The Bookinfo application displays information about a book, similar to a single catalog entry of an online book store.
Displayed on the page is a description of the book, book details (ISBN, number of pages, and other information), and book reviews.
The Bookinfo application consists of these microservices:
* The productpage microservice calls the details and reviews microservices to populate the page.
* The details microservice contains book information.
* The reviews microservice contains book reviews. It also calls the ratings microservice.
* The ratings microservice contains book ranking information that accompanies a book review.
There are three versions of the reviews microservice:
* Version v1 does not call the ratings Service.
* Version v2 calls the ratings Service and displays each rating as one to five black stars.
* Version v3 calls the ratings Service and displays each rating as one to five red stars.
The end-to-end architecture of the application is shown below.
Figure 1. Bookinfo Application End2End Overview
To use the bookinfo application inside service mesh, no code changes are required. Instead an Envoy proxy is added as a sidecar container to all containers (product, review, details) which intercepts the traffic.
You can also access the Productpage in your browser. When you reload the page several times, you will see different results for the Reviews. This comes due to 3 different versions: one without any rating, one with black stars and one with red stars. http://${GATEWAY_URL}/productpage
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
Figure 2. Bookinfo Application