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• Recreating OMS instances in a HA environment when instances on all nodes are lost

  - by rnigam

  Oracle highly recommends deploying EM in a HA environment. The best practices for HA deployments, backup and housekeeping of your Enterprise Manager environment are documented in the Oracle Enterprise Manager Advanced Configuration Guide. It is imperative that there is a good disaster recovery plan in place for your EM deployment. In this post I want to talk about a customer who failed to do the correct planning and housekeeping for EM and landed in a situation where we the all the OMSes were nearly blown away had we not jumped to help. We recently hit an issue at a customer site where we had a two node OMS setup of the Enterprise Manager and a RAC Database being used as the EM repository. An accidental delete of the OMS oracle home left us with a single node deployment. While we were trying to figure out a possible path to recover the first node, the second node was rebooted under a maintenance window. What followed was a complete site outage as the Admin and managed servers would not start on either of the nodes. In my situation there were - No backups of the Oracle Homes from any node - No OMS Configuration snapshots (created using the “emctl exportconfig oms” command) and the instance home was completely lost on node 1 which also had the Admin Server  We did however have: - A copy of the emkey.ora that I found under the OMS_ORACLE_HOME/ of the second node (NOTE: it is a bad practice to have your emkey present under the OMS Oracle home directory on the same server as the OMS. The backup of the emkey should be maintained on some other server. In this case however it was a savior in my situation since there were no backups - The oms oracle home on the second node but missing a number of files and had a number of changes done to the files in the home. There were a number of attempts to start the server by modifying various files based on the Weblogic server logs to have atleast node up and running but all of them failed. Here is how you can recover from this scenario: Follow these steps: STEP 1: Check status of emkey.ora Check whether the emkey exists is present in the EM repository or not. Run the following command: $OMS_ORACLE_HOME/bin/emctl status emkey If the output is something like this below then you are good to go and the key is present in the repository ./emctl status emkey Oracle Enterprise Manager 11g Release 1 Grid Control Copyright (c) 1996, 2010 Oracle Corporation. All rights reserved. Enter Enterprise Manager Root (SYSMAN) Password : The EMKey is configured properly. Here are the messages that you might see as the emctl status emkey output depending upon whether the EM Admin Server is up and if the key is configured properly: Case1:  AdminServer is up, emkey is proper in CredStore & not in repos. This is same as the output of the command shown above:The EMKey is configured properly Case 2: AdminServer is up, emkey is proper in CredStore & exists in repos:The EMKey is configured properly, but is not secure. Secure the EMKey by running "emctl config emkey -remove_from_repos".Case 3: AdminServer is down or emkey is corrupted in CredStore) & (emkey exists in repos): The EMKey exists in the Management Repository, but is not configured properly or is corrupted in the credential store.Configure the EMKey by running "emctl config emkey -copy_to_credstore".Case 4: (AdminServer is down or emkey is corrupted in CredStore) & (emkey does not exist in repos): The EMKey is not configured properly or is corrupted in the credential store and does not exist in the Management Repository. To correct the problem:1) Get the backed up emkey.ora file.2) Configure the emkey by running "emctl config emkey -copy_to_credstore_from_file". If not the key was not secured properly, we will have to be put in the repository before proceeding. Look at the next step 2 for doing this There may be cases (like mine) where running emctl may give errors like the following: $OMS_ORACLE_HOME/bin/emctl status emkey Exception in thread “Main Thread” java.lang.NoClassDefFoundError: oracle/security/pki/OracleWallet At oracle.sysman.emctl.config.oms.EMKeyCmds.main (EMKeyCmds.java:658) Just move to the next step to put the key back in the repository STEP 2: Put emkey.ora back in the repository Skip this step if your emkey.ora is present in the repository. If not, you need to put the key back in the repository See if you can run the following command (with sample output): $OMS_ORACLE_HOME/bin/emctl config emkey –copy_to_repos Oracle Enterprise Manager 11g Release 1 Grid Control Copyright (c) 1996, 2010 Oracle Corporation. All rights reserved. The EMKey has been copied to the Management Repository. This operation will cause the EMKey to become unsecure. After the required operation