moby / moby/libnetwork

Docker DNS Timeout Interval Too Big

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Dominant language
Go
Stars
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Forks
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Description

Feature Request
Current docker embedded DNS uses hardcoded 4 seconds timeout interval. External DNS server may get corrupted and become irresponsive. If primary external DNS goes down, it needs to wait for 4 seconds before trying secondary, which is too long. It would be nice if we can make extIOTimeout configurable or make it shorter.
https://github.com/docker/libnetwork/blob/9ff9b57c344df5cd47443ad9e65702ec85c5aeb0/resolver.go#L460

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start at resolver.go around line 460, where extIOTimeout is referenced, and trace how the Docker embedded DNS resolver handles primary and secondary external DNS servers. Determine whether the timeout should be configurable or shorter, then verify that DNS failover no longer waits unnecessarily when the primary server is unresponsive.

Written by the indexing model from the issue text.

Assessment

Tech stack
go
Domain
networking
Issue type
Feature
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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