refactor(clustering/rpc): support rpc batching on dp side

[chronolaw]

Summary

KAG-5934

Checklist

• The Pull Request has tests
• A changelog file has been created under changelog/unreleased/kong or skip-changelog label added on PR if changelog is unnecessary. README.md
• There is a user-facing docs PR against https://github.com/Kong/docs.konghq.com - PUT DOCS PR HERE

Issue reference

Fix #[issue number]

[chronolaw]

Since this feature is hard to test, I will add it to concentrator in another PR.

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Files not reviewed (1)

• kong/clustering/rpc/socket.lua: Language not supported

[StarlightIbuki]

Not blockers

[StarlightIbuki]

Suggested change

	local res, err = self:push_response(
	new_error(nil, jsonrpc.INVALID_REQUEST, "not a valid object"),
	collection)
	if not res then
	return nil, err
	end
	return true
	return self:push_response(
	new_error(nil, jsonrpc.INVALID_REQUEST, "not a valid object"),
	collection)

[chronolaw]

We could do it, but this style should be consistent with line 186:

186         local reso, erro = self:push_response(new_error(payload_id, jsonrpc.INTERNAL_ERROR),
187                                               "unable to send \"INTERNAL_ERROR\" error back to client: ",
188                                               collection)
189         if not reso then
190           return nil, erro
191         end
193         return nil, "unable to dispatch JSON-RPC callback: " .. err

[chobits]

I think we need to accept xuming's advice.

We should not block this improvement to try to align with L186. Because L186's error has a prefix error"unable to dispatch JSON-RPC callback: "

WIthout xuming's fix, otherwise, this logic always let reviewers feel odd.

[chobits]

Also I think we could return errno. without a prefix error. This is simpler

[chronolaw]

I will do it in another refactor PR.

[StarlightIbuki]

Same here. By simplifying the code we reduce the noise and improve readability

[chronolaw]

We keep the same call style of self:push_response in the code, as my opinion it may not be changed in this PR.