minio/pkg/event/targetlist.go

/*
 * Minio Cloud Storage, (C) 2018 Minio, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package event

import (
	"fmt"
	"sync"
)

// Target - event target interface
type Target interface {
	ID() TargetID
	Send(Event) error
	Close() error
}

// TargetList - holds list of targets indexed by target ID.
type TargetList struct {
	sync.RWMutex
	targets map[TargetID]Target
}

// Add - adds unique target to target list.
func (list *TargetList) Add(target Target) error {
	list.Lock()
	defer list.Unlock()

	if _, ok := list.targets[target.ID()]; ok {
		return fmt.Errorf("target %v already exists", target.ID())
	}

	list.targets[target.ID()] = target
	return nil
}

// Exists - checks whether target by target ID exists or not.
func (list *TargetList) Exists(id TargetID) bool {
	list.RLock()
	defer list.RUnlock()

	_, found := list.targets[id]
	return found
}

// Remove - closes and removes targets by given target IDs.
func (list *TargetList) Remove(ids ...TargetID) map[TargetID]error {
	list.Lock()
	defer list.Unlock()

	errors := make(map[TargetID]error)

	var wg sync.WaitGroup
	for _, id := range ids {
		if target, ok := list.targets[id]; ok {
			wg.Add(1)
			go func(id TargetID, target Target) {
				defer wg.Done()
				if err := target.Close(); err != nil {
					errors[id] = err
				}
			}(id, target)
		}
	}
	wg.Wait()

	for _, id := range ids {
		delete(list.targets, id)
	}

	return errors
}

// List - returns available target IDs.
func (list *TargetList) List() []TargetID {
	list.RLock()
	defer list.RUnlock()

	keys := []TargetID{}
	for k := range list.targets {
		keys = append(keys, k)
	}

	return keys
}

// Send - sends events to targets identified by target IDs.
func (list *TargetList) Send(event Event, targetIDs ...TargetID) map[TargetID]error {
	list.Lock()
	defer list.Unlock()

	errors := make(map[TargetID]error)

	var wg sync.WaitGroup
	for _, id := range targetIDs {
		if target, ok := list.targets[id]; ok {
			wg.Add(1)
			go func(id TargetID, target Target) {
				defer wg.Done()
				if err := target.Send(event); err != nil {
					errors[id] = err
				}
			}(id, target)
		}
	}
	wg.Wait()

	return errors
}

// NewTargetList - creates TargetList.
func NewTargetList() *TargetList {
	return &TargetList{targets: make(map[TargetID]Target)}
}