For people starting with docker and kubernetes, here’s simple example to understand it.
Imagine you are a farmer and you have a farm with different types of animals. Each animal has its own unique characteristics and requirements. You have cows, pigs, chickens, and sheep. You want to make sure that each animal is placed in the right area of the farm so that they are comfortable and can thrive.
Docker is like the barn on the farm. It’s a container that keeps each animal (or in this case, each application) separate from one another. Each container is like a separate stall in the barn, with its own feeding trough, bedding, and water supply. This way, the cows’ food and water doesn’t get mixed up with the pigs’ and the chickens’ eggs don’t get broken by the sheep.
Kubernetes is like the farm manager. It makes sure that the right number of animals (or containers) are in the right areas at the right time. If the cows are producing more milk, Kubernetes will automatically create more cow stalls (or containers) to accommodate the increased demand. If the pigs aren’t producing as much pork, Kubernetes will reduce the number of pig stalls (or containers) to save resources.
Just like on a farm, there may be situations where you don’t want certain animals to be placed in certain areas. This is where taints and tolerations come in. Taints are like “No Trespassing” signs that you can put on certain areas of the farm. Tolerations are like permission slips that certain animals (or containers) can have to enter those areas.
For example, you might have a special, organic section of the farm that you only want your organic chickens to be in. You would put a taint on that area and only give your organic chickens the toleration to enter. This way, your regular chickens can’t accidentally wander into the organic section and mix with the organic chickens.
Similarly, in a k8s environment, you may have a set of nodes on which you want to deploy only certain type of pods. You can taint those nodes and give toleration to those pods which are allowed to run on those tainted nodes.
In this way, using taints and tolerations allows you to control the scheduling of your applications and make sure that they are running in the right place, at the right time, with the right resources.
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