# jts-distributed-crash-rec: JTS and distributed crash recovery

Author: Tom Jenkinson
Level: Advanced
Technologies: JTS, Crash Recovery
Summary: The `jts-distributed-crash-rec` quickstart uses JTS and Byteman to demonstrate distributed crash recovery across multiple application servers.
Prerequisites: jts
Target Product: WildFly
Source: https://github.com/wildfly/quickstart/

## What is it?

The `jts-distributed-crash-rec` quickstart demonstrates a distributed crash recovery across multiple application servers in WildFly Application Server.

Crash recovery is a key feature provided by an application server and ensures an application's data consistency, even in the presence of failure. Providing reliable crash recovery helps qualify the pedigree of an application server, distributed crash recovery even more so.

This quickstart uses the application components from the `jts` quickstart. It provides a Byteman rule to inject a halt into the application server at a crucial point in the phase2 commit of the transaction. Byteman is used solely to raise an artificial fault. An IDE could also provide this simulation, although it is more complex to use an IDE for this purpose.

Apart from that, this quickstart works the same as the `jts` quickstart and if the Byteman rule is left out, this quickstart is the JTS quickstart.

As an overview, the sequence of events to expect:

1. Configure and start two WildFly servers.
2. Build and deploy the two application components.
3. Open a web browser and attempt to invoice two customers as with the `jts` quickstart.
4. WildFly server 1 will run through a two-phase commit (2PC), preparing the resources in WildFly server 1 and WildFly server 2. WildFly server 1 will then crash before it can call commit.
5. The user is invited to inspect the content of the transaction objectstore.
6. WildFly server 1 should be restarted. It will then recover the "invoices" delivered to the MDBs, just as it does in the `jts` quickstart.

## System Requirements

The application this project produces is designed to be run on WildFly Application Server 11 or later.

All you need to build this project is Java 8.0 (Java SDK 1.8) or later and Maven 3.3.1 or later. See Configure Maven for WildFly 11 to make sure you are configured correctly for testing the quickstarts.

## Download and Configure Byteman

This quickstart uses Byteman to help demonstrate crash recovery. You can find more information about Byteman here: Configure Byteman for Use with the Quickstarts

Follow the instructions here to download and configure Byteman: Download and Configure Byteman

## Prerequisites

Developers should be familiar with the concepts introduced in the following quickstarts:

- cmt
- jts

IMPORTANT: This quickstart depends on the deployment of the `jts` quickstart for its test. Before running this quickstart, see the jts README file for details on how to deploy it.

You can verify the deployment of the `jts` quickstart by accessing the following URL: http://localhost:8080/jts-1/.

## Use of WILDFLY_HOME

In the following instructions, replace `WILDFLY_HOME` with the actual path to your WildFly installation. The installation path is described in detail here: Use of WILDFLY_HOME and JBOSS_HOME Variables.

## Test the Application

Note: This quickstart README file uses the following replaceable values. When you encounter these values in a README file, be sure to replace them with the actual path to the correct WildFly server.

    `WILDFLY_HOME` denotes the path to the original WildFly installation.
    `WILDFLY_HOME_1` denotes the path to the modified WildFly server 1 configuration.
    `WILDFLY_HOME_2` denotes the path to the modified WildFly server 2 configuration.

1. If you have not yet done so, configure the two application servers and deploy the `jts` quickstart. Follow the instructions in the jts README file.

2. Configure Byteman to halt WildFly server 1

   - Stop both WildFly servers.
   - Follow the instructions here to clear the transaction objectstore remaining from any previous tests: Clear the Transaction ObjectStore
   - The following 2 lines of text must be appended to the server configuration file for server 1 only using the instructions located here: Use Byteman to Halt the Application

     For Linux:

         JAVA_OPTS="-javaagent:/BYTEMAN_HOME/lib/byteman.jar=script:/QUICKSTART_HOME/jts-distributed-crash-rec/byteman-scripts/failAfterPrepare.btm ${JAVA_OPTS}"
         JAVA_OPTS="-Dorg.jboss.byteman.transform.all -Djboss.modules.system.pkgs=org.jboss.byteman -Dorg.jboss.byteman.verbose=true ${JAVA_OPTS}"

     For Windows:

         JAVA_OPTS=%JAVA_OPTS% -javaagent:C:BYTEMAN_HOME\lib\byteman.jar=script:C:\QUICKSTART_HOME\jts-distributed-crash-rec\byteman-scripts\failAfterPrepare.btm %JAVA_OPTS%
         JAVA_OPTS=%JAVA_OPTS% -Dorg.jboss.byteman.transform.all -Djboss.modules.system.pkgs=org.jboss.byteman -Dorg.jboss.byteman.verbose=true

3. Start both of the WildFly servers

If you are using Linux:

        Server 1: WILDFLY_HOME_1/bin/standalone.sh -c standalone-full.xml -Djboss.tx.node.id=UNIQUE_NODE_ID_1
        Server 2: WILDFLY_HOME_2/bin/standalone.sh -c standalone-full.xml -Djboss.tx.node.id=UNIQUE_NODE_ID_2 -Djboss.socket.binding.port-offset=100