has been completed, secure the EMKey by running "emctl config emkey -remove_from_repos". Typically the key is present under $OMS_ORACLE_HOME/sysman/config directory before being removed after the install as a best practice. If you hit any errors while running emctl commands like the one mentioned in step 1, jump to step 3 and we will take care of the emkey.ora in Step 5 STEP 3: Get the port information Check for the existing port information in the emd.properties file under EM_INSTANCE_DIRECTORY (typically gc_inst directory right above the Middleware home where you have deployed em. For eg. /u01/app/oracle/product/gc_inst in case your oms home is /u01/app/oracle/product/Middleware/oms11g) In my case I got the information from the emgc.properties present in the gc_inst on the second node. If you can run emctl you may want to try the following command as well $OMS_ORACLE_HOME/bin/emctl status oms –details Note this information as this will be used in the next step STEP 4: Perform cleanup on Node 1 Note the oracle home of the Weblogic and OMS, get the list of applied patches in the homes (using opatch lsinventory command), take a backup copy of the home just in case we need it and then de-install/remove oracle homes, update inventory and cleanup processes on the first node STEP 5: Perform Software Only Installation of OMS on Node 1 Perform Weblogic 10.3.2 installation exactly under the same location as present in the earlier installation. Perform software only installation of the OMS using the following command. This will not run any configuration assistants and bypass all user interface validations runInstaller –noconfig -validationaswarnings Select the “Additional OMS” option while performing the installation. Provide the same path for OMS and Instance directories like the previous installation Use the port information collected in Step 3 while performing the installation. Once the installation is complete run the allroot.sh script to complete the binary deployment STEP 6: Apply one-off patches At this point you can apply any patches to the OMS Oracle Home previously. You only need to run opatch to install the patch in the home and not required to run the SQLs STEP 7: Copy EM key This step is only required if you were not able to use emctl command to put the emkey back into the EM repository in STEP 2 Copy the emkey.ora file of the old installation you have under $OMS_ORACLE_HOME/sysman/config directory of the newly installed OMS STEP 8: Configure Grid Control Domain Run the following command to configure the EM domain and OMS. Note that you need to use a different GC Domain name than what you used earlier. For example I have used GCDOMAIN11 as the new domain name when my previous domain name was GCDOMAIN $OMS_ORACLE_HOME/bin/omsca new –AS_USERNAME weblogic –EM_DOMAIN_NAME GCDOMAIN11 –NM_USER nodemanager -nostart This command as shown below will prompt for a number of inputs like Admin Server hostname, port, password, etc. Verify if the defaults shown are correct by pressing enter or provide a new value STEP 9: Run Add-ON Configuration Assistant After this step run the following add-on configuration assistant. This was used in my case to configure the virtualization add-on $OMS_ORACLE_HOME/addonca -oui -omsonly -name vt -install gc STEP 10: Start the OMS Now start the OMS using $OMS_ORACLE_HOME/bin/emctl start oms In a multi-node setup like mine you would either have a software load balancer or DNS round robin (using a virtual host name that resolves to one of multiple OMS hostnames) being used for load balancing. Secure the OMS against the SLB or DNS virtual hostname using the following $ OMS_HOME/bin/emctl secure oms -host slb.example.com -secure_port 1159 -slb_port 1159 -slb_console_port 443 STEP 11: Configure the Agent From the $AGENT_ORACLE_HOME/bin run the ./agentca –f At this point you should have your OMS on node 1 fully re-covered. Clean up node 2 and use the normal Additional OMS installation process documented in the official installation guide to add the additional OMS on node 2 Summary It took us nearly a little over two days to completely recover the environment with some other non-EM related issues that hit us along the way as well. In the end a situation like this could have been completely avoided had the proper housekeeping and backup of the Enterprise Manager Deployment been done in the first place. This is going to a topic that we cover in the next post. In the meantime please do refer to the Oracle Enterprise Manager Advanced Configuration Guide for planning your EM installation, backup and housekeeping procedures. This can be found here: http://download.oracle.com/docs/cd/E11857_01/index.htm Thanks This post would not have been possible without Raj Aggarwal, Prasad Chebrolu and Ravikumar Basa who helped to recover the environment and provided all the support we needed

