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8293562: KeepAliveCache Blocks Threads while Closing Connections #980

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8293562: KeepAliveCache Blocks Threads while Closing Connections #980

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124 changes: 56 additions & 68 deletions src/java.base/share/classes/sun/net/www/http/KeepAliveCache.java
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Original file line number Diff line number Diff line change
Expand Up @@ -121,6 +121,12 @@ public KeepAliveCache() {}
*/
@SuppressWarnings("removal")
public void put(final URL url, Object obj, HttpClient http) {
// this method may need to close an HttpClient, either because
// it is not cacheable, or because the cache is at its capacity.
// In the latter case, we close the least recently used client.
// The client to close is stored in oldClient, and is closed
// after cacheLock is released.
HttpClient oldClient = null;
cacheLock.lock();
try {
boolean startThread = (keepAliveTimer == null);
Expand Down Expand Up @@ -171,42 +177,29 @@ public Void run() {
// alive, which could be 0, if the user specified 0 for the property
assert keepAliveTimeout >= 0;
if (keepAliveTimeout == 0) {
http.closeServer();
oldClient = http;
} else {
v = new ClientVector(keepAliveTimeout * 1000);
v.put(http);
super.put(key, v);
}
} else {
v.put(http);
oldClient = v.put(http);
}
} finally {
cacheLock.unlock();
}
// close after releasing locks
if (oldClient != null) {
oldClient.closeServer();
}
}

// returns the keep alive set by user in system property or -1 if not set
private static int getUserKeepAlive(boolean isProxy) {
return isProxy ? userKeepAliveProxy : userKeepAliveServer;
}

/* remove an obsolete HttpClient from its VectorCache */
public void remove(HttpClient h, Object obj) {
cacheLock.lock();
try {
KeepAliveKey key = new KeepAliveKey(h.url, obj);
ClientVector v = super.get(key);
if (v != null) {
v.remove(h);
if (v.isEmpty()) {
removeVector(key);
}
}
} finally {
cacheLock.unlock();
}
}

/* called by a clientVector thread when all its connections have timed out
* and that vector of connections should be removed.
*/
Expand Down Expand Up @@ -242,6 +235,7 @@ public void run() {
try {
Thread.sleep(LIFETIME);
} catch (InterruptedException e) {}
List<HttpClient> closeList = null;

// Remove all outdated HttpClients.
cacheLock.lock();
Expand All @@ -253,15 +247,18 @@ public void run() {
ClientVector v = get(key);
v.lock();
try {
KeepAliveEntry e = v.peek();
KeepAliveEntry e = v.peekLast();
while (e != null) {
if ((currentTime - e.idleStartTime) > v.nap) {
v.poll();
e.hc.closeServer();
v.pollLast();
if (closeList == null) {
closeList = new ArrayList<>();
}
closeList.add(e.hc);
} else {
break;
}
e = v.peek();
e = v.peekLast();
}

if (v.isEmpty()) {
Expand All @@ -277,6 +274,12 @@ public void run() {
}
} finally {
cacheLock.unlock();
// close connections outside cacheLock
if (closeList != null) {
for (HttpClient hc : closeList) {
hc.closeServer();
}
}
}
} while (!isEmpty());
}
Expand All @@ -297,8 +300,8 @@ private void readObject(ObjectInputStream stream)
}
}

/* FILO order for recycling HttpClients, should run in a thread
* to time them out. If > maxConns are in use, block.
/* LIFO order for reusing HttpClients. Most recent entries at the front.
* If > maxConns are in use, discard oldest.
*/
class ClientVector extends ArrayDeque<KeepAliveEntry> {
@java.io.Serial
Expand All @@ -312,62 +315,47 @@ class ClientVector extends ArrayDeque<KeepAliveEntry> {
this.nap = nap;
}

/* return a still valid, idle HttpClient */
HttpClient get() {
lock();
try {
if (isEmpty()) {
// check the most recent connection, use if still valid
KeepAliveEntry e = peekFirst();
if (e == null) {
return null;
}

// Loop until we find a connection that has not timed out
HttpClient hc = null;
long currentTime = System.currentTimeMillis();
do {
KeepAliveEntry e = pop();
if ((currentTime - e.idleStartTime) > nap) {
e.hc.closeServer();
} else {
hc = e.hc;
if (KeepAliveCache.logger.isLoggable(PlatformLogger.Level.FINEST)) {
String msg = "cached HttpClient was idle for "
+ Long.toString(currentTime - e.idleStartTime);
KeepAliveCache.logger.finest(msg);
}
}
} while ((hc == null) && (!isEmpty()));
return hc;
} finally {
unlock();
}
}

/* return a still valid, unused HttpClient */
void put(HttpClient h) {
lock();
try {
if (size() >= KeepAliveCache.getMaxConnections()) {
h.closeServer(); // otherwise the connection remains in limbo
if ((currentTime - e.idleStartTime) > nap) {
return null; // all connections stale - will be cleaned up later
} else {
push(new KeepAliveEntry(h, System.currentTimeMillis()));
pollFirst();
if (KeepAliveCache.logger.isLoggable(PlatformLogger.Level.FINEST)) {
String msg = "cached HttpClient was idle for "
+ Long.toString(currentTime - e.idleStartTime);
KeepAliveCache.logger.finest(msg);
}
return e.hc;
}
} finally {
unlock();
}
}

/* remove an HttpClient */
boolean remove(HttpClient h) {
HttpClient put(HttpClient h) {
HttpClient staleClient = null;
lock();
try {
for (KeepAliveEntry curr : this) {
if (curr.hc == h) {
return super.remove(curr);
}
assert KeepAliveCache.getMaxConnections() > 0;
if (size() >= KeepAliveCache.getMaxConnections()) {
// remove oldest connection
staleClient = removeLast().hc;
}
return false;
addFirst(new KeepAliveEntry(h, System.currentTimeMillis()));
} finally {
unlock();
}
// close after releasing the locks
return staleClient;
}

final void lock() {
Expand Down Expand Up @@ -395,10 +383,10 @@ private void readObject(ObjectInputStream stream)
}

class KeepAliveKey {
private String protocol = null;
private String host = null;
private int port = 0;
private Object obj = null; // additional key, such as socketfactory
private final String protocol;
private final String host;
private final int port;
private final Object obj; // additional key, such as socketfactory

/**
* Constructor
Expand Down Expand Up @@ -439,8 +427,8 @@ public int hashCode() {
}

class KeepAliveEntry {
HttpClient hc;
long idleStartTime;
final HttpClient hc;
final long idleStartTime;

KeepAliveEntry(HttpClient hc, long idleStartTime) {
this.hc = hc;
Expand Down
9 changes: 9 additions & 0 deletions src/java.base/share/classes/sun/net/www/protocol/https/HttpsClient.java
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Original file line number Diff line number Diff line change
Expand Up @@ -436,6 +436,15 @@ protected Socket createSocket() throws IOException {
}
}

@Override
public void closeServer() {
try {
// SSLSocket.close may block up to timeout. Make sure it's short.
serverSocket.setSoTimeout(1);
} catch (Exception e) {}
super.closeServer();
}


@Override
public boolean needsTunneling() {
Expand Down
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