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Work in progress, treat this as a draft
The Kubernetes Ingress uses Istio Ingresscontroller (ultimately the Ingressgateway) running as a Daemonset on each worker node to route traffic to workload services and (in last instace) Pods.
The Istio Ingressgateway is implemented as an envoy instace that is configured via XDS (??) by the Istiod Control Plane. All configuration is derived from Kubernetes API Objects like the Service Objects as well as Istio specific custom resources: Gateway, VirtualService and DestinationRule.
The process of configuring the Ingressgateway is abstracted away from service owners/deployers via helm common_templates/0.4/_ingress_helpers.tpl so that it is enough to specify
.Values.ingress.enabled: true for a very basic setup.
- ingressgateway terminates TLS connections from clients
- ingressgateway establishes TLS connections to upstream (pods) which will be terminated on pod level by service-proxy
Setup and configuration
Istio (the control plane as well as components like the Ingressgateway) are installed and initially configured using
istioctl (from a deployment host) together with an environment specific config in custom_deploy.d/istio.
For initial installation or deploying updates, run (on a deployment host):
istioctl-1.9.5 apply -f <environment>/config.yaml
For details on how to configure Istio, please see:
Some parts of the configuration have to be (or can be) done via helm chart values. istioctl comes with embedded helm charts that get rendered and applied by istiotcl directly. You may find those embedded charts (to look up possible configuration options etc. at:
TLS certificates are generated and maintained by cert-manager and deployed into the istio-system namespace for the ingressgateway to pick them up. This is configured and deployed by SRE via helmfile.d/admin_ng/helmfile_namespace_certs.yaml ??. If a service needs to be made available under additional hostnames they need to be configured at as tlsHostname in the namespaces config (helmfile.d/admin_ng/values/*.yaml).
istioctl can be used to dump some information about the general config of the ingressgateway:
# Dump all configured listeners istioctl-1.9.5 -n istio-system proxy-config listeners daemonset/istio-ingressgateway # Dump all configured routes istioctl-1.9.5 -n istio-system proxy-config route daemonset/istio-ingressgateway
The Ingressgateway does emit access logs which can be viewed in logstash
Configuration (for service owners)
To enable Ingress for your chart you need to undertake the following steps:
- Make sure your chart uses the latest (at least 0.4) version of common_templates
- Make sure the common_templates/0.4/_ingress_helpers.tpl is linked to the templates directory of your chart
For the absolute basic setup, all you need to do not is enable ingress via your values.yaml:
ingress: enabled: true staging: true # If you are doing this for a staging service
This will make your service available as https://SERVICE_NAME.discovery.wmnet (https://SERVICE_NAME.staging.discovery.wmnet for staging) traffic will be routed as is to all pods of your service in a round-robin fashion.
You may configure more complex routing logic, listen to different or more than one hostname etc. via the ingress configuration stanza. Please keep in mind that for different or additional hostnames you may need SRE assistance to set up certificates etc.
The routing behavior may be modified via the ingress.httproutes stanza which supports all options described in https://istio.io/v1.9/docs/reference/config/networking/virtual-service/#HTTPRoute.
If you want to make several services available as subpaths of a hostname (https://SERVICE_NAME.discovery.wmnet/foo, https://SERVICE_NAME.discovery.wmnet/bar, ...) you need to make sure to configure only one Istio Gateway (in one of your helm chart releases) for this hostname and attach multiple HTTPRoute objects to it. Multiple Istio Gateway objects claiming the same hostname will simply be ignored.
Assuming you have two releases of your chart (one and two), you may configure ingress like in the following example to achieve that:
--- # release "one" values.yaml: # made available as https://SERVICE_NAME.discovery.wmnet/one # via default options + httproute ingress: enabled: true httproutes: - match: - uri: prefix: /one --- # release "two" values.yaml: # made available as https://SERVICE_NAME.discovery.wmnet/two # via the Gateway deployed by release "one" ingress: enabled: true existingGateway: "SERVICE_NAMESPACE/one" # referencing the Gateway deployed by the release "one" routeHosts: - SERVICE_NAME.discovery.wmnet # Attach the following routes to this hostname in the referenced Gateway httproutes: - match: - uri: prefix: /two route: - destination: host: two-tls-service.SERVICE_NAMESPACE.svc.cluster.local # The cluster internal DNS name for this releases service port: number: SERVICE_TLS_PUBLIC_PORT # Port you defined in .Values.tls.public_port