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• Following the Thread in OSB

  - by Antony Reynolds

  Threading in OSB The Scenario I recently led an OSB POC where we needed to get high throughput from an OSB pipeline that had the following logic: 1. Receive Request 2. Send Request to External System 3. If Response has a particular value   3.1 Modify Request   3.2 Resend Request to External System 4. Send Response back to Requestor All looks very straightforward and no nasty wrinkles along the way.  The flow was implemented in OSB as follows (see diagram for more details): Proxy Service to Receive Request and Send Response Request Pipeline   Copies Original Request for use in step 3 Route Node   Sends Request to External System exposed as a Business Service Response Pipeline   Checks Response to Check If Request Needs to Be Resubmitted Modify Request Callout to External System (same Business Service as Route Node) The Proxy and the Business Service were each assigned their own Work Manager, effectively giving each of them their own thread pool. The Surprise Imagine our surprise when, on stressing the system we saw it lock up, with large numbers of blocked threads.  The reason for the lock up is due to some subtleties in the OSB thread model which is the topic of this post.   Basic Thread Model OSB goes to great lengths to avoid holding on to threads.  Lets start by looking at how how OSB deals with a simple request/response routing to a business service in a route node. Most Business Services are implemented by OSB in two parts.  The first part uses the request thread to send the request to the target.  In the diagram this is represented by the thread T1.  After sending the request to the target (the Business Service in our diagram) the request thread is released back to whatever pool it came from.  A multiplexor (muxer) is used to wait for the response.  When the response is received the muxer hands off the response to a new thread that is used to execute the response pipeline, this is represented in the diagram by T2. OSB allows you to assign different Work Managers and hence different thread pools to each Proxy Service and Business Service.  In out example we have the “Proxy Service Work Manager” assigned to the Proxy Service and the “Business Service Work Manager” assigned to the Business Service.  Note that the Business Service Work Manager is only used to assign the thread to process the response, it is never used to process the request. This architecture means that while waiting for a response from a business service there are no threads in use, which makes for better scalability in terms of thread usage. First Wrinkle Note that if the Proxy and the Business Service both use the same Work Manager then there is potential for starvation.  For example: Request Pipeline makes a blocking callout, say to perform a database read. Business Service response tries to allocate a thread from thread pool but all threads are blocked in the database read. New requests arrive and contend with responses arriving for the available threads. Similar problems can occur if the response pipeline blocks for some reason, maybe a database update for example. Solution The solution to this is to make sure that the Proxy and Business Service use different Work Managers so that they do not contend with each other for threads. Do Nothing Route Thread Model So what happens if there is no route node?  In this case OSB just echoes the Request message as a Response message, but what happens to the threads?  OSB still uses a separate thread for the response, but in this case the Work Manager used is the Default Work Manager. So this is really a special case of the Basic Thread Model discussed above, except that the response pipeline will always execute on the Default Work Manager.   Proxy Chaining Thread Model So what happens when the route node is actually calling a Proxy Service rather than a Business Service, does the second Proxy Service use its own Thread or does it re-use the thread of the original Request Pipeline? Well as you can see from the diagram when a route node calls another proxy service then the original Work Manager is used for both request pipelines.  Similarly the response pipeline uses the Work Manager associated with the ultimate Business Service invoked via a Route Node.  This actually fits in with the earlier description I gave about Business Services and by extension Route Nodes they “… uses the request thread to send the request to the target”. Call Out Threading Model So what happens when you make a Service Callout to a Business Service from within a pipeline.  The documentation says that “The pipeline processor will block the thread until the response arrives asynchronously” when using a Service Callout.  