Graphite vs Prometheus vs RRDtool: What are the differences?

**Introduction**

Key differences between Graphite, Prometheus, and RRDtool are outlined below:

1. **Data Model**: Graphite stores data in a time-series database, while Prometheus uses a multidimensional data model with labels. RRDtool, on the other hand, uses round-robin databases to store data at fixed intervals.
   
2. **Query Language**: Prometheus offers a powerful PromQL query language that allows for flexible and expressive querying of metrics. Graphite utilizes its own query language to retrieve data, while RRDtool does not have a dedicated query language.
   
3. **Scalability**: Prometheus is more scalable than Graphite due to its distributed architecture and efficient storage mechanism. RRDtool can be limited in scalability due to its fixed-size storage files.
   
4. **Monitoring Approach**: Prometheus follows a pull-based model where it actively scrapes metrics from monitored targets. Graphite and RRDtool follow a push-based model where metrics are sent to the database.
   
5. **Alerting**: Prometheus has built-in alerting capabilities that allow users to set up alerts based on specified thresholds. Graphite and RRDtool do not have native alerting mechanisms and may require external tools for alerting functionalities.
   
6. **Graphing Capabilities**: Graphite and RRDtool provide graphing capabilities for visualizing data, while Prometheus relies on integrations with external tools like Grafana for advanced graphing features.

In Summary, the key differences between Graphite, Prometheus, and RRDtool lie in their data models, query languages, scalability, monitoring approaches, alerting functionalities, and graphing capabilities.