Merge pull request #528 from kubespray/proxy-nginx

Use nginx proxy on non-master nodes to proxy apiserver traffic

docs/ha-mode.md

@@ -33,15 +33,27 @@ Kube-apiserver
 --------------
 
 K8s components require a loadbalancer to access the apiservers via a reverse
-proxy. A kube-proxy does not support multiple apiservers for the time being so
+proxy. Kargo includes support for an nginx-based proxy that resides on each
+non-master Kubernetes node. This is referred to as localhost loadbalancing. It
+is less efficient than a dedicated load balancer because it creates extra
+health checks on the Kubernetes apiserver, but is more practical for scenarios
+where an external LB or virtual IP management is inconvenient.
+
+This option is configured by the variable `loadbalancer_apiserver_localhost`.
 you will need to configure your own loadbalancer to achieve HA. Note that
 deploying a loadbalancer is up to a user and is not covered by ansible roles
 in Kargo. By default, it only configures a non-HA endpoint, which points to
 the `access_ip` or IP address of the first server node in the `kube-master`
 group. It can also configure clients to use endpoints for a given loadbalancer
-type.
+type. The following diagram shows how traffic to the apiserver is directed.
 
-A loadbalancer (LB) may be an external or internal one. An external LB
+![Image](figures/loadbalancer_localhost.png?raw=true)
+
+..note:: Kubernetes master nodes still use insecure localhost access because
+  there are bugs in Kubernetes <1.5.0 in using TLS auth on master role
+  services.
+
+A user may opt to use an external loadbalancer (LB) instead. An external LB
 provides access for external clients, while the internal LB accepts client
 connections only to the localhost, similarly to the etcd-proxy HA endpoints.
 Given a frontend `VIP` address and `IP1, IP2` addresses of backends, here is
@@ -71,35 +83,11 @@ into the `/etc/hosts` file of all servers in the `k8s-cluster` group. Note that
 the HAProxy service should as well be HA and requires a VIP management, which
 is out of scope of this doc.
 
-The internal LB may be the case if you do not want to operate a VIP management
+Specifying an external LB overrides any internal localhost LB configuration.
-HA stack and require no external and no secure access to the K8s API. The group
+Note that for this example, the `kubernetes-apiserver-http` endpoint
-var `loadbalancer_apiserver_localhost` (defaults to `false`) controls that
+has backends receiving unencrypted traffic, which may be a security issue
-deployment layout. When enabled, it is expected each node in the `k8s-cluster`
+when interconnecting different nodes, or maybe not, if those belong to the
-group to run a loadbalancer that listens the localhost frontend and has all
+isolated management network without external access.
-of the apiservers as backends. Here is an example configuration for a HAProxy
- service acting as an internal LB:
-
-```
-listen kubernetes-apiserver-http
-  bind localhost:8080
-  mode tcp
-  timeout client 3h
-  timeout server 3h
-  server master1 <IP1>:8080
-  server master2 <IP2>:8080
-  balance leastconn
-```
-
-And the corresponding example global vars config:
-```
-loadbalancer_apiserver_localhost: true
-```
-
-This var overrides an external LB configuration, if any. Note that for this
-example, the `kubernetes-apiserver-http` endpoint has backends receiving
-unencrypted traffic, which may be a security issue when interconnecting
-different nodes, or may be not, if those belong to the isolated management
-network without external access.
 
 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
@@ -109,8 +97,8 @@ Access endpoints are evaluated automagically, as the following:
 
 | Endpoint type                | kube-master   | non-master          |
 |------------------------------|---------------|---------------------|
-| Local LB (overrides ext)     | http://lc:p   | http://lc:p         |
+| Local LB                     | http://lc:p   | http://lc:sp        |
-| External LB, no internal     | https://lb:lp | https://lb:lp       |
+| External LB, no internal     | http://lc:p   | https://lb:lp       |
 | No ext/int LB (default)      | http://lc:p   | https://m[0].aip:sp |
 
 Where:

inventory/group_vars/all.yml

@@ -64,8 +64,9 @@ ndots: 5
 # This may be the case if clients support and loadbalance multiple etcd servers  natively.
 etcd_multiaccess: false
 
