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plugin/autopath: slightly tweaks the docs (#4188)

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* plugin/autopath: slightly tweaks the docs

Make the first sentence of the intro slightly easier to read. Refer to a
bugs section, just like other plugins do.

Signed-off-by: Miek Gieben <miek@miek.nl>

* Update plugin/autopath/README.md

Co-authored-by: Chris O'Haver <cohaver@infoblox.com>

Co-authored-by: Chris O'Haver <cohaver@infoblox.com>
This commit is contained in:
Miek Gieben
2020-10-16 14:28:44 +02:00
committed by GitHub
parent 268781d355
commit 04f2ecc87f
1 changed files with 15 additions and 14 deletions
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29
plugin/autopath/README.md
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@@ -6,13 +6,13 @@
## Description
If it sees a query that matches the first element of the configured search path, *autopath* will
If the *autopath* plugin sees a query that matches the first element of the configured search path, it will
follow the chain of search path elements and return the first reply that is not NXDOMAIN. On any
failures, the original reply is returned. Because *autopath* returns a reply for a name that wasn't
the original question it will add a CNAME that points from the original name (with the search path
the original question, it will add a CNAME that points from the original name (with the search path
element in it) to the name of this answer.
**Note**: There are several known issues. See section below.
**Note**: There are several known issues, see the "Bugs" section below.
## Syntax
@@ -25,7 +25,7 @@ autopath [ZONE...] RESOLV-CONF
plugin. For instance `@kubernetes`, will call out to the kubernetes plugin (for each
query) to retrieve the search list it should use.
If a plugin implements the `AutoPather` interface then it can be used.
If a plugin implements the `AutoPather` interface then it can be used by *autopath*.
## Metrics
@@ -50,18 +50,19 @@ autopath @kubernetes
Use the search path dynamically retrieved from the *kubernetes* plugin.
## Known Issues
## Bugs
In Kubernetes, *autopath* can derive the wrong namespace of a client Pod (and therefore wrong search path)
in the following case. To properly build the search path of a client *autopath* needs to
know the namespace of the a Pod making a DNS request. To do this, it relies on the
*kubernetes* plugin's Pod cache to resolve the client's IP address to a Pod. The Pod cache is maintained by
an API watch on Pods. When Pod IP assignments change, the Kubernetes API notifies CoreDNS via the API watch.
In Kubernetes, *autopath* can derive the wrong namespace of a client Pod (and therefore wrong search
path) in the following case. To properly build the search path of a client *autopath* needs to know
the namespace of the a Pod making a DNS request. To do this, it relies on the *kubernetes* plugin's
Pod cache to resolve the client's IP address to a Pod. The Pod cache is maintained by an API watch
on Pods. When Pod IP assignments change, the Kubernetes API notifies CoreDNS via the API watch.
However, that notification is not instantaneous. In the case that a Pod is deleted, and it's IP is
immediately provisioned to a Pod in another namespace, and that new Pod make a DNS lookup *before* the API watch
can notify CoreDNS of the change, *autopath* will resolve the IP to the previous Pod's namespace.
immediately provisioned to a Pod in another namespace, and that new Pod make a DNS lookup *before*
the API watch can notify CoreDNS of the change, *autopath* will resolve the IP to the previous Pod's
namespace.
In Kubernetes, *autopath* is not compatible with Pods running from Windows nodes.
If the server side search ultimately results in a negative answer (e.g. `NXDOMAIN`), then the client will
fruitlessly search all paths manually, thus negating the *autopath* optimization.
If the server side search ultimately results in a negative answer (e.g. `NXDOMAIN`), then the client
will fruitlessly search all paths manually, thus negating the *autopath* optimization.