Hi Massimilian,

Ambari Metrics Service uses psutil library to collect system metrics. The 
metrics's explanation can be found here - https://pythonhosted.org/psutil/.

In case there is no metric in psutil with a given name in AMS, it might have 
been re-named. Please refer to the following file for renaming - 
https://github.com/apache/ambari/blob/trunk/ambari-metrics/ambari-metrics-host-monitoring/src/main/python/core/host_info.py.

--
Thanks and Regards,
Aravindan Vijayan

From: Massimilian Mattetti
Reply-To: "[email protected]<mailto:[email protected]>"
Date: Wednesday, February 8, 2017 at 12:41 AM
To: "[email protected]<mailto:[email protected]>"
Subject: how to interpret the host metrics retrieved from Rest API

Hi all,

I am trying to monitor the resource usage of a cluster by pulling the metrics 
from the rest API of Ambari (Version 2.4.2.0). I am sending request with the 
following path:
http://ambari-server:8080/api/v1/clusters/test/hosts?fields=Hosts/last_heartbeat_time,metrics<http://127.0.0.1:8080/api/v1/clusters/qbert/hosts?fields=Hosts/last_heartbeat_time,metrics>

There are few metrics that are really hard to understand. For instance, the 
metrics of the disk:

"disk" : {
          "disk_free" : 3278.83,
          "disk_total" : 4948.57,
          "read_bytes" : 5.0036226048E10,
          "read_count" : 197716.0,
          "read_time" : 8.7998397E7,
          "write_bytes" : 1.0003064832E10,
          "write_count" : 822311.0,
          "write_time" : 1.6088341E7
        },

How should I interpret the read_time? Why the values take minutes to change (I 
am pulling every 10 seconds) even if the host is under high disk I/O? Is there 
a legend that explains the meaning of each one of the metrics?
Thanks.

Best Regards,
Max

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