/**
* Only return transaction state objects that are ready to run. This is non-blocking. If the txn
* is not ready, then this will return null. <B>Note:</B> This should only be allowed to be called
* by one thread.
*/
@Override
public AbstractTransaction poll() {
AbstractTransaction retval = null;
if (trace.val)
LOG.trace(String.format("Partition %d :: Attempting to acquire lock", this.partitionId));
if (this.state == QueueState.UNBLOCKED) {
this.lock.lock();
try {
// if (this.state != QueueState.UNBLOCKED) {
// this.checkQueueState(false);
// }
if (this.state == QueueState.UNBLOCKED) {
// 2012-12-21
// So this is allow to be null because there is a race condition
// if another thread removes the txn from the queue.
retval = super.poll();
if (retval != null) {
if (debug.val)
LOG.debug(String.format("Partition %d :: poll() -> %s", this.partitionId, retval));
this.lastTxnPopped = retval.getTransactionId();
this.txnsPopped++;
}
// call this again to prime the next txn
this.checkQueueState(true);
}
} finally {
if (trace.val) LOG.trace(String.format("Partition %d :: Releasing lock", this.partitionId));
this.lock.unlock();
}
}
return (retval);
}
@Override
public boolean remove(Object obj) {
AbstractTransaction txn = (AbstractTransaction) obj;
boolean retval;
if (trace.val)
LOG.trace(String.format("Partition %d :: Attempting to acquire lock", this.partitionId));
this.lock.lock();
try {
// We have to check whether we are the first txn in the queue,
// because we will need to reset the blockTimestamp after
// delete ourselves so that the next guy can get executed
// This is not thread-safe...
boolean reset = txn.equals(super.peek());
retval = super.remove(txn);
if (debug.val) {
LOG.debug(String.format("Partition %d :: remove(%s) -> %s", this.partitionId, txn, retval));
// Sanity Check
assert (super.contains(txn) == false) : "Failed to remove " + txn + "???\n" + this.debug();
}
if (retval) this.checkQueueState(reset);
} finally {
if (trace.val) LOG.trace(String.format("Partition %d :: Releasing lock", this.partitionId));
this.lock.unlock();
}
return (retval);
}
/** Only return transaction state objects that are ready to run. */
@Override
public AbstractTransaction poll() {
AbstractTransaction retval = null;
// These invocations of poll() can return null if the next
// txn was speculatively executed
if (this.nextTxn == null) this.checkQueueState();
if (this.state == QueueState.BLOCKED_SAFETY) {
if (EstTime.currentTimeMillis() >= this.blockTime) {
retval = super.poll();
}
} else if (this.state == QueueState.UNBLOCKED) {
// assert(checkQueueState() == QueueState.UNBLOCKED);
retval = super.poll();
}
if (retval != null) {
assert (this.nextTxn.equals(retval))
: String.format(
"Partition %d :: Next txn is %s but our poll returned %s\n"
+ StringUtil.SINGLE_LINE
+ "%s",
this.partitionId,
this.nextTxn,
retval,
this.debug());
this.nextTxn = null;
this.lastTxnPopped = retval.getTransactionId();
}
if (d && retval != null)
LOG.debug(String.format("Partition %d :: poll() -> %s", this.partitionId, retval));
this.checkQueueState();
return retval;
}
/**
* Update the information stored about the latest transaction seen from each initiator. Compute
* the newest safe transaction id.
