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
    Major trends and emerging technologies – from virtual reality and IoT, to Big Data and algorithms – are helping organizations innovate in the digital era. However, to create real business value, IT must think beyond the ‘what’ of digital transformation to the ‘how’ to harness emerging trends, innovation and disruption. Architecture is the key that underpins and ties all these efforts together. In the digital age, it’s important to invest in architecture, extend the enterprise footprint to the cl...
    Video experiences should be unique and exciting! But that doesn’t mean you need to patch all the pieces yourself. Users demand rich and engaging experiences and new ways to connect with you. But creating robust video applications at scale can be complicated, time-consuming and expensive. In his session at @ThingsExpo, Zohar Babin, Vice President of Platform, Ecosystem and Community at Kaltura, will discuss how VPaaS enables you to move fast, creating scalable video experiences that reach your...
    DevOps at Cloud Expo, taking place Nov 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 19th Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The widespread success of cloud computing is driving the DevOps revolution in enterprise IT. Now as never before, development teams must communicate and collaborate in a dynamic, 24/7/365 environment. There is no time to wait for long dev...
    In his keynote at 18th Cloud Expo, Andrew Keys, Co-Founder of ConsenSys Enterprise, provided an overview of the evolution of the Internet and the Database and the future of their combination – the Blockchain. Andrew Keys is Co-Founder of ConsenSys Enterprise. He comes to ConsenSys Enterprise with capital markets, technology and entrepreneurial experience. Previously, he worked for UBS investment bank in equities analysis. Later, he was responsible for the creation and distribution of life sett...
    SYS-CON Events announced today that SoftLayer, an IBM Company, has been named “Gold Sponsor” of SYS-CON's 18th Cloud Expo, which will take place on June 7-9, 2016, at the Javits Center in New York, New York. SoftLayer, an IBM Company, provides cloud infrastructure as a service from a growing number of data centers and network points of presence around the world. SoftLayer’s customers range from Web startups to global enterprises.
    SYS-CON Events announced today that Bsquare has been named “Silver Sponsor” of SYS-CON's @ThingsExpo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. For more than two decades, Bsquare has helped its customers extract business value from a broad array of physical assets by making them intelligent, connecting them, and using the data they generate to optimize business processes.
    SYS-CON Events announced today that ReadyTalk, a leading provider of online conferencing and webinar services, has been named Vendor Presentation Sponsor at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. ReadyTalk delivers audio and web conferencing services that inspire collaboration and enable the Future of Work for today’s increasingly digital and mobile workforce. By combining intuitive, innovative tec...
    Big Data has been changing the world. IoT fuels the further transformation recently. How are Big Data and IoT related? In his session at @BigDataExpo, Tony Shan, a renowned visionary and thought leader, will explore the interplay of Big Data and IoT. He will anatomize Big Data and IoT separately in terms of what, which, why, where, when, who, how and how much. He will then analyze the relationship between IoT and Big Data, specifically the drilldown of how the 4Vs of Big Data (Volume, Variety,...
    Cognitive Computing is becoming the foundation for a new generation of solutions that have the potential to transform business. Unlike traditional approaches to building solutions, a cognitive computing approach allows the data to help determine the way applications are designed. This contrasts with conventional software development that begins with defining logic based on the current way a business operates. In her session at 18th Cloud Expo, Judith S. Hurwitz, President and CEO of Hurwitz & ...
    WebRTC adoption has generated a wave of creative uses of communications and collaboration through websites, sales apps, customer care and business applications. As WebRTC has become more mainstream it has evolved to use cases beyond the original peer-to-peer case, which has led to a repeating requirement for interoperability with existing infrastructures. In his session at @ThingsExpo, Graham Holt, Executive Vice President of Daitan Group, will cover implementation examples that have enabled ea...
    The vision of a connected smart home is becoming reality with the application of integrated wireless technologies in devices and appliances. The use of standardized and TCP/IP networked wireless technologies in line-powered and battery operated sensors and controls has led to the adoption of radios in the 2.4GHz band, including Wi-Fi, BT/BLE and 802.15.4 applied ZigBee and Thread. This is driving the need for robust wireless coexistence for multiple radios to ensure throughput performance and th...
    Vidyo, Inc., has joined the Alliance for Open Media. The Alliance for Open Media is a non-profit organization working to define and develop media technologies that address the need for an open standard for video compression and delivery over the web. As a member of the Alliance, Vidyo will collaborate with industry leaders in pursuit of an open and royalty-free AOMedia Video codec, AV1. Vidyo’s contributions to the organization will bring to bear its long history of expertise in codec technolo...
    SYS-CON Events announced today that Commvault, a global leader in enterprise data protection and information management, has been named “Bronze Sponsor” of SYS-CON's 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Commvault is a leading provider of data protection and information management solutions, helping companies worldwide activate their data to drive more value and business insight and to transform moder...
    If you’re responsible for an application that depends on the data or functionality of various IoT endpoints – either sensors or devices – your brand reputation depends on the security, reliability, and compliance of its many integrated parts. If your application fails to deliver the expected business results, your customers and partners won't care if that failure stems from the code you developed or from a component that you integrated. What can you do to ensure that the endpoints work as expect...
    An IoT product’s log files speak volumes about what’s happening with your products in the field, pinpointing current and potential issues, and enabling you to predict failures and save millions of dollars in inventory. But until recently, no one knew how to listen. In his session at @ThingsExpo, Dan Gettens, Chief Research Officer at OnProcess, will discuss recent research by Massachusetts Institute of Technology and OnProcess Technology, where MIT created a new, breakthrough analytics model f...
    Technology vendors and analysts are eager to paint a rosy picture of how wonderful IoT is and why your deployment will be great with the use of their products and services. While it is easy to showcase successful IoT solutions, identifying IoT systems that missed the mark or failed can often provide more in the way of key lessons learned. In his session at @ThingsExpo, Peter Vanderminden, Principal Industry Analyst for IoT & Digital Supply Chain to Flatiron Strategies, will focus on how IoT de...
    Fact is, enterprises have significant legacy voice infrastructure that’s costly to replace with pure IP solutions. How can we bring this analog infrastructure into our shiny new cloud applications? There are proven methods to bind both legacy voice applications and traditional PSTN audio into cloud-based applications and services at a carrier scale. Some of the most successful implementations leverage WebRTC, WebSockets, SIP and other open source technologies. In his session at @ThingsExpo, Da...
    SYS-CON Events announced today that Roundee / LinearHub will exhibit at the WebRTC Summit at @ThingsExpo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. LinearHub provides Roundee Service, a smart platform for enterprise video conferencing with enhanced features such as automatic recording and transcription service. Slack users can integrate Roundee to their team via Slack’s App Directory, and '/roundee' command lets your video conference ...
    Digital transformation is too big and important for our future success to not understand the rules that apply to it. The first three rules for winning in this age of hyper-digital transformation are: Advantages in speed, analytics and operational tempos must be captured by implementing an optimized information logistics system (OILS) Real-time operational tempos (IT, people and business processes) must be achieved Businesses that can "analyze data and act and with speed" will dominate those t...
    Information technology is an industry that has always experienced change, and the dramatic change sweeping across the industry today could not be truthfully described as the first time we've seen such widespread change impacting customer investments. However, the rate of the change, and the potential outcomes from today's digital transformation has the distinct potential to separate the industry into two camps: Organizations that see the change coming, embrace it, and successful leverage it; and...