Restarting Failed Process Sentinels

Process Sentinels consist of two processes: a worker process and a watcher process. These two processes are initiated on each server in a TIBCO iProcess Engine cluster. This architecture is designed so that each process can monitor the other one and restart it if it fails. This makes sure that the Process Sentinels are always running. The watcher and worker processes perform different tasks:

Watcher Process

After starting the worker process and establishing a two-way communication channel with the worker process, the watcher process monitors the worker process and can restart it on a failure. If any errors occur, an error message is logged in the SWDIR\logs\sw_error file.

On the DB2 version, the watcher process also runs the iProcess event daemon (see Event Handling).

Worker Process

The worker process monitors the TIBCO iProcess Engine processes and restarts them if they fail. The worker process also monitors the watcher process to make sure that it is always running and will restart it if it fails. The following is the start-up routine for the worker process:

1.

Initialize process by processing its command line arguments.

2.

Establish a communication channel with its watcher process.

3.

Connect to the database and read the node_cluster table to determine if the server is configured to be part of the TIBCO iProcess Engine. It can also determine if it needs to operate as a master or slave.

If there is no entry for this server in the node_cluster table, an error message is logged to the operating system event log (syslogd). The worker process will shut down and also shut down the watcher process.

4.

Read the process_config table to build an in a memory process hierarchy model.

5.

Start process monitoring.