Looks like graphite:

https://www.google.com/search?q=graphite+graphs&tbm=isch

To be explicitly pedantic -- graphite-web plots the graph, whereas graphite manages time series data processing and storage.

To increase the pedantic-levels: these are not plotted by graphite-web. In this case graphite-web only spits out source data in csv or json, actual plotting is done by Grafana (see stereo typical Grafana legends on the screenshots).