return context timeout error for deallocate

[pperiyasamy]

return context timeout error back to cni/kubelet in case of pod delete, this would allow kubelet to retry for deallocate and avoids stale ip pool entries in the datastore after pod delete.

context timeout errors (due to default 10s request timeout) are frequently seen in highly scaled setup.

Signed-off-by: Periyasamy Palanisamy periyasamy.palanisamy@est.tech

[pperiyasamy]

/cc @JanScheurich

[s1061123]

In https://github.com/containernetworking/cni/blob/spec-v0.4.0/SPEC.md, there is following section and your change violates the CNI specification because your code may return error in DEL action.

Plugins should generally complete a DEL action without error even if some resources are missing.

In addition, some case, upper CNI plugin expects that only one DEL command is invoked (without error), so the code might not be effective to various CNI plugins.

[JanScheurich]

Not returning an error means whereabouts accumulates stale IP addresses in its IP pools. It would require an off-line audit function to find and delete such stale IPs.
I read the CNI specification a bit differently: The CNI should not return an error at DEL if (part of) the resources to be deleted are missing already. But in our case, the actual deletion fails (typically due to too many collisions on the storage back-end).

[pperiyasamy]

Plugins should generally complete a DEL action without error even if some resources are missing.

@s1061123 thanks for this cni spec pointer! good info. just found an issue with ovs-cni due to missing net ns directory. it needs fixing there.
but in this case, as jan mentioned, whereabouts needs to propagate context timeout error back to cni/kubelet when ip entry is not removed from datastore. otherwise having error return type for cmdDel doesn't make any sense at all.

[coveralls]

Pull Request Test Coverage Report for Build 1014889463

• 14 of 46 (30.43%) changed or added relevant lines in 3 files are covered.
• 3 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.1%) to 36.963%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
cmd/whereabouts.go	1	5	20.0%
pkg/storage/storage.go	0	28	0.0%

Files with Coverage Reduction	New Missed Lines	%
pkg/storage/storage.go	3	0%

Totals
Change from base Build 986532013:	-0.1%
Covered Lines:	353
Relevant Lines:	955

---

💛 - Coveralls

[dougbtv]

Any chance you could rebase and see if this is still an issue, thanks!