Understanding the iHub System process model
The Actuate BIRT iHub System platform uses a multi-threaded, multi-process model, running single instances of the following components on each iHub node:
Encyclopedia volume
Stores metadata in an OOTB (PostgreSQL) or alternative RDBMS and coordinates processing for designs, documents, information objects, and other iHub data objects stored in the file system.
Process Management Daemon (PMD)
Distributes service requests among available iHub services and nodes.
iHub servlet container
Provides the run-time environment for client applications, such as Actuate Information, Management, and Configuration Consoles. Client applications communicate with iHub System using SOAP-based messaging.
In addition, the iHub platform supports multiple instances of the following services on each node:
Factory
Executes requests to generate documents and perform server-side printing.
View
Supports viewing documents in DHTML and other output formats, such as CSV and PDF. Handles requests to download files from an Encyclopedia volume.
Integration
Coordinates the running of data object files that extract data from multiple data sources.
This loosely coupled iHub architecture model provides the following maintenance and performance benefits:
Startup and shutdown of an iHub node is fast because it is independent of the RDBMS that manages the Encyclopedia volume. The database server can remain online when shutting down an iHub node and is available when the node starts up.
Controlling the sequence of an Encyclopedia volume startup is not necessary. All volumes are either already online in the database server or come online as the database server starts.
Downtime to apply a patch or diagnostic fix for an iHub node is reduced. The RDBMS does not have to be shutdown.