*/
public Long noteTransactionRecievedAndReturnLastSeen(AbstractTransaction ts) {
// this doesn't exclude dummy txnid but is also a sanity check
assert (ts != null);
// we've decided that this can happen, and it's fine... just ignore it
if (d) {
if (this.lastTxnPopped != null && this.lastTxnPopped.compareTo(ts.getTransactionId()) > 0) {
LOG.warn(
String.format(
"Txn ordering deadlock at Partition %d ::> LastTxn: %s / NewTxn: %s",
this.partitionId, this.lastTxnPopped, ts));
LOG.warn("LAST: " + this.lastTxnPopped);
LOG.warn("NEW: " + ts);
}
}
// update the latest transaction for the specified initiator
if (this.lastSeenTxn == null || ts.getTransactionId().compareTo(this.lastSeenTxn) < 0) {
if (t) LOG.trace("SET lastSeenTxnId = " + ts);
this.lastSeenTxn = ts.getTransactionId();
}
// this minimum is the newest safe transaction to run
// but you still need to check if a transaction has been confirmed
// by its initiator
// (note: this check is done when peeking/polling from the queue)
// if (t) LOG.trace("SET this.newestCandidateTransaction = " + this.lastSeenTxn);
// this.newestCandidateTransaction = this.lastSeenTxn;
// this will update the state of the queue if needed
this.checkQueueState();
// return the last seen id for the originating initiator
return this.lastSeenTxn;
}
@Override
public final boolean equals(Object obj) {
if (obj instanceof AbstractTransaction) {
AbstractTransaction other = (AbstractTransaction) obj;
if (this.txn_id == null) {
return (this.hashCode() != other.hashCode());
}
return (this.txn_id.equals(other.txn_id));
}
return (false);
}
protected QueueState checkQueueState() {
QueueState newState = QueueState.UNBLOCKED;
AbstractTransaction ts = super.peek();
if (ts == null) {
if (t) LOG.trace(String.format("Partition %d :: Queue is empty.", this.partitionId));
newState = QueueState.BLOCKED_EMPTY;
}
// Check whether can unblock now
else if (ts == this.nextTxn && this.state != QueueState.UNBLOCKED) {
if (EstTime.currentTimeMillis() < this.blockTime) {
newState = QueueState.BLOCKED_SAFETY;
} else if (d) {
LOG.debug(
String.format(
"Partition %d :: Wait time for %s has passed. Unblocking...",
this.partitionId, this.nextTxn));
}
}
// This is a new txn and we should wait...
else if (this.nextTxn != ts) {
long txnTimestamp =
TransactionIdManager.getTimestampFromTransactionId(ts.getTransactionId().longValue());
long timestamp = EstTime.currentTimeMillis();
long waitTime = Math.max(0, this.waitTime - (timestamp - txnTimestamp));
newState = (waitTime > 0 ? QueueState.BLOCKED_SAFETY : QueueState.UNBLOCKED);
this.blockTime = timestamp + waitTime;
this.nextTxn = ts;
if (d) {
String debug = "";
if (t) {
Map<String, Object> m = new LinkedHashMap<String, Object>();
m.put("Txn Init Timestamp", txnTimestamp);
m.put("Current Timestamp", timestamp);
m.put("Block Time Remaining", (this.blockTime - timestamp));
debug = "\n" + StringUtil.formatMaps(m);
}
LOG.debug(
String.format(
"Partition %d :: Blocking %s for %d ms [maxWait=%d]%s",
this.partitionId, ts, (this.blockTime - timestamp), this.waitTime, debug));
}
}
if (newState != this.state) {
this.state = newState;
if (d)
LOG.debug(
String.format(
"Partition %d :: State:%s / NextTxn:%s",
this.partitionId, this.state, this.nextTxn));
}
return this.state;
}
/** Drop data for unknown initiators. This is the only valid add interface. */
@Override
public boolean offer(AbstractTransaction ts) {
assert (ts != null);
// Check whether this new txn is less than the current this.nextTxn
// If it is and there is still time remaining before it is released,
// then we'll switch and become the new next this.nextTxn
if (this.nextTxn != null && ts.compareTo(this.nextTxn) < 0) {
this.checkQueueState();
if (this.state != QueueState.UNBLOCKED) {
if (d)
LOG.debug(
String.format(
"Partition %d :: Switching %s as new next txn [old=%s]",
this.partitionId, ts, this.nextTxn));
this.nextTxn = ts;
} else {
if (d)
LOG.warn(
String.format(
"Partition %d :: offer(%s) -> %s [next=%s]",
this.partitionId, ts, "REJECTED", this.nextTxn));
return (false);
}
}
boolean retval = super.offer(ts);
if (d)
LOG.debug(String.format("Partition %d :: offer(%s) -> %s", this.partitionId, ts, retval));
if (retval) this.checkQueueState();
return retval;
}
/** Add in a transaction to the queue. It is safe to call this from any thread if you need to */
@Override
public boolean offer(AbstractTransaction ts, boolean force) {
assert (ts != null);
assert (ts.isInitialized())
: String.format(
"Unexpected uninitialized transaction %s [partition=%d]", ts, this.partitionId);
boolean retval = super.offer(ts, force);
if (debug.val)
LOG.debug(String.format("Partition %d :: offer(%s) -> %s", this.partitionId, ts, retval));
if (retval) {
if (trace.val)
LOG.trace(String.format("Partition %d :: Attempting to acquire lock", this.partitionId));
this.lock.lock();
try {
if (retval) this.checkQueueState(false);
} finally {
if (trace.val) LOG.trace(String.format("Partition %d :: Releasing lock", this.partitionId));
this.lock.unlock();
}
}
return (retval);
}
/**
* This is the most important method of the queue. This will figure out the next state and how
* long we must wait until we can release the next transaction. <B>Note:</B> I believe that this
* is the only thing that needs to be synchronized
*
* @param afterRemoval If this flag is set to true, then it means that who ever is calling this
* method just removed something from the queue. That means that we need to go and check
* whether the lastSafeTxnId should change.
