Abstract: Multiple application server instances can be arranged in a cluster that implements a distributed EJB timer system. A high availability database can store EJB timer info. The EJB timer jobs can be distributed among the application server instances of the cluster that implement the distributed EJB timer system. In case of a failure of an application server instance, the EJB timer info can be used to reassign the EJB timer jobs associated with the failed application server instance.

Abstract: Servers in a network cluster can each store a copy of a data item in local cache, providing read access to these copies through read-only entity beans. The original data item in the database can be updated through a read/write entity bean one of the cluster servers. That cluster server has access to an invalidation target, which contains identification information relating to copies of the data item stored on servers in the cluster. Once the read/write bean updates the data item in the database, an invalidate request can be sent or multicast to all cluster members, or to any read-only bean or server contained in the invalidation target. Each server or read-only bean receiving the request knows to drop any copy of the data item in local cache, and can request a current copy of the data item from the database.

Abstract: A clustered enterprise distributed processing system. The distributed processing system includes a first and a second computer coupled to a communication medium. The first computer includes a virtual machine (JVM) and kernel software layer for transferring messages, including a remote virtual machine (RJVM). The second computer includes a JVM and a kernel software layer having a RJVM. Messages are passed from a RJVM to the JVM in one computer to the JVM and RJVM in the second computer. Messages may be forwarded through an intermediate server or rerouted after a network reconfiguration. Each computer includes a Smart stub having a replica handler, including a load balancing software component and a failover software component. Each computer includes a duplicated service naming tree for storing a pool of Smart stubs at a node.

Abstract: A system for managing a message store in a network includes an object acting as a message store. In one embodiment, the message store is for Java Message Service. A lead server is selected from several servers. The lead server uses a distributed consensus algorithm to select a host server. The selected host server hosts the message store, providing sole access to the message store. The other servers are notified of the new host by messaging. In one embodiment, servers can send messages to the message store on the host and pick up any messages from the message store.

Abstract: A session replication system provides real-time data replication without unnecessarily slowing down the user experience. A system in accordance with the present invention may utilize a primary server to serve requests from a network client, as well as a secondary server to replicate the session information. When a request is received on the session, an attempt may be made to serve the request on the primary server. If the primary is unable to receive or respond to the request, the request may be served on the secondary server or on a new primary server. If the secondary server receives the request, the secondary server may become the new primary server. If a new primary server is selected, the new primary may request the session information from the secondary server.

Abstract: A timer master can assign scheduled jobs to other application servers of a cluster. Leases for the timer master can be started in a lease table. The timer master can store job info for the scheduled jobs in a database. In case of a crash of the application server, another application server of the cluster can be assigned the time master and use the job information to assign scheduled jobs.

Abstract: A system for managing objects in a clustered network includes a file system containing at least one copy of a data object. The system can include several clustered servers in communication with the file system. A distributed consensus algorithm is used to select a host server. The selected host server can contain a copy of the data object, such as in local cache, providing access to the local copy to any other server in the cluster. Any change made to an item hosted by the host server can also be updated in the file system. If the host server becomes unable to host the object, a new host can be chosen using the distributed consensus algorithm. The other servers are then notified of the new host by multicast messaging.

Abstract: Data can be replicated over a network using a one or two phase method. For the one phase method, a master server containing an original copy of the data sends a version number for the current state of the data to each slave on the network so that each slave can request a delta from the master. The delta that is requested contains the data necessary to update the slave to the appropriate version of the data. For the two phase method, the master server sends a packet of information to each slave. The packet of information can be committed by the slaves if each slave is able to process the commit.

Abstract: A system and a method for scheduling disk writes for use with an application server, transactional system, or other server. The disk scheduler and method is independent of the underlying operating system and the disk hardware. This allows it to be used without porting to the various settings in which application server might be deployed. In some embodiments, a high-performance, transactional filestore is also provided to minimize the latency of small, synchronous writes to disk. The implementation uses a log-structured file system combined with disk scheduling. By relaxing the requirement that log records be physically contiguous, every modification to the disk can be scheduled.

Abstract: A method for managing objects in a clustered network includes a file system containing at least one copy of a data object. The method can involve several clustered servers in communication with the file system. A distributed consensus algorithm is used to select a host server. The selected host server can contain a copy of the data object, such as in local cache, providing access to the local copy to any other server in the cluster. Any change made to an item hosted by the host server can also be updated in the file system. If the host server becomes unable to host the object, a new host can be chosen using the distributed consensus algorithm. The other servers are then notified of the new host by multicast messaging.

