Zero Application States
As of M4 Zero Applications have 3 steady states: stopped, started, activated. The following sections describe the aforementioned states from various perspectives.
Client Perspective
From the client side perspective, an application is either available to service to requests or it is not. When the Application is stopped any requests for the application from the client to the server will fail with a connection refused error. Server side requests will be serviced when the application is in either the started or activated states.
Server Perspective
Stopped State
In the stopped state their are no application processes thus the application is consuming no server resources other than disk space.
Started State
In the started state the application is running and available to service requests. From a server perspective the application consists of a single lightweight process which is bound to and listening on the application ports. When a request is detected the application will shift from started to the active state to process the request
Active State
In the active state the application actively processing requests, or has recently processed requests. In this state the application is performing at its peak responding to requests quickly.
Zero Process Model
A active Zero application logically consists of two processes: the zero socket opener (zso) and the application JVM.
Zero Socket Opener (ZSO)
The ZSO's primary function minimize the application resource utilization when idle while still enabling the application to respond to requests as needed, On-Demand.
To perform the requisite on-demand starting the ZSO currently assumes two major responsibilities
- Listening for Incoming Requests for the application when the Application JVM is not running
- Watching for Application JVM exit and taking the appropriate action depending how how the application JVM exited
-- tom - 28 Jan 2008