-# Assume there are no internal loadbalancers for apiservers exist
+# Assume there are no internal loadbalancers for apiservers exist and listen on
-loadbalancer_apiserver_localhost: false
+# kube_apiserver_port (default 443)
+loadbalancer_apiserver_localhost: true
 
 # Choose network plugin (calico, weave or flannel)
 kube_network_plugin: flannel

roles/kubernetes/node/defaults/main.yml

@@ -14,3 +14,6 @@ kube_proxy_masquerade_all: true
 # kube_api_runtime_config:
 #   - extensions/v1beta1/daemonsets=true
 #   - extensions/v1beta1/deployments=true
+
+nginx_image_repo: nginx
+nginx_image_tag: 1.11.4-alpine

roles/kubernetes/node/tasks/main.yml

@@ -1,6 +1,9 @@
 ---
 - include: install.yml
 
+- include: nginx-proxy.yml
+  when: is_kube_master == false and loadbalancer_apiserver_localhost|default(false)
+
 - name: Write Calico cni config
   template:
     src: "cni-calico.conf.j2"

roles/kubernetes/node/tasks/nginx-proxy.yml

@@ -0,0 +1,9 @@
+---
+- name: nginx-proxy | Write static pod
+  template: src=manifests/nginx-proxy.manifest.j2 dest=/etc/kubernetes/manifests/nginx-proxy.yml
+
+- name: nginx-proxy | Make nginx directory
+  file: path=/etc/nginx state=directory mode=0700 owner=root
+
+- name: nginx-proxy | Write nginx-proxy configuration
+  template: src=nginx.conf.j2 dest="/etc/nginx/nginx.conf" owner=root mode=0755 backup=yes

roles/kubernetes/node/templates/manifests/nginx-proxy.manifest.j2

@@ -0,0 +1,20 @@
+apiVersion: v1
+kind: Pod
+metadata:
+  name: nginx-proxy
+  namespace: kube-system
+spec:
+  hostNetwork: true
+  containers:
+  - name: nginx-proxy
+    image: {{ nginx_image_repo }}:{{ nginx_image_tag }}
+    securityContext:
+      privileged: true
+    volumeMounts:
+    - mountPath: /etc/nginx
+      name: etc-nginx
+      readOnly: true
+  volumes:
+  - name: etc-nginx
+    hostPath:
+      path: /etc/nginx

roles/kubernetes/node/templates/nginx.conf.j2

@@ -0,0 +1,26 @@
+error_log stderr notice;
+
+worker_processes auto;
+events {
+  multi_accept on;
+  use epoll;
+  worker_connections 1024;
+}
+
+stream {
+        upstream kube_apiserver {
+            least_conn;
+            {% for host in groups['kube-master'] -%}
+            server {{ hostvars[host]['access_ip'] | default(hostvars[host]['ip'] | default(hostvars[host]['ansible_default_ipv4']['address'])) }}:{{ kube_apiserver_port }};
+            {% endfor %}
+        }
+
+        server {
+            listen        {{ kube_apiserver_port }};
+            proxy_pass    kube_apiserver;
+            proxy_timeout 3s;
+            proxy_connect_timeout 1s;
+
+        }
+
+}

roles/kubernetes/preinstall/defaults/main.yml

@@ -21,6 +21,8 @@ kube_log_dir: "/var/log/kubernetes"
 # pods on startup
 kube_manifest_dir: "{{ kube_config_dir }}/manifests"
 
+# change to 0.0.0.0 to enable insecure access from anywhere (not recommended)
+kube_apiserver_insecure_bind_address: 127.0.0.1
 
 common_required_pkgs:
   - python-httplib2

roles/kubernetes/preinstall/tasks/set_facts.yml

@@ -5,12 +5,12 @@
 - set_fact: is_kube_master="{{ inventory_hostname in groups['kube-master'] }}"
 - set_fact: first_kube_master="{{ hostvars[groups['kube-master'][0]]['access_ip'] | default(hostvars[groups['kube-master'][0]]['ip'] | default(hostvars[groups['kube-master'][0]]['ansible_default_ipv4']['address'])) }}"
 - set_fact:
-    kube_apiserver_insecure_bind_address: |-
+    loadbalancer_apiserver_localhost: false
-      {% if loadbalancer_apiserver_localhost %}{{ kube_apiserver_address }}{% else %}127.0.0.1{% endif %}
+    when: loadbalancer_apiserver is defined
 - set_fact:
     kube_apiserver_endpoint: |-
-      {% if loadbalancer_apiserver_localhost -%}
+      {% if not is_kube_master and loadbalancer_apiserver_localhost -%}
-           http://127.0.0.1:{{ kube_apiserver_insecure_port }}
+           https://localhost:{{ kube_apiserver_port }}
       {%- elif is_kube_master and loadbalancer_apiserver is not defined -%}
            http://127.0.0.1:{{ kube_apiserver_insecure_port }}
       {%- else -%}

