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From Jay Vyas <jayunit...@gmail.com>
Subject Convention question for using DFSConfigKey constants : are zeros magic?
Date Fri, 19 Apr 2013 16:10:13 GMT
I recently looked into the HDFS source tree to determine idioms with
respect to a hairy debate about the threshold between what is and is not a
magic number, and found that :  And it appears that the number zero is NOT
considered magic - at least not in the HDFS source code.

I found that that DFSConfigKeys.java defines DEFAULT values of zeros for
some fields, and those defaults result in non-quantitative interpretation
of the field.

For example:

Is commented like so:
public static final long DFS_IMAGE_TRANSFER_RATE_DEFAULT = 0;  //no

However in the implementation of these defaults, "magic" zeros are used
without commenting:
if (transferBandwidth > 0) {
      throttler = new DataTransferThrottler(transferBandwidth);


Seems like the 0 above would be better replaced with
DFS_IMAGE_TRANSFER_RATE_DEFAULT since the "no throttling" behaviour is
defined with the constant in the DFSConfigKeys file, and not defined in the


Trying to get a feel for if there are conventions  to enforce in some code
reviews for our hadoop dependent configuration code.  We'd like to follow
hadoopy idioms if possible..

Jay Vyas

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