collectd

Collectd is an open-source daemon for collecting and storing system performance statistics. It runs on many Unix-like operating systems and is designed to be lightweight and extensible through a plugin architecture, enabling the gathering of metrics from the host and from applications with minimal resource use.

Its architecture centers on a small core and a large set of plugins. Plugins provide data-collection capabilities for metrics such as CPU, memory, disk, network interfaces, load, and processes, among others, and there are also write plugins that handle data export and storage. Data types are defined in a central types.db, and the collected data is stored locally by default using a Round-Robin Database through the rrdtool backend. Data can also be sent to external backends such as Graphite, OpenTSDB, or InfluxDB.

Configuration is done in a single file, typically collectd.conf, where you enable plugins, set collection intervals, define data types, and specify write destinations. The configuration supports modular loading of plugins and per-plugin options, allowing users to tailor collection to their environment while keeping overhead low.

Usage and ecosystem: Collectd is commonly deployed as part of monitoring stacks, providing time-series data for visualization and alerting systems. It can be integrated with dashboard and analytics tools via its various backends, making it a flexible component for system and application monitoring.