// Got a response UDP packet, or completed a large TCP answer-receive.
// Install it as The Answer packet and wake up anybody waiting on an answer.
// On all paths, send an ACKACK back
static AutoBuffer ackack(AutoBuffer ab, int tnum) {
return ab.clearForWriting(H2O.ACK_ACK_PRIORITY).putTask(UDP.udp.ackack.ordinal(), tnum);
}
// Handle traffic, from a client to this server asking for work to be done.
// Called from either a F/J thread (generally with a UDP packet) or from the
// TCPReceiver thread.
static void remote_exec(AutoBuffer ab) {
long lo = ab.get8(0), hi = ab._size >= 16 ? ab.get8(8) : 0;
final int task = ab.getTask();
final int flag = ab.getFlag();
assert flag == CLIENT_UDP_SEND || flag == CLIENT_TCP_SEND; // Client-side send
// Atomically record an instance of this task, one-time-only replacing a
// null with an RPCCall, a placeholder while we work on a proper response -
// and it serves to let us discard dup UDP requests.
RPCCall old = ab._h2o.has_task(task);
// This is a UDP packet requesting an answer back for a request sent via
// TCP but the UDP packet has arrived ahead of the TCP. Just drop the UDP
// and wait for the TCP to appear.
if (old == null && flag == CLIENT_TCP_SEND) {
Log.warn(
"got tcp with existing task #, FROM "
+ ab._h2o.toString()
+ " AB: " /* + UDP.printx16(lo,hi)*/);
assert !ab.hasTCP()
: "ERROR: got tcp with existing task #, FROM "
+ ab._h2o.toString()
+ " AB: " /* + UDP.printx16(lo,hi)*/; // All the resends should be UDP only
// DROP PACKET
} else if (old == null) { // New task?
RPCCall rpc;
try {
// Read the DTask Right Now. If we are the TCPReceiver thread, then we
// are reading in that thread... and thus TCP reads are single-threaded.
rpc = new RPCCall(ab.get(water.DTask.class), ab._h2o, task);
} catch (AutoBuffer.AutoBufferException e) {
// Here we assume it's a TCP fail on read - and ignore the remote_exec
// request. The caller will send it again. NOTE: this case is
// indistinguishable from a broken short-writer/long-reader bug, except
// that we'll re-send endlessly and fail endlessly.
Log.info(
"Network congestion OR short-writer/long-reader: TCP "
+ e._ioe.getMessage()
+ ", AB="
+ ab
+ ", ignoring partial send");
ab.drainClose();
return;
}
RPCCall rpc2 = ab._h2o.record_task(rpc);
if (rpc2 == null) { // Atomically insert (to avoid double-work)
if (rpc._dt instanceof MRTask && rpc._dt.logVerbose())
Log.debug("Start remote task#" + task + " " + rpc._dt.getClass() + " from " + ab._h2o);
H2O.submitTask(rpc); // And execute!
} else { // Else lost the task-insertion race
if (ab.hasTCP()) ab.drainClose();
// DROP PACKET
}
} else if (!old._computedAndReplied) {
// This packet has not been fully computed. Hence it's still a work-in-
// progress locally. We have no answer to reply but we do not want to
// re-offer the packet for repeated work. Send back a NACK, letting the
// client know we're Working On It
assert !ab.hasTCP()
: "got tcp with existing task #, FROM "
+ ab._h2o.toString()
+ " AB: "
+ UDP.printx16(lo, hi)
+ ", position = "
+ ab._bb.position();
ab.clearForWriting(udp.nack._prior).putTask(UDP.udp.nack.ordinal(), task);
// DROP PACKET
} else {
// This is an old re-send of the same thing we've answered to before.
// Send back the same old answer ACK. If we sent via TCP before, then
// we know the answer got there so just send a control-ACK back. If we
// sent via UDP, resend the whole answer.
if (ab.hasTCP()) {
Log.warn(
"got tcp with existing task #, FROM "
+ ab._h2o.toString()
+ " AB: "
+ UDP.printx16(lo, hi)); // All the resends should be UDP only
ab.drainClose();
}
if (old._dt != null) { // already ackacked
++old._ackResendCnt;
if (old._ackResendCnt % 10 == 0)
Log.err(
"Possibly broken network, can not send ack through, got "
+ old._ackResendCnt
+ " for task # "
+ old._tsknum
+ ", dt == null?"
+ (old._dt == null));
old.resend_ack();
}
}
ab.close();
}