roles/kubernetes/secrets/files/make-ssl.sh

@@ -68,6 +68,7 @@ openssl req -x509 -new -nodes -key ca-key.pem -days 10000 -out ca.pem -subj "/CN
 openssl genrsa -out apiserver-key.pem 2048 > /dev/null 2>&1
 openssl req -new -key apiserver-key.pem -out apiserver.csr -subj "/CN=kube-apiserver" -config ${CONFIG} > /dev/null 2>&1
 openssl x509 -req -in apiserver.csr -CA ca.pem -CAkey ca-key.pem -CAcreateserial -out apiserver.pem -days 365 -extensions v3_req -extfile ${CONFIG} > /dev/null 2>&1
+cat ca.pem >> apiserver.pem
 
 # Nodes and Admin
 for i in node admin; do

roles/kubernetes/secrets/tasks/gen_certs.yml

@@ -65,3 +65,30 @@
   shell: chmod 0600 {{ kube_cert_dir}}/*key.pem
   when: inventory_hostname in groups['kube-master']
   changed_when: false
+
+- name: Gen_certs | target ca-certificates directory
+  set_fact:
+    ca_cert_dir: |-
+      {% if ansible_os_family == "Debian" -%}
+      /usr/local/share/ca-certificates
+      {%- elif ansible_os_family == "RedHat" -%}
+      /etc/pki/ca-trust/source/anchors
+      {%- elif ansible_os_family == "CoreOS" -%}
+      /etc/ssl/certs
+      {%- endif %}
+
+- name: Gen_certs | add CA to trusted CA dir
+  copy:
+    src: "{{ kube_cert_dir }}/ca.pem"
+    dest: "{{ ca_cert_dir }}/kube-ca.crt"
+    remote_src: true
+  register: kube_ca_cert
+
+- name: Gen_certs | update ca-certificates (Debian/Ubuntu/CoreOS)
+  command: update-ca-certificates
+  when: kube_ca_cert.changed and ansible_os_family in ["Debian", "CoreOS"]
+
+- name: Gen_certs | update ca-certificatesa (RedHat)
+  command: update-ca-trust extract
+  when: kube_ca_cert.changed and ansible_os_family == "RedHat"
+

roles/kubernetes/secrets/templates/openssl.conf.j2

@@ -11,12 +11,18 @@ DNS.1 = kubernetes
 DNS.2 = kubernetes.default
 DNS.3 = kubernetes.default.svc
 DNS.4 = kubernetes.default.svc.{{ dns_domain }}
+DNS.5 = localhost
+{% for host in groups['kube-master'] %}
+DNS.{{ 5 + loop.index }} = {{ host }}
+{% endfor %}
 {% if loadbalancer_apiserver is defined  and apiserver_loadbalancer_domain_name is defined %}
-DNS.5 = {{ apiserver_loadbalancer_domain_name }}
+{% set idx =  groups['kube-master'] | length | int + 5 %}
+DNS.{{ idx | string }} = {{ apiserver_loadbalancer_domain_name }}
 {% endif %}
 {% for host in groups['kube-master'] %}
 IP.{{ 2 * loop.index - 1 }} = {{ hostvars[host]['access_ip'] | default(hostvars[host]['ansible_default_ipv4']['address']) }}
 IP.{{ 2 * loop.index }} = {{ hostvars[host]['ip'] | default(hostvars[host]['ansible_default_ipv4']['address']) }}
 {% endfor %}
 {% set idx =  groups['kube-master'] | length | int * 2 + 1 %}
-IP.{{ idx | string }} = {{ kube_apiserver_ip }}
+IP.{{ idx }} = {{ kube_apiserver_ip }}
+IP.{{ idx + 1 }} = 127.0.0.1