.Errorf("could not get autoscaling group: %w", err)
}

state, err := internal.NewState(workerPool, asg)
if err != nil {
return fmt.Errorf("could not create state: %w", err)
}

// Let's make sure that for each of the in-service instances we have a
// corresponding worker in Spacelift, or that we have "stray" machines.
if strayInstances := state.StrayInstances(); len(strayInstances) > 0 {
// There's a question of what to do with the "stray" machines. The
// decision will be made based on the creation timestamp.
instances, err := controller.DescribeInstances(ctx, strayInstances)
if err != nil {
return fmt.Errorf("could not list EC2 instances: %w", err)
}

for _, instance := range instances {
logger = logger.With("instance_id", *instance.InstanceId)
instanceAge := time.Since(*instance.LaunchTime)

logger = logger.With(
"launch_timestamp", instance.LaunchTime.Unix(),
"instance_age", instanceAge,
)

// If the machine was only created recently (say a generous window of 10
// minutes), it is possible that it hasn't managed to register itself with
// Spacelift yet. But if it's been around for a while we will want to kill
// it and remove it from the ASG.
if instanceAge > 10*time.Minute {
logger.Warn("instance has no corresponding worker in Spacelift, removing from the ASG")

if err := controller.KillInstance(ctx, *instance.InstanceId); err != nil {
return fmt.Errorf("could not kill instance: %w", err)
}

// We don't want to kill too many instances at once, so let's
// return after the first successfully killed one.
logger.Info("instance successfully removed from the ASG and terminated")

return nil
}
}
}

decision := state.Decide(cfg.AutoscalingMaxCreate, cfg.AutoscalingMaxKill)

if decision.ScalingDirection == internal.ScalingDirectionNone {
logger.Info("no scaling decision to be made")
return nil
}

if decision.ScalingDirection == internal.ScalingDirectionUp {
logger.With("instances", decision.ScalingSize).Info("scaling up the ASG")

if err := controller.ScaleUpASG(ctx, *asg.DesiredCapacity+int32(decision.ScalingSize)); err != nil {
return fmt.Errorf("could not scale up ASG: %w", err)
}

return nil
}

// If we got this far, we're scaling down.
logger.With("instances", decision.ScalingSize).Info("scaling down ASG")

idleWorkers := state.IdleWorkers()

for i := 0; i < decision.ScalingSize; i++ {
worker := idleWorkers[i]

_, instanceID, _ := worker.InstanceIdentity()

logger = logger.With(
"worker_id", worker.ID,
"instance_id", instanceID,
)
logger.Info("scaling down ASG and killing worker")

drained, err := controller.DrainWorker(ctx, worker.ID)
if err != nil {
return fmt.Errorf("could not drain worker: %w", err)
}

if !drained {
logger.Warn("worker was busy, stopping the scaling down process")
return nil
}

if err := controller.KillInstance(ctx, string(instanceID)); err != nil {
return fmt.Errorf("could not kill instance: %w", err)
}
}

return nil
return internal.NewAutoScaler(controller, logger).Scale(ctx, cfg)
}
141 changes: 141 additions & 0 deletions internal/auto_scaler.go
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Original file line number Diff line number Diff line change
@@ -0,0 +1,141 @@
package internal

import (
"context"
"fmt"
"time"

autoscalingtypes "github.com/aws/aws-sdk-go-v2/service/autoscaling/types"
ec2types "github.com/aws/aws-sdk-go-v2/service/ec2/types"
"golang.org/x/exp/slog"
)

