Click here to close now.

Welcome!

Weblogic Authors: Elizabeth White, Michael Meiner, Michael Bushong, Avi Rosenthal

Related Topics: Weblogic

Weblogic: Article

'HTTP Session Replication Failure' Issues

Moving away from the primary thought

Sometimes, HTTP session states are not replicated from the primary server to the secondary server.

Symptoms

  1. The application using HTTP session does not function as designed and you see a loss of session data.
  2. You might be asked to re-log into the application even when the session has still not timed out.
  3. You see errors and warnings related to HTTP session failures in the server's log file.
  4. The request is not failed over to another server properly.

There are several reasons as to why session replication fails. We will look at ways to diagnose the issue, possible reasons for it, and the ways to address them.

Types of HTTP Session Replication
There are five different implementations of session persistence:

  • Memory (single-server, non-replicated): When you use memory-based storage, all session information is stored in memory and is lost when you stop and restart WebLogic Server.
  • File system persistence: Session information is stored in a file under the PersistentStoreDir specified.
  • JDBC persistence: Session information is stored in a database table.
  • Cookie-based session persistence: Session information is stored in a cookie.
  • In-memory replication (across a cluster): Session data is copied from one server instance to another into memory.

Diagnosing the Issue
Consider a scenario with two servers (MyServer-1, MyServer-2) in a cluster. When you enable the debug flags (see the "Enable the Debug Flags to Track Session Replication Failures"section), you will see the messages below when a request from a client is sent the very first time.

On MyServer-1:

<Oct 9, 2003 12:38:21 PM PDT> <Debug> <Cluster> <000000>
<Creating primary 5165892837402719733>
<Oct 9, 2003 12:38:21 PM PDT> <Debug> <Cluster> <000000>
<Created secondary for 5165892837402719733 on -7957889153726652135S:
192.168.11.112: [9001,9001, -1, -1,9001, -1, -1]: mydomain: MyServer-2>

This logging message means that the primary server is MyServer-1 and a secondary has been created on MyServer-2. A message like the one shown below will be logged on MyServer-2 to confirm that.

ExecuteThread: '1' for queue: 'Replication'> <kernel identity> <>
<000000> <Creating secondary 5165892837402719733>
####<Oct 9, 2003 12:38:21 PM PDT> <Debug> <Cluster>
<rvimala-c840> <MyServer-2> <ExecuteThread:
'1' for queue: 'Replication'>
<kernel identity> <> <000000>
<Updated local secondary of 5165892837402719733>

If you check the JSESSIONID it looks like:

JSESSIONID=1E9Xwn7nLYfOsc1obgRZIwW5s72an7HPPvSD7iaWHMXzpHga5cQj
!-1587343083!-1587348922

JSESSIONID is the default name of the cookie, which could be changed to anything in weblogic.xml. The format of JSESSIONID is

SessionId!PrimaryServer JVM Hash!SecondaryServer JVMHash

Every time data is changed (either set/get or removed) in the session you'll see the logging message.

On MyServer-1:

<Oct 9, 2003 12:38:21 PM PDT> <Debug> <Cluster> <000000>
<Updated remote secondary for 5165892837402719733>

On MyServer-2:

####<Oct 9, 2003 12:38:21 PM PDT> <Debug> <Cluster>
<rvimala-c840> <MyServer-2> <ExecuteThread:
'1' for queue: 'Replication'> <kernel identity> <> <000000>
<Updated local secondary of 5165892837402719733>

If for any reason session replication fails, you will see the message below in the MyServer-1 log:

<Nov 6, 2003 12:59:12 PM EST> <Debug> <Cluster> <000000>
<Unable to create secondary for -5165892837402719733>
<Nov 6, 2003 12:59:12 PM EST> <Debug> <Cluster> <000000>
<Error creating secondary 5165892837402719733 on -7957889153726652135S:
192.168.11.112:[9001,9001,-1,-1,9001,-1,-1]:mydomain:MyServer-2>

And, the JSESSIONID would appear as

JSESSIONID=1E9Xwn7nLYfOsc1obgRZIwW5s72an7HPPvSD7iaWHMXzpHga5cQj!-1587343083!NONE

The secondary server hash would become NONE

Enable the Debug Flags to Track Session Replication Failures
You can enable the flags DebugCluster, DebugClusterAnnouncements, DebugFailOver, DebugReplication, and DebugReplicationDetails.

