Interface DGC

Method Detail

• dirty

  Lease dirty(ObjID[] ids,
            long sequenceNum,
            Lease lease)
              throws RemoteException

  The dirty call requests leases for the remote object references associated with the object identifiers contained in the array 'ids'. The 'lease' contains a client's unique VM identifier (VMID) and a requested lease period. For each remote object exported in the local VM, the garbage collector maintains a reference list-a list of clients that hold references to it. If the lease is granted, the garbage collector adds the client's VMID to the reference list for each remote object indicated in 'ids'. The 'sequenceNum' parameter is a sequence number that is used to detect and discard late calls to the garbage collector. The sequence number should always increase for each subsequent call to the garbage collector. Some clients are unable to generate a VMID, since a VMID is a universally unique identifier that contains a host address which some clients are unable to obtain due to security restrictions. In this case, a client can use a VMID of null, and the distributed garbage collector will assign a VMID for the client. The dirty call returns a Lease object that contains the VMID used and the lease period granted for the remote references (a server may decide to grant a smaller lease period than the client requests). A client must use the VMID the garbage collector uses in order to make corresponding clean calls when the client drops remote object references. A client VM need only make one initial dirty call for each remote reference referenced in the VM (even if it has multiple references to the same remote object). The client must also make a dirty call to renew leases on remote references before such leases expire. When the client no longer has any references to a specific remote object, it must schedule a clean call for the object ID associated with the reference.

  Parameters:

  ids - IDs of objects to mark as referenced by calling client

  sequenceNum - sequence number

  lease - requested lease

  Returns:

  granted lease

  Throws:

  RemoteException - if dirty call fails

• clean

  void clean(ObjID[] ids,
           long sequenceNum,
           VMID vmid,
           boolean strong)
             throws RemoteException

  The clean call removes the 'vmid' from the reference list of each remote object indicated in 'id's. The sequence number is used to detect late clean calls. If the argument 'strong' is true, then the clean call is a result of a failed dirty call, thus the sequence number for the client 'vmid' needs to be remembered.

  Parameters:

  ids - IDs of objects to mark as unreferenced by calling client

  sequenceNum - sequence number

  vmid - client VMID

  strong - make 'strong' clean call

  Throws:

  RemoteException - if clean call fails