/**
* creates a server socket listening on port specified in the object constructor, and then
* enters an infinite loop waiting for incoming socket connection requests representing a worker
* process attempting to connect to this server, which it handles via the enclosing server's
* <CODE>addNewWorkerConnection(s)</CODE> method.
*/
public void run() {
try {
ServerSocket ss = new ServerSocket(_port);
System.out.println("Srv: Now Accepting Worker Connections");
while (true) {
try {
Socket s = ss.accept();
System.out.println("Srv: Incoming New Worker Connection to the Network");
System.out.println(
"Srv: Thread may have to wait if an init_cmd has not yet arrived from the client");
addNewWorkerConnection(s);
System.out.println("Srv: finished adding new worker connection to the _workers");
} catch (Exception e) {
utils.Messenger.getInstance()
.msg(
"PDBTExecSingleCltWrkInitSrv.W2Thread.run(): "
+ "An error occured while adding new worker connection",
2);
// e.printStackTrace();
}
}
} catch (IOException e) {
// e.printStackTrace();
utils.Messenger.getInstance()
.msg(
"PDBTExecSingleCltWrkInitSrv.W2Thread.run(): "
+ "Failed to create Server Socket, Server exiting.",
0);
System.exit(-1);
}
}
/**
* simply calls the method <CODE>t.runObject(req)</CODE> wrapped in some debug messages, and
* returns the result of the call.
*
* @param req TaskObjectsExecutionRequest
* @param t PDBTEW2Listener
* @return TaskObjectsExecutionResults
* @throws IOException
* @throws PDBatchTaskExecutorException
*/
private TaskObjectsExecutionResults submitWork(TaskObjectsExecutionRequest req, PDBTEW2Listener t)
throws IOException, PDBatchTaskExecutorException {
utils.Messenger.getInstance()
.msg("PDBTExecSingleCltWrkInitSrv.submitWork(req,t): sending request", 1);
TaskObjectsExecutionResults res = t.runObject(req);
utils.Messenger.getInstance()
.msg("PDBTExecSingleCltWrkInitSrv.submitWork(req,t): response received", 1);
return res;
}
/**
* there is an issue with this method: if it is called often enough, the <CODE>
* _s.sendUrgentData(0);</CODE> method that it invokes, will force the <CODE>_s</CODE> socket to
* close on the other end, at least on Windows systems. This behavior is due to the fact that
* OOB data handling is problematic since there are conflicting specifications in TCP.
* Therefore, it is required that the method is not called with high frequency (see the <CODE>
* PDBTExecSingleCltWrkInitSrv._CHECK_PERIOD_MSECS</CODE> flag in this file.)
*
* @return true iff the worker is available to accept work according to all evidence.
*/
private synchronized boolean getAvailability() {
boolean res = _isAvail && _s != null && _s.isClosed() == false;
if (res && _OK2SendOOB) { // work-around the OOB data issue
// last test using OOB sending of data
try {
_OK2SendOOB = false; // indicates should not send OOB data until set to true
_s.sendUrgentData(0); // unfortunately, if this method is called often enough,
// it will cause the socket to close???
res = true;
} catch (IOException e) {
// e.printStackTrace();
utils.Messenger.getInstance()
.msg("PDBTExecSingleCltWrkInitSrv.getAvailability(): Socket has been closed", 0);
res = false;
_isAvail = false; // declare availability to false as well
// try graceful exit
try {
_s.shutdownOutput();
_s.close(); // Now we can close the Socket
} catch (IOException e2) {
// silently ignore
}
}
}
return res;
}
/**
* creates a server socket listening on the port specified in the parameter of the constructor,
* and waits for a single incoming client connection which it handles by invoking the <CODE>
* addNewClientConnection(s)</CODE> method of the enclosing server, and then the thread exits.
