Servers crash all the time. But it is important to make sure applications, and hence the business, doesn’t suffer. This is why service availability is one of biggest concerns for operational engineers deploying applications in the cloud.
Fleet—a CoreOS tool—solves this problem and frees you from worry by automatically routing application execution to healthy nodes.
So, how does this work?
How does Fleet know if a node is down? How does the rerouting happen?
We covered this in detail in a previous post. But if you’re in a hurry, I will recap.
Each node in a CoreOS cluster runs the fleet daemon, which keeps a tab on the node’s health and is responsible for communicating with other nodes. The daemons coordinate to elect a leader during cluster startup, or when the current leader fails. The leader schedules new services on the nodes whenever a new service request is submitted to the cluster, or when a node goes down taking services with it.
In this miniseries, we’ll get some services up-and-running on a cluster, then take down a node to see how fleet reshuffles things. We’ll then move on and take a closer look at some additional fleet functionality.Read More