Restrictions on the string that can be used for the hadoop key

[Marc Harris]

Are there any restrictions on the string that can be used as the key for
an hbase row? I ask because I am using strings of the form:
    <URL><space><alphanumerics><comma><numerics>

and I frequently get problems that seem to start with the following log
message (in my regionserver log file):

2008-01-18 17:24:21,512 FATAL org.apache.hadoop.hbase.HRegionServer: Set
stop flag in regionserver/0:0:0:0:0:0:0:0:60020.splitOrCompactChecker
java.lang.IllegalArgumentException: java.net.URISyntaxException: Illegal
character in scheme name at index 7:
hregion_pagefetch,http://someurl.com/fo/bar%20abcd1,5538225121025076292

This region server then appears to shut down, and restarting everything
(hbase and all hadoop processes) still fails with that same error. I end
up having to re-format the entire hadoop directory.

Can anyone shell some light on what may be happening? It looks to me
like something is adding the prefix "hregion_" to the beginning of my
key, and something else is interpreting the whole thing as a URL and
getting very confused.

Thanks.