* @return
*/
private QueueState checkQueueState(boolean afterRemoval) {
if (trace.val && super.isEmpty() == false)
LOG.trace(
String.format(
"Partition %d :: checkQueueState(afterPoll=%s) [current=%s]",
this.partitionId, afterRemoval, this.state));
QueueState newState = (afterRemoval ? QueueState.BLOCKED_SAFETY : QueueState.UNBLOCKED);
long currentTimestamp = -1l;
AbstractTransaction ts = super.peek(); // BLOCKING
Long txnId = null;
if (ts == null) {
// if (trace.val)
// LOG.trace(String.format("Partition %d :: Queue is empty.",
// this.partitionId));
newState = QueueState.BLOCKED_EMPTY;
}
// Check whether can unblock now
else {
assert (ts.isInitialized())
: String.format(
"Unexpected uninitialized transaction %s [partition=%d]", ts, this.partitionId);
txnId = ts.getTransactionId();
// HACK: Ignore null txnIds
if (txnId == null) {
LOG.warn(
String.format(
"Partition %d :: Uninitialized transaction handle %s", this.partitionId, ts));
return (this.state);
}
assert (txnId != null) : "Null transaction id from " + txnId;
// If this txnId is greater than the last safe one that we've seen, then we know
// that the lastSafeTxnId has been polled. That means that we need to
// wait for an appropriate amount of time before we're allow to be executed.
if (txnId.compareTo(this.lastSafeTxnId) > 0 && afterRemoval == false) {
newState = QueueState.BLOCKED_ORDERING;
if (debug.val)
LOG.debug(
String.format(
"Partition %d :: txnId[%d] > lastSafeTxnId[%d]",
this.partitionId, txnId, this.lastSafeTxnId));
}
// If our current block time is negative, then we know that we're the first txnId
// that's been in the system. We'll also want to wait a bit before we're
// allowed to be executed.
else if (this.blockTimestamp == NULL_BLOCK_TIMESTAMP) {
newState = QueueState.BLOCKED_SAFETY;
if (debug.val)
LOG.debug(
String.format(
"Partition %d :: txnId[%d] ==> %s (blockTime=%d)",
this.partitionId, txnId, newState, this.blockTimestamp));
}
// Check whether it's safe to unblock this mofo
else if ((currentTimestamp = System.currentTimeMillis()) < this.blockTimestamp) {
newState = QueueState.BLOCKED_SAFETY;
if (debug.val)
LOG.debug(
String.format(
"Partition %d :: txnId[%d] ==> %s (blockTime[%d] - current[%d] = %d)",
this.partitionId,
txnId,
newState,
this.blockTimestamp,
currentTimestamp,
Math.max(0, this.blockTimestamp - currentTimestamp)));
}
// We didn't find any reason to block this txn, so it's sail yo for it...
