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Fix HA docs API access endpoints explained (#2126)

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* Fix HA docs API access endpoints explained

Follow-up commit 81347298a3
and fix the endpoint value provided in HA docs.

Signed-off-by: Bogdan Dobrelya <bogdando@mail.ru>

* Clarify internal LB with external LB use case

* Clarify how to use both internal and external, non-cluster aware and
  not managed with Kubespray, LB solutions.
* Clarify the requirements, like TLS/SSL termination, for such an external LB.
  Unlike to the 'cluster-aware' external LB config, endpoints' security must be
  managed by that non-cluster aware external LB.
* Note that masters always contact their local apiservers via https://bip:sp.
  It's highly unlikely to go down and it reduces latency that might be
  introduced when going host->lb->host. Only computes go that path.

Signed-off-by: Bogdan Dobrelya <bogdando@mail.ru>

* Add a note for supplementary_addresses_in_ssl_keys

Explain how to benefit from supplementary_addresses_in_ssl_keys

Signed-off-by: Bogdan Dobrelya <bogdando@mail.ru>
This commit is contained in:
Bogdan Dobrelya 2018-01-09 14:01:50 +01:00 committed by Matthew Mosesohn
parent 1401286910
commit 278ac08087
1 changed files with 36 additions and 15 deletions
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51
docs/ha-mode.md
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@ -68,7 +68,10 @@ listen kubernetes-apiserver-https
balance roundrobin
```
And the corresponding example global vars config:
Note: That's an example config managed elsewhere outside of Kubespray.
And the corresponding example global vars for such a "cluster-aware"
external LB with the cluster API access modes configured in Kubespray:
```
apiserver_loadbalancer_domain_name: "my-apiserver-lb.example.com"
loadbalancer_apiserver:
@ -78,40 +81,58 @@ loadbalancer_apiserver:
Note: The default kubernetes apiserver configuration binds to all interfaces,
so you will need to use a different port for the vip from that the API is
listening on, or set the kube_apiserver_bind_address so that the API only
listening on, or set the `kube_apiserver_bind_address` so that the API only
listens on a specific interface (to avoid conflict with haproxy binding the
port on the VIP adddress)
This domain name, or default "lb-apiserver.kubernetes.local", will be inserted
into the `/etc/hosts` file of all servers in the `k8s-cluster` group. Note that
into the `/etc/hosts` file of all servers in the `k8s-cluster` group and wired
into the generated self-signed TLS/SSL certificates as well. Note that
the HAProxy service should as well be HA and requires a VIP management, which
is out of scope of this doc. Specifying an external LB overrides any internal
localhost LB configuration.
is out of scope of this doc.
Note: In order to achieve HA for HAProxy instances, those must be running on
the each node in the `k8s-cluster` group as well, but require no VIP, thus
no VIP management.
There is a special case for an internal and an externally configured (not with
Kubespray) LB used simultaneously. Keep in mind that the cluster is not aware
of such an external LB and you need no to specify any configuration variables
for it.
Note: TLS/SSL termination for externally accessed API endpoints' will **not**
be covered by Kubespray for that case. Make sure your external LB provides it.
Alternatively you may specify an externally load balanced VIPs in the
`supplementary_addresses_in_ssl_keys` list. Then, kubespray will add them into
the generated cluster certifactes as well.
Aside of that specific case, the `loadbalancer_apiserver` considered mutually
exclusive to `loadbalancer_apiserver_localhost`.
Access API endpoints are evaluated automagically, as the following:
| Endpoint type | kube-master | non-master |
|------------------------------|----------------|---------------------|
| Local LB (default) | https://lc:sp | https://lc:nsp |
| External LB, no internal | https://lb:lp | https://lb:lp |
| No ext/int LB, bind 0.0.0.0 | https://lc:sp | https://m[0].aip:sp |
| No ext/int LB, a custom bind | https://bip:sp | https://m[0].aip:sp |
| Endpoint type | kube-master | non-master | external |
|------------------------------|----------------|---------------------|---------------------|
| Local LB (default) | https://bip:sp | https://lc:nsp | https://m[0].aip:sp |
| Local LB + Unmanaged here LB | https://bip:sp | https://lc:nsp | https://ext |
| External LB, no internal | https://bip:sp | https://lb:lp | https://lb:lp |
| No ext/int LB | https://bip:sp | https://m[0].aip:sp | https://m[0].aip:sp |
Where:
* `m[0]` - the first node in the `kube-master` group;
* `lb` - LB FQDN, `apiserver_loadbalancer_domain_name`;
* `ext` - Externally load balanced VIP:port and FQDN, not managed by Kubespray;
* `lc` - localhost;
* `bip` - a custom bind IP value (defaults to '0.0.0.0');
* `bip` - a custom bind IP or localhost for the default bind IP '0.0.0.0';
* `nsp` - nginx secure port, `nginx_kube_apiserver_port`, defers to `sp`;
* `sp` - secure port, `kube_apiserver_port`;
* `lp` - LB port, `loadbalancer_apiserver.port`, defers to the secure port;
* `ip` - the node IP, defers to the ansible IP;
* `aip` - `access_ip`, defers to the ip.
A second and a third column represent internal cluster access modes. The last
column illustrates an example URI to access the cluster APIs externally.
Kubespray has nothing to do with it, this is informational only.
As you can see, the masters' internal API endpoints are always
contacted via the local bind IP, which is `https://bip:sp`.
**Note** that for some cases, like healthchecks of applications deployed by
Kubespray, the masters' APIs are accessed via the insecure endpoint, which
consists of the local `kube_apiserver_insecure_bind_address` and