feat: Add support for IncludeLinkedAccounts Options

[gtn3010]

Add support for IncludeLinkedAccounts Options
Related to #861

[tuananh]

@cristiangreco could you help taking a look at this? if you have other idea how to do this, please let us know. we will update accordingly.

[tuananh]

@cristiangreco friendly ping. could you take a look at this?

[tuananh]

@cristiangreco anything we need to update to get this in?

[l-baszak]

@cristiangreco Any update on this? It is really needed.

[cristiangreco]

This PR needs to be rebased before it can be reviewed. Additionally, please extend the documentation to i) describe the new config option and ii) describe more generally why/when this is useful.

[l-baszak]

@cristiangreco Can this be deployed?

[gham-khaled]

@tuananh Thank you for the effort ! Anything we can help to get this merged in ? We really need it.

[tuananh]

@tuananh Thank you for the effort ! Anything we can help to get this merged in ? We really need it.

We need @cristiangreco to take a look at it. Or if he has idea for another way of doing, we're happy to update the PR accordingly.

We've been using this feature in-house because we need it for our aws org. Would be nice to have it merged upstream.

[cristiangreco]

Hi, it is not clear to me how this problem is addressed:

Has anyone figured out if in this case it is possible to get resource tags for linked accounts via the monitoring account? It seems that only metric data itself when linked is obtainable via monitoring account but not resource tags, which means there's no easy way to associate resources from linked accounts.

From #861 (comment)

[gtn3010]

Only metric data is obtained and no resource tags from linked accounts. For logic getting tagged resources, I return nil when enabling config IncludeLinkedAccounts, since querying resource tags from linked accounts requires more permissions in AWS cross-account.

[cristiangreco]

Only metric data is obtained and no resource tags from linked accounts. For logic getting tagged resources, I return nil when enabling config IncludeLinkedAccounts, since querying resource tags from linked accounts requires more permissions in AWS cross-account.

This means that the metric data you get back is not associated with the correct resource? How's that useful? (genuine question)

[gtn3010]

I think the metrics data (metrics and dimensions) from cloudwatch is enough for us. For linked accounts, no metrics _info of each resource is acceptable, we haven't used these _info metrics yet. Currently, we only clone the dashboard from cloudwatch to Grafana.

Example:
aws_applicationelb_healthy_host_count_minimum{cluster="nonprod", dimension_AvailabilityZone="", dimension_LoadBalancer="app/non-prod-xxxxxxxx/11111111111", dimension_TargetGroup="targetgroup/k8s-devitcor-backenda-24266686864/46ff4111174faacf", name="global", namespace="monitoring"}
I rely on the LB name dimension to aggregate data.