Service Mesh Integration

Istio provides the service mesh for Big Bang. The service mesh assists with secure traffic routing in the cluster. This document will show you how to update your package to support Big Bang’s configuration of Istio.

Prerequisites

• Helm
• Kubectl
• Git
• A multi-node Kubernetes cluster to deploy Big Bang and your package
• A Big Bang project containing the upstream Helm chart

Throughout this document, we will be setting up an application called podinfo as a demonstration

Sidecar

The Istio sidecar is a container that can be automatically injected into all package pods to provide encrypted traffic using mutual TLS. It also enables detailed packet tracing and network traffic metrics.

When Istio is enabled in the values, we want the sidecar to automatically be injected. This can be achieved by adding the following to bigbang/templates/podinfo/namespace.yaml:

metadata:
  labels:
    {{- if .Values.istio.enabled }}
    istio-injection: "enabled"
    {{- end }}

Most packages are compatible with Istio’s sidecar, but if you need to disable this, change the label to istio-injection: "disabled" in bigbang/templates/podinfo/namespace.yaml.

Virtual Service

If your package has an externally facing service (e.g. URL, port), you will need to setup a VirtualService in Istio to access it from outside the cluster.

Connections from inside the cluster can use the Service and do not require a VirtualService

For https connections, Istio will provide end-to-end encryption using TLS termination and mutual TLS to the sidecar. Therefore, the http connection on the pod can be used for the virtual service.

In some cases, you may have multiple services that need to be exposed. A separate VirtualService should be created for each one. See this example

virtualservice.yaml

Setup chart/templates/bigbang/virtualservice.yaml with the following default content:

{{- $pkg := "podinfo" }}
{{- if and .Values.istio.enabled (get .Values.istio $pkg).enabled }}
apiVersion: networking.istio.io/v1beta1
kind: VirtualService
metadata:
  name: {{ $pkg }}
  namespace: {{ .Release.Namespace }}
  labels:
    {{- include (printf "%s.labels" $pkg) . | nindent 4 }}
    app.kubernetes.io/instance: {{ .Release.Name }}
spec:
  gateways:
  {{- range (get .Values.istio $pkg).gateways }}
    - {{ . }}
  {{- end }}
  hosts:
  {{- range (get .Values.istio $pkg).hosts }}
    - {{ tpl . $}}
  {{- end }}
  http:
  - route:
    - destination:
        port:
          number: {{ .Values.port | default "8080" }}
        host: {{ $pkg }}.{{ .Release.Namespace }}.svc.cluster.local
{{- end }}

The virtual service must be adjusted to make it compatible with the upstream chart by making the following changes:

• Change the service name to use the same pattern as other resources in the package. For podinfo, this is template "podinfo.fullname" ..
• Adjust the labels to adhere to the standard Helm labels
• Re-use _helper.tpl functions from the upstream chart for common labels. In this case, we are including the helper podinfo.labels.
• Supplement the missing labels from the helper function. In our case, the helper function was missing app.kubernetes.io/instance.
• Typically, there is a value for the http port in chart/values.yaml. Use this in spec.http[0].route[0].destination.port.number. In this case, we need to change .Values.port to .Values.service.externalPort.
• If your service name is not the same as the package name, you will need to change spec.http[0].route[0].destination.host to the service name. For podinfo, it uses the helper podinfo.fullname to create the service name.

The final virtualservice.yaml looks like this:

{{- $pkg := "podinfo" }}
{{- if and .Values.istio.enabled (get .Values.istio $pkg).enabled }}
apiVersion: networking.istio.io/v1beta1
kind: VirtualService
metadata:
  name: {{ template "podinfo.fullname" . }}
  namespace: {{ .Release.Namespace }}
  labels:
    {{- include (printf "%s.labels" $pkg) . | nindent 4 }}
    app.kubernetes.io/instance: {{ .Release.Name }}
spec:
  gateways:
  {{- range (get .Values.istio $pkg).gateways }}
    - {{ . }}
  {{- end }}
  hosts:
  {{- range (get .Values.istio $pkg).hosts }}
    - {{ tpl . $}}
  {{- end }}
  http:
  - route:
    - destination:
        port:
          number: {{ .Values.service.externalPort | default "8080" }}
        host: {{ template "podinfo.fullname" . }}.{{ .Release.Namespace }}.svc.cluster.local
{{- end }}

For configuring a connection for something other than http, read Istio’s documentation on traffic management to determine the best course of action.

