The BookInfo microservice is a polyglot application that contains six services:
- Product Page: Programmed using Python
- Reviews (v1, v2, and v3) Pages: Programmed using Java
- Detail Page: Programmed using Ruby
- Ratings Page: Programmed using Node.js
The following diagram shows the flow of a polyglot microservice application:
When we run the Bookinfo application, the productpage service receives traffic from the outside world through the Istio Ingress gateway. The productpage microservice calls the following:
- The details microservice, to get the details of the book
- The reviews microservice, to get the reviews of the book
As shown in the preceding diagram, the reviews microservices have three versions. By default, the requests from productpage will be round-robined to all three versions of the reviews. reviews-v1 does not call the ratings service at all, unlike reviews-v2 and reviews-v3, reviews-v1 returns immediately and shows no stars on the productpage display, and reviews-v2 displays black stars, whereas reviews-v3 shows red stars on the productpage display. Due to the absence and color of the stars, we can identify which specific version of the reviews served the request from productpage. Let's take a look at this structure:
- First, users will log in to the main page, which is the main view. This is called the Product page.
- Next, users can submit a book rating through the reviews microservice, which has three versions: v1 has no stars, v2 has black stars, and v3 has red stars.
- Finally, the Details microservice provides a high-level overview of the selected book.
The following image of the BookInfo application shows the product page, which contains the details, reviews, and ratings microservices:
In the upcoming sections of this chapter, we will provide a walkthrough of how to deploy BookInfo and validating that deployment by checking its availability and overall access to an external network.