To Enable
Use the weblogic.Admin command-line utility to dynamically turn the debug options on and off. For example, to turn on DebugCluster on all administration instances of ServerDebug MBean (i.e., Admin Server or al Managed Server):

java weblogic.Admin -url t3://localhost:7001 -username system -password weblogic
SET -type ServerDebug -property DebugCluster true

Or, edit the config.xml and the MBean element in the <ServerDebug/> stanza for each server that you want to debug and set it to a value of "true" to enable or "false" to disable. Then you must restart the Admin Server. Managed Servers will reconnect to the Admin Server and the debug flags will then dynamically take effect. For example:

<ServerDebug DebugCluster="true" Name="myserver"/>

At the end, with all the flags set, in your config.xml the ServerDebug tag would look like:

<ServerDebug ClassFinder="true" DebugCluster="true"
DebugClusterAnnouncements="true" DebugFailOver="true"
DebugReplication="true" DebugReplicationDetails="true" Name="MyServer1"/>

Make sure the stdOutSeverity level of the server is INFO and StdoutDebugEnabled is set to "true". The debug information will be logged into the server log as well as to the standard out.

Checklist for Each Session Persistence Type
Memory (Single Server, Nonreplicated)

  1. When you use memory-based storage, all session information is stored in memory and is lost when you stop and restart BEA WebLogic Server.
  2. Make sure you have allocated sufficient heap size when running WebLogic Server; otherwise, your server may run out of memory under heavy load.
  3. Not a recommended type for Cluster configuration (because the data is kept in heap and is not available to any other server).

File System Persistence

  1. Verify that the directory where BEA WebLogic Server stores the sessions is correctly specified in weblogic.xml. You must also create this directory yourself and make sure appropriate access privileges have been assigned to the directory.
  2. Make sure you have enough disk space.

JDBC Persistence
Make sure the connection pool that connects to the database has read/write access for the database table used.

Cookie-Based Persistence

  1. Make sure you have not stored anything other than java.lang.String in the HTTP session.
  2. Do not flush the HTTP response object in your application code.
  3. Make sure that the content length of the response exceeds the buffer size set (default is 8192 bytes).
  4. Make sure that cookies are enabled in the browser.
  5. Make sure that you do not use commas (,) in a string when using cookie-based session persistence.

In-Memory Replication

  1. Make sure that the BEA WebLogic Server is accessed only via a proxy server or a hardware load balancer
  2. The hardware load balancer should support a compatible passive or active cookie persistence mechanism, and SSL persistence.
  3. Recommended type in a cluster.

Validate the weblogic.xml Entries
Make sure weblogic.xml has all the parameters that need to be set for each Session Replication type. For example, when using in-memory replication the sample weblogic.xml would look like:

<session-descriptor> <session-param> <param-name> PersistentStoreType </param-name> <param-value> replicated </param-value> </session-param> </session-descriptor>

Note: The debug files are subjected to change with each version of BEA WebLogic Server.

Session Data Must Be Serializable
To support in-memory replication of HTTP session states, all servlet and JSP session data must be serializable or else session replication would fail.

When debugging is enabled, BEA WebLogic Server would output the warning messages below by indicating that the session is not replicated. After this, session replication would stop.

Debug Message:

<Oct 8, 2003 2:10:45 PM PDT> <Error> <Cluster> <000126>
<All session objects should be serializable to replicate.
Please check the objects in your session.
Failed to replicate non-serializable object>

On the subsequent request the JSESSIONID will be missing the secondary server and will be marked NONE, e.g.:

JSESSIONID=1E9Xwn7nLYfOsc1obgRZIwW5s72an7HPPvSD7iaWHMXzpHga5cQj!-1587343083!NONE

Solution: Find out the page the error is thrown from and make sure that all the data put into the session is serializable.

Check for Network/Multicast Issues
Make sure that the network is fine and there are no multicast issues. Do the multicast test to make sure that the multicast IP is working fine.