Package Defaults

In chart/values.yaml, default values for Istio are required as placeholders for the Helm templating. We should assume that Istio is not installed in our defaults. Add the following content to the values:

# Big Bang Values
domain: bigbang.dev
istio:
  enabled: false
  podinfo:
    enabled: true
    gateways:
    - istio-system/main
    hosts:
    - podinfo.{{ .Values.domain }}

Some notes on the defaults:

• Always add a comment to modifications made to the upstream chart to assist with upgrading in the future
• istio-system/main is the default gateway created by the Istio Helm chart. Big Bang will override this with istio-system/public, which it uses as the default gateway.
• The default FQDN is podinfo.bigbang.dev, which can be overridden if desired

Big Bang Defaults

Set the following in bigbang/values.yaml to enable Istio for integration testing. These values will be used in the next section:

# Update existing values
istioOperator:
  enabled: true
istio:
  enabled: true

# Add new value
podinfo:
  ingress:
    gateway: ""

Big Bang Passdowns

Big Bang must override the default values for the package to pass-down configuration. It uses bigbang/templates/podinfo/values.yaml to do this. Add the following content to the bigbang.defaults.podinfo definition:

{{- define "bigbang.defaults.podinfo" -}}
# hostname is deprecated and replaced with domain. But if hostname exists then use it.
domain: {{ default .Values.domain .Values.hostname }}
istio:
  enabled: {{ .Values.istio.enabled }}
  podinfo:
    gateways:
    - istio-system/{{ default "public" .Values.podinfo.ingress.gateway }}
{{- end }}

Dependencies

If we have enabled sidecar injection or created a virtual service, we will need to make sure Istio is deployed before our package. This is done in the HelmRelease resource using dependsOn. Add the following to bigbang/templates/podinfo/helmrelease.yaml:

spec:
  {{- if .Values.istio.enabled }}
  dependsOn:
    {{- if .Values.istio.enabled }}
    - name: istio
      namespace: {{ .Release.Namespace }}
    {{- end }}
  {{- end }}

There are two conditionals on purpose. As we add more dependencies, the outer conditional will be used to determine if any dependencies are enabled. The inner conditional(s) will be used to print each dependency.

Validation

Test the following items to ensure Istio is working properly with your application:

1. Verify syntax and resolve errors:

   helm template -n bigbang -f ~/bigbang/chart/values.yaml -f bigbang/values.yaml bigbang-podinfo bigbang
   

2. Commit changes

   git add -A
   git commit -m "feat: Istio integration"
   git push
   

3. Install Big Bang core with bigbang.dev certificate

   # Iron Bank credentials are required since you are pulling Big Bang images from Iron Bank
   helm upgrade -i -n bigbang --create-namespace -f ~/bigbang/chart/values.yaml -f ~/bigbang/chart/ingress-certs.yaml -f bigbang/values.yaml --set registryCredentials.username=<your Iron Bank username> --set registryCredentials.password=<your Iron Bank PAT> bigbang ~/bigbang/chart
   

4. Install the package

   # Iron Bank credentials are optional until we migrate the package to an Iron Bank image
   helm upgrade -i -n bigbang --create-namespace -f ~/bigbang/chart/values.yaml -f ~/bigbang/chart/ingress-certs.yaml -f bigbang/values.yaml --set registryCredentials.username=<your Iron Bank username> --set registryCredentials.password=<your Iron Bank PAT> bigbang-podinfo bigbang
   

5. Watch the GitRepository, HelmRelease, and Pods by running watch kubectl get gitrepo,hr,po -A. Istio operator, Istio control plane, and the package should all be installed.

6. Troubleshoot any deployment errors

7. Validate the TLS certificate is in the secret istio-system/public-cert. This is the certificate Istio uses to provide https access to your package from outside the cluster.

   kubectl get secret -n istio-system public-cert -o 'go-template={{ index .data "tls.crt" }}' | base64 -d
   
   ## OUTPUT ##
   -----BEGIN CERTIFICATE-----
   MIIFYDCCB...
   

   Istio self generates a different certificate for mutual TLS encryption between the Istio control plane and the Istio sidecar inside the pod for traffic into the pod.

8. Validate Istio’s Ingress Gateway service is running. This is the load balancer that listens for traffic coming from outside the cluster.

   kubectl describe services -n istio-system public-ingressgateway
   
   ## OUTPUT ##
   Name:                     public-ingressgateway
   Namespace:                istio-system
   Labels: ...
   

   Big Bang defaults to a single ingress gateway called public-ingressgateway.

