apple/swift-nio

ClientBootstrap.resolver is hard to use for single-use resolvers

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#2,434 opened on May 26, 2023

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good first issuekind/enhancement

Description

Some resolvers (like NIO's internal GAIResolver) are use-exactly-once objects. They work only if used once (not 0 times, not twice).

ClientBootstrap.resolver is hard to use with those objects because one might want to pass around a pre-configured ClientBootstrap and then not use it or use it multiple times.

Maybe ClientBootstrap could offer a resolverFactory method that gets invoked exactly when we actually do the resolution.

The other option would that NIO could provide a Resolver type that wraps use-once resolvers and managed their lifetime (creates a fresh one when a resolution actually happens).

Contributor guide

Tech stack
swift
Domain
backend
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
SwiftNIO basicsDNS resolution concepts
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
35
Research direction
Investigate the ClientBootstrap.resolver property and its usage in the codebase (e.g., file Sources/NIO/ClientBootstrap.swift). Understand how GAIResolver works as a use once resolver. Review the comments on the issue for any additional design suggestions. Consider implementing either the resolverFactory method on ClientBootstrap or a wrapping Resolver type that creates fresh instances per resolution attempt.