private void sendAck() {
// Send results back
DTask dt, origDt = _dt; // _dt can go null the instant it is send over wire
assert origDt != null; // Freed after completion
while ((dt = _dt) != null) { // Retry loop for broken TCP sends
AutoBuffer ab = null;
try {
// Start the ACK with results back to client. If the client is
// asking for a class/id mapping (or any job running at FETCH_ACK
// priority) then return a udp.fetchack byte instead of a udp.ack.
// The receiver thread then knows to handle the mapping at the higher
// priority.
UDP.udp udp = dt.priority() == H2O.FETCH_ACK_PRIORITY ? UDP.udp.fetchack : UDP.udp.ack;
ab = new AutoBuffer(_client, udp._prior).putTask(udp, _tsknum).put1(SERVER_UDP_SEND);
assert ab.position() == 1 + 2 + 4 + 1;
dt.write(ab); // Write the DTask - could be very large write
dt._repliedTcp = ab.hasTCP(); // Resends do not need to repeat TCP result
ab.close(); // Then close; send final byte
_computedAndReplied = true; // After the final handshake, set computed+replied bit
break; // Break out of retry loop
} catch (AutoBuffer.AutoBufferException e) {
if (!_client._heartbeat._client) // Report on servers only; clients allowed to be flaky
Log.info(
"IOException during ACK, "
+ e._ioe.getMessage()
+ ", t#"
+ _tsknum
+ " AB="
+ ab
+ ", waiting and retrying...");
ab.drainClose();
if (_client._heartbeat._client) // Dead client will not accept a TCP ACK response?
this.CAS_DT(dt, null); // cancel the ACK
try {
Thread.sleep(100);
} catch (InterruptedException ignore) {
}
} catch (Exception e) { // Custom serializer just barfed?
Log.err(e); // Log custom serializer exception
ab.drainClose();
}
} // end of while(true)
if (dt == null)
Log.info(
"Cancelled remote task#"
+ _tsknum
+ " "
+ origDt.getClass()
+ " to "
+ _client
+ " has been cancelled by remote");
else {
if (dt instanceof MRTask && dt.logVerbose())
Log.debug("Done remote task#" + _tsknum + " " + dt.getClass() + " to " + _client);
_client.record_task_answer(this); // Setup for retrying Ack & AckAck, if not canceled
}
}
// 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();
}
protected AutoBuffer response(AutoBuffer ab) {
assert _tasknum == ab.getTask();
if (_done) {
if (!ab.hasTCP()) return ackack(ab, _tasknum); // Ignore duplicate response packet
ab.drainClose();
} else {
int flag = ab.getFlag(); // Must read flag also, to advance ab
if (flag == SERVER_TCP_SEND) return ackack(ab, _tasknum); // Ignore UDP packet for a TCP reply
assert flag == SERVER_UDP_SEND : "flag = " + flag;
synchronized (this) { // Install the answer under lock
if (_done) {
if (!ab.hasTCP()) return ackack(ab, _tasknum); // Ignore duplicate response packet
ab.drainClose();
} else {
// UDPTimeOutThread.PENDING.remove(_tasknum);
_dt.read(ab); // Read the answer (under lock?)
_size_rez = ab.size(); // Record received size
ab
.close(); // Also finish the read (under lock? even if canceled, since need to drain
// TCP)
if (!isCancelled()) // Can be canceled already (locally by MRTask while recieving remote
// answer)
_dt.onAck(); // One time only execute (before sending ACKACK)
_done = true; // Only read one (of many) response packets
ab._h2o.taskRemove(_tasknum); // Flag as task-completed, even if the result is null
notifyAll(); // And notify in any case
}
if (!isCancelled()) // Can be canceled already
doAllCompletions(); // Send all tasks needing completion to the work queues
}
}
// AckAck back on a fresh AutoBuffer, since actually closed() the incoming one
return new AutoBuffer(ab._h2o, H2O.ACK_ACK_PRIORITY)
.putTask(UDP.udp.ackack.ordinal(), _tasknum);
}
// 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) {
// Get the RPC we're waiting on
int task = ab.getTask();
RPC rpc = TASKS.get(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) {
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.
rpc.response(ab);
}
// ACKACK the remote, telling him "we got the answer"
new AutoBuffer(ab._h2o).putTask(UDP.udp.ackack.ordinal(), task).close(true);
}
// 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();
}
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);
}
}