Google Cloud Platform Blog: What makes a container cluster?

Google Cloud Platform Blog

Product updates, customer stories, and tips and tricks on Google Cloud Platform

What makes a container cluster?

2015年1月22日星期四

a post What makes a container cluster?DockerKubernetespostIt is a dynamic system that reacts to conditions and inputs in real time. Why run a container cluster?

Microservices in order to keep moving parts manageable. Having a cluster manager enables us to break down an application into smaller parts that are separately manageable and scalable. This lets us scale up our organization by having clear interfaces between smaller teams of engineers.

Self healing systems in the face of failures. The cluster manager automatically restarts work from failed machines on healthy machines.

Low friction horizontal scaling. A container cluster provides tools for horizontal scaling, such that adding more capacity can be as easy as changing a setting (replication count).

High utilization and efficiency rates. Google was able to dramatically increase resource utilization and efficiency after moving to containers.

Specialized roles for cluster and application operations teams. Developers are able to focus much more on the service they are building rather than on the underlying infrastructure that supports it. For example, the GMail operations and development teams rarely have to talk directly to the cluster operations team. Having a separation of concerns here allows (but doesn't force) operation teams to be more widely leveraged.

you Ingredient 1: Dynamic container placementThe cluster management system should decide where to actually run your workload¹concept known as a pod

Ingredient 2: Thinking in setslabels and replication controllerslabels

Figure 1 - Filtering pods using labels

Scalingreplication controllerobject replication_controller { property num_replicas property template property label_selector runReplicationController(num_desired_pods, template, label_selector) { loop forever { num_pods = length(query(label_selector)) if num_pods > num_desired_pods { kill_pods(num_pods - num_desired_pods) } else if num_pods < num_desired_pods { create_pods(template, num_desired_pods - num_pods) } } } } desired state

Figure 2 - The Replication Controller enforces desired state

Ingredient 3: Connecting within a clusterservicesgraphnaming resolution systemshard assignment¹service proxyKubernetes roadmap Voila!hereroadmap to v1.0Try it outfile bug reportsask for helpsend a pull request (PR) 1 This is the classic knapsack problem which is NP-hard in the general case. 2 The "Watch API pattern" is a way to deliver async events from a service. It is common on lock server systems (zookeeper, etc.) that are derived from the original Google Chubby paper. The client essentially reaches out and "hangs" a request until there are changes. This is usually coupled with version numbers so that the client stay current on any changes.