Merge pull request #518 from bogdando/issues/516

Allow subdomains of dns_domain and fix kubelet restarts
This commit is contained in:
Smaine Kahlouch 2016-09-28 10:11:44 +02:00 committed by GitHub
commit c96a9bfdfd
7 changed files with 63 additions and 36 deletions

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@ -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.

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@ -33,6 +33,8 @@ kube_users:
# Kubernetes cluster name, also will be used as DNS domain
cluster_name: cluster.local
# Subdomains of DNS domain to be resolved via /etc/resolv.conf
ndots: 5
# For some environments, each node has a pubilcally accessible
# address and an address it should bind services to. These are

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@ -17,5 +17,18 @@
when: ansible_os_family != "RedHat" and ansible_os_family != "CoreOS"
- name: Dnsmasq | update resolvconf
command: /bin/true
notify:
- Dnsmasq | reload resolvconf
- Dnsmasq | reload kubelet
- name: Dnsmasq | reload resolvconf
command: /sbin/resolvconf -u
ignore_errors: true
- name: Dnsmasq | reload kubelet
service:
name: kubelet
state: restarted
when: "{{ inventory_hostname in groups['kube-master'] }}"
ignore_errors: true

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@ -72,6 +72,7 @@
backup: yes
follow: yes
with_items:
- ndots:{{ ndots }}
- timeout:2
- attempts:2
notify: Dnsmasq | update resolvconf

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@ -21,7 +21,7 @@ spec:
spec:
containers:
- name: kubedns
image: gcr.io/google_containers/kubedns-amd64:1.6
image: gcr.io/google_containers/kubedns-amd64:1.7
resources:
# TODO: Set memory limits when we've profiled the container for large
# clusters, then set request = limit to keep this container in

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@ -4,12 +4,14 @@
notify:
- Master | reload systemd
- Master | reload kubelet
- Master | wait for master static pods
- name: wait for master static pods
- name: Master | wait for master static pods
command: /bin/true
notify:
- wait for kube-scheduler
- wait for kube-controller-manager
- Master | wait for the apiserver to be running
- Master | wait for kube-scheduler
- Master | wait for kube-controller-manager
- name: Master | reload systemd
command: systemctl daemon-reload
@ -20,16 +22,23 @@
name: kubelet
state: restarted
- name: wait for kube-scheduler
- name: Master | wait for kube-scheduler
uri: url=http://localhost:10251/healthz
register: scheduler_result
until: scheduler_result.status == 200
retries: 15
delay: 5
- name: wait for kube-controller-manager
- name: Master | wait for kube-controller-manager
uri: url=http://localhost:10252/healthz
register: controller_manager_result
until: controller_manager_result.status == 200
retries: 15
delay: 5
- name: Master | wait for the apiserver to be running
uri: url=http://localhost:8080/healthz
register: result
until: result.status == 200
retries: 10
delay: 6

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@ -19,17 +19,9 @@
template:
src: manifests/kube-apiserver.manifest.j2
dest: "{{ kube_manifest_dir }}/kube-apiserver.manifest"
register: apiserver_manifest
notify: Master | restart kubelet
- name: wait for the apiserver to be running
uri: url=http://localhost:8080/healthz
register: result
until: result.status == 200
retries: 10
delay: 6
notify: Master | wait for the apiserver to be running
- meta: flush_handlers
# Create kube-system namespace
- name: copy 'kube-system' namespace manifest
copy: src=namespace.yml dest=/etc/kubernetes/kube-system-ns.yml
@ -43,7 +35,6 @@
failed_when: False
run_once: yes
- name: Create 'kube-system' namespace
command: "{{ bin_dir }}/kubectl create -f /etc/kubernetes/kube-system-ns.yml"
changed_when: False
@ -54,12 +45,10 @@
template:
src: manifests/kube-controller-manager.manifest.j2
dest: "{{ kube_manifest_dir }}/kube-controller-manager.manifest"
notify: wait for kube-controller-manager
notify: Master | wait for kube-controller-manager
- name: Write kube-scheduler manifest
template:
src: manifests/kube-scheduler.manifest.j2
dest: "{{ kube_manifest_dir }}/kube-scheduler.manifest"
notify: wait for kube-scheduler
- meta: flush_handlers
notify: Master | wait for kube-scheduler