Syntax

java utils.MulticastTest -n name -a address [-p portnumber] [-t timeout] [-s send]

(http://edocs.bea.com/wls/docs81/adminref/utils.html#1199798)

Validate Cluster Configuration
The primary and secondary servers are selected from the cluster list. In a cluster of two servers, if the cluster doesn't have all the servers, then a secondary might not be chosen, resulting in the session data not being replicated.

To verify, execute the following commands:

  1. Make sure weblogic.jar is in the classpath.
  2. To get all the servers in a cluster:

java weblogic.Admin -username weblogic -password weblogic -url
http://oneofthemanagedserverurlinthecluster:7001/ GET -type ClusterRuntime -pretty

This will list all the servers in a cluster. The URL could be changed to every server in the cluster to make sure they all have the same entries.

Application Code Diagnostics
Make sure you use only setAttribute/removeAttribute methods of the HTTP session in your application code to update the HTTP session. If you use other set methods to change objects within a session, BEA WebLogic Server does not replicate those changes.

Please do not use the methods putValue and removeValue of the HTTP session as they are deprecated and there could be issues with session data replication when using such methods in your application. Instead, use only the setAttribute/removeAttribute methods of the Http session.

Cookies vs URL Rewriting
In some situations, a browser or wireless device may not accept cookies, which makes session tracking with cookies impossible. URL rewriting is a solution to this situation that can be substituted automatically when WebLogic Server detects that the browser does not accept cookies. Enable URL rewriting in BEA WebLogic Server by setting the URLRewritingEnabled attribute in the WebLogic-specific deployment descriptor, weblogic.xml, under the <session-param> element. The default value for this attribute is true.

Performance Issues

  • Consider serialization overhead: Serializing session data introduces some overhead for replicating the session state. The overhead increases as the size of the serialized objects grows. If you plan to create very large objects in the session, test the performance of your servlet to ensure that performance is acceptable.
  • Control frame access to session data: If you are designing a Web application that utilizes multiple frames, keep in mind that there is no synchronization of requests made by frames in a given frameset. For example, it is possible for multiple frames in a frameset to create multiple sessions on behalf of the client application, even though the client should logically create only a single session.

    To avoid unexpected application behavior, carefully plan how you access session data with frames. You can apply one of the following general rules to avoid common problems:
    - In a given frameset, ensure that only one frame creates and modifies session data.
    - Always create the session in a frame of the first frameset your application uses (for example, create the session in the first HTML page that is visited). After the session has been created, access the session data only in framesets other than the first frameset.

  • Storing larger amounts of data in the session: JDBC persistence and File persistence won't be faster as the session data has to be stored and retrieved from an external resource. There is also a performance overhead because of JDBC access for each session update. If you want to store large objects in the session, then JDBC or File persistence should be considered.
  • Storing small amount of data in the session: Cookie-based session persistence is most useful when you do not need to store large amounts of data in the session. Cookie-based session persistence can make managing your BEA WebLogic Server installation easier because clustering failover logic is not required.

    Further Information
    For additional information go to http://support.bea.com for some published solutions on session replication failures. You can also query ASK BEA at http://websupport.beasys.com/index.jsp.

    If none of these help you towards a solution or an identifier in your application, then contact BEA Customer Support for further diagnosis. You can open a case with a valid support contract by logging in at http://support.bea.com/login.jsp

  • More Stories By Vimala Ranganthan

    Vimala Ranganathan is a backline developer relations engineer with BEA Systems. She specializes in troubleshooting and solving complex customer issues with their mission-critical applications on BEA products. Vimala holds a bachelor's degree in computer science.

    Comments (0)

    Share your thoughts on this story.

