[CONF] Apache Connectors Framework > FAQ

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Space: Apache Connectors Framework (https://cwiki.apache.org/confluence/display/CONNECTORS)
Page: FAQ (https://cwiki.apache.org/confluence/display/CONNECTORS/FAQ)


Edited by Karl Wright:
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h1. Frequently asked questions

h3. Security model

*Q. What exactly are the ACCESS_TOKEN and DENY_TOKEN values that are sent to an output connector, and presumably stored in the index?*

*A.* The ACCESS_TOKEN and DENY_TOKEN values are, in one sense, arbitrary strings that represent a contract between an ManifoldCF authority connection and the ManifoldCF repository connection that picks up the documents (from wherever).  These tokens thus have no real meaning outside of ManifoldCF.  You must regard them as opaque.

The contract, however, states that if you use the ManifoldCF authority service to obtain tokens for an authenticated user, you will get back a set that is CONSISTENT with the tokens that were attached to the documents ManifoldCF sent to Solr for indexing in the first place.  So, you don't have to worry about it, and that's kind of the idea.  So you imagine the following flow:

1. Use ManifoldCF to fetch documents and send them to Solr
2. When searching, use the ManifoldCF authority service to get the desired user's access tokens
3. Either filter the results, or modify the query, to be sure the access tokens all match up properly

For the AD authority, the ManifoldCF access tokens consist, in part, of the user's SIDs.  For other authorities, the access tokens are wildly different.  You really don't want to know what's in them, since that's the job of the ManifoldCF authority to determine.

ManifoldCF is not, by the way, joined at the hip with AD.  However, in practice, most enterprises in the world use some form of AD single signon for their web applications, and even if they're using some repository with its own idea of security, there's a mapping between the AD users and the repository's users.  Doing that mapping is also the job of the ManifoldCF authority for that repository.

*Q. What is the relationship between stored data (documents) and authority access/deny attributes?  Do you have any examples of what an access_token value might contain?*

*A.* Documents have access/deny attributes; authorities simply provide the list of tokens that belong to an authenticated user.  Thus, there's no access/deny for an authority; that's attached to the document (as it is in real-world repositories).
 
Let's run a quick example, using Active Directory and a Windows file system.  Suppose that you have a directory with documents in it, call it DirectoryA, and the directory allows read access to the following SIDs:
 
S-123-456-76890
S-23-64-12345
 
These SIDs correspond to active directory groups, let's call them Group1 and Group2, respectively.
 
DirectoryB also has documents in it, and those documents have just the SID S-123-456-76890 attached, because only Group1 can read its contents.
 
Now, pretend that someone has created an ManifoldCF Active Directory authority connection (in the ManifoldCF UI), which is called "myAD", and this connection is set up to talk to the governing AD domain controller for this Windows file system.  We now know enough to describe the document indexing process:
 
* Each file in DirectoryA will have the following __ALLOW_TOKEN__document attributes inside Solr: "myAD:S-123-456-76890", and "myAD:S-23-64-12345".
* Each file in DirectoryB will have the following __ALLOW_TOKEN__document attributes inside Solr: "myAD:S-123-456-76890"
 
Now, suppose that a user (let's call him "Peter") is authenticated with the AD domain controller.  Peter belongs to Group2, so his SIDs are (say):
 
S-1-1-0 (the 'everyone' SID)
S-323-999-12345 (his own personal user SID)
S-23-64-12345 (the SID he gets because he belongs to group 2)
 
We want to look up the documents in the search index that he can see.  So, we ask the ManifoldCF authority service what his tokens are, and we get back:
 
"myAD:S-1-1-0", "myAD:S-323-999-12345", and "myAD:S-23-64-12345"
 
The documents we should return in his search are the ones matching his search criteria, PLUS the intersection of his tokens with the document ALLOW tokens, MINUS the intersection of his tokens with the document DENY tokens (there aren't any involved in this example).  So only files that have one of his three tokens as an ALLOW attribute would be returned.
 
