epostnikof/kubespray
1
0
Fork 0
mirror of https://github.com/kubernetes-sigs/kubespray.git synced 2025-12-14 13:54:37 +03:00
Code Issues Packages Projects Releases Wiki Activity

Allow subdomains of dns_domain and fix kubelet restarts

Browse Source 
* Add a var for ndots (default 5) and put it hosts' /etc/resolv.conf.
* Poke kube dns container image to v1.7
* In order to apply changes to kubelet, notify it to
be restarted on changes made to /etc/resolv.conf. Ignore errors as the kubelet
may yet to be present up to the moment of the notification being processed.
* Remove unnecessary kubelet restart for master role as the node role ensures
it is up and running. Notify master static pods waiters for apiserver,
scheduler, controller-manager instead.

Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>
This commit is contained in:
Bogdan Dobrelya
2016-09-27 11:54:12 +02:00
parent 0f461282c8
commit 5fd43b7cf0
7 changed files with 63 additions and 36 deletions
Download Patch File Download Diff File Expand all files Collapse all files

43
docs/dns-stack.md
View File

@@ -7,7 +7,7 @@ to serve as an authoritative DNS server for a given ``dns_domain`` and its
``svc, default.svc`` default subdomains (a total of ``ndots: 5`` max levels).
Note, additional search (sub)domains may be defined in the ``searchdomains``
var. And additional recursive DNS resolvers in the `` upstream_dns_servers``,
and ``ndots`` vars. And additional recursive DNS resolvers in the `` upstream_dns_servers``,
``nameservers`` vars. Intranet DNS resolvers should be specified in the first
place, followed by external resolvers, for example:
@@ -21,17 +21,10 @@ or
skip_dnsmasq: false
upstream_dns_servers: [172.18.32.6, 172.18.32.7, 8.8.8.8, 8.8.8.4]
```
The vars are explained below as well.
Remember the limitations (the vars are explained below):
* the ``searchdomains`` have a limitation of a 6 names and 256 chars
length. Due to default ``svc, default.svc`` subdomains, the actual
limits are a 4 names and 239 chars respectively.
* the ``nameservers`` have a limitation of a 3 servers, although there
is a way to mitigate that with the ``upstream_dns_servers``,
see below. Anyway, the ``nameservers`` can take no more than a two
custom DNS servers because of one slot is reserved for a Kubernetes
cluster needs.
DNS configuration details
-------------------------
Here is an approximate picture of how DNS things working and
being configured by Kargo ansible playbooks:
@@ -73,7 +66,27 @@ Those may be specified either in ``nameservers`` or ``upstream_dns_servers``
and will be merged together with the ``skydns_server`` IP into the hots'
``/etc/resolv.conf``.
Kargo has yet ways to configure Kubedns addon to forward requests SkyDns can
not answer with authority to arbitrary recursive resolvers. This task is left
for future. See [official SkyDns docs](https://github.com/skynetservices/skydns)
for details.
Limitations
-----------
* Kargo has yet ways to configure Kubedns addon to forward requests SkyDns can
not answer with authority to arbitrary recursive resolvers. This task is left
for future. See [official SkyDns docs](https://github.com/skynetservices/skydns)
for details.
* There is
[no way to specify a custom value](https://github.com/kubernetes/kubernetes/issues/33554)
for the SkyDNS ``ndots`` param via an
[option for KubeDNS](https://github.com/kubernetes/kubernetes/blob/master/cmd/kube-dns/app/options/options.go)
add-on, while SkyDNS supports it though. Thus, DNS SRV records may not work
as expected as they require the ``ndots:7``.
* the ``searchdomains`` have a limitation of a 6 names and 256 chars
length. Due to default ``svc, default.svc`` subdomains, the actual
limits are a 4 names and 239 chars respectively.
* the ``nameservers`` have a limitation of a 3 servers, although there
is a way to mitigate that with the ``upstream_dns_servers``,
see below. Anyway, the ``nameservers`` can take no more than a two
custom DNS servers because of one slot is reserved for a Kubernetes
cluster needs.