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8262027: Improve how HttpConnection detects a closed channel when tak…
…ing/returning a connection to the pool

Reviewed-by: chegar, michaelm
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dfuch committed Feb 24, 2021
1 parent 382e38d commit 0d2dbd299550f2a6b3319f211f980fc79b4ea1c5
@@ -1,5 +1,5 @@
* Copyright (c) 2015, 2020, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2015, 2021, Oracle and/or its affiliates. All rights reserved.
* This code is free software; you can redistribute it and/or modify it
@@ -150,6 +150,51 @@ final boolean isOpen() {
(connected() ? !getConnectionFlow().isFinished() : true);

* Forces a call to the native implementation of the
* connection's channel to verify that this channel is still
* open.
* <p>
* This method should only be called just after an HTTP/1.1
* connection is retrieved from the HTTP/1.1 connection pool.
* It is used to trigger an early detection of the channel state,
* before handling the connection over to the HTTP stack.
* It helps minimizing race conditions where the selector manager
* thread hasn't woken up - or hasn't raised the event, before
* the connection was retrieved from the pool. It helps reduce
* the occurrence of "HTTP/1.1 parser received no bytes"
* exception, when the server closes the connection while
* it's being taken out of the pool.
* <p>
* This method attempts to read one byte from the underlying
* channel. Because the connection was in the pool - there
* should be nothing to read.
* <p>
* If {@code read} manages to read a byte off the connection, this is a
* protocol error: the method closes the connection and returns false.
* If {@code read} returns EOF, the method closes the connection and
* returns false.
* If {@code read} throws an exception, the method returns false.
* Otherwise, {@code read} returns 0, the channel appears to be
* still open, and the method returns true.
* @return true if the channel appears to be still open.
final boolean checkOpen() {
if (isOpen()) {
try {
// channel is non blocking
int read = channel().read(ByteBuffer.allocate(1));
if (read == 0) return true;
} catch (IOException x) {
debug.log("Pooled connection is no longer operational: %s",
return false;
return false;

interface HttpPublisher extends FlowTube.TubePublisher {
void enqueue(List<ByteBuffer> buffers) throws IOException;
void enqueueUnordered(List<ByteBuffer> buffers) throws IOException;
@@ -206,7 +251,7 @@ public static HttpConnection getConnection(InetSocketAddress addr,

if (!secure) {
c = pool.getConnection(false, addr, proxy);
if (c != null && c.isOpen() /* may have been eof/closed when in the pool */) {
if (c != null && c.checkOpen() /* may have been eof/closed when in the pool */) {
final HttpConnection conn = c;
if (DEBUG_LOGGER.on())
@@ -350,7 +395,7 @@ void closeOrReturnToCache(HttpHeaders hdrs) {
.map((s) -> !s.equalsIgnoreCase("close"))

if (keepAlive && isOpen()) {
if (keepAlive && checkOpen()) {
Log.logTrace("Returning connection to the pool: {0}", this);
} else {

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