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InfluxDB
Power Real-Time Data Analytics at Scale. Get real-time insights from all types of time series data with InfluxDB. Ingest, query, and analyze billions of data points in real-time with unbounded cardinality.
Once you've spun up a server, you'll need some sort of software to relay messages between the clients. In my opinion it's hard to go wrong with IRC here. Inspircd is pretty painless to install and configure.
NOTE:
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Hence, a higher number means a more popular project.