dns: refactor cares_wrap internals

[jasnell]

This is the first step of a significant refactoring of the DNS subsystem. The first step is to simplify and modernize the code structure, eliminate some duplicate code, and apply some of the more modern patterns that we have implemented elsewhere in the code.

Additional refactorings will come in additional PRs.

Signed-off-by: James M Snell jasnell@gmail.com

[targos]

I guess this is now in conflict with #38184 ?

[XadillaX]

I guess this is now in conflict with #38184 ?

same question too.

[jasnell]

No. I've talked to @devsnek about it. That other pr is semver major and makes a number of larger breaking changes. This is semver-patch and is good for everything >= 16.x.

[addaleax]

@jasnell So, just practically speaking … it’s virtually impossible to review PRs that move large chunks of code around and make some minor adjustments in a bunch of places. I’m not sure how to progress here.

[targos]

I'm like Anna, I don't know how to tackle this review.

[jasnell]

I'd look at it as a new contribution, largely ignoring the old bits that were changed, focus on the new bits. There's only one test change because one of the internal classes was renamed. There should be absolutely no change in actual behavior.

[addaleax]

@jasnell I think in that case there will be a lot of comments … but yeah, I can do that sometime this week

[jasnell]

The changes that were made are:

• Class declarations were removed from node_cares.cc and moved into a new node_cares.h
• node_ares_task was renamed to NodeAresTask and the associated Hash and Equal impls were moved into NodeAresTask.
• node_ares_task_list was changed to a using List inside NodeAresTask.
• class ChannelWrap : => class ChannelWrap final :
• class GetAddrInfoReqWrap : => class GetAddrInfoReqWrap final :
• class GetNameInfoReqWrap : => class GetNameInfoReqWrap final :
• class QueryWrap was changed into a final template class. Rather than being subclassed for each individual query type, a using ... = QueryWrap<...> pattern is used for each type, matching the changes that have been made elsewhere in the codebase (e.g. in crypto).
• Added the struct QueryTraits template to allow eliminating duplicated code (previously, every query type subclass had nearly identical implementations of Send().
• Eliminated a dead code path (an unused override of Send() that was in every query type subclass.
• Introduced the HostentPointer smart pointer (using DeleteFnPtr) to make cleanup of hostent* a bit nicer
• Other small cleanups to match formatting and eliminate unnecessary assignments (e.g. removing auto context = env->context() calls and replacing context with env->context().

There should be no observable functional changes with the exception of the rename of node_ares_task_list to NodeAresTask::List in a generated heapdump. All existing dns related tests and benchmarks should continue to operate correctly without modification.

[jasnell]

@addaleax

I think in that case there will be a lot of comments

I would expect nothing less ;-)

This particular bit of code has always been far from perfect and I have many more changes in the works to improve it so a detailed review is helpful.

[mcollina]

lgtm

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/37489/ 💚

[jasnell]

@addaleax ... this is generally ready to go. Did you have any more feedback on it before I land later today?

[addaleax]

@jasnell No, feel free to merge 👍

[jasnell]

Awesome ok. I know there's still a lot in this code that can be improved but with the possible move to getdns in the work, I'm not sure how much more effort we should put into it. I'll merge later on this afternoon. (although, I guess since the getdns change is semver major, and 16 will be around for a while, it would at least make sense to explore some good perf improvements here still)

[jasnell]

Landed in bc31dc0