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fix: concurrency bug when doing high volume pull query over java client (alternative) #10077

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merged 2 commits into from
Oct 6, 2023
Merged

fix: concurrency bug when doing high volume pull query over java client (alternative) #10077

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9303951
alternative bugfix
lucasbru Oct 5, 2023
a06a964
unit test fix
lucasbru Oct 5, 2023
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12 changes: 5 additions & 7 deletions ksqldb-engine/src/main/java/io/confluent/ksql/query/PullQueryWriteStream.java
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Original file line number Diff line number Diff line change
Expand Up @@ -28,9 +28,11 @@
import io.confluent.ksql.util.KsqlHostInfo;
import io.confluent.ksql.util.RowMetadata;
import io.vertx.core.AsyncResult;
import io.vertx.core.Context;
import io.vertx.core.Future;
import io.vertx.core.Handler;
import io.vertx.core.Promise;
import io.vertx.core.Vertx;
import io.vertx.core.impl.ConcurrentHashSet;
import io.vertx.core.impl.future.SucceededFuture;
import io.vertx.core.streams.WriteStream;
Expand Down Expand Up @@ -97,12 +99,6 @@ public PullQueryWriteStream(
) {
this.queryLimit = queryLimit;
this.translator = translator;

// register a drainHandler that will wake up anyone waiting on hasCapacity
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I don't see how this is necessary, since every time we call the drain handlers, we anyways acquire the monitor.

drainHandler.add(ignored -> {
monitor.enter();
monitor.leave();
});
}

private static final class HandledRow {
Expand Down Expand Up @@ -211,6 +207,7 @@ private PullQueryRow pollRow() {
if (monitor.enterIf(atHalfCapacity)) {
try {
drainHandler.forEach(h -> h.handle(null));
drainHandler.clear();
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It seems like other implementors only allow one handler at a time, and they just clobber any previous one rather than keeping a list, but I couldn't find good documentation on this.

I also think proper callers also reregister after every callback they get, but I couldn't find a very good documentation of this either.

Ultimately, the only user of these APIs are the http response objects, so if we test it out with them, we're good.

} finally {
monitor.leave();
}
Expand Down Expand Up @@ -273,7 +270,8 @@ public PullQueryWriteStream exceptionHandler(final Handler<Throwable> handler) {

@Override
public PullQueryWriteStream drainHandler(final Handler<Void> handler) {
drainHandler.add(handler);
final Context context = Vertx.currentContext();
drainHandler.add(v -> context.runOnContext(handler));
return this;
}

Expand Down