Note that what we are attempting to do in this case is enforce AD's security with the search results we present.  There is no need to define a whole new security mechanism, because AD already has one that people use.


*Q. Do the ManifoldCF authority connections authenticate users?*

*A.* The authority connectors don't perform authentication at this time.  In fact, ManifoldCF has nothing to do with authentication at all - just authorization.  It is almost never the case that somebody wants to provide multiple credentials in order to be able see their results.  Most enterprises who have multiple repositories authenticate against AD and then map AD user names to repository user names in order to access those repositories.  For a pure-java authentication solution, we are currently recommending JAAS plus sun's kerb5 login module (com.sun.security.auth.module.Krb5LoginModule) for handling the "authenticate against AD" case, which covers some 95%+ of the real world authentication needed out there.  We may have more complete recommendations in the future.

*Q. I have a question regarding how multiple identifiers for a given user is handled in the authority service.  Let say that I want to get the access tokens for the user John Smith against all the authority connectors defined in ManifoldCF.  Let say that John is known as john.smith in AD, known as j.smith in document and so on.  If I'm not wrong, the only parameter used to identify a user in the authority service is "username".  I'm wondering how user id reconciliation is performed inside the authority service in that case? Is there something done about that or is it a work that should be performed externally?*

*A.* The user name mapping is the job of the individual authority.  So, for example, the Documentum authority would be responsible for any user name mapping that would need to be done prior to looking up the tokens for that user within Documentum, and the LiveLink authority needs to do something similar for mapping to LiveLink user names.
 
It turns out that most enterprises that have coexisting repositories of disparate kinds make an effort to keep their user name spaces consistent across these repositories.  Otherwise, enterprise-wide single signon would be impossible.  In the cases where the convention for mapping is ad-hoc (e.g. LiveLink), the authority connectors included with ManifoldCF were built with a simple regular-expression-based mapping feature, which you get to configure right in the crawler ui as part of defining the authority connection.
 
Many repository companies also have added AD synchronization features as their products have matured.  Documentum is one such repository, where the repository software establishes a feature for operating with AD.  For those repositories, we did not add a mapping function, because it would typically be unnecessary if the repository integrator followed the recommended best practices for deploying that repository.

*Q. I don't like the idea of storing document access tokens in an index.  What happens if/when you want to add explicit user access to some [group of] documents? (i.e. not via a group)*

*A.* In ManifoldCF, you would change the permissions on the appropriate resource, and then you run your ManifoldCF job again to update those permissions.  Since ManifoldCF is an incremental crawler, it is smart enough to only re-index those documents whose permissions have changed, which makes it a fairly fast operation on most repositories.  Also, in my experience, this is a relatively infrequent kind of situation, and most enterprises are pretty resilient against there being a reasonable delay in getting document permissions updated in an index.

However, if this is still a concern, remember that your main alternative is to go directly to the repository on every document as you filter a resultset.  That's slow for most situations.  Performance might be improved with caching, but only if you knew that the same results would be returned for multiple queries.  So no solution is perfect.

*Q. I don't like the idea of storing document access tokens in an index.  What happens if you need to revoke a users rights, or change a user's group affinity?*

*A.* The access tokens for a user are obtained from the authorities in real time, so there is no delay.  Only access tokens attached to documents require a job run to be changed.

*Q. I don't like the idea of storing Active Directory SIDs in an index.  They might be changed.*

*A.* Once again, this is a very infrequent occurrence, and when it does happen, ManifoldCF is well equipped to handle the re-indexing in the most efficient way possible.

*Q. How has ManifoldCF performed (the example configuration) on what kind of hardware?*

*A.* The example, running on Derby, has not had performance tests run against it.  The example running with PostgreSQL 8.3 on a Dell laptop with disk encryption is capable of doing a file system crawl at 35 documents/second.  A real server will, of course, run significantly faster.  At MetaCarta, we discovered that almost always the repository being crawled was the bottleneck.  Only exceptions are RSS and Web crawls.
On a crawl that is executing optimally, the system will be CPU-bound.  If you are seeing low rates of CPU utilization, it may mean you have inadequate disk performance.  There are also known bugs with Derby that result in the Derby database deadlocking and recovering, which also leads to very poor system utilization.

