// TCP large RECEIVE of results. Note that 'this' is NOT the RPC object
// that is hoping to get the received object, nor is the current thread the
// RPC thread blocking for the object. The current thread is the TCP
// reader thread.
static void tcp_ack(final AutoBuffer ab) throws IOException {
// Get the RPC we're waiting on
int task = ab.getTask();
RPC rpc = ab._h2o.taskGet(task);
// Race with canceling a large RPC fetch: Task is already dead. Do not
// bother reading from the TCP socket, just bail out & close socket.
if (rpc == null || rpc._done) {
ab.drainClose();
} else {
assert rpc._tasknum == task;
assert !rpc._done;
// Here we have the result, and we're on the correct Node but wrong
// Thread. If we just return, the TCP reader thread will close the
// remote, the remote will UDP ACK the RPC back, and back on the current
// Node but in the correct Thread, we'd wake up and realize we received a
// large result.
try {
rpc.response(ab);
} catch (AutoBuffer.AutoBufferException e) {
// If TCP fails, we will have done a short-read crushing the original
// _dt object, and be unable to resend. This is fatal right now.
// Really: an unimplemented feature; fix is to notice that a partial
// TCP read means that the server (1) got our remote_exec request, (2)
// has computed an answer and was trying to send it to us, (3) failed
// sending via TCP hence the server knows it failed and will send again
// without any further work from us. We need to disable all the resend
// & retry logic, and wait for the server to re-send our result.
// Meanwhile the _dt object is crushed with half-read crap, and cannot
// be trusted except in the base fields.
throw Log.throwErr(e._ioe);
}
}
// ACKACK the remote, telling him "we got the answer"
new AutoBuffer(ab._h2o, H2O.ACK_ACK_PRIORITY).putTask(UDP.udp.ackack.ordinal(), task).close();
}
public synchronized RPC<V> call() {
// Any Completer will not be carried over to remote; add it to the RPC call
// so completion is signaled after the remote comes back.
CountedCompleter cc = _dt.getCompleter();
if (cc != null) handleCompleter(cc);
// If running on self, just submit to queues & do locally
if (_target == H2O.SELF) return handleLocal();
// Keep a global record, for awhile
if (_target != null) _target.taskPut(_tasknum, this);
try {
if (_nack) return this; // Racing Nack rechecked under lock; no need to send retry
// We could be racing timeouts-vs-replies. Blow off timeout if we have an answer.
if (isDone()) {
if (_target != null) _target.taskRemove(_tasknum);
return this;
}
// Default strategy: (re)fire the packet and (re)start the timeout. We
// "count" exactly 1 failure: just whether or not we shipped via TCP ever
// once. After that we fearlessly (re)send UDP-sized packets until the
// server replies.
// Pack classloader/class & the instance data into the outgoing
// AutoBuffer. If it fits in a single UDP packet, ship it. If not,
// finish off the current AutoBuffer (which is now going TCP style), and
// make a new UDP-sized packet. On a re-send of a TCP-sized hunk, just
// send the basic UDP control packet.
if (!_sentTcp) {
while (true) { // Retry loop for broken TCP sends
AutoBuffer ab = new AutoBuffer(_target, _dt.priority());
try {
final boolean t;
int offset = ab.position();
ab.putTask(UDP.udp.exec, _tasknum).put1(CLIENT_UDP_SEND);
ab.put(_dt);
t = ab.hasTCP();
assert sz_check(ab)
: "Resend of "
+ _dt.getClass()
+ " changes size from "
+ _size
+ " to "
+ ab.size()
+ " for task#"
+ _tasknum;
ab.close(); // Then close; send final byte
_sentTcp = t; // Set after close (and any other possible fail)
break; // Break out of retry loop
} catch (AutoBuffer.AutoBufferException e) {
Log.info(
"IOException during RPC call: "
+ e._ioe.getMessage()
+ ", AB="
+ ab
+ ", for task#"
+ _tasknum
+ ", waiting and retrying...");
ab.drainClose();
try {
Thread.sleep(500);
} catch (InterruptedException ignore) {
}
}
} // end of while(true)
} else {
// Else it was sent via TCP in a prior attempt, and we've timed out.
// This means the caller's ACK/answer probably got dropped and we need
// him to resend it (or else the caller is still processing our
// request). Send a UDP reminder - but with the CLIENT_TCP_SEND flag
// instead of the UDP send, and no DTask (since it previously went via
// TCP, no need to resend it).
AutoBuffer ab = new AutoBuffer(_target, _dt.priority()).putTask(UDP.udp.exec, _tasknum);
ab.put1(CLIENT_TCP_SEND).close();
}
// Double retry until we exceed existing age. This is the time to delay
// until we try again. Note that we come here immediately on creation,
// so the first doubling happens before anybody does any waiting. Also
// note the generous 5sec cap: ping at least every 5 sec.
_retry += (_retry < MAX_TIMEOUT) ? _retry : MAX_TIMEOUT;
// Put self on the "TBD" list of tasks awaiting Timeout.
// So: dont really 'forget' but remember me in a little bit.
// UDPTimeOutThread.PENDING.put(_tasknum, this);
return this;
} catch (Throwable t) {
t.printStackTrace();
throw Log.throwErr(t);
}
}
