metrics: add cilium_datapath_nat_gc_entries

[ArthurChiao]

This patch adds NAT GC metrics to current metrics list. As NAT entries are
GC'd alongside CT entries and NAT module has no dedicated GC jobs, we
calculate the NAT metrics in CT module's GC job.

Signed-off-by: ArthurChiao arthurchiao@hotmail.com

[coveralls]

Coverage decreased (-0.009%) to 37.109% when pulling bd04add9130af51329efe46d78bfb6850041b6c7 on ctripcloud:add_nat_metrics_github into 5195789 on cilium:master.

[brb]

Thanks for your PR!

Unfortunately, iterating over all NAT entries just to update metrics counters each time we do GC of CT entries is too expensive operation. We might introduce such iteration in #12686. So, I suggest to wait until the latter has been done.

[ArthurChiao]

Thanks @brb , then should I close this PR right now?

[brb]

Thanks @brb , then should I close this PR right now?

Let's keep it open. I've just changed its state to draft.

[stale]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[stale]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[stale]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[brb]

@ArthurChiao #13912 got merged. Mind rebasing your PR and adding metrics?

[ArthurChiao]

Thanks for reminding me @brb.

Yeah, we definitely need the metric for it. I will add it as a follow up.

I closed this PR as i saw the above message in #13912. So not sure if my PR is still needed?

[brb]

@ArthurChiao Yeah, the metrics part is still needed (I've only added the logging).

[ArthurChiao]

I'll have a look, thanks! @brb

[ArthurChiao]

Hi @brb, rebased to master, please have a review, thanks!

Note: currently this metric could only be enabled/disabled along with cilium_datapath_conntrack_gc_entries,
seems there is no need to add a dedicated flag to control NAT gc metric on/off?

Test output:

# HELP cilium_datapath_nat_gc_entries The number of alive and deleted nat entries at the end of a garbage collector run labeled by datapath family.
# TYPE cilium_datapath_nat_gc_entries gauge
cilium_datapath_nat_gc_entries{direction="egress",family="ipv4",status="deleted"} 0
cilium_datapath_nat_gc_entries{direction="ingress",family="ipv4",status="alive"} 11800
cilium_datapath_nat_gc_entries{direction="ingress",family="ipv4",status="deleted"} 0

[brb]

test-me-please