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Configurable DNS resolvers #4236

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@ysbaddaden ysbaddaden commented Apr 4, 2017

This pull request is a rework of #2829 with an alternative solution: introduce a configurable resolver. The initial issue is that we may have either:

  • a system call (getaddrinfo), which resolves everything but blocks the event loop;
  • an evented resolver (libevent), which is fully evented, but limited compared to the syscall (e.g. Docker, NSS, ...).

An usual solution to this problem is to have worker threads that will resolve domains asynchronously using the system call, whilst not blocking the event loop. This is okayish, but requires to have dedicated threads and communication.

This pull request doesn't choose one solution, but instead allows the developer to chose which one is the best for its application: a blocking resolver (default), an evented resolver or a threaded resolver, or any other solution.

There is one last thing I'd like to change: drop the per-request DNS timeout. It should be configured globally, either on the system, or when creating the resolver, if it's configurable. Actually, only the evented resolver has a DNS timeout configuration (global).

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Hey @ysbaddaden, what's the current status on this?

@ysbaddaden ysbaddaden mentioned this pull request Mar 29, 2018
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Nowhere. It should be reviewed, the failing specs be fixed, and the threaded resolver be extracted into a shard, since it doesn't fit the stdlib, leaving only the blocking and evented resolvers.

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@ysbaddaden failing specs seems to be IPv4 to IPv6 representation difference ?

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@ysbaddaden What is the current status on this?

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rdp commented Nov 20, 2019

apparently libuv uses a thread pool for it as well: FWIW...

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rdp commented Nov 29, 2019

I'd still loove to see an "all native" option for resolving DNS... :)

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6 participants