//go:generate mockery --output ./ --name ControllerInterface --filename mock_controller_test.go --outpkg internal_test --structname MockController
type ControllerInterface interface {
DescribeInstances(ctx context.Context, instanceIDs []string) (instances []ec2types.Instance, err error)
GetAutoscalingGroup(ctx context.Context) (out *autoscalingtypes.AutoScalingGroup, err error)
GetWorkerPool(ctx context.Context) (out *WorkerPool, err error)
DrainWorker(ctx context.Context, workerID string) (drained bool, err error)
KillInstance(ctx context.Context, instanceID string) (err error)
ScaleUpASG(ctx context.Context, desiredCapacity int32) (err error)
}

type AutoScaler struct {
controller ControllerInterface
logger *slog.Logger
}

func NewAutoScaler(controller ControllerInterface, logger *slog.Logger) *AutoScaler {
return &AutoScaler{controller: controller, logger: logger}
}

func (s AutoScaler) Scale(ctx context.Context, cfg RuntimeConfig) error {
logger := s.logger.With(
"asg_arn", cfg.AutoscalingGroupARN,
"worker_pool_id", cfg.SpaceliftWorkerPoolID,
)

workerPool, err := s.controller.GetWorkerPool(ctx)
if err != nil {
return fmt.Errorf("could not get worker pool: %w", err)
}

asg, err := s.controller.GetAutoscalingGroup(ctx)
if err != nil {
return fmt.Errorf("could not get autoscaling group: %w", err)
}

state, err := NewState(workerPool, asg)
if err != nil {
return fmt.Errorf("could not create state: %w", err)
}

// Let's make sure that for each of the in-service instances we have a
// corresponding worker in Spacelift, or that we have "stray" machines.
if strayInstances := state.StrayInstances(); len(strayInstances) > 0 {
// There's a question of what to do with the "stray" machines. The
// decision will be made based on the creation timestamp.
instances, err := s.controller.DescribeInstances(ctx, strayInstances)
if err != nil {
return fmt.Errorf("could not list EC2 instances: %w", err)
}

for _, instance := range instances {
logger = logger.With("instance_id", *instance.InstanceId)
instanceAge := time.Since(*instance.LaunchTime)

logger = logger.With(
"launch_timestamp", instance.LaunchTime.Unix(),
"instance_age", instanceAge,
)

// If the machine was only created recently (say a generous window of 10
// minutes), it is possible that it hasn't managed to register itself with
// Spacelift yet. But if it's been around for a while we will want to kill
// it and remove it from the ASG.
if instanceAge > 10*time.Minute {
logger.Warn("instance has no corresponding worker in Spacelift, removing from the ASG")

if err := s.controller.KillInstance(ctx, *instance.InstanceId); err != nil {
return fmt.Errorf("could not kill instance: %w", err)
}

// We don't want to kill too many instances at once, so let's
// return after the first successfully killed one.
logger.Info("instance successfully removed from the ASG and terminated")

return nil
}
}
}

decision := state.Decide(cfg.AutoscalingMaxCreate, cfg.AutoscalingMaxKill)

if decision.ScalingDirection == ScalingDirectionNone {
logger.Info("no scaling decision to be made")
return nil
}

if decision.ScalingDirection == ScalingDirectionUp {
logger.With("instances", decision.ScalingSize).Info("scaling up the ASG")

if err := s.controller.ScaleUpASG(ctx, *asg.DesiredCapacity+int32(decision.ScalingSize)); err != nil {
return fmt.Errorf("could not scale up ASG: %w", err)
}

return nil
}

// If we got this far, we're scaling down.
logger.With("instances", decision.ScalingSize).Info("scaling down ASG")

idleWorkers := state.IdleWorkers()

for i := 0; i < decision.ScalingSize; i++ {
worker := idleWorkers[i]

_, instanceID, _ := worker.InstanceIdentity()

logger = logger.With(
"worker_id", worker.ID,
"instance_id", instanceID,
)
logger.Info("scaling down ASG and killing worker")

drained, err := s.controller.DrainWorker(ctx, worker.ID)
if err != nil {
return fmt.Errorf("could not drain worker: %w", err)
}

if !drained {
logger.Warn("worker was busy, stopping the scaling down process")
return nil
}

if err := s.controller.KillInstance(ctx, string(instanceID)); err != nil {
return fmt.Errorf("could not kill instance: %w", err)
}
}

return nil
}
122 changes: 122 additions & 0 deletions internal/auto_scaler_test.go
View file
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Original file line number Diff line number Diff line change
@@ -0,0 +1,122 @@
package internal_test

import (
"bytes"
"context"
"testing"

