JVM – Data Engineering and Analytics in Cloud

Hadoop, JVM, Memory, YARN

Hadoop YARN – Container Virtual Memory – Understanding and Solving “Container is running beyond virtual memory limits” Errors

February 19, 2020
In the previous article about YARN container memory (see, Tez Memory Tuning – Container is Running Beyond Physical Memory Limits) I wrote about the physical memory. Now I would like to pay attention to the virtual memory in YARN.

A typical YARN memory error may look like this:
```
Container is running beyond virtual memory limits. Current usage: 1.0 GB of 1.1 GB physical memory used; 2.9 GB of 2.4 GB virtual memory used. Killing container.
```
So what is the virtual memory, how to solve such errors and why is the virtual memory size often so large?
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dmtolpeko
Hive, JVM, Tez

Apache Hive on Tez – Quick On The Fly Profiling of Long Running Tasks Using Jstack Probes and Flame Graphs

November 20, 2019

I was asked to diagnose and tune a long and complex ad-hoc Hive query that spent more than 4 hours on the reduce stage. The fetch from the map tasks and the merge phase completed fairly quickly (within 10 minutes) and the reducers spent most of their time iterating the input rows and performing the aggregations defined by the query – MIN, SUM, COUNT and PERCENTILE_APPROX and others on the specific columns.

After the merge phase a Tez reducer does not output many log records to help you diagnose the performance issues and find the bottlenecks. In this article I will describe how you can profile an already running Tez task without restarting the job.

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dmtolpeko