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Posted to dev@tomcat.apache.org by bu...@apache.org on 2018/09/28 19:02:12 UTC

[Bug 62773] New: Change DeltaManager to handle session deserialization problems more robustly

https://bz.apache.org/bugzilla/show_bug.cgi?id=62773

            Bug ID: 62773
           Summary: Change DeltaManager to handle session deserialization
                    problems more robustly
           Product: Tomcat 9
           Version: 9.0.12
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: Cluster
          Assignee: dev@tomcat.apache.org
          Reporter: mitch@claborn.net
  Target Milestone: -----

See discussion at
http://mail-archives.apache.org/mod_mbox/tomcat-dev/201809.mbox/%3C694b5737-fb87-a976-440f-2ed0719c1e1a%40claborn.net%3E

Problems:
1. When processing a received "all sessions" message, and there is an Exception
when deserializing a session, there is no logging of what session field or
attribute caused the error.  This makes it very difficult for the application
developer to diagnose and correct problems in the application that caused the
error. 

2. When such an exception occurs, the session in error and all remaining
sessions in that chunk (sendAllSessionsSize) are discarded by the receiving
node. There would be significantly less user impact if only the session in
error was discarded.  

I am working on a patch that will address these issues in DeltaManager. Changes
in that patch:

1. Update
   org.apache.catalina.ha.session.DeltaManager.deserializeSessions(byte[])
   and
   org.apache.catalina.ha.session.DeltaSession.doReadObject(ObjectInput)
   to produce a more detailed error message when a session is in
   error.  New error message includes: the session index in the list of
   sessions, the session ID, the last field or attribute that was
   attempted to be read.
2. Introduce new XML attribute verifySerializedSessions for DeltaManager with a
default value of false (since the true setting will result in significant
overhead when sending all sessions). 
3. If verifySerializedSessions="true",
   org.apache.catalina.ha.session.DeltaManager.serializeSessions(Session[])
   will first serialize each session then immediately deserialize it.
   If all is good, send the session as usual.  If any errors are
   encountered, create and send a dummy session with a known session ID
   instead. (This keeps the session count, which has already been put
   in the output stream, correct for the receiving node.)
4. Update
   org.apache.catalina.ha.session.DeltaManager.deserializeSessions(byte[])
   to discard any received session that has the known dummy session ID.

I'll will attach the patch here when it is ready.

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[Bug 62773] Change DeltaManager to handle session deserialization problems more robustly

Posted by bu...@apache.org.
https://bz.apache.org/bugzilla/show_bug.cgi?id=62773

--- Comment #1 from Mitch Claborn <mi...@claborn.net> ---
Created attachment 36208
  --> https://bz.apache.org/bugzilla/attachment.cgi?id=36208&action=edit
patch that implements the described changes

This code has been running in our moderately busy website for several weeks
with no problems.

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[Bug 62773] Change DeltaManager to handle session deserialization problems more robustly

Posted by bu...@apache.org.
https://bz.apache.org/bugzilla/show_bug.cgi?id=62773

Mitch Claborn <mi...@claborn.net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mitch@claborn.net

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