Add new FallbackExecutor and update DNS Factory to use fallback DNS servers when DNS Config lists multiple servers
#180
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This was referenced Jun 24, 2021
WyriHaximus
approved these changes
Jun 25, 2021
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This changeset adds a new
FallbackExecutorand subsequently updates the DNSFactoryto use fallback DNS servers when DNSConfiglists multiple servers.Previous versions would only use the first DNS server listed in the DNS
Config. With these changes applied, it will take up to three DNS servers from this list. This is artificially limited to match default limits in place in most systems (seeMAXNSconfig). Internally, it will implement the same strategy that is used in most systems: Always query the first DNS server and if this fails (or times out), use the second DNS server and so on. See alsoman resolv.conffor details.Most systems (citation needed) use only a single DNS server and would not be affected by this change. A reasonable number of systems (citation needed) use multiple DNS servers as a fallback just in case and have a functioning primary DNS server and would not be affected by this change. A very small number of systems would use multiple DNS servers and have broken connectivity with their primary DNS server, these systems can now resolve DNS queries, albeit with a noticeable delay.
Accordingly, this is a pure future addition that works across all supported platforms and does not affect BC.
Builds on top of #179
Resolves / closes #6
Supersedes / closes #131