"github.com/aws/aws-sdk-go-v2/service/autoscaling/types"
"github.com/stretchr/testify/mock"
"github.com/stretchr/testify/require"
"golang.org/x/exp/slog"

"github.com/spacelift-io/awsautoscalr/internal"
)

func TestAutoScalerScalingNone(t *testing.T) {
var buf bytes.Buffer
h := slog.NewTextHandler(&buf, nil)

cfg := internal.RuntimeConfig{}

ctrl := new(MockController)
defer ctrl.AssertExpectations(t)

scaler := internal.NewAutoScaler(ctrl, slog.New(h))

ctrl.On("GetWorkerPool", mock.Anything).Return(&internal.WorkerPool{
Workers: []internal.Worker{
{
ID: "1",
Metadata: `{"asg_id": "group", "instance_id": "instance"}`,
},
},
}, nil)
ctrl.On("GetAutoscalingGroup", mock.Anything).Return(&types.AutoScalingGroup{
AutoScalingGroupName: ptr("group"),
MinSize: ptr(int32(1)),
MaxSize: ptr(int32(3)),
DesiredCapacity: ptr(int32(2)),
}, nil)
err := scaler.Scale(context.Background(), cfg)
require.NoError(t, err)
}

func TestAutoScalerScalingUp(t *testing.T) {
var buf bytes.Buffer
h := slog.NewTextHandler(&buf, nil)

cfg := internal.RuntimeConfig{}

ctrl := new(MockController)
defer ctrl.AssertExpectations(t)

scaler := internal.NewAutoScaler(ctrl, slog.New(h))

ctrl.On("GetWorkerPool", mock.Anything).Return(&internal.WorkerPool{
Workers: []internal.Worker{
{
ID: "1",
Metadata: `{"asg_id": "group", "instance_id": "instance"}`,
},
},
PendingRuns: 2,
}, nil)
ctrl.On("GetAutoscalingGroup", mock.Anything).Return(&types.AutoScalingGroup{
AutoScalingGroupName: ptr("group"),
MinSize: ptr(int32(1)),
MaxSize: ptr(int32(3)),
DesiredCapacity: ptr(int32(2)),
Instances: []types.Instance{
{},
},
}, nil)
ctrl.On("ScaleUpASG", mock.Anything, int32(2)).Return(nil)
err := scaler.Scale(context.Background(), cfg)
require.NoError(t, err)
}

func TestAutoScalerScalingDown(t *testing.T) {
var buf bytes.Buffer
h := slog.NewTextHandler(&buf, nil)

cfg := internal.RuntimeConfig{
AutoscalingMaxKill: 1,
}

ctrl := new(MockController)
defer ctrl.AssertExpectations(t)

scaler := internal.NewAutoScaler(ctrl, slog.New(h))

ctrl.On("GetWorkerPool", mock.Anything).Return(&internal.WorkerPool{
Workers: []internal.Worker{
{
ID: "1",
Metadata: `{"asg_id": "group", "instance_id": "instance"}`,
},
{
ID: "2",
Metadata: `{"asg_id": "group", "instance_id": "instance2"}`,
},
},
}, nil)
ctrl.On("GetAutoscalingGroup", mock.Anything).Return(&types.AutoScalingGroup{
AutoScalingGroupName: ptr("group"),
MinSize: ptr(int32(1)),
MaxSize: ptr(int32(3)),
DesiredCapacity: ptr(int32(2)),
Instances: []types.Instance{
{},
{},
},
}, nil)
ctrl.On("DrainWorker", mock.Anything, "1").Return(true, nil)
ctrl.On("KillInstance", mock.Anything, "instance").Return(nil)
err := scaler.Scale(context.Background(), cfg)
require.NoError(t, err)
}

func ptr[T any](v T) *T {
return &v
}
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