Agent Controller Assisted File Transfer – An overview

Revision History

Date	Version	Description	Author(s)
28 January 2005	1.0	First draft	Giridhar S (giridhar.s@in.ibm.com)
10 January 2006	1.0.0.1	Removed extra white space, renamed "RAC" to "Agent Controller"	RL

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Agent Controller Assisted File Transfer – An overview

Requirements

The Agent Controller Assisted File Transfer service is intended to provide the Hyades Data Collection Engine with the ability to transfer files (binary as well as text) between any Agent Controller client machine and the Agent Controller host machine. The goal of the service is to transfer files between the two machines in a reliable manner and also delete specified files from the host machine, by providing an abstraction over the lower level details like differences in the machines’ “endian” ness, and underlying operating systems, file systems etc.

Design

Component Interaction for file transfer

Sequence Diagram

Current Implementation/Working

The file transfer service is now a part of the Hyades data collection engine.

The component which is responsible for initiating the file transfer is the File Server. The File Server is started by the Agent Controller during its startup phase. Subsequently, the File Server listens for incoming file transfer requests from clients on a designated port and performs the task of transferring the requested files. The port on which the file server listens for incoming requests can be configured by editing the configuration file.

When a client wants a file to be transferred to/from or deleted from the host machine, it has to make use of the file transfer APIs available through the IFileManager interface. The current implementation of the IFileManager interface is the FileManagerImpl class which takes care of contacting the file server and completing the file transfer/file deletion.

For parties interested in implementing the IFileManager interface, it would be useful to know the protocol involved in communicating with the file server. The interaction between the FileManager, Agent Controller, File Server and other necessary components is described below.

Ø The FileManager performing the file transfer sends a message to the Agent Controller, querying the port number on which the File Server is running. Since the Agent Controller is responsible for starting the file server during its initialization phase, it is aware of the port number, and this information is passed back to the FileManager.

Ø The FileManager then connects to specified file server port. The file server hands off each connection request it receives, to a connection handler, which in turn creates a new thread and allocates a client handler to take care of the file transfer needs of that particular client. The client handler performs the actual task of transferring the files.

Ø It is the responsibility of the FileManager to provide the details like the name of the file to be transferred, nature of operation (get, put or delete) to the client handler. This information is passed to the client handler through the socket connecting the File Manager and the client handler, because the client handler expects the first few bytes of incoming information to be details about the current file transfer operation.

Ø Once the client handler has enough information to begin the file transfer, it starts the file transfer i.e. sending the files if the operation is a “get” and receiving the file contents if the operation is a “put”. Note that for the “delete” operation, the Agent Controller performs the task of deleting the file from the file system, and not the file manager, file server or related components.

APIs and usage of the service

The file transfer feature can be accessed through the use of the following APIs available from within the IFileManager interface.

public interface IFileManager {

public void getFile (String localName, String remoteName) throws IOException;

public void putFile (String localName, String remoteName) throws IOException;

public void deleteFile (String absFileName) throws IOException;

}

Currently, an implementation of the IFileManager interface is available through the FiieManagerImpl class. To make use of the FileManagerImpl class, one of the following approaches can be taken:

1) An instance of the FileManagerImpl class can be queried from an instance of the org.eclipse.hyades.execution.local.NodeImpl class, after it has been properly instantiated and connected to an Agent Controller successfully. To illustrate:

INode node = new NodeImpl(“win-giri01”);

ISession session = node.connect(“10002”, null);/* Connect to the Agent Controller */

IFileManager fileManager = ((NodeImpl)node).getFileManager();

fileManager.getFile(localFile, remoteFile); /* Transfer the file */

Note: The task of moving the getFileManager method from the NodeImpl implementation into the INode interface is on the list of things to be done.

2) An object of the class FileManagerImpl can be constructed, by passing it a valid Connection object, and then this object can be used to perform the file transfer.

Node node = NodeFactory.createNode(“win-giri01”);

node.connect(10002); /* Connect to the Agent Controller on win-giri01 */

IFileManager fileManager = new FileManagerImpl(node.getConnection);

fileManager.getFile(localFile, remoteFile); /* Transfer the file */

Limitations/Tasks to be done

1) The getFileManager method, currently present only within the NodeImpl implementation of the INode interface, needs to be moved into the interface to enable a generic API that returns a FileManager object that can be used for file transfer.

2) The filePort variable must be included in the dtd document corresponding to the service configuration framework.