Virtual Outbound
This policy lets you customize hostnames and ports for communicating with data plane proxies.
Possible use cases are:
- Preserving hostnames when migrating to service mesh.
- Providing multiple hostnames for reaching the same service, for example when renaming or for usability.
- Providing specific routes, for example to reach a specific pod in a service with StatefulSets on Kubernetes, or to add a URL to reach a specific version of a service.
- Expose multiple inbounds on different ports.
Limitations:
- When duplicate
(hostname, port)
combinations are detected, the virtual outbound with the highest priority takes over. For more information, see the documentation on how Kuma chooses the right policy. All duplicate instances are logged.
conf.host
and conf.port
are processed as go text templates with a key-value pair derived from conf.parameters
.
conf.selectors
are used to specify which proxies this policy applies to.
For example a proxy with this definition:
type: Dataplane
mesh: default
name: backend-1
networking:
address: 192.168.0.2
inbound:
- port: 9000
servicePort: 6379
tags:
kuma.io/service: backend
version: v1
port: 1800
and a virtual outbound with this definition:
apiVersion: kuma.io/v1alpha1
kind: VirtualOutbound
mesh: default
metadata:
name: test
spec:
selectors:
- match:
kuma.io/service: "*"
conf:
host: "{{.v}}.{{.service}}.mesh"
port: "{{.port}}"
parameters:
- name: service
tagKey: "kuma.io/service"
- name: port
tagKey: "k8s.kuma.io/service-port"
- name: v
tagKey: version
produce the hostname: v1.backend.mesh
with port: 1800
.
Additional Requirements:
- Transparent proxying must be enabled.
- Either:
- Data plane proxy DNS must be enabled.
- Or, the value of
conf.host
must end with the value ofdns_server.domain
, which defaults to.mesh
.
- Parameter names must be alphanumeric. These names are used as Go template keys.
- Parameter names must be unique. This ensures that each parameter can be referenced unambiguously.
- Parameter with the
kuma.io/service
tagKey must be specified even if it is not used in the template. This prevents hostnames from being defined that could span multiple services.
The default value of tagKey
is the value of name
.
For each virtual outbound, the Kuma control plane processes all data plane proxies that match the selector.
It then applies the templates for conf.host
and conf.port
and assigns a virtual IP address for each hostname.
Examples
The following examples show how to use virtual outbounds for different use cases.
Same as the default DNS
apiVersion: kuma.io/v1alpha1
kind: VirtualOutbound
mesh: default
metadata:
name: default
spec:
selectors:
- match:
kuma.io/service: "*"
conf:
host: "{{.service}}.mesh"
port: "80"
parameters:
- name: service
tagKey: "kuma.io/service"
One hostname per version
apiVersion: kuma.io/v1alpha1
kind: VirtualOutbound
mesh: default
metadata:
name: versioned
spec:
selectors:
- match:
kuma.io/service: "*"
conf:
host: "{{.service}}.{{.version}}.mesh"
port: "80"
parameters:
- name: service
tagKey: "kuma.io/service"
- name: version
tagKey: "kuma.io/version"
Custom tag to define the hostname and port
apiVersion: kuma.io/v1alpha1
kind: VirtualOutbound
mesh: default
metadata:
name: host-port
spec:
selectors:
- match:
kuma.io/service: "*"
conf:
host: "{{.hostname}}"
port: "{{.port}}"
parameters:
- name: hostname
tagKey: "my.mesh/hostname"
- name: port
tagKey: "my.mesh/port"
One hostname per instance
Enables reaching specific data plane proxies for a service. Useful for running distributed databases such as Kafka or Zookeeper.
apiVersion: kuma.io/v1alpha1
kind: VirtualOutbound
mesh: default
metadata:
name: instance
spec:
selectors:
- match:
kuma.io/service: "*"
statefulset.kubernetes.io/pod-name: "*"
conf:
host: "{{.svc}}.{{.inst}}.mesh"
port: "8080"
parameters:
- name: "svc"
tagKey: "kuma.io/service"
- name: "inst"
tagKey: "statefulset.kubernetes.io/pod-name"