What this means is that the target Business Service is called using the pipeline thread but the response is also handled by the pipeline thread.  This implies that the pipeline thread blocks waiting for a response.  It is the handling of this response that behaves in an unexpected way. When a Business Service is called via a Service Callout, the calling thread is suspended after sending the request, but unlike the Route Node case the thread is not released, it waits for the response.  The muxer uses the Business Service Work Manager to allocate a thread to process the response, but in this case processing the response means getting the response and notifying the blocked pipeline thread that the response is available.  The original pipeline thread can then continue to process the response. Second Wrinkle This leads to an unfortunate wrinkle.  If the Business Service is using the same Work Manager as the Pipeline then it is possible for starvation or a deadlock to occur.  The scenario is as follows: Pipeline makes a Callout and the thread is suspended but still allocated Multiple Pipeline instances using the same Work Manager are in this state (common for a system under load) Response comes back but all Work Manager threads are allocated to blocked pipelines. Response cannot be processed and so pipeline threads never unblock – deadlock! Solution The solution to this is to make sure that any Business Services used by a Callout in a pipeline use a different Work Manager to the pipeline itself. The Solution to My Problem Looking back at my original workflow we see that the same Business Service is called twice, once in a Routing Node and once in a Response Pipeline Callout.  This was what was causing my problem because the response pipeline was using the Business Service Work Manager, but the Service Callout wanted to use the same Work Manager to handle the responses and so eventually my Response Pipeline hogged all the available threads so no responses could be processed. The solution was to create a second Business Service pointing to the same location as the original Business Service, the only difference was to assign a different Work Manager to this Business Service.  This ensured that when the Service Callout completed there were always threads available to process the response because the response processing from the Service Callout had its own dedicated Work Manager. Summary Request Pipeline Executes on Proxy Work Manager (WM) Thread so limited by setting of that WM.  If no WM specified then uses WLS default WM. Route Node Request sent using Proxy WM Thread Proxy WM Thread is released before getting response Muxer is used to handle response Muxer hands off response to Business Service (BS) WM Response Pipeline Executes on Routed Business Service WM Thread so limited by setting of that WM.  If no WM specified then uses WLS default WM. No Route Node (Echo functionality) Proxy WM thread released New thread from the default WM used for response pipeline Service Callout Request sent using proxy pipeline thread Proxy thread is suspended (not released) until the response comes back Notification of response handled by BS WM thread so limited by setting of that WM.  If no WM specified then uses WLS default WM. Note this is a very short lived use of the thread After notification by callout BS WM thread that thread is released and execution continues on the original pipeline thread. Route/Callout to Proxy Service Request Pipeline of callee executes on requestor thread Response Pipeline of caller executes on response thread of requested proxy Throttling Request message may be queued if limit reached. Requesting thread is released (route node) or suspended (callout) So what this means is that you may get deadlocks caused by thread starvation if you use the same thread pool for the business service in a route node and the business service in a callout from the response pipeline because the callout will need a notification thread from the same thread pool as the response pipeline.  This was the problem we were having. You get a similar problem if you use the same work manager for the proxy request pipeline and a business service callout from that request pipeline. It also means you may want to have different work managers for the proxy and business service in the route node. Basically you need to think carefully about how threading impacts your proxy services. References Thanks to Jay Kasi, Gerald Nunn and Deb Ayers for helping to explain this to me.  Any errors are my own and not theirs.  Also thanks to my colleagues Milind Pandit and Prasad Bopardikar who travelled this road with me. OSB Thread Model Great Blog Post on Thread Usage in OSB