If you are using Windows

        Server 1: WILDFLY_HOME_1\bin\standalone.bat -c standalone-full.xml -Djboss.tx.node.id=UNIQUE_NODE_ID_1
        Server 2: WILDFLY_HOME_2\bin\standalone.bat -c standalone-full.xml -Djboss.tx.node.id=UNIQUE_NODE_ID_2 -Djboss.socket.binding.port-offset=100

1. Access the application at the following URL: http://localhost:8080/jts-1/

   - When you enter a name and click to "add" that customer, you will see the following in the application server 1 console:

         INFO  [org.jboss.ejb.client] (default task-2) JBoss EJB Client version 2.1.4.Final-redhat-1
         INFO  [stdout] (default task-2) Rule.execute called for Fail 2PC after prepare_0
         INFO  [stdout] (default task-2) HelperManager.install for helper class org.jboss.byteman.rule.helper.Helper
         INFO  [stdout] (default task-2) calling activated() for helper class org.jboss.byteman.rule.helper.Helper
         INFO  [stdout] (default task-2) Default helper activated
         INFO  [stdout] (default task-2) calling installed(Fail 2PC after prepare) for helper classorg.jboss.byteman.rule.helper.Helper
         INFO  [stdout] (default task-2) Installed rule using default helper : Fail 2PC after prepare
         INFO  [stdout] (default task-2) Fail 2PC after prepare execute
         INFO  [stdout] (default task-2) rule.debug{Fail 2PC after prepare} : Prepare completed
         INFO  [stdout] (default task-2) rule.debug{Fail 2PC after prepare} : !!!killing JVM!!!

2. At this point, Byteman halts or crashes server 1. You should be able to view the contents of the object store for this server by typing the following in the terminal for server 1. Be sure to replace `WILDFLY_HOME_1` with the path to the first server.

       tree WILDFLY_HOME_1/standalone/data/tx-object-store

   This should display:

       WILDFLY_HOME_1/standalone/data/tx-object-store
        -- ShadowNoFileLockStore
            -- defaultStore
               |-- CosTransactions
               |   -- XAResourceRecord
               |       -- 0_ffffc0a8013c_38e104bd_4f280cdb_1d
               |-- Recovery
               |   -- FactoryContact
               |       |-- 0_ffffc0a8013c_38e104bd_4f280cdb_17
               |       |-- 0_ffffc0a8013c_-671009a_4f280e7e_17
               |       -- 0_ffffc0a8013c_6d5d82b5_4f280a16_f
               |-- RecoveryCoordinator
               |   -- 0_ffff52e38d0c_c91_4140398c_0
                -- StateManager
                   -- BasicAction
                       -- TwoPhaseCoordinator
                           -- ArjunaTransactionImple
                               -- 0_ffffc0a8013c_38e104bd_4f280cdb_19

   View the contents of the object store for the second server by typing the following in the terminal for server 2. Be sure to replace `WILDFLY_HOME_2` with the path to the second server.

        tree WILDFLY_HOME_2/standalone/data/tx-object-store

   This should display:

       WILDFLY_HOME_2/standalone/data/tx-object-store
       -- ShadowNoFileLockStore
           -- defaultStore
               |-- CosTransactions
               |   -- XAResourceRecord
               |       -- 0_ffffc0a8013c_-2eb1158b_4f280ce3_1e
               |-- Recovery
               |   -- FactoryContact
               |       |-- 0_ffffc0a8013c_-2eb1158b_4f280ce3_18
               |       -- 0_ffffc0a8013c_4f6459f0_4f280a24_f
               |-- RecoveryCoordinator
               |   -- 0_ffff52e38d0c_c91_4140398c_0
                -- StateManager
                   -- BasicAction
                       -- TwoPhaseCoordinator
                           -- ArjunaTransactionImple
                               -- ServerTransaction
                                   -- 0_ffffc0a8013c_-2eb1158b_4f280ce3_1a

3. Disable the Byteman script by restoring the backup configuration file for server 1.

4. Follow the steps above to restart server 1 and wait for recovery to complete.

   IMPORTANT: By default, the recovery process checks the transactional state every two minutes, therefore it can take a while for recovery to happen. Also recovery for each server will take place at its own recovery interval. * You will know when recovery is complete for server 2 as you will see the following in application-server-2 console:

           INFO  [org.jboss.ejb.client] (RequestProcessor-10) JBoss EJB Client version 2.1.2.Final
           INFO  [class org.jboss.as.quickstarts.cmt.jts.mdb.HelloWorldMDB] (Thread-3 (group:ActiveMQ-client-global-threads-649946595)) Received Message: Created invoice for customer named: Tom

   - NOTE: You will also get several stack traces in WildFly server 1 console during recovery, these are to be expected as not all resources are available at all stages of recovery.

