Prometheus

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Project website: http://prometheus.io/ GitHub: https://github.com/prometheus


Memory-mapping of head chunks from disk

This brought down the memory usage of Promtheus by upto 50%. This was achieved with the combination of PR#6830 and PR#6679. You can read more about it in this blog post.


'@' modifier in PromQL

Based on this design doc, the @ modifier for PromQL was added in PR#8121. Learn more in this blog post.


Subquery support in PromQL

With PR#4831, subqueries of the form

<instant_query> '[' <range> ':' [ <resolution> ] ']' [ offset <duration> ]

was introduced in Prometheus. You can read more about it in this blog post.


Vertical compaction and queries in TSDB

With PR#370, Prometheus was able to handle time-overlapping blocks of data. This enabled backfilling of old data into Prometheus.


Persist for state of alerts across restarts

GSoC 2018 work. Read more about it in my blog post.


Unit tests of rules in promtool

GSoC 2018 work. Read more about it in my blog post.


Performance and memory optimizations

It's more about the investigation than the final fix.