Thanos Compactor

The Thanos Compactor component is responsible for compacting and downsampling TSDB blocks stored in our Object Storage provider. Since we’ve disabled local compaction of TSDB blocks on the Prometheus instance, we still need to compact them somehow to ensure efficient storage of our data. Hence, the Thanos project provides a component for compaction.

Thanos Compactor handles compaction in the same way that Prometheus does – it takes several small blocks and compacts their indices and samples to make a larger block with an index that uses less space than if all the composite blocks still maintained a separate index. This relies on the presupposition that most time series exist across multiple sequential blocks, which should almost always be the case.

There’s not much to note about how Thanos achieves this other than the requisite changes to account for the fact that the Compactor must download the blocks from object storage to compact them...