Fix operation start to not start the same application twice.

x-pack/elastic-agent/pkg/agent/operation/operation.go

@@ -23,7 +23,7 @@ type operation interface {
 	// examples:
 	// - Start does not need to run if process is running
 	// - Fetch does not need to run if package is already present
-	Check() (bool, error)
+	Check(application Application) (bool, error)
 	// Run runs the operation
 	Run(ctx context.Context, application Application) error
 }

x-pack/elastic-agent/pkg/agent/operation/operation_config.go

@@ -46,11 +46,10 @@ func (o *operationConfig) Name() string {
 	return "operation-config"
 }
 
-// Check checks whether operation needs to be run
-// examples:
-// - Start does not need to run if process is running
-// - Fetch does not need to run if package is already present
-func (o *operationConfig) Check() (bool, error) { return true, nil }
+// Check checks whether config needs to be run.
+//
+// Always returns true.
+func (o *operationConfig) Check(_ Application) (bool, error) { return true, nil }
 
 // Run runs the operation
 func (o *operationConfig) Run(ctx context.Context, application Application) (err error) {

x-pack/elastic-agent/pkg/agent/operation/operation_fetch.go

@@ -46,11 +46,10 @@ func (o *operationFetch) Name() string {
 	return "operation-fetch"
 }
 
-// Check checks whether operation needs to be run
-// examples:
-// - Start does not need to run if process is running
-// - Fetch does not need to run if package is already present
-func (o *operationFetch) Check() (bool, error) {
+// Check checks whether fetch needs to occur.
+//
+// If the artifacts already exists then fetch will not be ran.
+func (o *operationFetch) Check(_ Application) (bool, error) {
 	downloadConfig := o.operatorConfig.DownloadConfig
 	fullPath, err := artifact.GetArtifactPath(o.program.BinaryName(), o.program.Version(), downloadConfig.OS(), downloadConfig.Arch(), downloadConfig.TargetDirectory)
 	if err != nil {

x-pack/elastic-agent/pkg/agent/operation/operation_install.go

@@ -45,11 +45,10 @@ func (o *operationInstall) Name() string {
 	return "operation-install"
 }
 
-// Check checks whether operation needs to be run
-// examples:
-// - Start does not need to run if process is running
-// - Fetch does not need to run if package is already present
-func (o *operationInstall) Check() (bool, error) {
+// Check checks whether install needs to be ran.
+//
+// If the installation directory already exists then it will not be ran.
+func (o *operationInstall) Check(_ Application) (bool, error) {
 	installDir := o.program.Directory()
 	_, err := os.Stat(installDir)
 	return os.IsNotExist(err), nil

x-pack/elastic-agent/pkg/agent/operation/operation_remove.go

@@ -24,11 +24,10 @@ func (o *operationRemove) Name() string {
 	return "operation-remove"
 }
 
-// Check checks whether operation needs to be run
-// examples:
-// - Start does not need to run if process is running
-// - Fetch does not need to run if package is already present
-func (o *operationRemove) Check() (bool, error) {
+// Check checks whether remove needs to run.
+//
+// Always returns false.
+func (o *operationRemove) Check(_ Application) (bool, error) {
 	return false, nil
 }
 

x-pack/elastic-agent/pkg/agent/operation/operation_start.go

@@ -7,6 +7,8 @@ package operation
 import (
 	"context"
 
+	"github.com/elastic/beats/v7/x-pack/elastic-agent/pkg/core/plugin/state"
+
 	"github.com/elastic/beats/v7/x-pack/elastic-agent/pkg/agent/errors"
 	"github.com/elastic/beats/v7/x-pack/elastic-agent/pkg/agent/operation/config"
 	"github.com/elastic/beats/v7/x-pack/elastic-agent/pkg/core/logger"
@@ -47,14 +49,16 @@ func (o *operationStart) Name() string {
 	return "operation-start"
 }
 
-// Check checks whether operation needs to be run
-// examples:
-// - Start does not need to run if process is running
-// - Fetch does not need to run if package is already present
-func (o *operationStart) Check() (bool, error) {
-	// TODO: get running processes and compare hashes
-
-	return true, nil
+// Check checks whether application needs to be started.
+//
+// Only starts the application when in stopped state, any other state
+// and the application is handled by the life cycle inside of the `Application`
+// implementation.
+func (o *operationStart) Check(application Application) (bool, error) {
+	if application.State().Status == state.Stopped {
+		return true, nil
+	}
+	return false, nil
 }
 
 // Run runs the operation

x-pack/elastic-agent/pkg/agent/operation/operation_stop.go

@@ -7,6 +7,8 @@ package operation
 import (
 	"context"
 
+	"github.com/elastic/beats/v7/x-pack/elastic-agent/pkg/core/plugin/state"
+
 	"github.com/elastic/beats/v7/x-pack/elastic-agent/pkg/agent/errors"
 	"github.com/elastic/beats/v7/x-pack/elastic-agent/pkg/agent/operation/config"
 	"github.com/elastic/beats/v7/x-pack/elastic-agent/pkg/core/logger"
@@ -36,12 +38,14 @@ func (o *operationStop) Name() string {
 	return "operation-stop"
 }
 
-// Check checks whether operation needs to be run
-// examples:
-// - Start does not need to run if process is running
-// - Fetch does not need to run if package is already present
-func (o *operationStop) Check() (bool, error) {
-	return true, nil
+// Check checks whether application needs to be stopped.
+//
+// If the application state is not stopped then stop should be performed.
+func (o *operationStop) Check(application Application) (bool, error) {
+	if application.State().Status != state.Stopped {
+		return true, nil
+	}
+	return false, nil
 }
 
 // Run runs the operation

x-pack/elastic-agent/pkg/agent/operation/operation_verify.go

@@ -42,11 +42,10 @@ func (o *operationVerify) Name() string {
 	return "operation-verify"
 }
 
-// Check checks whether operation needs to be run
-// examples:
-// - Start does not need to run if process is running
-// - Fetch does not need to run if package is already present
-func (o *operationVerify) Check() (bool, error) {
+// Check checks whether verify needs to occur.
+//
+// Only if the artifacts exists does it need to be verified.
+func (o *operationVerify) Check(_ Application) (bool, error) {
 	downloadConfig := o.operatorConfig.DownloadConfig
 	fullPath, err := artifact.GetArtifactPath(o.program.BinaryName(), o.program.Version(), downloadConfig.OS(), downloadConfig.Arch(), downloadConfig.TargetDirectory)
 	if err != nil {

x-pack/elastic-agent/pkg/agent/operation/operator.go

@@ -204,7 +204,7 @@ func (o *Operator) runFlow(p Descriptor, operations []operation) error {
 			return err
 		}
 
-		shouldRun, err := op.Check()
+		shouldRun, err := op.Check(app)
 		if err != nil {
 			return err
 		}