Abstract: A registration applet embedded in a registration page of a browser program allows a user to associate a user-specified group name with a plurality of UTRLs, HTTP POST or GET requests or other network service identifiers, such that the group name designates a category of information provided by corresponding network services. An access applet embedded in an access page of the browser allows a user to select one of several previously-registered group names, and an access mode for processing responses to service requests. A processor running the access applet automatically issues parallel requests to the network services associated with a selected group name in response to entry of a command by the user.

Abstract: The present invention relates to systems for sharing idle workstation computers that are connected together through a network and shared file system. More particularly, a user of a local host workstation may submit jobs for execution on remote workstations. The systems of the present invention select a remote host that is idle in accordance with a decentralized scheduling scheme and then continuously monitor the activity of the remote host on which the job is executing. If the system detects certain activity on the remote host by one of the remote host's primary users, the execution of the job is immediately suspended to prevent inconvenience to the primary users. The system also suspends job execution if the remote host's load average gets too high. Either way, the suspended job is migrated by selecting another idle remote workstation to resume execution of the suspended job (from the point in time at which the last checkpoint occurred).

Abstract: Techniques for fault-tolerant computing which do not require fault-tolerant hardware or a fault-tolerant operating system. The techniques employ a monitor daemon which is implemented as one or more user processes and a fault-tolerant library which can be bound into application programs. A user process which is executing on ordinary hardware under an ordinary operating system is made fault tolerant by registering it with the monitor daemon. The degree of fault tolerance can be controlled by means of the fault-tolerant library. Included in the fault-tolerant library is a function which defines portions of a user process's memory as critical memory, a function which copies the critical memory to persistent storage, and a function which restores the critical memory from persistent storage. The monitor daemon monitors fault-tolerant processes, and when such a process hangs or crashes, the daemon restarts it.

Abstract: Software rejuvenation techniques which improve reliability of a software system by stopping execution of the system and restarting the execution with "clean" state. The rejuvenation techniques are generally available to applications executing in a computer system. The techniques are implemented using a daemon process which observes applications registered with it and restarts them if they crash or hang and a process like the cron process of the UNIX operating system. The daemon process responds to a rejuvenation specification which indicates that an application which is registerd with it be rejuvenated by making a script for the cron process which specifies that the application's process be killed. When the cron process executes the script and kills the application, the daemon process observes that the application is dead and restarts it. In restarting the application, the daemon process may use state previously saved by the application for that purpose.

Abstract: A progressive retry recovery system based on checkpointing, message logging, rollback, message replaying and message reordering is disclosed. The disclosed progressive retry system minimizes the number of involved processes as well as the total rollback distance. The progressive retry method consists of a number of retry steps which gradually increase the scope of the rollback when a previous retry step fails. Step one attempts to bypass a software fault by having the faulty process replay the messages in its message log. Step two will attempt to bypass the software fault by having the faulty process reorder and then replay the messages in its message log. Step three will attempt to bypass the software fault by having the processes which have sent messages to the faulty process resend those messages to the faulty process. Step four will attempt to bypass the software fault by having the processes which have sent messages to the faulty process reorder and then resend their in-transit messages.

Abstract: A backup file system which can be used without modification of application programs, the operating system, or the hardware. The backup file system is implemented by means of a dynamically-linkable replacement library and user-level processes on a primary computer system and a backup computer system. The dynamically-linkable replacement library has the same interfaces as a standard dynamically-linkable library of file operations. The functions in the replacement library perform the same file operations as their counterparts in the standard library; in addition, they send messages specifying the just-performed operation to a user-level process on the backup computer system. The user-level process executes the operation specified in the message on a backup file in the backup computer system. The files to be backed up are specified by identifying subtrees in the namespace of the primary file system; the subtrees make up a user-defined namespace.

Abstract: A software failure bypass system based on checkpointing, input logging, rollback and input sequence reordering is disclosed. The software fault bypass system minimizes the number of involved processes as well as the total rollback distance. The software fault bypass system includes a progressive retry recovery algorithm which gradually increases the scope of the recovery when a previous retry step fails to bypass the detected fault and a reorder recovery algorithm which will attempt to bypass the detected fault by reordering and reprocessing the inputs that have been received by the faulty application process. The fault tolerant system includes a mechanism which utilizes information about the particular application process or the cause of the detected fault to determine if the recovery of a particular application process should proceed directly to the reorder recovery algorithm.

Abstract: A progressive retry recovery system based on checkpointing, message logging, rollback, message replaying and message reordering is disclosed. The disclosed progressive retry system minimizes the number of involved processes as well as the total rollback distance. The progressive retry recovery system includes a fault tolerant software library which provides a number of functions which may be invoked by application processes to implement fault tolerance. Fault tolerant functions are provided for allowing an application process to generate a heartbeat message at specified intervals indicating that the application process is still active. In addition, fault tolerance implementation functions are provided for specifying critical memory, for executing checkpoints to store backup copies of critical data, and for restoring critical data during a recovery. In addition, functions are provided which process messages that are sent or received by an application process and maintain logs of the sent and received messages.