Terminology, internal services, and concepts

This section defines Control Center terminology, internal services that enable Control Center to function, and concepts that are used in this guide and other documentation.

application
One or more software services packaged in Docker containers.
cluster
The collection of hosts in one or more Control Center resource pools.
delegate host
A host that runs the application services scheduled for the resource pool to which it belongs. A system can be configured as delegate or master.
Docker Community Edition (Docker CE, or just Docker)
An open-source application for building, shipping, and running distributed applications.
Elasticsearch
(Control Center internal service) A distributed, real-time search and analytics engine. Control Center uses it to index log files and store service definitions.
Kibana
(Control Center internal service) A browser-based user interface that enables the display and search of Elasticsearch databases, including the log files that Control Center monitors.
Logstash
(Control Center internal service) A log file collector and aggregator that forwards parsed log file entries to Elasticsearch.
master host
The host that runs the application services scheduler, the Docker registry, the distributed file system, and other internal services, including the HTTP server for the Control Center browser interface and application browser interface. A system can be configured as delegate or master. Only one system in a Control Center cluster can be the master.
OpenTSDB
(Control Center internal service) A time series database that Control Center uses to store its service performance metrics.
resource pool
A collection of one or more hosts, each with its own compute, network, and storage resources. All of the hosts in a resource pool must have identical hardware resources, and must be located in the same data center and on the same subnet. If a resource pool host is a hypervisor guest system, all of the hosts in the resource pool must be guests of the same hypervisor host system.
service
A process and its supporting files that Control Center runs in a single container to provide specific functionality as part of an application.
serviced
The name of the Control Center service and a command-line client for interacting with the service.
tenant
An application that Control Center manages.
ZooKeeper (Apache ZooKeeper)
(Control Center internal service) A centralized service that Control Center uses for configuration maintenance, naming, distributed synchronization, and providing group services.