envoyproxy/envoy

strict_dns: allow to keep stale targets for a specified amount of time

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#15,457 opened on Mar 12, 2021

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area/dnshelp wanted

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Description

Problem: When a DNS does not return all targets on each resolve, strict_dns will continually be adding and draining targets. For this case logical_dns is better, but it's still not great, it keeps track of a single logical target even though connections are made to several, for the given resolution interval all connections and traffic will flow to a single IP address, also I really don't know how outlier_detection and other advanced features can play with a logical_dns cluster. original_dst cluster supports cleaning unused targets and be an option, but it's also probably unsafe since it allows connecting to any IP address.

Proposed Solutions:

  • Adding support for cleanup_interval for strict_dns clusters like original_dst does, and remove them when they have not been returned for a given time.
  • Adding a "mixed dns" cluster which supports this sort of behavior.

Contributor guide

Research direction
Examine the existing `strict dns` cluster implementation and compare with `original dst` cluster's `cleanup interval` feature. Understand how targets are added and removed. Then design a new `cleanup interval` option for `strict dns` that removes targets that haven't been returned for a specified duration.
Tech stack
ccpp
Domain
networkingbackend
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.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
GitC++
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50