*Q. How do I use PostgreSQL with the quick-start example?*

*A.* First, install PostgreSQL, and remember the superuser database name and password (usually "postgres" is the name).  Then, change the properties.xml file in the following way:
Change:
<property name="org.apache.manifoldcf.databaseimplementationclass" value="org.apache.manifoldcf.core.database.DBInterfaceDerby"/>
to:
<property name="org.apache.manifoldcf.databaseimplementationclass" value="org.apache.manifoldcf.core.database.DBInterfacePostgreSQL"/>
Add:
<property name="org.apache.manifoldcf.dbsuperusername" value="postgres"/>
<property name="org.apache.manifoldcf.dbsuperuserpassword" value="*******"/>

Then, start the quick-start example normally, and everything should initialize properly.

*Q. How do you configure Eclipse to build the ManifoldCF project?*

*A.* Here are the steps using Eclipse 3.4:
# Install Subclipse for Eclipse 3.x, follow the steps from http://subclipse.tigris.org/servlets/ProjectProcess?pageID=p4wYuA
# In Eclipse, switch to the "SVN Repository Exploring" perspective
# Add a new SVN repository using the URL http://svn.apache.org/repos/asf/incubator/lcf/trunk
# Right click on the svn repo and select "Check Out"
  #* May want to change the default name from truck to ManifoldCF, if you don't change the name Eclipse will ask for a project type, pick General/Project.
# Wait for the source to extract
# Switch to Java Perspective and right click on the project that was added (referred to as MCF in the rest of the steps) and select "Properties"
# Select "Builders" and click New
# Select "Ant Builder" and click Ok
# Give your builder a name, like ManifoldCF Ant Builder
# In the "Buildfile" section, press the "Browse Workspace" button
# Select the MCF project, drill down to "modules" subfolder and select "build.xml" file then press Ok
# In the "Base Directory" section, press the "Browse Workspace" button
# Expand the MCF project and select "modules" then press Ok
# Note, you can further configure the different targets if you wish for a clean, regular, and auto build
# Press Ok in the "Edit launch configuration properties" to complete the Eclipse configuration
# Make sure you have the system variable JAVA_HOME pointing to your jdk, also you need the jdk bin directory listed in your path so java doc would work
# Now you can issue "Project/Build Project" and watch the console for the ant output


The build will also run through the junit tests which increases the build time.  For those who like to do incremental build as they code, you may want to configure a "build" target without the final unit test ("run-tests" in "all" target), which reduces build time from 5 to 1 minute.

*Q. What is the proper setting for number of worker threads?*

*A.* The number of worker threads, number of delete threads, number of expiration threads, database pool size, and maximum number of database handles (in PostgreSQL) are related as follows for the Quick Start:

(num_worker + num_delete + num_expiration + 10) < database_pool_size <= maximum_database_handles - 2

The formula is somewhat different if you have multiple ManifoldCF processes, e.g. you are running the crawler separately from the web applications.  In that case you need to add up ALL the processes, because each of them will have their own pool of the designated size:

database_pool_size * num_processes <= maximum_database_handles - 2

The overall idea is so you don't run out of database handles in the pool (which can cause ManifoldCF to deadlock even), and you don't run out of real database handles either (which will cause a database error that stops your jobs).  The value of "2" adjustment is simply so you can get into the database while ManifoldCF is running using tools like psql, and can do things like vacuuming.

The first four values are all properties you can (and should!) set in properties.xml.  They are described in the "how to build and deploy" document on the site.  The last property requires you to configure the database (probably postgresql).  There are also general instructions for doing that in "how to build and deploy".

The relationship between worker threads and all of the other kinds depends on your usage.  Generally, though, 10 expiration threads and 10 deletion threads are fine, since they do less of the overall work involved.




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