   In the description, you can see the following: - Type is LoadBalancer - status-port is configured for a health status check on ingress - http is configured to listen on port 80 and forward to port 8080 - https is configured to listen on port 443 and forward to port 8443 - LoadBalancer Ingress IPs are external IPs assigned to the load balancer that can be accessed outside of the cluster.

9. Validate Istio’s Gateway is configured correctly. Istio will use the Gateway’s configuration for TLS encryption and host/port-based traffic matching.

   kubectl describe gateway -n istio-system
   
   ## OUTPUT ##
   Name:         public
   Namespace:    istio-system
   Labels: ...
   

   Big Bang defaults to a single Gateway called public.

   By default the Gateway is setup with the following:

   • Connected to the public-ingressgateway using spec.selector
   • http:
   • Matches traffic for any hostname
   • Listen on port 8080
   • Redirects all traffic to https
   • https:
   • Matches all hosts in domain (*.bigbang.dev)
   • Listen on port 8443
   • Uses TLS certificate from public-cert for encryption/decryption

10. Validate the package’s virtual service. The virtual service controls the traffic routing between Istio and the package.

    kubectl describe virtualservice -n podinfo
    
    ## OUTPUT ##
    Name:         podinfo-podinfo
    Namespace:    podinfo
    Labels:  ...
    

    The virtual service should have the following configured: - Connection to Istio’s istio-system/public Gateway using spec.gateway - Matches specific host for package (podinfo.bigbang.dev) - Routes http traffic to package’s service and port. You can view the service name and http port using kubectl describe service -n podinfo.

11. Validate Istio’s sidecar is running in the package’s pod.

    # Get "ready" status of running containers
    kubectl get pods -n podinfo -o jsonpath='{range .items[*].status.containerStatuses[*]}{@.name}{" "}{@.ready}{"\n"}'
    
    ## OUTPUT ##
    istio-proxy true
    podinfo true
    

    If istio-proxy is not listed in the running containers, try restarting your pod. Use kubectl get deploy,sts,ds -n podinfo to get the name and kubectl rollout restart -n podinfo <name> to restart it. Then, check for the istio-proxy container again.

12. Check the package’s URL

    The hostname *.bigbang.dev points to your local IP address of 127.0.0.1. If you are running the cluster on a different machine, you will need to add the hostname and host machine’s IP to /etc/hosts.

    curl -sL https://podinfo.bigbang.dev
    
    ## OUTPUT ##
    {
      "hostname": "podinfo-podinfo-86b4b9d85c-rnd4z",
      "version": "6.0.0",
      "revision": "",
      "color": "#34577c",
      "logo": "https://raw.githubusercontent.com/stefanprodan/podinfo/gh-pages/cuddle_clap.gif",
      "message": "greetings from podinfo v6.0.0",
      "goos": "linux",
      "goarch": "amd64",
      "runtime": "go1.15.7",
      "num_goroutine": "8",
      "num_cpu": "32"
    }
    

You have now verified Istio is working properly with the package. To recap, incoming traffic to the cluster is first processed by Istio’s ingress gateway listening on specific ports on each node. http and https traffic is forwarded to internal ports 8080 and 8443 respectively. The Istio Gateway configuration redirects http traffic to https and https traffic matching the domain (bigbang.dev) is TLS decrypted. The Virtual Service configuration processes https traffic from the Gateway matching the package’s hostname (podinfo.bigbang.dev) and routes traffic to the package’s service and http port. The service then directs traffic to the pod for handling. Since the pod has the Istio sidecar running, the mutual TLS Istio feature will automatically encrypt traffic from the gateway to the pod inside the cluster (even though its http). The sidecar will then decrypt to package before sending it over to the package for handling. The following diagram illustrates this flow:

15006 is the port reserved for Istio Proxy incoming traffic

graph
    A(Browser) -->|https://podinfo.bigbang.dev| B
    B(Ingress Gateway) -->|https://*:8443| C
    C(Gateway) -->|mTLS-http://*.bigbang.dev:15006| D
    D(Virtual Service) -->|mTLS-http://podinfo.bigbang.dev:15006| E
    E(Service) --> |mTLS-http://<pod IP>:15006| F
    F(Pod/Istio-Proxy) --> |http://localhost:8989| G
    G(Pod/PodInfo)

As a final test, you can use your browser to navigate to https://podinfo.bigbang.dev to see the web user interface for podinfo.

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Last update: 2023-09-13 by Jonathan Braswell