Change in vdsm[master]: utils: Add changehash function for change detection

alitke at redhat.com alitke at redhat.com
Mon Mar 14 13:46:21 UTC 2016


Adam Litke has posted comments on this change.

Change subject: utils: Add changehash function for change detection
......................................................................


Patch Set 4:

(2 comments)

https://gerrit.ovirt.org/#/c/33045/4/lib/vdsm/utils.py
File lib/vdsm/utils.py:

Line 1223: def changehash(*strings):
Line 1224:     """
Line 1225:     Returns a hash of strings, suitable for change detection.
Line 1226: 
Line 1227:     Tipically changehash(string) is sent to client frequently. When a client
Typically
Line 1228:     detect that the hash changed, it ask for string itself, which is typically
Line 1229:     much bigger.
Line 1230:     """
Line 1231:     h = hashlib.sha1()


Line 1231:     h = hashlib.sha1()
Line 1232:     for s in strings:
Line 1233:         h.update(s)
Line 1234:     # Engine stores this in varchar(30)
Line 1235:     return h.hexdigest()[:30]
How likely are we to experience a hash collision since we're taking only the last 30 chars?  That seems like a bug in engine to me.  Why don't we let them truncate the hash if they want to misuse it.


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Gerrit-MessageType: comment
Gerrit-Change-Id: I2242a594383e2d2fe64e3a581f18b8ac662648b0
Gerrit-PatchSet: 4
Gerrit-Project: vdsm
Gerrit-Branch: master
Gerrit-Owner: Nir Soffer <nsoffer at redhat.com>
Gerrit-Reviewer: Adam Litke <alitke at redhat.com>
Gerrit-Reviewer: Allon Mureinik <amureini at redhat.com>
Gerrit-Reviewer: Dan Kenigsberg <danken at redhat.com>
Gerrit-Reviewer: Federico Simoncelli <fsimonce at redhat.com>
Gerrit-Reviewer: Francesco Romani <fromani at redhat.com>
Gerrit-Reviewer: Jenkins CI
Gerrit-Reviewer: Jenkins CI RO
Gerrit-Reviewer: Nir Soffer <nsoffer at redhat.com>
Gerrit-Reviewer: Roy Golan <rgolan at redhat.com>
Gerrit-Reviewer: Vinzenz Feenstra <vfeenstr at redhat.com>
Gerrit-Reviewer: gerrit-hooks <automation at ovirt.org>
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