SCATTER consists of three main files:

ScatterServer.pl : This is the main server program. Its function is to open a TCP/IP port and then spawn clients. It is a multi-threaded version which implies that each client is serviced by a separate thread. It also allocates jobs to the different clients based on a First Come First Served policy. There are plans to do some more effective load balancing in future.

ScatterClient.pl: This is the client file. Its only function is to wait on the server and process the jobs as and when it gets them.

clientfile: This file contains information on the client nodes in the cluster that are to be used for the BLAST run. The formatting is quite simple and consists of a list of node names, one on each line.

SCATTER is based on a client-server architecture (see Figure 1). The server program ScatterServer.pl resides on the server. It opens a TCP/IP port, spawns the ScatterClient.pl programs on the clients (listed in clientfile) and waits for connections from the client machines. Once the connections are established, the server starts distributing queries to the clients from a central query queue that is maintained on the server side. Since the main server directory is NFS mounted on all the client machines, the communication consists essentially in passing the names of the queries to be sequenced, to the client machines. Hence, the communication overheads are minimized to a large extent.