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• Ajax, Lizard Brain Web Design, JSF, Struts, JavaScript, Mobile Web, Flash, jQuery, GWT, Harmony at I

  - by Kim Won

  Great Indian Developer Summit 2010 – India's Biggest Polyglot Conference and Workshops for IT Software Professionals Bangalore, April 9, 2010: The GIDS.Web Conference and Workshops has announced the complete program of over 30 sessions on how browser and rich web technologies such as AJAX, DHTML, Mashups, Web 2.0, Enterprise 2.0 technologies, and Rich UI technologies are making money and gaining market-share for some of the leading businesses in the world. The GIDS.Web track at Great Indian Developer Summit takes place 21 and 23 April 2010, at the Indian Institute of Science in Bangalore. As one of the longest running independent developer conferences in India, GIDS.Web at the Great Indian Developer Summit 2010 is uniquely positioned to provide a blend of practical, pragmatic and immediately applicable knowledge and a glimpse of the future of technology. During 21 and 23 April 2010, GIDS.Web offers a multi-track conference, workshops, expo show floor, and networking opportunities. The first keynote at GIDS.Web is led by the leading Java EE and Ajax developer, speaker, and author Marty Hall. The best of India's Java and RIA programmers have learnt the subject from Marty's seminal books Core Servlets and JavaServer Pages (first and second editions), More Servlets and JavaServer Pages, and Core Web Programming (first and second editions) from Prentice Hall and Sun Microsystems Press. Marty's keynote address is a comparison of approaches to building rich Internet applications with Ajax. Marty says Ajax development is difficult, and there are several fundamentally different strategies to building Ajaxified Web applications. The keynote address will survey the three most important of these approaches: using an Ajax-enabled JavaScript library such as jQuery, Prototype, Scriptaculous, Dojo, or Ext/JS; using a Web framework such as JSF 2.0 or Struts 2 that has integrated Ajax support; using the Google Web Toolkit (GWT) to build "pure Java" Ajax applications. The talk will compare and contrast these three approaches, discussing the types of applications that fit best for each option. Over the course of the summit Marty will conduct several more sessions on "Choosing an Ajax/JavaScript Toolkit: A Comparison of the Most Popular JavaScript Libraries", "Pure Java Ajax: An Overview of GWT 2.0", "Integrated Ajax Support in JSF 2.0" and "Ajax Support in the Prototype JavaScript Library". The second keynote by the head of Adobe's Flash initiative in India, Ramesh Srinivasaraghavan, explores the state of art in web application development and identify trends that could transform the way we create and use web applications. The talk explains how the Adobe Flash Platform has fuelled this revolution with an integrated set of technologies for delivering the most compelling applications, content and video to the widest possible audience. The Director of Forum Nokia will explain how cloud computing coupled with mobile applications enable consumers to have access to powerful services and improved user experiences never before thought possible. IEEE's 2010 President-Elect Sorel Reisman's afternoon address steps to improve the IT profession in India. Featured talks at GID.Web also include: Web 2.0 Checklist - Deconstructing Modern Websites, Scott Davis Choosing an Ajax/JavaScript Toolkit: Comparison of Popular JavaScript Libraries, Marty Hall Lizard Brain Web Design, Scott Davis Effective Design Processes and Resources for Mobile Web Development, Arabella David NoSQL: The Shift to a Non-relational World, Nosh Petigara Open Source Web Debugging Tools, Matthew McCullough Building Line of Business Applications with Silverlight 4.0, Stephen Forte Hadoop - Divide and Conquer, Matthew McCullough Adobe Flash Catalyst for Agile Interaction Design, Harish Sivaramakrishnan Using jQuery and AJAX to Build Front-ends for ASP.NET and ASP.NET MVC, Pandurang Nayak First Steps to IT Heaven Through the Cloud. Part II: .WEB, Simone Brunozzi Building Rich Internet Applications with SL RIA Web Services, Pandurang Nayak Enriching Cloud Applications with Adobe Flash Platform, Ramesh Srinivasaraghavan Payments for the Web.future, Khurram Khan and Praveen Alavilli Longevity of Scalable Systems, Nishad Kamat Transform yourself into a Mobile App Developer Using Web Run Time, Balagopal K S Developing Multi Screen Applications on Adobe Flash Platform, Hemanth Sharma Why Harmony and For Whom?, Himanshu Goyal IIS Hosting Solution for ASP.net and PHP Web Sites, Nahas Mohammed Building Pluggable Web applications using Django, Lakshman Prasad Workshop: The 180-min AJAX and JSON Spike Class, Scott Davis Workshop: Essence of Functional Programming, Venkat Subramaniam Workshop: Agile Development, Tools, and Teams and Scrum Certification, Stephen Forte Workshop: PHP + Adobe Flex = Killer RIA, Shyamprasad P Workshop: Cloud Computing Boot Camp on the Google App Engine, Matthew McCullough Workshop: Building Data Centric Applications using Adobe Flex and Java, Prashant Singh Workshop: Building Your First Amazon App, Simone Brunozzi Workshop: Windows Azure Deep Dive, Ramaprasanna Chellamuthu Workshop: Monetizing your Apps with PayPal X Payments Platform, Khurram Khan, Praveen Alavilli Workshop: User Expereince Evaluation Model Walkthrough, Sanna Häiväläinen Sponsors of Great Indian Developer Summit 2010 include: Platinum sponsors Microsoft, Oracle Forum Nokia and Adobe; Gold sponsors Intel and SAP; Silver sponsors Quest Software, PayPal, Telerik and AMT. About Great Indian Developer Summit Great Indian Developer Summit is the gold standard for India's software developer ecosystem for gaining exposure to and evaluating new projects, tools, services, platforms, languages, software and standards. Packed with premium knowledge, action plans and advise from been-there-done-it veterans, creators, and visionaries, the 2010 edition of Great Indian Developer Summit features focused sessions, case studies, workshops and power panels that will transform you into a force to reckon with. Featuring 3 co-located conferences: GIDS.NET, GIDS.Web, GIDS.Java and an exclusive day of in-depth tutorials - GIDS.Workshops, from 20 April to 24 April at the IISc campus in Bangalore. At GIDS you'll participate in hundreds of sessions encompassing the full range of Microsoft computing, Java, Agile, RIA, Rich Web, open source/standards, languages, frameworks and platforms, practical tutorials that deep dive into technical skill and best practices, inspirational keynote presentations, an Expo Hall featuring dozens of the latest projects and products activities, engaging networking events, and the interact with the best and brightest of speakers from around the world. For further information on GIDS 2010, please visit the summit on the web http://www.developersummit.com/ A Saltmarch Media Press Release E: [email protected] Ph: +91 80 4005 1000

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