Trickle messages let applications communicate with the server during the execution of a workunit. They are intended for applications that have long work units (multiple days). Trickle messages may go in either direction: 'trickle up' messages go from application to server, 'trickle down' messages go from server to application. Typical uses of this mechanism:

• The application sends a trickle-up message containing its current CPU usage, so that users can be granted incremental credit (rather than waiting until the end of the work unit).
• The application sends a trickle-up message containing a summary of the computational state, so that server logic can decide if the computation should be aborted.
• The server sends a trickle-down message telling the application to abort.
• The server sends a trickle-down message containing the user's current total credit.

Trickle messages are asynchronous and reliable. Trickle messages are conveyed in scheduler RPC messages, so they may not be delivered immediately after being generated.

To handle trickle-down messages a project must include the line

<trickle_down/>