         WARN  [com.arjuna.ats.jts] (Periodic Recovery) ARJUNA022223: ExtendedResourceRecord.topLevelCommit caught exception: org.omg.CORBA.OBJECT_NOT_EXIST: ----------BEGIN server-side stack trace----------
         org.omg.CORBA.OBJECT_NOT_EXIST:   vmcid: SUN  minor code: 1004  completed: No
             at com.sun.corba.se.impl.logging.POASystemException.nullServant(POASystemException.java:2040)
             at com.sun.corba.se.impl.logging.POASystemException.nullServant(POASystemException.java:2062)
             at com.sun.corba.se.impl.oa.poa.POAPolicyMediatorImpl_R_AOM.internalGetServant(POAPolicyMediatorImpl_R_AOM.java:68)
             at com.sun.corba.se.impl.oa.poa.POAPolicyMediatorBase.getInvocationServant(POAPolicyMediatorBase.java:121)
             at com.sun.corba.se.impl.oa.poa.POAImpl.getInvocationServant(POAImpl.java:1634)
             at com.sun.corba.se.impl.protocol.CorbaServerRequestDispatcherImpl.getServant(CorbaServerRequestDispatcherImpl.java:326)
             at com.sun.corba.se.impl.protocol.CorbaServerRequestDispatcherImpl.getServantWithPI(CorbaServerRequestDispatcherImpl.java:360)
             at com.sun.corba.se.impl.protocol.CorbaServerRequestDispatcherImpl.dispatch(CorbaServerRequestDispatcherImpl.java:202)
             at com.sun.corba.se.impl.protocol.CorbaMessageMediatorImpl.handleRequestRequest(CorbaMessageMediatorImpl.java:1700)
             at com.sun.corba.se.impl.protocol.SharedCDRClientRequestDispatcherImpl.marshalingComplete(SharedCDRClientRequestDispatcherImpl.java:180)
             at com.sun.corba.se.impl.protocol.CorbaClientDelegateImpl.invoke(CorbaClientDelegateImpl.java:148)
             at org.omg.CORBA.portable.ObjectImpl._invoke(ObjectImpl.java:475)
             at com.arjuna.ArjunaOTS._ArjunaSubtranAwareResourceStub.commit(_ArjunaSubtranAwareResourceStub.java:124)
             at com.arjuna.ats.internal.jts.resources.ExtendedResourceRecord.topLevelCommit(ExtendedResourceRecord.java:502)
           ...

   - The easiest way to check when WildFly server 1 is recovered is to look in the object store and check that all the records are now cleaned up. The records that should be cleared are the ones in the defaultStore/CosTransactions/XAResourceRecord and defaultStore/StateManager/BasicAction/TwoPhaseCoordinator/ArjunaTransactionImple.
   - Records will remain in defaultStore/Recovery/FactoryContact and defaultStore/RecoveryCoordinator for server 1 and that is to be expected. Run:

         tree WILDFLY_HOME_1/standalone/data/tx-object-store

   You should see this output:

           WILDFLY_HOME_1/standalone/data/tx-object-store
           -- ShadowNoFileLockStore
               -- defaultStore
                   |-- CosTransactions
                   |   -- XAResourceRecord
                   |-- Recovery
                   |   -- FactoryContact
                   |       |-- 0_ffffc0a8013c_38e104bd_4f280cdb_17
                   |       |-- 0_ffffc0a8013c_-671009a_4f280e7e_17
                   |       -- 0_ffffc0a8013c_6d5d82b5_4f280a16_f
                   |-- RecoveryCoordinator
                   |   -- 0_ffff52e38d0c_c91_4140398c_0
                    -- StateManager
                       -- BasicAction
                           -- TwoPhaseCoordinator
                             -- ArjunaTransactionImple

   View the contents of the object store for the second server by typing the following in the terminal for server 2. Be sure to replace `WILDFLY_HOME_2` with the path to the second server.

           tree WILDFLY_HOME_2/standalone/data/tx-object-store

   This should display:

           WILDFLY_HOME_2/standalone/data/tx-object-store
           -- ShadowNoFileLockStore
               -- defaultStore
                   |-- CosTransactions
                   |   -- XAResourceRecord
                   |-- Recovery
                   |   -- FactoryContact
                   |       |-- 0_ffffc0a8013c_-2eb1158b_4f280ce3_18
                   |       -- 0_ffffc0a8013c_4f6459f0_4f280a24_f
                   |-- RecoveryCoordinator
                   |   -- 0_ffff52e38d0c_c91_4140398c_0
                   -- StateManager
                       -- BasicAction
                           -- TwoPhaseCoordinator
                               -- ArjunaTransactionImple
                                   -- ServerTransaction

5. After recovery is complete, access the application URL http://localhost:8080/jts-1/customers.jsf. The user you created should now appear in the list.

6. Do NOT forget to Disable the Byteman script by restoring the backup server configuration file. The Byteman rule must be removed to ensure that your application server will be able to commit 2PC transactions!