    Add your comment
    You must be signed in to add a comment. Sign-in | Register

    In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


    @ThingsExpo Stories
    Dale Kim is the Director of Industry Solutions at MapR. His background includes a variety of technical and management roles at information technology companies. While his experience includes work with relational databases, much of his career pertains to non-relational data in the areas of search, content management, and NoSQL, and includes senior roles in technical marketing, sales engineering, and support engineering. Dale holds an MBA from Santa Clara University, and a BA in Computer Science from the University of California, Berkeley.
    The cloud is now a fact of life but generating recurring revenues that are driven by solutions and services on a consumption model have been hard to implement, until now. In their session at 16th Cloud Expo, Ermanno Bonifazi, CEO & Founder of Solgenia, and Ian Khan, Global Strategic Positioning & Brand Manager at Solgenia, will discuss how a top European telco has leveraged the innovative recurring revenue generating capability of the consumption cloud to enable a unique cloud monetization model to drive results.
    As organizations shift toward IT-as-a-service models, the need for managing and protecting data residing across physical, virtual, and now cloud environments grows with it. CommVault can ensure protection &E-Discovery of your data – whether in a private cloud, a Service Provider delivered public cloud, or a hybrid cloud environment – across the heterogeneous enterprise. In his session at 16th Cloud Expo, Randy De Meno, Chief Technologist - Windows Products and Microsoft Partnerships, will discuss how to cut costs, scale easily, and unleash insight with CommVault Simpana software, the only si...
    Analytics is the foundation of smart data and now, with the ability to run Hadoop directly on smart storage systems like Cloudian HyperStore, enterprises will gain huge business advantages in terms of scalability, efficiency and cost savings as they move closer to realizing the potential of the Internet of Things. In his session at 16th Cloud Expo, Paul Turner, technology evangelist and CMO at Cloudian, Inc., will discuss the revolutionary notion that the storage world is transitioning from mere Big Data to smart data. He will argue that today’s hybrid cloud storage solutions, with commodity...
    Every innovation or invention was originally a daydream. You like to imagine a “what-if” scenario. And with all the attention being paid to the so-called Internet of Things (IoT) you don’t have to stretch the imagination too much to see how this may impact commercial and homeowners insurance. We’re beyond the point of accepting this as a leap of faith. The groundwork is laid. Now it’s just a matter of time. We can thank the inventors of smart thermostats for developing a practical business application that everyone can relate to. Gone are the salad days of smart home apps, the early chalkb...
    Cloud data governance was previously an avoided function when cloud deployments were relatively small. With the rapid adoption in public cloud – both rogue and sanctioned, it’s not uncommon to find regulated data dumped into public cloud and unprotected. This is why enterprises and cloud providers alike need to embrace a cloud data governance function and map policies, processes and technology controls accordingly. In her session at 15th Cloud Expo, Evelyn de Souza, Data Privacy and Compliance Strategy Leader at Cisco Systems, will focus on how to set up a cloud data governance program and s...
    Roberto Medrano, Executive Vice President at SOA Software, had reached 30,000 page views on his home page - http://RobertoMedrano.SYS-CON.com/ - on the SYS-CON family of online magazines, which includes Cloud Computing Journal, Internet of Things Journal, Big Data Journal, and SOA World Magazine. He is a recognized executive in the information technology fields of SOA, internet security, governance, and compliance. He has extensive experience with both start-ups and large companies, having been involved at the beginning of four IT industries: EDA, Open Systems, Computer Security and now SOA.
    The industrial software market has treated data with the mentality of “collect everything now, worry about how to use it later.” We now find ourselves buried in data, with the pervasive connectivity of the (Industrial) Internet of Things only piling on more numbers. There’s too much data and not enough information. In his session at @ThingsExpo, Bob Gates, Global Marketing Director, GE’s Intelligent Platforms business, to discuss how realizing the power of IoT, software developers are now focused on understanding how industrial data can create intelligence for industrial operations. Imagine ...
    We certainly live in interesting technological times. And no more interesting than the current competing IoT standards for connectivity. Various standards bodies, approaches, and ecosystems are vying for mindshare and positioning for a competitive edge. It is clear that when the dust settles, we will have new protocols, evolved protocols, that will change the way we interact with devices and infrastructure. We will also have evolved web protocols, like HTTP/2, that will be changing the very core of our infrastructures. At the same time, we have old approaches made new again like micro-services...
