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pkg/fall: add (a lot of) guidance (#3450)

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update the pkg doc to talk about various trade off

Fixes #2723

Signed-off-by: Miek Gieben <miek@miek.nl>
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Miek Gieben 2019-11-15 14:14:29 +00:00 committed by Chris O'Haver
parent e1782c46e8
commit 1e3330c12b
1 changed files with 13 additions and 1 deletions
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14
plugin/pkg/fall/fall.go
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@ -1,4 +1,16 @@
// Package fall handles the fallthrough logic used in plugins that support it. // Package fall handles the fallthrough logic used in plugins that support it. Be careful when including this
// functionality in your plugin. Why? In the DNS only 1 source is authoritative for a set of names. Fallthrough
// breaks this convention by allowing a plugin to query multiple sources, depending on the replies it got sofar.
//
// This may cause issues in downstream caches, where different answers for the same query can potentially confuse clients.
// On the other hand this is a powerful feature that can aid in migration or other edge cases.
//
// The take away: be mindful of this and don't blindly assume it's a good feature to have in your plugin.
//
// See http://github.com/coredns/coredns/issues/2723 for some discussion on this, which includes this quote:
//
// TL;DR: `fallthrough` is indeed risky and hackish, but still a good feature of CoreDNS as it allows to quickly answer boring edge cases.
//
package fall package fall
import ( import (