*/
public void run() {
try {
ServerSocket ss = new ServerSocket(_port);
System.out.println("Srv: Now Accepting Single Client Connection");
// while (true) {
try {
Socket s = ss.accept();
System.out.println("Srv: Client Added to the Network");
addNewClientConnection(s);
System.out.println("Srv: finished adding client connection");
} catch (Exception e) {
// e.printStackTrace();
System.err.println("Client Connection failed, exiting...");
System.exit(-1);
}
// }
} catch (IOException e) {
// e.printStackTrace();
utils.Messenger.getInstance()
.msg(
"PDBTExecSingleCltWrkInitSrv.C2Thread.run(): "
+ "Failed to create Server Socket, Server exiting.",
0);
System.exit(-1);
}
}
private void secondChance(RRObject obj) throws ClassNotFoundException, IOException {
try {
obj.runProtocol(_srv, _ois, _oos);
} catch (PDBatchTaskExecutorException e2) {
utils.Messenger.getInstance()
.msg(
"PDBTEC2ListenerThread.run(): sending NoWorkerAvailableResponse() to client...", 1);
// e.printStackTrace();
_oos.writeObject(new NoWorkerAvailableResponse(((TaskObjectsExecutionRequest) obj)._tasks));
_oos.flush();
} catch (IOException e2) {
utils.Messenger.getInstance()
.msg("PDBTEC2ListenerThread.run(): sending FailedReply to client...", 1);
// e.printStackTrace();
_oos.writeObject(new FailedReply());
_oos.flush();
}
}
/**
* no need to synchronize any block in this method, as it is already synchronized on _srv since
* it's only called by the <CODE>_srv.addNewWorkerConnection(s)</CODE> method.
*
* @throws IOException
*/
private void init() throws IOException {
// wait until the _initCmd is ready, and send it over the socket
while (_initCmd == null) {
try {
utils.Messenger.getInstance()
.msg(
"PDBTExecSingleCltWrkInitSrv.PDBTEW2Listener.init(): "
+ "W2Thread waiting on server to obtain init_cmd from client...",
1);
_srv.wait(); // the thread calling this method is already synchronized on _srv.
} catch (InterruptedException e) {
// e.printStackTrace();
Thread.currentThread().interrupt();
}
}
_oos.writeObject(_initCmd);
_oos.flush();
utils.Messenger.getInstance()
.msg("PDBTExecSingleCltWrkInitSrv.PDBTEW2Listener.init(): done.", 1);
}
private void processException(Exception e) {
// e.printStackTrace();
try {
_ois.close();
_oos.close();
_s.close();
} catch (Exception e2) {
// e2.printStackTrace();
} finally {
synchronized (_srv) {
getWorkers().remove(_s);
utils.Messenger.getInstance()
.msg("PDBTExecSingleCltWrkInitSrv: Worker Network Connection Closed", 0);
}
_ois = null;
_oos = null;
_s = null;
}
}
/**
* reads from the input stream the initialization command sent to it, sends back to the client
* an <CODE>OKReply</CODE> "ACK" msg, and then enters an infinite loop waiting to read from the
* input stream an <CODE>RRObject</CODE> obj that should really be of type <CODE>
* TaskObjectsExecutionRequest</CODE>, on which it executes its method <CODE>
* obj.runProtocol(_srv,_ois, _oos)</CODE>.
*/
public void run() {
// first, read from socket the worker-initialization object that will
// be broadcast for execution to every worker connecting to this server.