    Operational Hadoop and the Lambda Architecture for Streaming Data Apache Hadoop is emerging as a distributed platform for handling large and fast incoming streams of data. Predictive maintenance, supply chain optimization, and Internet-of-Things analysis are examples where Hadoop provides the scalable storage, processing, and analytics platform to gain meaningful insights from granular data that is typically only valuable from a large-scale, aggregate view. One architecture useful for capturing and analyzing streaming data is the Lambda Architecture, representing a model of how to analyze rea...
    SYS-CON Events announced today that Vitria Technology, Inc. will exhibit at SYS-CON’s @ThingsExpo, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. Vitria will showcase the company’s new IoT Analytics Platform through live demonstrations at booth #330. Vitria’s IoT Analytics Platform, fully integrated and powered by an operational intelligence engine, enables customers to rapidly build and operationalize advanced analytics to deliver timely business outcomes for use cases across the industrial, enterprise, and consumer segments.
    Today’s enterprise is being driven by disruptive competitive and human capital requirements to provide enterprise application access through not only desktops, but also mobile devices. To retrofit existing programs across all these devices using traditional programming methods is very costly and time consuming – often prohibitively so. In his session at @ThingsExpo, Jesse Shiah, CEO, President, and Co-Founder of AgilePoint Inc., discussed how you can create applications that run on all mobile devices as well as laptops and desktops using a visual drag-and-drop application – and eForms-buildi...
    Containers and microservices have become topics of intense interest throughout the cloud developer and enterprise IT communities. Accordingly, attendees at the upcoming 16th Cloud Expo at the Javits Center in New York June 9-11 will find fresh new content in a new track called PaaS | Containers & Microservices Containers are not being considered for the first time by the cloud community, but a current era of re-consideration has pushed them to the top of the cloud agenda. With the launch of Docker's initial release in March of 2013, interest was revved up several notches. Then late last...
    SYS-CON Events announced today that Dyn, the worldwide leader in Internet Performance, will exhibit at SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. Dyn is a cloud-based Internet Performance company. Dyn helps companies monitor, control, and optimize online infrastructure for an exceptional end-user experience. Through a world-class network and unrivaled, objective intelligence into Internet conditions, Dyn ensures traffic gets delivered faster, safer, and more reliably than ever.
    CommVault has announced that top industry technology visionaries have joined its leadership team. The addition of leaders from companies such as Oracle, SAP, Microsoft, Cisco, PwC and EMC signals the continuation of CommVault Next, the company's business transformation for sales, go-to-market strategies, pricing and packaging and technology innovation. The company also announced that it had realigned its structure to create business units to more directly match how customers evaluate, deploy, operate, and purchase technology.
    In their session at @ThingsExpo, Shyam Varan Nath, Principal Architect at GE, and Ibrahim Gokcen, who leads GE's advanced IoT analytics, focused on the Internet of Things / Industrial Internet and how to make it operational for business end-users. Learn about the challenges posed by machine and sensor data and how to marry it with enterprise data. They also discussed the tips and tricks to provide the Industrial Internet as an end-user consumable service using Big Data Analytics and Industrial Cloud.
    The explosion of connected devices / sensors is creating an ever-expanding set of new and valuable data. In parallel the emerging capability of Big Data technologies to store, access, analyze, and react to this data is producing changes in business models under the umbrella of the Internet of Things (IoT). In particular within the Insurance industry, IoT appears positioned to enable deep changes by altering relationships between insurers, distributors, and the insured. In his session at @ThingsExpo, Michael Sick, a Senior Manager and Big Data Architect within Ernst and Young's Financial Servi...
    Performance is the intersection of power, agility, control, and choice. If you value performance, and more specifically consistent performance, you need to look beyond simple virtualized compute. Many factors need to be considered to create a truly performant environment. In his General Session at 15th Cloud Expo, Harold Hannon, Sr. Software Architect at SoftLayer, discussed how to take advantage of a multitude of compute options and platform features to make cloud the cornerstone of your online presence.
    Almost everyone sees the potential of Internet of Things but how can businesses truly unlock that potential. The key will be in the ability to discover business insight in the midst of an ocean of Big Data generated from billions of embedded devices via Systems of Discover. Businesses will also need to ensure that they can sustain that insight by leveraging the cloud for global reach, scale and elasticity.
    IoT is still a vague buzzword for many people. In his session at @ThingsExpo, Mike Kavis, Vice President & Principal Cloud Architect at Cloud Technology Partners, discussed the business value of IoT that goes far beyond the general public's perception that IoT is all about wearables and home consumer services. He also discussed how IoT is perceived by investors and how venture capitalist access this space. Other topics discussed were barriers to success, what is new, what is old, and what the future may hold. Mike Kavis is Vice President & Principal Cloud Architect at Cloud Technology Pa...