3 The following components require a highly available endpoints:
6 * kube-apiserver service instances.
8 The latter relies on a 3rd side reverse proxy, like Nginx or HAProxy, to
13 The etcd clients (kube-api-masters) are configured with the list of all etcd peers. If the etcd-cluster has multiple instances, it's configured in HA already.
17 K8s components require a loadbalancer to access the apiservers via a reverse
18 proxy. Kubespray includes support for an nginx-based proxy that resides on each
19 non-master Kubernetes node. This is referred to as localhost loadbalancing. It
20 is less efficient than a dedicated load balancer because it creates extra
21 health checks on the Kubernetes apiserver, but is more practical for scenarios
22 where an external LB or virtual IP management is inconvenient. This option is
23 configured by the variable `loadbalancer_apiserver_localhost` (defaults to
24 `True`. Or `False`, if there is an external `loadbalancer_apiserver` defined).
25 You may also define the port the local internal loadbalancer uses by changing,
26 `loadbalancer_apiserver_port`. This defaults to the value of
27 `kube_apiserver_port`. It is also important to note that Kubespray will only
28 configure kubelet and kube-proxy on non-master nodes to use the local internal
31 If you choose to NOT use the local internal loadbalancer, you will need to
32 use the [kube-vip](kube-vip.md) ansible role or configure your own loadbalancer to achieve HA. By default, it only configures a non-HA endpoint, which points to the
33 `access_ip` or IP address of the first server node in the `kube_control_plane` group.
34 It can also configure clients to use endpoints for a given loadbalancer type.
35 The following diagram shows how traffic to the apiserver is directed.
37 ![Image](figures/loadbalancer_localhost.png?raw=true)
39 A user may opt to use an external loadbalancer (LB) instead. An external LB
40 provides access for external clients, while the internal LB accepts client
41 connections only to the localhost.
42 Given a frontend `VIP` address and `IP1, IP2` addresses of backends, here is
43 an example configuration for a HAProxy service acting as an external LB:
46 listen kubernetes-apiserver-https
49 option log-health-checks
52 server master1 <IP1>:6443 check check-ssl verify none inter 10000
53 server master2 <IP2>:6443 check check-ssl verify none inter 10000
57 Note: That's an example config managed elsewhere outside of Kubespray.
59 And the corresponding example global vars for such a "cluster-aware"
60 external LB with the cluster API access modes configured in Kubespray:
63 apiserver_loadbalancer_domain_name: "my-apiserver-lb.example.com"
64 loadbalancer_apiserver:
69 Note: The default kubernetes apiserver configuration binds to all interfaces,
70 so you will need to use a different port for the vip from that the API is
71 listening on, or set the `kube_apiserver_bind_address` so that the API only
72 listens on a specific interface (to avoid conflict with haproxy binding the
73 port on the VIP address)
75 This domain name, or default "lb-apiserver.kubernetes.local", will be inserted
76 into the `/etc/hosts` file of all servers in the `k8s_cluster` group and wired
77 into the generated self-signed TLS/SSL certificates as well. Note that
78 the HAProxy service should as well be HA and requires a VIP management, which
79 is out of scope of this doc.
81 There is a special case for an internal and an externally configured (not with
82 Kubespray) LB used simultaneously. Keep in mind that the cluster is not aware
83 of such an external LB and you need no to specify any configuration variables
86 Note: TLS/SSL termination for externally accessed API endpoints' will **not**
87 be covered by Kubespray for that case. Make sure your external LB provides it.
88 Alternatively you may specify an externally load balanced VIPs in the
89 `supplementary_addresses_in_ssl_keys` list. Then, kubespray will add them into
90 the generated cluster certificates as well.
92 Aside of that specific case, the `loadbalancer_apiserver` considered mutually
93 exclusive to `loadbalancer_apiserver_localhost`.
95 Access API endpoints are evaluated automatically, as the following:
97 | Endpoint type | kube_control_plane | non-master | external |
98 |------------------------------|------------------------------------------|-------------------------|-----------------------|
99 | Local LB (default) | `https://dbip:sp` | `https://lc:nsp` | `https://m[0].aip:sp` |
100 | Local LB (default) + cbip | `https://cbip:sp` and `https://lc:nsp` | `https://lc:nsp` | `https://m[0].aip:sp` |
101 | Local LB + Unmanaged here LB | `https://dbip:sp` | `https://lc:nsp` | `https://ext` |
102 | External LB, no internal | `https://dbip:sp` | `<https://lb:lp>` | `https://lb:lp` |
103 | No ext/int LB | `https://dbip:sp` | `<https://m[0].aip:sp>` | `https://m[0].aip:sp` |
107 * `m[0]` - the first node in the `kube_control_plane` group;
108 * `lb` - LB FQDN, `apiserver_loadbalancer_domain_name`;
109 * `ext` - Externally load balanced VIP:port and FQDN, not managed by Kubespray;
111 * `cbip` - a custom bind IP, `kube_apiserver_bind_address`;
112 * `dbip` - localhost for the default bind IP '0.0.0.0';
113 * `nsp` - nginx secure port, `loadbalancer_apiserver_port`, defers to `sp`;
114 * `sp` - secure port, `kube_apiserver_port`;
115 * `lp` - LB port, `loadbalancer_apiserver.port`, defers to the secure port;
116 * `ip` - the node IP, defers to the ansible IP;
117 * `aip` - `access_ip`, defers to the ip.
119 A second and a third column represent internal cluster access modes. The last
120 column illustrates an example URI to access the cluster APIs externally.
121 Kubespray has nothing to do with it, this is informational only.
123 As you can see, the masters' internal API endpoints are always
124 contacted via the local bind IP, which is `https://bip:sp`.
126 ## Optional configurations
130 In order to use an external loadbalancing (L4/TCP or L7 w/ SSL Passthrough VIP), the following variables need to be overridden in group_vars
132 * `etcd_access_addresses`
134 * `etcd_cert_alt_names`
135 * `etcd_cert_alt_ips`
137 #### Example of a VIP w/ FQDN
140 etcd_access_addresses: https://etcd.example.com:2379
141 etcd_client_url: https://etcd.example.com:2379
143 - "etcd.kube-system.svc.{{ dns_domain }}"
144 - "etcd.kube-system.svc"
147 - "etcd.example.com" # This one needs to be added to the default etcd_cert_alt_names
150 #### Example of a VIP w/o FQDN (IP only)
153 etcd_access_addresses: https://2.3.7.9:2379
154 etcd_client_url: https://2.3.7.9:2379