Adding EBS watcher implementation

agent/ebs/watcher.go

@@ -0,0 +1,175 @@
+// Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License"). You may
+// not use this file except in compliance with the License. A copy of the
+// License is located at
+//
+//	http://aws.amazon.com/apache2.0/
+//
+// or in the "license" file accompanying this file. This file 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 ebs
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/aws/amazon-ecs-agent/agent/engine/dockerstate"
+	"github.com/aws/amazon-ecs-agent/agent/statechange"
+	apiebs "github.com/aws/amazon-ecs-agent/ecs-agent/api/resource"
+	log "github.com/cihub/seelog"
+)
+
+type EBSWatcher struct {
+	ctx        context.Context
+	cancel     context.CancelFunc
+	agentState dockerstate.TaskEngineState
+	// TODO: The ebsChangeEvent will be used to send over the state change event for EBS attachments once it's been found and mounted/resize/format.
+	ebsChangeEvent chan<- statechange.Event
+	// TODO: The dataClient will be used to save to agent's data client as well as start the ACK timer. This will be added once the data client functionality have been added
+	// dataClient     data.Client
+	discoveryClient apiebs.EBSDiscovery
+	scanTicker      *time.Ticker
+}
+
+// NewWatcher is used to return a new instance of the EBSWatcher struct
+func NewWatcher(ctx context.Context,
+	state dockerstate.TaskEngineState,
+	stateChangeEvents chan<- statechange.Event) *EBSWatcher {
+	derivedContext, cancel := context.WithCancel(ctx)
+	discoveryClient := apiebs.NewDiscoveryClient(derivedContext)
+	return &EBSWatcher{
+		ctx:             derivedContext,
+		cancel:          cancel,
+		agentState:      state,
+		ebsChangeEvent:  stateChangeEvents,
+		discoveryClient: discoveryClient,
+	}
+}
+
+// Start is used to kick off the periodic scanning process of the EBS volume attachments for the EBS watcher.
+// It will be start and continue to run whenever there's a pending EBS volume attachment that hasn't been found.
+// If there aren't any, the scan ticker will not start up/scan for volumes.
+func (w *EBSWatcher) Start() {
+	log.Info("Starting EBS watcher.")
+	w.scanTicker = time.NewTicker(apiebs.ScanPeriod)
+	for {
+		select {
+		case <-w.scanTicker.C:
+			pendingEBS := w.agentState.GetAllPendingEBSAttachmentsWithKey()
+			if len(pendingEBS) > 0 {
+				foundVolumes := apiebs.ScanEBSVolumes(pendingEBS, w.discoveryClient)
+				w.NotifyFound(foundVolumes)
+			}
+		case <-w.ctx.Done():
+			w.scanTicker.Stop()
+			log.Info("EBS Watcher Stopped due to agent stop")
+			return
+		}
+	}
+}
+
+// Stop will stop the EBS watcher
+func (w *EBSWatcher) Stop() {
+	log.Info("Stopping EBS watcher.")
+	w.cancel()
+}
+
+// HandleResourceAttachment processes the resource attachment message. It will:
+// 1. Check whether we already have this attachment in state and if so it's a noop.
+// 2. Otherwise add the attachment to state, start its ack timer, and save to the agent state.
+func (w *EBSWatcher) HandleResourceAttachment(ebs *apiebs.ResourceAttachment) error {
+	attachmentType := ebs.GetAttachmentProperties(apiebs.ResourceTypeName)
+	if attachmentType != apiebs.ElasticBlockStorage {
+		log.Warnf("Resource type not Elastic Block Storage. Skip handling resource attachment with type: %v.", attachmentType)
+		return nil
+	}
+
+	volumeId := ebs.GetAttachmentProperties(apiebs.VolumeIdName)
+	_, ok := w.agentState.GetEBSByVolumeId(volumeId)
+	if ok {
+		log.Infof("EBS Volume attachment already exists. Skip handling EBS attachment %v.", ebs.EBSToString())
+		return nil
+	}
+
+	if err := w.addEBSAttachmentToState(ebs); err != nil {
+		return fmt.Errorf("%w; attach %v message handler: unable to add ebs attachment to engine state: %v",
+			err, attachmentType, ebs.EBSToString())
+	}
+
+	return nil
+}
+
+// NotifyFound will go through the list of found EBS volumes from the scanning process and mark them as found.
+func (w *EBSWatcher) NotifyFound(foundVolumes []string) {
+	for _, volumeId := range foundVolumes {
+		w.notifyFoundEBS(volumeId)
+	}
+}
+
+// notifyFoundEBS will mark it as found within the agent state
+func (w *EBSWatcher) notifyFoundEBS(volumeId string) {
+	// TODO: Add the EBS volume to data client
+	ebs, ok := w.agentState.GetEBSByVolumeId(volumeId)
+	if !ok {
+		log.Warnf("Unable to find EBS volume with volume ID: %v.", volumeId)
+		return
+	}
+
+	if ebs.HasExpired() {
+		log.Warnf("EBS status expired, no longer tracking EBS volume: %v.", ebs.EBSToString())
+		return
+	}
+
+	if ebs.IsSent() {
+		log.Warnf("State change event has already been emitted for EBS volume: %v.", ebs.EBSToString())
+		return
+	}
+
+	if ebs.IsAttached() {
+		log.Infof("EBS volume: %v, has been found already.", ebs.EBSToString())
+		return
+	}
+
+	ebs.StopAckTimer()
+	ebs.SetAttachedStatus()
+
+	log.Infof("Successfully found attached EBS volume: %v", ebs.EBSToString())
+}
+
+// removeEBSAttachment removes a EBS volume with a specific volume ID
+func (w *EBSWatcher) removeEBSAttachment(volumeID string) {
+	// TODO: Remove the EBS volume from the data client.
+	w.agentState.RemoveEBSAttachment(volumeID)
+}
+
+// addEBSAttachmentToState adds an EBS attachment to state, and start its ack timer
+func (w *EBSWatcher) addEBSAttachmentToState(ebs *apiebs.ResourceAttachment) error {
+	volumeId := ebs.AttachmentProperties[apiebs.VolumeIdName]
+	err := ebs.StartTimer(func() {
+		w.handleEBSAckTimeout(volumeId)
+	})
+	if err != nil {
+		return err
+	}
+
+	w.agentState.AddEBSAttachment(ebs)
+	return nil
+}
+
+// handleEBSAckTimeout removes EBS attachment from agent state after the EBS ack timeout
+func (w *EBSWatcher) handleEBSAckTimeout(volumeId string) {
+	ebsAttachment, ok := w.agentState.GetEBSByVolumeId(volumeId)
+	if !ok {
+		log.Warnf("Ignoring unmanaged EBS attachment volume ID=%v", volumeId)
+		return
+	}
+	if !ebsAttachment.IsSent() {
+		log.Warnf("Timed out waiting for EBS ack; removing EBS attachment record %v", ebsAttachment.EBSToString())
+		w.removeEBSAttachment(volumeId)
+	}
+}