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Introduction to Service Mesh
To understand service mesh, we need a good use case.
We need some service-to-service communication.
A basic microservice architecture will do.
A simple Web UI: videos-web
Consider videos-web
It's an HTML application that lists a bunch of playlists with videos in them.
+------------+
| videos-web |
| |
+------------+
A simple API: playlists-api
For videos-web to get any content, it needs to make a call to playlists-api
+------------+ +---------------+
| videos-web +---->+ playlists-api |
| | | |
+------------+ +---------------+
Playlists consist of data like title, description etc, and a list of videos.
Playlists are stored in a database.
playlists-api stores its data in a database
+------------+ +---------------+ +--------------+
| videos-web +---->+ playlists-api +--->+ playlists-db |
| | | | | |
+------------+ +---------------+ +--------------+
A little complexity
Each playlist item contains only a list of video id's.
A playlist does not have the full metadata of each video.
Example playlist:
{
"id" : "playlist-01",
"title": "Cool playlist",
"videos" : [ "video-1", "video-x" , "video-b"]
}
Take not above videos: [] is a list of video id's
Videos have their own title and description and other metadata.
To get this data, we need a videos-api
This videos-api has its own database too
+------------+ +-----------+
| videos-api +------>+ videos-db |
| | | |
+------------+ +-----------+
For the playlists-api to load all the video data, it needs to call videos-api for each video ID it has.
Traffic flow
A single `GET` request to the `playlists-api` will get all the playlists from its database with a single DB call
For every playlist and every video in each list, a separate GET call will be made to the videos-api which will
retrieve the video metadata from its database.
This will result in many network fanouts between playlists-api and videos-api and many call to its database.
This is intentional to demonstrate a busy network.
Full architecture
+------------+ +---------------+ +--------------+
| videos-web +---->+ playlists-api +--->+ playlists-db |
| | | | | |
+------------+ +-----+---------+ +--------------+
|
v
+-----+------+ +-----------+
| videos-api +------>+ videos-db |
| | | |
+------------+ +-----------+
Run the apps: Docker
There is a `docker-compose.yaml` in this directory.
Change your terminal to this folder and run:
docker-compose build
docker-compose up
You can access the app on http://localhost
Run the apps: Kubernetes
Create a cluster with kind
kind create cluster --name servicemesh --image kindest/node:v1.18.4
Deploy videos-web
cd ./kubernetes/servicemesh/
kubectl apply -f applications/videos-web/deploy.yaml
kubectl port-forward svc/videos-web 80:80
You should see blank page at http://localhost/
It's blank because it needs the playlists-api to get data
Deploy playlists-api and database
cd ./kubernetes/servicemesh/
kubectl apply -f applications/playlists-api/deploy.yaml
kubectl port-forward svc/playlists-api 81:80
You should see empty playlists page at http://localhost/
Playlists are empty because it needs the videos-api to get video data
Deploy videos-api and database
cd ./kubernetes/servicemesh/
kubectl apply -f applications/videos-api/deploy.yaml
Refresh page at http://localhost/
You should now see the complete architecture in the browser