else if (debug.val) {
LOG.debug(
String.format(
"Partition %d :: Safe to Execute %d [currentTime=%d]",
this.partitionId, txnId, System.currentTimeMillis()));
}
}
if (newState != this.state) {
// note if we get non-empty but blocked
if ((newState == QueueState.BLOCKED_ORDERING) || (newState == QueueState.BLOCKED_SAFETY)) {
if (trace.val)
LOG.trace(
String.format("Partition %d :: NewState=%s --> %s", this.partitionId, newState, ts));
long txnTimestamp = TransactionIdManager.getTimestampFromTransactionId(txnId.longValue());
if (currentTimestamp == -1) currentTimestamp = System.currentTimeMillis();
// Calculate how long we need to wait before this txn is safe to run
// If we're blocking on "safety", then we can use an offset based
// on when the txnId was created. If we're blocking for "ordering",
// then we'll want to wait for the full wait time.
int waitTime = this.waitTime;
if (newState == QueueState.BLOCKED_SAFETY) {
waitTime = (int) Math.max(0, this.waitTime - (currentTimestamp - txnTimestamp));
}
this.blockTimestamp = currentTimestamp + waitTime;
if (trace.val)
LOG.trace(
String.format(
"Partition %d :: SET blockTimestamp = %d --> %s",
this.partitionId, this.blockTimestamp, ts));
if (this.blockTimestamp <= currentTimestamp) {
newState = QueueState.UNBLOCKED;
}
if (this.profiler != null && this.lastSafeTxnId.equals(txnId) == false)
this.profiler.waitTimes.put(newState == QueueState.UNBLOCKED ? 0 : waitTime);
if (debug.val)
LOG.debug(
String.format(
"Partition %d :: SET lastSafeTxnId = %d --> %s",
this.partitionId, this.lastSafeTxnId, ts));
if (trace.val) {
LOG.trace(
String.format(
"Partition %d :: SET lastSafeTxnId = %d --> %s",
this.partitionId, this.lastSafeTxnId, ts));
String debug = "";
if (trace.val) {
Map<String, Object> m = new LinkedHashMap<String, Object>();
m.put("Txn Init Timestamp", txnTimestamp);
m.put("Current Timestamp", currentTimestamp);
m.put("Block Time Remaining", (this.blockTimestamp - currentTimestamp));
debug = "\n" + StringUtil.formatMaps(m);
}
LOG.trace(
String.format(
"Partition %d :: Blocking %s for %d ms "
+ "[maxWait=%d, origState=%s, newState=%s]\n%s%s",
this.partitionId,
ts,
(this.blockTimestamp - currentTimestamp),
this.waitTime,
this.state,
newState,
this.debug(),
debug));
}
} else if (newState == QueueState.UNBLOCKED) {
if (currentTimestamp == -1) currentTimestamp = System.currentTimeMillis();
if (this.blockTimestamp > currentTimestamp) {
newState = QueueState.BLOCKED_SAFETY;
}
}
} // IF
// This txn should always becomes our next safeTxnId.
// This is essentially the next txn
// that should be executed, but somebody *could* come along and add in
// a new txn with a lower id. But that's ok because we've synchronized setting
// the id up above. This is actually probably the only part of this entire method
// that needs to be protected...
if (txnId != null) this.lastSafeTxnId = txnId;
// Set the new state
if (newState != this.state) {
if (trace.val)
LOG.trace(
String.format(
"Partition %d :: ORIG[%s]->NEW[%s] / LastSafeTxn:%d",
this.partitionId, this.state, newState, this.lastSafeTxnId));
if (this.profiler != null) {
this.profiler.queueStates.get(this.state).stopIfStarted();
this.profiler.queueStates.get(newState).start();
}
this.state = newState;
// Always poke anybody that is blocking on this queue.
// The txn may not be ready to run just yet, but at least they'll be
// able to recompute a new sleep time.
this.isReady.signal();
} else if (this.profiler != null) {
this.profiler.queueStates.get(this.state).restart();
}
// Sanity Check
if ((this.state == QueueState.BLOCKED_ORDERING) || (this.state == QueueState.BLOCKED_SAFETY)) {
assert (this.state != QueueState.BLOCKED_EMPTY);
}
// Make sure that we're always in a valid state to avoid livelock problems
assert (this.state != QueueState.BLOCKED_SAFETY
|| (this.state == QueueState.BLOCKED_SAFETY
&& this.blockTimestamp != NULL_BLOCK_TIMESTAMP))
: String.format("Invalid state %s with NULL blocked timestamp", this.state);
assert (this.state != QueueState.BLOCKED_ORDERING
|| (this.state == QueueState.BLOCKED_ORDERING
&& this.blockTimestamp != NULL_BLOCK_TIMESTAMP))
: String.format("Invalid state %s with NULL blocked timestamp", this.state);
return this.state;
}
/**
* Only return transaction state objects that are ready to run. This method will wait until the
* transaction's block time has passed.
