RRDtool
RRDtool (Round Robin Database tool) is an open-source data logging and graphing system designed for time-series data, such as network bandwidth, temperatures, or CPU load. It efficiently stores data in a round-robin database that automatically archives older data to maintain a fixed size, and includes powerful graphing capabilities to visualize trends over time. It is widely used in monitoring applications, particularly with tools like Cacti and MRTG.
Developers should learn RRDtool when building or maintaining monitoring systems that require efficient storage and visualization of time-series metrics, such as in network management, server performance tracking, or IoT data logging. It is especially valuable for its ability to handle large volumes of data with minimal storage overhead and its integration with popular monitoring frameworks, making it a go-to tool for system administrators and DevOps engineers.