agent/app/agent.go
func (agent *ecsAgent) registerContainerInstance(
	stateManager statemanager.StateManager,
	client api.ECSClient,
	additionalAttributes []*ecs.Attribute) error {
	// Preflight request to make sure they're good
	if preflightCreds, err := agent.credentialProvider.Get(); err != nil || preflightCreds.AccessKeyID == "" {
		seelog.Warnf("Error getting valid credentials (AKID %s): %v", preflightCreds.AccessKeyID, err)
	}

	agentCapabilities, err := agent.capabilities()
	if err != nil {
		return err
	}
	capabilities := append(agentCapabilities, additionalAttributes...)

	// Get the tags of this container instance defined in config file
	tags := utils.MapToTags(agent.cfg.ContainerInstanceTags)
	if agent.cfg.ContainerInstancePropagateTagsFrom == config.ContainerInstancePropagateTagsFromEC2InstanceType {
		ec2Tags, err := agent.getContainerInstanceTagsFromEC2API()
		// If we are unable to call the API, we should not treat it as a transient error,
		// because we've already retried several times, we may throttle the API if we
		// keep retrying.
		if err != nil {
			return err
		}
		seelog.Infof("Retrieved Tags from EC2 DescribeTags API:\n%v", ec2Tags)
		tags = mergeTags(tags, ec2Tags)
	}

	platformDevices := agent.getPlatformDevices()

	if agent.containerInstanceARN != "" {
		seelog.Infof("Restored from checkpoint file. I am running as '%s' in cluster '%s'", agent.containerInstanceARN, agent.cfg.Cluster)
		return agent.reregisterContainerInstance(client, capabilities, tags, uuid.New(), platformDevices)
	}

	seelog.Info("Registering Instance with ECS")
	containerInstanceArn, availabilityZone, err := client.RegisterContainerInstance("", capabilities, tags, uuid.New(), platformDevices)
	if err != nil {
		seelog.Errorf("Error registering: %v", err)
		if retriable, ok := err.(apierrors.Retriable); ok && !retriable.Retry() {
			return err
		}
		if utils.IsAWSErrorCodeEqual(err, ecs.ErrCodeInvalidParameterException) {
			seelog.Critical("Instance registration attempt with an invalid parameter")
			return err
		}
		if _, ok := err.(apierrors.AttributeError); ok {
			seelog.Critical("Instance registration attempt with an invalid attribute")
			return err
		}
		return transientError{err}
	}
	seelog.Infof("Registration completed successfully. I am running as '%s' in cluster '%s'", containerInstanceArn, agent.cfg.Cluster)
	agent.containerInstanceARN = containerInstanceArn
	agent.availabilityZone = availabilityZone
	// Save our shiny new containerInstanceArn
	stateManager.Save()
	return nil
}
func (agent *ecsAgent) registerContainerInstance(
	stateManager statemanager.StateManager,
	client api.ECSClient,
	additionalAttributes []*ecs.Attribute) error {
	// Preflight request to make sure they're good
	if preflightCreds, err := agent.credentialProvider.Get(); err != nil || preflightCreds.AccessKeyID == "" {
		seelog.Warnf("Error getting valid credentials (AKID %s): %v", preflightCreds.AccessKeyID, err)
	}

	agentCapabilities, err := agent.capabilities()
	if err != nil {
		return err
	}
	capabilities := append(agentCapabilities, additionalAttributes...)

	// Get the tags of this container instance defined in config file
	tags := utils.MapToTags(agent.cfg.ContainerInstanceTags)
	if agent.cfg.ContainerInstancePropagateTagsFrom == config.ContainerInstancePropagateTagsFromEC2InstanceType {
		ec2Tags, err := agent.getContainerInstanceTagsFromEC2API()
		// If we are unable to call the API, we should not treat it as a transient error,
		// because we've already retried several times, we may throttle the API if we
		// keep retrying.
		if err != nil {
			return err
		}
		seelog.Infof("Retrieved Tags from EC2 DescribeTags API:\n%v", ec2Tags)
		tags = mergeTags(tags, ec2Tags)
	}

	platformDevices := agent.getPlatformDevices()

	if agent.containerInstanceARN != "" {
		seelog.Infof("Restored from checkpoint file. I am running as '%s' in cluster '%s'", agent.containerInstanceARN, agent.cfg.Cluster)
		return agent.reregisterContainerInstance(client, capabilities, tags, uuid.New(), platformDevices)
	}

	seelog.Info("Registering Instance with ECS")
	containerInstanceArn, availabilityZone, err := client.RegisterContainerInstance("", capabilities, tags, uuid.New(), platformDevices)
	if err != nil {
		seelog.Errorf("Error registering: %v", err)
		if retriable, ok := err.(apierrors.Retriable); ok && !retriable.Retry() {
			return err
		}
		if utils.IsAWSErrorCodeEqual(err, ecs.ErrCodeInvalidParameterException) {
			seelog.Critical("Instance registration attempt with an invalid parameter")
			return err
		}
		if _, ok := err.(apierrors.AttributeError); ok {
			seelog.Critical("Instance registration attempt with an invalid attribute")
			return err
		}
		return transientError{err}
	}
	seelog.Infof("Registration completed successfully. I am running as '%s' in cluster '%s'", containerInstanceArn, agent.cfg.Cluster)
	agent.containerInstanceARN = containerInstanceArn
	agent.availabilityZone = availabilityZone
	// Save our shiny new containerInstanceArn
	stateManager.Save()
	return nil
}
// registerContainerInstance registers the container instance ID for the ECS Agent