The following is only a selection of some of the major features we plan to implement in the near future. To get a more complete overview of planned features and current work, see the issue trackers for the various repositories, for example, the Prometheus server.
Currently Prometheus has support for storing samples on local disk, as well as experimental support for writing data into OpenTSDB and InfluxDB. We plan to improve long-term storage support, although the details are not determined yet. This might include read-back support from OpenTSDB/InfluxDB in Prometheus, or support for other long-term storage backends.
GitHub issue: #10
Currently Prometheus omits time series from query results if the timestamp for which the query is executed is more than 5 minutes away from the nearest sample. This means that time series will grow "stale" in instant queries after not receiving samples for 5 minutes. This currently prevents usage of client-side timestamps from the Pushgateway or CloudWatch Exporter, which might indicate a time more than 5 minutes in the past. We plan on only considering a time series stale if it was not present in the most recent scrape.
GitHub issue: #398
At this time, metric types and other metadata are only used in the client libraries and in the exposition format, but not persisted or utilized in the Prometheus server. We plan on making use of this metadata in the future. For example, we could suggest automatic rates over counters, warn users if they take the rate of a gauge, or display metric documentation strings. Some metric types, like the upcoming server-side histograms, could also be stored and processed in a more efficient way. The details of this are still to be determined.
Prometheus has a range of client libraries and exporters. There are always more languages that could be supported, or systems that would be useful to export metrics from. We will add more as we need them. We are also happy to accept pull requests and advise on how best to integrate with Prometheus.