ankitsultana commented on code in PR #10289:
URL: https://github.com/apache/pinot/pull/10289#discussion_r1111432772
##########
pinot-query-runtime/src/main/java/org/apache/pinot/query/runtime/executor/OpChainScheduler.java:
##########
@@ -18,52 +18,67 @@
*/
package org.apache.pinot.query.runtime.executor;
+import java.util.concurrent.TimeUnit;
+import javax.annotation.concurrent.ThreadSafe;
import org.apache.pinot.query.mailbox.MailboxIdentifier;
import org.apache.pinot.query.runtime.operator.OpChain;
/**
- * An interface that defines different scheduling strategies to work with the
- * {@link OpChainSchedulerService}. All methods are thread safe and can be
guaranteed
- * to never be called concurrently - therefore all implementations may use data
- * structures that are not concurrent.
+ * An interface that defines different scheduling strategies to work with the
{@link OpChainSchedulerService}.
*/
+@ThreadSafe
public interface OpChainScheduler {
-
/**
+ * Registers a new OpChain with the scheduler.
* @param operatorChain the operator chain to register
- * @param isNew whether or not this is the first time the operator
is scheduled
*/
- void register(OpChain operatorChain, boolean isNew);
+ void register(OpChain operatorChain);
/**
- * This method is called whenever {@code mailbox} has new data available to
consume,
- * this can be useful for advanced scheduling algorithms
- *
- * @param mailbox the mailbox ID
+ * When the OpChain is finished, error or otherwise, deregister is called
for it so the scheduler can do any required
+ * cleanup. After an OpChain is de-registered, the scheduler service will
never call any other method for it.
+ * However, the {@link #onDataAvailable} callback may be called even after
an OpChain is de-registered, and the
+ * scheduler should handle that scenario.
+ * @param operatorChain an operator chain that is finished (error or
otherwise).
*/
- void onDataAvailable(MailboxIdentifier mailbox);
+ void deregister(OpChain operatorChain);
/**
- * This method is called when scheduler is terminating. It should clean up
all of the resources if there are any.
- * register() and onDataAvailable() shouldn't be called anymore after
shutDown is called.
+ * Used by {@link OpChainSchedulerService} to indicate that a given OpChain
can be suspended until it receives some
+ * data. Note that this method is only used by the scheduler service to
"indicate" that an OpChain can be suspended.
+ * The decision on whether to actually suspend or not can be taken by the
scheduler.
*/
- void shutDown();
+ void yield(OpChain opChain);
/**
- * @return whether or not there is any work for the scheduler to do
+ * A callback called whenever data is received for the given mailbox. This
can be used by the scheduler
+ * implementations to re-scheduled suspended OpChains. This method may be
called for an OpChain that has not yet
+ * been scheduled, or an OpChain that has already been de-registered.
+ * @param mailbox the mailbox ID
*/
- boolean hasNext();
+ void onDataAvailable(MailboxIdentifier mailbox);
/**
- * @return the next operator chain to process
- * @throws java.util.NoSuchElementException if {@link #hasNext()} returns
false
- * prior to this call
+ * Returns an OpChain that is ready to be run by {@link
OpChainSchedulerService}, waiting for the given time if
+ * there are no such OpChains ready yet. Will return null if there's no
ready OpChains even after the specified time.
+ *
+ * @param time non-negative value that determines the time the scheduler
will wait for new OpChains to be ready.
+ * @param timeUnit TimeUnit for the await time.
+ * @return a non-null OpChain that's ready to be run, or null if there's no
OpChain ready even after waiting for the
+ * given time.
+ * @throws InterruptedException if the wait for a ready OpChain was
interrupted.
*/
- OpChain next();
+ OpChain next(long time, TimeUnit timeUnit)
Review Comment:
This will return null if no OpChain is ready to run right now. There are
many cases where this may be true: all op-chains are already running, no
op-chain is registered, etc.
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