added checking of result when building demos

[urisagit/Stem.git] / Design / switch_notes

Stem::Switch

The Stem::Switch cell is a very simple but powerful object which can 
be used in a wide range of applications.  Its primary function is to 
receive a message and to copy and redirect it to a list of 
destination cells.  It can be used as a multiplexer in many-to-one, 
one-to-many, and many-to-many configurations.  Currently it is used 
as the heart of the chat server demo and the Inetd demo. 

Stem::Switch has two maps: the input map is used to translate the 
incoming target address to entries in the output map.  Each input map 
entry can have multiple output targets and that list can be set via a 
configuration file at start-up time or a command message at runtime. 
The output map just converts the output name to an actual cell 
address and is one-to-one; it also is set via the configuration file 
or by runtime command messages.  In addition to the explicit command 
message technique for changing the maps, a publish/subscribe 
interface is supported.  A given cell can announce to a Stem::Switch 
cell that it will be publishing messages to a given target address in 
the switch.  Other cells can send a subscribe message which will 
cause all messages sent to the selected publish address to be 
forwarded to themselves.