utils.Messenger mger = utils.Messenger.getInstance();
try {
mger.msg("PDBTEC2ListenerThread: waiting to read the init_cmd from client", 1);
RRObject initCmd = (RRObject) _ois.readObject();
mger.msg("PDBTEC2ListenerThread: done reading the init_cmd from client", 1);
setInitCmd(initCmd);
mger.msg("PDBTEC2ListenerThread: done setting the init_cmd", 2);
// send back to the clt an "ACK" message
_oos.writeObject(new OKReply());
_oos.flush();
mger.msg("PDBTEC2ListenerThread: done sending OKReply through the socket", MIN_PRIORITY);
} catch (Exception e) { // client closed connection
// e.printStackTrace();
try {
_ois.close();
_oos.close();
_s.close();
} catch (Exception e2) {
// e2.printStackTrace();
}
mger.msg("PDBTEC2ListenerThread: Client Network Connection Closed", 0);
System.exit(-1);
}
while (true) {
try {
mger.msg("PDBTEC2ListenerThread.run(): waiting to read an RRObject...", 2);
// 1. read from socket input
RRObject obj = (RRObject) _ois.readObject(); // obj is an TaskObjectsExecutionRequest
mger.msg("PDBTEC2ListenerThread.run(): RRObject read", 2);
// 2. take appropriate action
try {
obj.runProtocol(_srv, _ois, _oos);
} catch (PDBatchTaskExecutorException e) {
mger.msg(
"PDBTEC2ListenerThread.run(): calling obj.runProtocol() "
+ "issued PDBatchTaskExecutorException, will try one more time.",
1);
secondChance(obj);
} catch (
IOException e) { // worker somehow failed, give srv one more shot, then notify client
mger.msg(
"PDBTEC2ListenerThread.run(): calling obj.runProtocol() "
+ "issued IOException, will try one more time.",
1);
secondChance(obj);
}
} catch (Exception e) { // client closed connection
// e.printStackTrace();
try {
_ois.close();
_oos.close();
_s.close();
} catch (Exception e2) {
// e2.printStackTrace();
}
mger.msg(
"PDBTExecSingleCltWrkInitSrv: Client Network Connection Closed "
+ "(exception '"
+ e
+ "' caught)",
0);
System.exit(-1);
}
}
}
TaskObjectsExecutionResults submitWork(Vector originating_clients, TaskObject[] tasks)
throws IOException, ClassNotFoundException, PDBatchTaskExecutorException {
Set workers2rm = new HashSet(); // Set<PDBTEW2Listener>
PDBTEW2Listener t = null;
utils.Messenger.getInstance()
.msg(
"PDBTExecSingleCltWrkInitSrv.submitWork(clts,tasks): "
+ "finding an available worker connection among "
+ getNumWorkers()
+ " known workers",
1);
// 1. find a worker (via Round-Robin)
synchronized (this) {
boolean cont = true;
while (cont) {
workers2rm.clear();
Iterator sit = getWorkers().keySet().iterator();
while (sit.hasNext()) {
Socket s = (Socket) sit.next();
t = (PDBTEW2Listener) getWorkers().get(s);
boolean is_avail = t.getAvailability() && !getWorking().contains(t);
// the _working set is needed so that submitWork() is guaranteed not
// to choose twice the same worker before the worker is done with the
// first request.
if (is_avail) {
cont = false; // break out of the top-level while-loop too
getWorking().add(t);
break;
} else {
if (t.isConnectionLost()) workers2rm.add(t);
t = null; // reset to null
}
}
// remove any "lost connections" worker listeners
Iterator it = workers2rm.iterator();
while (it.hasNext()) getWorkers().remove(it.next());
if (t == null) {
// before trying again to find an available worker, wait a while
try {
wait(_CHECK_PERIOD_MSECS); // wait out the workers for some time
} catch (InterruptedException e) {
// e.printStackTrace();
Thread.currentThread().interrupt(); // recommended
}
}
}
} // synchronized (this)
if (t == null) { // failed to find an available thread
utils.Messenger.getInstance()
.msg("PDBTExecSingleCltWrkInitSrv.submitWork(clt,tasks): no available threads...", 1);
throw new PDBatchTaskExecutorException("no available worker or known srv to undertake work");
}
utils.Messenger.getInstance()
.msg("PDBTExecSingleCltWrkInitSrv.submitWork(clt,tasks): found an available worker", 1);
// 2. submit tasks and get back results
TaskObjectsExecutionRequest req = new TaskObjectsExecutionRequest(originating_clients, tasks);
utils.Messenger.getInstance()
.msg(
"PDBTExecSingleCltWrkInitSrv.submitWork(clt,tasks): created the TaskObjectsExecutionRequest to send",
1);
RRObject res = submitWork(req, t);
utils.Messenger.getInstance()
.msg(
"PDBTExecSingleCltWrkInitSrv.submitWork(tasks): finished running submitWork(req,ois,oos)",
1);
synchronized (this) {
getWorking().remove(t); // declare worker's availability again
notifyAll(); // declare I'm done. With only a single client connected, not of much use.
}
if (res instanceof TaskObjectsExecutionResults) return (TaskObjectsExecutionResults) res;
else {
throw new PDBatchTaskExecutorException(
"PDBTExecSingleCltWrkInitSrv.submitWork(tasks): worker failed to process tasks.");
}
}