egor-ryashin commented on a change in pull request #7038: Fix and document
concurrency of EventReceiverFirehose and TimedShutoffFirehose; Refine
concurrency specification of Firehose
URL: https://github.com/apache/incubator-druid/pull/7038#discussion_r255305171
##########
File path:
server/src/main/java/org/apache/druid/segment/realtime/firehose/EventReceiverFirehoseFactory.java
##########
@@ -453,61 +569,57 @@ public boolean isClosed()
final String producerId = req.getHeader("X-Firehose-Producer-Id");
if (producerId == null) {
- return Optional.empty();
+ return null;
}
final String sequenceValue = req.getHeader("X-Firehose-Producer-Seq");
if (sequenceValue == null) {
- return Optional.of(
- Response.status(Response.Status.BAD_REQUEST)
- .entity(ImmutableMap.<String, Object>of("error",
"Producer sequence value is missing"))
- .build()
- );
+ return Response
+ .status(Response.Status.BAD_REQUEST)
+ .entity(ImmutableMap.<String, Object>of("error", "Producer
sequence value is missing"))
+ .build();
}
Long producerSequence = producerSequences.computeIfAbsent(producerId,
key -> Long.MIN_VALUE);
if (producerSequences.size() >= MAX_FIREHOSE_PRODUCERS) {
- return Optional.of(
- Response.status(Response.Status.FORBIDDEN)
- .entity(
- ImmutableMap.<String, Object>of(
- "error",
- "Too many individual producer IDs for this
firehose. Max is " + MAX_FIREHOSE_PRODUCERS
- )
- )
- .build()
- );
+ return Response
+ .status(Response.Status.FORBIDDEN)
+ .entity(
+ ImmutableMap.of(
+ "error",
+ "Too many individual producer IDs for this firehose. Max
is " + MAX_FIREHOSE_PRODUCERS
+ )
+ )
+ .build();
}
try {
Long newSequence = Long.parseLong(sequenceValue);
- if (newSequence <= producerSequence) {
- return Optional.of(
- Response.ok(
- responseMapper.writeValueAsString(
- ImmutableMap.of("eventCount", 0, "skipped", true)
- ),
- responseContentType
- ).build()
- );
- }
- producerSequences.put(producerId, newSequence);
+ while (true) {
+ if (newSequence <= producerSequence) {
+ return Response.ok(
+
responseMapper.writeValueAsString(ImmutableMap.of("eventCount", 0, "skipped",
true)),
+ responseContentType
+ ).build();
+ }
+ if (producerSequences.replace(producerId, producerSequence,
newSequence)) {
+ return null;
+ }
+ producerSequence = producerSequences.get(producerId);
Review comment:
I believe this method shouldn't be called by multiple threads of the same
producer, as we don't guarantee exactly-once event processing that way, this
code block actually detects an illegal state of the application environment (a
single producerId with multiple threads) and we should report an error
different from `skipped`.
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