[
https://issues.apache.org/jira/browse/HADOOP-8052?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13204982#comment-13204982
]
Matt Foley commented on HADOOP-8052:
------------------------------------
If the size of the constants is being reduced from double to float, the private
variables min and max and the public method max() should also become float,
shouldn't they?
Since the inputs can be double, I would also recommend doing clipping functions
in appropriate places to prevent NaN ("Infinity") results from over/underflow,
eg "if (value > Float.MAX_VALUE) value = Float.MAX_VALUE;" etc., where "value"
is a double.
> Hadoop Metrics2 should emit Float.MAX_VALUE (instead of Double.MAX_VALUE) to
> avoid making Ganglia's gmetad core
> ---------------------------------------------------------------------------------------------------------------
>
> Key: HADOOP-8052
> URL: https://issues.apache.org/jira/browse/HADOOP-8052
> Project: Hadoop Common
> Issue Type: Bug
> Components: metrics
> Affects Versions: 0.23.0, 1.0.0
> Reporter: Varun Kapoor
> Assignee: Varun Kapoor
> Labels: patch
> Attachments: HADOOP-8052-branch-1.patch, HADOOP-8052.patch
>
>
> Ganglia's gmetad converts the doubles emitted by Hadoop's Metrics2 system to
> strings, and the buffer it uses is 256 bytes wide.
> When the SampleStat.MinMax class (in org.apache.hadoop.metrics2.util) emits
> its default min value (currently initialized to Double.MAX_VALUE), it ends up
> causing a buffer overflow in gmetad, which causes it to core, effectively
> rendering Ganglia useless (for some, the core is continuous; for others who
> are more fortunate, it's only a one-time Hadoop-startup-time thing).
> The fix needed to Ganglia is simple - the buffer needs to be bumped up to be
> 512 bytes wide, and all will be well - but instead of requiring a minimum
> version of Ganglia to work with Hadoop's Metrics2 system, it might be more
> prudent to just use Float.MAX_VALUE.
> An additional problem caused in librrd (which Ganglia uses
> beneath-the-covers) by the use of Double.MIN_VALUE (which functions as the
> default max value) is an underflow when librrd runs the received strings
> through libc's strtod(), but the librrd code is good enough to check for
> this, and only emits a warning - moving to Float.MIN_VALUE fixes that as well.
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators:
https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa
For more information on JIRA, see: http://www.atlassian.com/software/jira
