engine_apply.go

package apply

import (
	"github.com/Aptomi/aptomi/pkg/engine/actual"
	"github.com/Aptomi/aptomi/pkg/engine/apply/action"
	"github.com/Aptomi/aptomi/pkg/engine/resolve"
	"github.com/Aptomi/aptomi/pkg/event"
	"github.com/Aptomi/aptomi/pkg/external"
	"github.com/Aptomi/aptomi/pkg/lang"
	"github.com/Aptomi/aptomi/pkg/plugin"
)

// EngineApply executes actions to get from an actual state to desired state
type EngineApply struct {
	// References to desired/actual objects
	desiredPolicy      *lang.Policy
	desiredState       *resolve.PolicyResolution
	actualStateUpdater actual.StateUpdater
	externalData       *external.Data
	plugins            plugin.Registry

	// Action plan to be applied
	actionPlan *action.Plan

	// Buffered event log - gets populated while applying actions
	eventLog *event.Log

	// Result/progress updater
	updater action.ApplyResultUpdater
}

// NewEngineApply creates an instance of EngineApply
// todo(slukjanov): make sure that plugins are created once per revision, b/c we need to cache only for single policy, when it changed some credentials could change as well
// todo(slukjanov): run cleanup on all plugins after apply done for the revision
func NewEngineApply(desiredPolicy *lang.Policy, desiredState *resolve.PolicyResolution, actualStateUpdater actual.StateUpdater, externalData *external.Data, plugins plugin.Registry, actionPlan *action.Plan, eventLog *event.Log, updater action.ApplyResultUpdater) *EngineApply {
	return &EngineApply{
		desiredPolicy:      desiredPolicy,
		desiredState:       desiredState,
		actualStateUpdater: actualStateUpdater,
		externalData:       externalData,
		plugins:            plugins,
		actionPlan:         actionPlan,
		eventLog:           eventLog,
		updater:            updater,
	}
}

// Apply method executes all actions, actions call plugins to apply changes and roll them out to the cloud.
// It returns the updated actual state inside PolicyResolution and event log, as well as result/stats about how many actions
// have been applied successfully vs. failed vs. skipped.
//
// As actions get executed, they will instantiate/update/delete components according to the resolved
// policy, as well as configure the underlying cloud components appropriately. In case of errors (e.g. cloud is not
// available), actual state may not be equal to desired state after performing all the actions.
func (apply *EngineApply) Apply(maxConcurrentActions int) (*resolve.PolicyResolution, *action.ApplyResult) {
	// process all actions
	context := action.NewContext(
		apply.desiredPolicy,
		apply.desiredState,
		apply.actualStateUpdater,
		apply.externalData,
		apply.plugins,
		apply.eventLog,
	)

	// Note that the action plan will call function in different go routines by apply
	result := apply.actionPlan.Apply(action.WrapParallelWithLimit(maxConcurrentActions, func(act action.Interface) error {
		err := act.Apply(context)
		if err != nil {
			context.EventLog.NewEntry().Errorf("error while applying action '%s': %s", act, err)
		}
		return err
	}), apply.updater)

	// No errors occurred
	return apply.actualStateUpdater.GetUpdatedActualState(), result
}