From a recent case, we found a lack documented “Issue” you may run into while setting up and configuring a content type hub or trying to publish content types.

Scenario:
You have a site dedicated to be your Content type HUB (how to do that, check the “Repro-Steps” section below).

You have also created some content types you may publish via your managed meta data service. Once you hit the button “publish”,

you get an error on page:

Error
No valid Proxy can be found to do this operation.

In ULS logs you may find something  like this:

Cause

Note:
In this case, it was depending on two causes but in general, the main thing is to watch the URL you’re using to type into the “Managed Meta Data Services” !!

a) Wrong URL settings on the managed meta data service application.
– The content type hub was set on URL http://sp2k10a/sites/CTHUB/SitePages/Home.aspx
– This URL was also set in the MMS app
b) Missing entry in the AAM’s
– The MMS web service was listening on address http://hostname:32843/… But in AAM settings we only had a map to http://hostname:4000 which is the CA 

Resolution

Note:
Unfortunately this is not very well documented and therefore not obvious, which URL or part of it should be used on the MMS configuration!
Changing the configured URL from the content type HUB in the MMS service application.

Example:
We configured the content type HUB URL with: http://sp2k10a/sites/CTHUB/SitePages/Home.aspx

Note:
When setting up the FULL URL with the part  […/SitesPages/Home.aspx] it simply does not work!  
In this case, the URL has to be this one:   http://sp2k10a/sites/CTHUB/

To change an already configured URL in the MMS, you need to do this with powershell:

Set-SPMetadataServiceApplication “Managed Metadata Service” –HubUri  http://sp2k10a/sites/CTHUB 

Also we set an additional AAM for the map http://hostsps10.de.company.net -> http://hostname:32843/  
because hostsps10.de.company.net is a DNS alias and hostname is the physical servername.

After that, we were able to publish the content types from the syndicated content type HUB site as expected.

—-

So back to the question on “How to set up and configure the Content Type HUB”, I’ll send the Kudo’s to Steve Peschka for his post “Publish and Subscribe to Content Types in SharePoint 2010” about it!
I took some parts of his post for the below repro description just to your convenience.  There are some other posts out there but the most important part is nowhere mentioned: 
“To know what URL and/or part of it you need to set correctly”

Therefore I’ll just repeat in short the “Repro-Steps” to this post and how the issue was found!

REPRO-Steps

– create a brand new web app and site collection, site template=blank site => this will be your Content Type HUB Site

– on site settings, enable in “site collection features”, the “Content Type Syndication Hub” feature

– on this new site (your Content type HUB), go to site settings – galleries – site columns

As of taken from Steve Peschka’s post:
– create three new site columns called [Product Name] (Single line of text), [Product Description] (Single line of text), and [Product ID] (number)

  
– go to site settings – galleries – Site content types,

  
– create a custom content type called “Product”, and add the three site columns just created to it.

Note:  
On the site content type information, you’ll see now the “manage publishing for this content type” in section “settings”

– click there and check the bullet for “publish”, click “ok” (==> here you’ll get the “No proxy error” when the URL is not set correctly!!!)

Note:
You need to set the “basic part of the URL only”! 
Remember:  http://sp2k10a/sites/CTHUB/    instead of   http://sp2k10a/sites/CTHUB/SitePages/Home.aspx  or   http://sp2k10a/sites/CTHUB/SitePages/
any other URL as the first one shown will not work either in this case!

– Next, go to service application services, Managed Meta Data Services and mark the MMS
  Do not click directly on the link as this will only bring you up to the management page for the terms and keywords!:

– on ribbon bar, click “properties” and scroll down to the foot of the page,

– for “content type HUB”, put in the URL (i.e. http://servername/sites/CTHUB) but no extension to any aspx page or next folder! Just the pure URL!

– check the “report syndication…” box and click ok

– back on service application page, mark the associated proxy below the MMS and in ribbon also click properties

– check the “Consumes content types from the Content Type Gallery at http://sp2k10a/sites/CTHUB” and click ok.

– go into Central Admin, click on the Monitoring section, and click on “Review job definitions” in the Timer Jobs section
– look for the [Content Type Hub] job and the [Content Type Subscriber] job for the according web applications,

  
– run these jobs immediately to get pushed all changes to the publishing content types and syndication
– on any other site, go to site settings, [Site Collection Administration], [Content type publishing] => here you’ll see the MMS URL pointing to your HUB site and the already subscribed content types from your HUB!

Howdy, you’re done!  If the URL is correct set, you will not get the error “No valid Proxy…” 
If still getting it!

– recheck the URL’s
– recheck for Alternate Access Mappings (AAM)

This is already reported internally and I’ll update this post, once a fix or KB or any other news around it will be available!

Other related links:

Plan to share terminology and content types (SharePoint Server 2010) – http://technet.microsoft.com/en-us/library/ee519603.aspx  
Managed metadata service application overview (SharePoint Server 2010) – http://technet.microsoft.com/en-us/library/ee424403.aspx  
managed metadata service application (SharePoint Server 2010) – http://technet.microsoft.com/en-us/library/ee530392.aspx  
(Video) How Do I: Use the SharePoint 2010 Managed MetaData Service? – http://technet.microsoft.com/en-us/sharepoint/ff394027.aspx  
Timer job reference (SharePoint Server 2010) – http://technet.microsoft.com/en-us/library/cc678870.aspx  

cheers and have fun,
Steve