WCM Syndication may fail if ifixes on the subscriber and syndicator are not at the same level

Assume you ran into some WCM related issues and you were lucky enough to identify a iFix which might fix the problem, The general thought is to apply the iFix on the QA/Stage (Syndicator) and then do the testing and verification, once the testign is passsed apply it on production (Subscriber). This might work well for most of the ifixes which are not related to WCM, but in case of WCM ifixes it might break the syndication between the "Authoring" and the "Rendering" server if the synidcation happens between the time you test in syndicator and before applying to the subscriber. You might see the java.io.InvalidClassException in the logs as shown below during syndication and syndicator status will show a failure.

on Aug 1 17:11:26 EDT 2007 Failed to transform: {7c0007a717ed72a1, com.aptrix.pluto.cmpnt.HTMLCmpnt, 1187030230711, 63}, Url: http://SomeHost:9081/wps/wcm/connect/?MOD=ItemDispatcher&syndicatorId=e28f92771cc acce&subscriberId=79aeb89771ce1991&subscriptionId=e28f92771ccacce&itemName=7c0 007a717ed72a1:com.aptrix.pluto.cmpnt.HTMLCmpnt:1187030230711:63,Error: com.aptrix.deployment.subscriber.TransformationException: Code #100, phrase: Generic internal responder error, detail: Exception occurred while trying to retrieve document from item.(Cause: java.io.InvalidClassException: com.aptrix.pluto.cmpnt.ProfileCmpnt; local class incompatible: stream classdesc serialVersionUID = -7211000162118777127, local class serialVersionUID = 611017038877300726 

The failure reason being is during syndication, WCM objects are serialized and transferred across the network to the subscriber where is get deserialized and stored. So in order for the serialization and deserialization to work properly the Class serialVersionUID of the object should match, so if the ifixes installed are not at the same level then Class serialVersionUID will mismatch which will further result in syndication failure.

So make sure you plan well so that your testing and verification cycle is shorter than your syndication cycle to avoid unnecesary problems. There are also some other reasons that you might encounter this same error , check this technote How to troubleshoot "InvalidClassException" errors during Web Content Management (WCM) syndication to identify and resolve them.