Graphite
Graphite is a visualization tool for statistics configured from various sources. You can create customizable reports and dashboards, and it is one of the preferred backends for Statsd
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Instrumental
Instrumental is a real-time, high-scale application and server monitoring tool with intelligent alerts, a powerful query language, and free development accounts.
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KairosDB
KairosDB is a fast distributed scalable time series database written on top of Cassandra. RESTful JSON-based query/results. Includes flot-based visualization.
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