Re: [druid-user] Historical nodes crashing

Hi Diego,

The historical heap is used to store the following:

-Unmerged query results
-Per-segment and per-column information

Very large lookups can use a lot of heap. Complex queries covering a large interval can use require a lot of heap.

Typically, the last of these is not a big factor, as druid stores maybe a few KB per segment and a few hundred bytes per segment-column in memory. However, if you have a lot of segments or very many columns per segment, this can add up. For example, with 100k segments and 1,000 columns per segment, you’d need about ~10GB of heap for this alone.

If you are encountering OOMs, you will need to figure out where they are happening; there should be clues in the stack trace. But, most likely, you will need to increase the heap available to the historical process.