Part 3 of tutorial series OpenShift 4 and Service Mesh will show you how to create a Gateway and a VirtualService, so external traffic actually reaches your Mesh. It also provides an example script to run some curl in a loop.
Configure Gateway and VirtualService Example
With the microservices deployed during Issue #2, it makes sense to test the access somehow. In order to bring traffic into the application a Gateway object and a VirtualService object must be created.
The Gateway will be the entry point which forward the traffic to the istio ingressgateway
Get all istio-io related objects of your project. These objects represent the network objects of Service Mesh, like Gateway, VirtualService and DestinationRule (explained later)
oc get istio-io -n tutorial
NAME HOST AGE
destinationrule.networking.istio.io/recommendation recommendation 3d21h
NAME AGE
gateway.networking.istio.io/ingress-gateway 4d15h
NAME GATEWAYS HOSTS AGE
virtualservice.networking.istio.io/ingress-gateway [ingress-gateway] [*] 4d15h
Create some example traffic
Before we start, lets fetch the default route of our Service Mesh:
export GATEWAY_URL=$(oc -n istio-system get route istio-ingressgateway -o jsonpath='{.spec.host}')
This should return: istio-ingressgateway-istio-system.apps.<clustername>
Now, let’s create a shell script to run some curl commands in a loop and can be easily reused for other scenarios:
#!/bin/bash
numberOfRequests=$1
host2check=$2
if [ $# -eq 0 ]; then
echo "better define: <script> #ofrequests hostname2check"
echo "Example: run.sh 100 hello.com"
let "numberOfRequests=100"
else
let "i = 0"
while [ $i -lt $numberOfRequests ]; do
echo -n "# $i: "; curl $2
let "i=$((i + 1))"
done
fi
Classic Kubernetes/OpenShift offer a feature called NetworkPolicy that allows users to control the traffic to and from their assigned Namespace. NetworkPolicies are designed to give project owners or tenants the ability to protect their own namespace. Sometimes, however, I worked with customers where the cluster administrators or a dedicated (network) team need to enforce these policies.
Since the NetworkPolicy API is namespace-scoped, it is not possible to enforce policies across namespaces. The only solution was to create custom (project) admin and edit roles, and remove the ability of creating, modifying or deleting NetworkPolicy objects. Technically, this is possible and easily done. But shifts the whole network security to cluster administrators.
Luckily, this is where AdminNetworkPolicy (ANP) and BaselineAdminNetworkPolicy (BANP) comes into play.
Lately I came across several issues where a given Helm Chart must be modified after it has been rendered by Argo CD. Argo CD does a helm template to render a Chart. Sometimes, especially when you work with Subcharts or when a specific setting is not yet supported by the Chart, you need to modify it later … you need to post-render the Chart.
In this very short article, I would like to demonstrate this on a real-live example I had to do. I would like to inject annotations to a Route objects, so that the certificate can be injected. This is done by the cert-utils operator. For the post-rendering the Argo CD repo pod will be extended with a sidecar container, that is watching for the repos and patches them if required.
The article SSL Certificate Management for OpenShift on AWS explains how to use the Cert-Manager Operator to request and install a new SSL Certificate. This time, I would like to leverage the GitOps approach using the Helm Chart cert-manager I have prepared to deploy the Operator and order new Certificates.
I will use an ACME Letsencrypt issuer with a DNS challenge. My domain is hosted at AWS Route 53.
However, any other integration can be easily used.
During a GitOps journey at one point, the question arises, how to update a cluster? Nowadays it is very easy to update a cluster using CLI or WebUI, so why bother with GitOps in that case? The reason is simple: Using GitOps you can be sure that all clusters are updated to the correct, required version and the version of each cluster is also managed in Git.
All you need is the channel you want to use and the desired cluster version. Optionally, you can define the exact image SHA. This might be required when you are operating in a restricted environment.
Argo CD or OpenShift GitOps uses Applications or ApplicationSets to define the relationship between a source (Git) and a cluster. Typically, this is a 1:1 link, which means one Application is using one source to compare the cluster status. This can be a limitation. For example, if you are working with Helm Charts and a Helm repository, you do not want to re-build (or re-release) the whole chart just because you made a small change in the values file that is packaged into the repository. You want to separate the configuration of the chart with the Helm package.
The most common scenarios for multiple sources are (see: Argo CD documentation):
Your organization wants to use an external/public Helm chart
You want to override the Helm values with your own local values
You don’t want to clone the Helm chart locally as well because that would lead to duplication and you would need to monitor it manually for upstream changes.
This small article describes three different ways with a working example and tries to cover the advantages and disadvantages of each of them. They might be opinionated but some of them proved to be easier to use and manage.
Thomas Jungbauer
( Lastmod: 2024-05-05 )
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2 min read