Configuring event slot propagation

Events can be processed locally or selectively propagated to other cells. To configure the event slots that must be propagated when they are changed, and in which direction (forward/backward), you configure the propagation configuration file mcell.propagate. The mcell.propagate file lists all of the slots whose modifications are propagated.

In addition, using the gateways, events can be propagated to a third-party program in a specific format that is described in a gateway configuration file, gateway.GWType.

The default location for these files is installationDirectory\pw\server\etc.

When an event has been propagated to a destination and that event is later modified, the modifications are then propagated to the same destination. The event can be propagated through a Propagate rule. If the destination is a gateway, gateway configuration rules also apply.

For the mcell.propagate file to be effective, one or more Propagate rules must be running. For information about Propagate rules, see Propagate rules.

The format is <Slotname> = <Value>

where,

Slotname = slot name or CLASS for class-specific slots and

value= sequence of {b = backward f = forward}

You can specify a slot in the base CORE_EVENT class. However, if you want to specify a slot outside those in the base CORE_EVENT class you must use the CLASS specifier, which means that all class-specific slots are propagated in the direction given.

The following table lists the parameters in the mcell.propagate file and the defaults.

Default mcell.propagate options

If you have multiple remote cells installed, you might want to use event propagation to distribute the event processing load among the cells or to back up events on another cell for failover.

The following figure illustrates a cell network that is collecting and processing numerous events in a distributed environment.

Distributed event management using event propagation

In this illustration, the lower-level cells process the source events and then propagate (or forward) the events on to higher-level cells according to a Propagate rule or an Event Propagation policy. As events pass through a series of cells, the cells discard unneeded events, identify and leave behind unimportant events, and resolve some of the problems reported by other events.

To enable event propagation, perform the following tasks:

• Enable cell-to-cell communication in mcell.dir 
• Configure propagation parameters in mcell.conf 
• Specify the slots whose modification has to propagate in mcell.propagate 
• Either write a Propagate rule or define an Event Propagation policy
  
  

How unpropagated events are buffered

When the cell is started, the buffers are set to a minimum workable size. The default minimum size is 5000 events for each destination buffer and 5000 requests for the propagation buffer.

If the cell cannot propagate events, the cell stores the events to be propagated in the destination buffers and the requests for propagation of those events in the propagation buffer. When the buffers become full, the cell automatically expands the buffer size by a specified percentage (10 percent, by default), unless the buffer has exceeded a maximum size. By default, the maximum buffer size is unlimited, although the practical limit of the buffer size is the amount of available memory. After the maximum defined buffer size is reached, additional requests fail.

When automatic expansion occurs, an MC_CELL_RESOURCE_EXPANSION event is generated.

An expanded buffer contains free space after propagation has resumed. To free memory resources, the buffer is reduced when it contains more than the specified amount of free space. Reduction leaves enough free space to avoid the need for an immediate expansion. The buffer is never reduced below the specified minimum size. When the buffer is reduced, an MC_CELL_RESOURCE_REDUCTION event is generated.

Parameters controlling the buffer size are located in the mcell.conf file. For information about configuring these parameters, see Propagation parameters.