*
* @return
* @throws InterruptedException
*/
public AbstractTransaction take() throws InterruptedException {
AbstractTransaction retval = null;
// Ok now here is the tricky part. We don't have a txn that is
// ready to run, so we need to block ourselves until we get one.
// This could be for two reasons:
// (1) The queue is empty.
// (2) The waiting period for the next txn hasn't passed yet.
//
// Note that we can't simply attach ourselves to our inner queue because
// we don't want to get back the txn right when it gets added.
// We want to wait until the time period has passed.
if (trace.val)
LOG.trace(String.format("Partition %d :: Attempting to acquire lock", this.partitionId));
this.lock.lockInterruptibly();
try {
if (debug.val && this.state != QueueState.UNBLOCKED)
LOG.debug(
String.format(
"Partition %d :: take() -> " + "Current state is %s. Blocking until ready",
this.partitionId, this.state));
while (this.state != QueueState.UNBLOCKED) {
if (trace.val)
LOG.trace(
String.format(
"Partition %d :: take() -> Calculating how long to block", this.partitionId));
long waitTime = -1;
boolean isEmpty = (this.state == QueueState.BLOCKED_EMPTY);
boolean needsUpdateQueue = false;
// If the queue isn't empty, then we need to figure out
// how long we should sleep for
if (isEmpty == false) {
// If we're blocked because of an ordering issue (i.e., we have a new txn
// in the system that is less than our current head of the queue, but we
// haven't inserted it yet), then we will want to wait for the full timeout
// period. We won't actually have to wait this long because somebody will poke
// us after the new txn is added to the queue.
if (this.state == QueueState.BLOCKED_ORDERING) {
waitTime = this.waitTime;
} else {
waitTime = this.blockTimestamp - System.currentTimeMillis();
}
}
try {
// If we're empty, then we need to block indefinitely until we're poked
if (isEmpty) {
if (debug.val)
LOG.debug(
String.format(
"Partition %d :: take() -> " + "Blocking because queue is empty",
this.partitionId));
this.isReady.await();
}
// Otherwise, we'll sleep until our time out and then
// check the queue status for ourselves
else if (waitTime > 0) {
// We are going to wait for the specified time
// The Condition will return true if somebody poked us, which
// means that somebody changed the queue state to UNBLOCKED
// for us. If we are woken because of a timeout, then the
// return status will be false, which means that we need to
// queue state ourself.
if (debug.val)
LOG.debug(
String.format(
"Partition %d :: take() -> " + "Blocking for %d ms",
this.partitionId, waitTime));
needsUpdateQueue = (this.isReady.await(waitTime, TimeUnit.MILLISECONDS) == false);
}
// Our txn is ready to run now, so we don't need to block
else {
if (debug.val)
LOG.debug(
String.format(
"Partition %d :: take() -> "
+ "Ready to retrieve next txn immediately [waitTime=%d, isEmpty=%s]",
this.partitionId, waitTime, isEmpty));
needsUpdateQueue = true;
}
} catch (InterruptedException ex) {
this.isReady.signal();
throw ex;
}
if (needsUpdateQueue) this.checkQueueState(false);
} // WHILE
// The next txn is ready to run now!
assert (this.state == QueueState.UNBLOCKED);
retval = super.poll();
// 2012-01-06
// This could be null because there is a race condition if all of the
// txns are removed by another thread right before we try to
// poll our queue.
if (retval != null) {
this.lastTxnPopped = retval.getTransactionId();
this.txnsPopped++;
// Call this again to prime the next txn
this.checkQueueState(true);
}
if (trace.val)
LOG.trace(
String.format("Partition %d :: take() -> Leaving blocking section", this.partitionId));
} finally {
if (trace.val) LOG.trace(String.format("Partition %d :: Releasing lock", this.partitionId));
this.lock.unlock();
}
if (debug.val)
LOG.debug(String.format("Partition %d :: take() -> %s", this.partitionId, retval));
return (retval);
}