Abstract: A system for managing a message store in a network includes an object acting as a message store. In one embodiment, the message store is for Java Message Service. A lead server is selected from several servers. The lead server uses a distributed consensus algorithm to select a host server. The selected host server hosts the message store, providing sole access to the message store. The other servers are notified of the new host by messaging. In one embodiment, servers can send messages to the message store on the host and pick up any messages from the message store.

Abstract: Concurrency can be maintained in cluster caching when processing an update request on network server that is storing a local copy of a data item. The request can be processed using the local copy of the data item. A predicated update request can be sent to a network database storing the data item, wherein the database can commit the update if the local copy is current with the data item. If the local copy is not current, the network server can request a new copy, process the request using the current copy, and try another predicated request. The process can continue until the update is committed to the database or aborted. Once committed, any other servers in the cluster can be notified that the data item has been updated. Those other servers can drop any local copy of the data item and can request an updated copy of the data item.

Abstract: A computer readable storage medium stores instructions for managing objects in a clustered network. Several clustered servers are in communication with a file system containing at least one copy of a data object. A distributed consensus algorithm is used to select a host server. The selected host server can contain a copy of the data object, such as in local cache, providing access to the local copy to any other server in the cluster. Any change made to an item hosted by the host server can also be updated in the file system. If the host server becomes unable to host the object, a new host can be chosen using the distributed consensus algorithm. The other servers are then notified of the new host by multicast messaging.

Abstract: A system for managing a JMS message store in a clustered network includes an object acting as a message store for Java Message Service (JMS). A lead server is selected from several clustered servers. The lead server uses a distributed consensus algorithm to select a host server, utilizing multicast messaging while executing rounds of the algorithm. The selected host server hosts the JMS message store, providing sole access to JMS. The other servers are notified of the new host by multicast messaging. All servers in the cluster can use JMS, but they must send messages to the message store on the host and pick up any messages from the message store.

Abstract: A session replication system provides real-time data replication without unnecessarily slowing down the user experience. A system in accordance with the present invention may utilize a primary server to serve requests from a network client, as well as a secondary server to replicate the session information. When a request is received on the session, an attempt may be made to serve the request on the primary server. If the primary is unable to receive or respond to the request, the request may be served on the secondary application server or on a new primary server. If the secondary server receives the request, the secondary server may become the new primary server. If a new primary server is selected, the new primary may request the session information from the secondary server.

Abstract: A system for managing objects in a clustered network includes a file system containing at least one copy of a data object. The system can include several clustered servers in communication with the file system. A distributed consensus algorithm is used to select a host server. The selected host server can contain a copy of the data object, such as in local cache, providing access to the local copy to any other server in the cluster. Any change made to an item hosted by the host server can also be updated in the file system. If the host server becomes unable to host the object, a new host can be chosen using the distributed consensus algorithm. The other servers are then notified of the new host by multicast messaging.

Abstract: Transactions are granted concurrent access to a data item through the use of an optimistic concurrency algorithm. Each transaction gets its own instance of the data item, such as in a cache or in an entity bean, such that it is not necessary to lock the data. The instances can come from the data or from other instances. When a transaction updates the data item, the optimistic concurrency algorithm ensures that the other instances are notified that the data item has been changed and that it is necessary to read a new instance, from the database or from an update instance.

Abstract: A timer master can assign scheduled jobs to other application servers of a cluster. Leases for the timer master can be started in a lease table. The timer master can store job info for the scheduled jobs in a database. In case of a crash of the application server, another application server of the cluster can be assigned the time master and use the job information to assign scheduled jobs.

Abstract: A system for managing objects in a clustered network includes a file system containing at least one copy of a data object. The system can include several clustered servers in communication with the file system. A distributed consensus algorithm is used to select a host server. The selected host server can contain a copy of the data object, such as in local cache, providing access to the local copy to any other server in the cluster. Any change made to an item hosted by the host server can also be updated in the file system. If the host server becomes unable to host the object, a new host can be chosen using the distributed consensus algorithm. The other servers are then notified of the new host by multicast messaging.

Abstract: Servers in a network cluster can each store a copy of a data item in local cache, providing read access to these copies through read-only entity beans. The original data item in the database can be updated through a read/write entity bean one of the cluster servers. That cluster server has access to an invalidation target, which contains identification information relating to copies of the data item stored on servers in the cluster. Once the read/write bean updates the data item in the database, an invalidate request can be sent or multicast to all cluster members, or to any read-only bean or server contained in the invalidation target. Each server or read-only bean receiving the request knows to drop any copy of the data item in local cache, and can request a current copy of the data item from the database.