How are Ambari Enhanced Config / Guided Config default values determined

[#1]

The Ambari Enhanced Configs (called "Guided Configuration" in the Hortonworks Admin-1 Class) feature is really useful: cluster admin staff don't need to keep referring to the docs to work out what the maxima, minima and recommended values are for critical parameters in the Hadoop cluster, for example HDFS NameNode Java heap size, YARN minimum and maximum container memory size, etc.

I would really like to find out how the Enhanced Config values - especially the default and recommended values - are calculated. Does Ambari dynamically calculate these values? Or is Ambari relying on some behind-the-scenes script to prepopulate some file somewhere?

This page https://cwiki.apache.org/confluence/display/AMBARI/Enhanced+Configs (see step 2) gives some clues - but appears to be mainly about how to create your own Enhanced Config. Is there some documentation somewhere that explains the Enhanced Configs as implemented in HDP? Where can I drill into the documentation or source-code to determine the maths behind each value in Enhanced Config?

[#2 · Accepted solution]

@Justin Watkins

This is the script I believe you are looking for:

https://github.com/apache/ambari/blob/trunk/ambari-server/src/main/resources/stacks/stack_advisor.py

Currently stack advisors script in Ambari provide following abilities:

- Recommend where services should be installed in cluster

- Recommend configurations based on host hardware

- Validate user selection of where services are installed on cluster

- Validate user configuration values

[#3]

Thanks @Pardeep. This looks like it will help.