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From David Nickerson <davidnickerson4mailingli...@gmail.com>
Subject Sanitizing ZooKeeper znode names
Date Fri, 06 Jul 2012 16:10:46 GMT
I'm writing a distributed locking API based on ZooKeeper. I create nodes
based on the resource names, but I have no control over what the client
chooses as their resource name. (Quite often the client uses linux file
paths, so I have to remove or escape all of the front slashes.)

To clean the node names, I wrote a method that escapes the bad characters.
The method is called 'normalize': http://pastebin.com/hakkb9Nw .

For example, a front slash becomes \x2f. This method works, but it has a
few drawbacks. It doesn't deal with unicode characters greater then 16 bits
in size, and it's impossible to reverse the escape process. Also,
crucially, it is possible that two different resources will result in the
same znode name, which could cause all kinds of trouble.

A more reliable approach would be to convert the resource name into hex.
For example:

import javax.xml.bind.DatatypeConverter;


This would always result in a safe and unique node name. (It will never
result in the token "zookeeper" because "zookeeper" has an odd number of
characters.) The only problem with this is that it becomes impossible to
read and understand the resource names from ZooKeeper unless you reverse
the process:

new String(DatatypeConverter.parseHexBinary(hex))

So I'm wondering, is there a standard or recommended practice for
sanitizing znode names? If not, which approach would you recommend?

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