5.1.1. Requests, Operations, Files
At the core of the RMS are Requests, Operations and Files.
A Request is like a TODO list associated to a User and group. For example, this TODO list could be what is left to do at the end of a job (setting the job status, moving the output file to its final destination, etc).
Each item on this TODO list is described by an Operation. There are several types of Operation, for example ReplicateAndRegister (to copy a file), RemoveFile (guess..), ForwardDISET (to execute DISET calls), etc.
When an Operation acts on LFNs, Files corresponding to the LFNs are associated to the Operation.
The list of available Operations, as well as the state machines are described in RMS objects
5.1.2. ReqManager & ReqProxy
The ReqManager is the service that receives or distributes Requests to be excuted. Every operation is synchronous with the ReqDB database.
If the ReqManager is unreachable when a client wants to send a Request, the client will automatically failover to a ReqProxy. This proxy will accept the Request, hold it in a local cache, and will periodically try to send it to the ReqManager until it succeeds. This system ensures that no Request is lost.
The RequestExecutingAgent (RequestExecutingAgent) is in charge of executing the Requests.
Because the database can grow very large, the CleanReqDBAgent is in charge of removing old Requests in a final state.