amrishlal commented on a change in pull request #6596:
URL: https://github.com/apache/incubator-pinot/pull/6596#discussion_r581501167
##########
File path:
pinot-core/src/main/java/org/apache/pinot/core/transport/InstanceRequestHandler.java
##########
@@ -60,67 +64,107 @@ public InstanceRequestHandler(QueryScheduler
queryScheduler, ServerMetrics serve
_serverMetrics = serverMetrics;
}
+ /**
+ * Always return a response even when query execution throws exception;
otherwise, broker
+ * will keep waiting until timeout.
+ */
@Override
protected void channelRead0(ChannelHandlerContext ctx, ByteBuf msg) {
- long queryArrivalTimeMs = System.currentTimeMillis();
- _serverMetrics.addMeteredGlobalValue(ServerMeter.QUERIES, 1);
- int requestSize = msg.readableBytes();
-
_serverMetrics.addMeteredGlobalValue(ServerMeter.NETTY_CONNECTION_BYTES_RECEIVED,
requestSize);
- byte[] requestBytes = new byte[requestSize];
- msg.readBytes(requestBytes);
+ final long queryArrivalTimeMs = System.currentTimeMillis();
+ final int requestSize = msg.readableBytes();
InstanceRequest instanceRequest = new InstanceRequest();
+ ServerQueryRequest queryRequest;
+ byte[] requestBytes = new byte[requestSize];
+
try {
+ _serverMetrics.addMeteredGlobalValue(ServerMeter.QUERIES, 1);
+
_serverMetrics.addMeteredGlobalValue(ServerMeter.NETTY_CONNECTION_BYTES_RECEIVED,
requestSize);
+
+ // parse instance request into a query result.
+ msg.readBytes(requestBytes);
_deserializer.deserialize(instanceRequest, requestBytes);
+ queryRequest = new ServerQueryRequest(instanceRequest, _serverMetrics,
queryArrivalTimeMs);
+
queryRequest.getTimerContext().startNewPhaseTimer(ServerQueryPhase.REQUEST_DESERIALIZATION,
queryArrivalTimeMs)
+ .stopAndRecord();
} catch (Exception e) {
- LOGGER
- .error("Caught exception while deserializing the instance request:
{}", BytesUtils.toHexString(requestBytes),
- e);
-
_serverMetrics.addMeteredGlobalValue(ServerMeter.REQUEST_DESERIALIZATION_EXCEPTIONS,
1);
+ LOGGER.error("Exception while deserializing the instance request: {}",
BytesUtils.toHexString(requestBytes), e);
+ sendResponse(ctx, instanceRequest.getRequestId(), queryArrivalTimeMs,
new DataTableImplV2(), e);
return;
}
- ServerQueryRequest queryRequest = new ServerQueryRequest(instanceRequest,
_serverMetrics, queryArrivalTimeMs);
-
queryRequest.getTimerContext().startNewPhaseTimer(ServerQueryPhase.REQUEST_DESERIALIZATION,
queryArrivalTimeMs)
- .stopAndRecord();
-
- // NOTE: executor must be provided as addCallback(future, callback) is
removed from newer guava version
+ // Submit query for execution and register callback for execution results.
Futures.addCallback(_queryScheduler.submit(queryRequest), new
FutureCallback<byte[]>() {
@Override
public void onSuccess(@Nullable byte[] responseBytes) {
- // NOTE: response bytes can be null if data table serialization throws
exception
if (responseBytes != null) {
- long sendResponseStartTimeMs = System.currentTimeMillis();
- int queryProcessingTimeMs = (int) (sendResponseStartTimeMs -
queryArrivalTimeMs);
-
ctx.writeAndFlush(Unpooled.wrappedBuffer(responseBytes)).addListener(f -> {
- long sendResponseEndTimeMs = System.currentTimeMillis();
- int sendResponseLatencyMs = (int) (sendResponseEndTimeMs -
sendResponseStartTimeMs);
-
_serverMetrics.addMeteredGlobalValue(ServerMeter.NETTY_CONNECTION_RESPONSES_SENT,
1);
-
_serverMetrics.addMeteredGlobalValue(ServerMeter.NETTY_CONNECTION_BYTES_SENT,
responseBytes.length);
-
_serverMetrics.addTimedValue(ServerTimer.NETTY_CONNECTION_SEND_RESPONSE_LATENCY,
sendResponseLatencyMs,
- TimeUnit.MILLISECONDS);
-
- int totalQueryTimeMs = (int) (sendResponseEndTimeMs -
queryArrivalTimeMs);
- if (totalQueryTimeMs > SLOW_QUERY_LATENCY_THRESHOLD_MS) {
- LOGGER.info(
- "Slow query: request handler processing time: {}, send
response latency: {}, total time to handle request: {}",
- queryProcessingTimeMs, sendResponseLatencyMs,
totalQueryTimeMs);
- }
- });
+ // responseBytes contains either query results or exception.
+ sendResponse(ctx, queryArrivalTimeMs, responseBytes);
+ } else {
+ // Send exception response.
+ sendResponse(ctx, queryRequest.getRequestId(), queryArrivalTimeMs,
new DataTableImplV2(),
+ new Exception("Null query response."));
}
}
@Override
public void onFailure(Throwable t) {
- LOGGER.error("Caught exception while processing instance request", t);
- _serverMetrics.addMeteredGlobalValue(ServerMeter.UNCAUGHT_EXCEPTIONS,
1);
+ // Send exception response.
+ LOGGER.error("Exception while processing instance request", t);
+ sendResponse(ctx, instanceRequest.getRequestId(), queryArrivalTimeMs,
new DataTableImplV2(), new Exception(t));
}
}, MoreExecutors.directExecutor());
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
- LOGGER.error("Caught exception while fetching instance request", cause);
- _serverMetrics.addMeteredGlobalValue(ServerMeter.REQUEST_FETCH_EXCEPTIONS,
1);
+ // Since we do not know the requestId of the original request here, there
is no way for Broker to know which query
+ // request this response belongs to. Hence, Broker will continue to wait
for the original request until time out.
+ // To prevent broker from waiting unncessarily,try to catch and handle all
exceptions in channelRead0 method so that
+ // this function is never called.
+ LOGGER.error("Unhandled Exception in " + getClass().getCanonicalName(),
cause);
+ sendResponse(ctx, 0, System.currentTimeMillis(), new DataTableImplV2(),
new Exception(cause));
+ }
+
+ /**
+ * Send an exception back to broker as response to the query request.
+ */
+ private void sendResponse(ChannelHandlerContext ctx, long requestId, long
queryArrivalTimeMs, DataTable dataTable,
Review comment:
I renamed the first function to `sendErrorResponse` for clarity.
Although further refactoring can organize the code better, but the refactoring
seems a bit outside the scope of this issue. For example, currently, the
success (and some failure cases) inside QuerySchedular
`_queryScheduler.submit(queryRequest)` and we get the response bytes back
through a callback.
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