On 6/15/11 5:19 PM, Emmanuel Lecharny wrote:
Hi,
sadly, things are not as rosy as I exepected...
I have written a few tests to check if we correctly detect cycles
while processing a search, and at some point, I found that cycle are
not an issue at all. But wait, it's not a good news :/
Let's say you have the following entries :
cn=test
cn=foo,cn=test
cn=barAlias,cn=foo,cn=test -> cn=bar,cn=test
cn=bar,cn=test
cn=dohAlias,cn=foo,cn=test -> cn=doh,cn=test
cn=doh,cn=test
Logically, doing a SUBTREE search on cn=foo,cn=test, you should get
the following entries :
cn=foo,cn=test
cn=bar,cn=test
cn=doh,cn=test
This is *not* what we get. Currently, you'll have :
cn=foo,cn=test
cn=bar,cn=test
The second alias dereferencing is never done.
Obviously, it helps when it come sto avoid cycle, but this is
certainly not the expected behavior.
Now, if we want to do alias chasing on the server, we will have to
modify the way we handle alias : each one of them will issue a new
search, wth a new cursor.
Hopefully, stacking the aliases to be processed works well with the
fact that we have to stack the aliases for cycle detection. One
possible solution would be to process this stack alias after alias,
and if we get back an alias, we add it in the stack if it's not
already present (otherwise, that means we have a cycle).
In our sample, we will have the following stack :
() : empty stack
(cn=barAlias,cn=foo,cn=test) : first alias met
-> here, we have processed all the entries for the initial search
[cn=foo,cn=test]
[cn=bar,cn=test] (the dereferenced alias)
-> now, we get the leftmost element in the stack, and launch a new search
(<cn=barAlias,cn=foo,cn=test>) : this alias is being processed, thus
the <>
(<cn=barAlias,cn=foo,cn=test>, cn=dohAlias,cn=foo,cn=test) : second
alias met
-> again, all the entries have been processed, we take the next alias
in the stack
[cn=doh,cn=test]
(<cn=barAlias,cn=foo,cn=test>, <cn=dohAlias,cn=foo,cn=test>) : second
alias met
-> there are no further entries. We are done
Seems to work... Did I miss something ?
Yes, I missed something (thanks Pierre-Arnaud for pointing this out) :
if the alias get dereferenced to an entry below one of the DN already
stored in the stack, or to the descendant of one of the stored DNs, then
we don't need to proceed the search for this alias, as the entries have
already been provided. That will avoid sending duplicate entries to the
user.
--
Regards,
Cordialement,
Emmanuel Lécharny
www.iktek.com
