聊聊httpclient的CPool
序
本文主要研究一下httpclient的CPool
ConnPool
org/apache/http/pool/ConnPool.java
public interface ConnPool {
/**
* Attempts to lease a connection for the given route and with the given
* state from the pool.
*
* @param route route of the connection.
* @param state arbitrary object that represents a particular state
* (usually a security principal or a unique token identifying
* the user whose credentials have been used while establishing the connection).
* May be {@code null}.
* @param callback operation completion callback.
*
* @return future for a leased pool entry.
*/
Future lease(final T route, final Object state, final FutureCallback callback);
/**
* Releases the pool entry back to the pool.
*
* @param entry pool entry leased from the pool
* @param reusable flag indicating whether or not the released connection
* is in a consistent state and is safe for further use.
*/
void release(E entry, boolean reusable);
}
ConnPool定义了lease及release方法，其中定义了两个泛型，T表示route，E表示poolEntry
ConnPoolControl
public interface ConnPoolControl {
void setMaxTotal(int max);
int getMaxTotal();
void setDefaultMaxPerRoute(int max);
int getDefaultMaxPerRoute();
void setMaxPerRoute(final T route, int max);
int getMaxPerRoute(final T route);
PoolStats getTotalStats();
PoolStats getStats(final T route);
}
ConnPoolControl接口定义了设置和访问maxTotal、defaultMaxPerRoute及PoolStats的方法
AbstractConnPool
org/apache/http/pool/AbstractConnPool.java
@Contract(threading = ThreadingBehavior.SAFE_CONDITIONAL)
public abstract class AbstractConnPool>
implements ConnPool, ConnPoolControl {
private final Lock lock;
private final Condition condition;
private final ConnFactory connFactory;
private final Map> routeToPool;
private final Set leased;
private final LinkedList available;
private final LinkedList> pending;
private final Map maxPerRoute;
private volatile boolean isShutDown;
private volatile int defaultMaxPerRoute;
private volatile int maxTotal;
private volatile int validateAfterInactivity;
public AbstractConnPool(
final ConnFactory connFactory,
final int defaultMaxPerRoute,
final int maxTotal) {
super();
this.connFactory = Args.notNull(connFactory, "Connection factory");
this.defaultMaxPerRoute = Args.positive(defaultMaxPerRoute, "Max per route value");
this.maxTotal = Args.positive(maxTotal, "Max total value");
this.lock = new ReentrantLock();
this.condition = this.lock.newCondition();
this.routeToPool = new HashMap>();
this.leased = new HashSet();
this.available = new LinkedList();
this.pending = new LinkedList>();
this.maxPerRoute = new HashMap();
}
/**
* Creates a new entry for the given connection with the given route.
*/
protected abstract E createEntry(T route, C conn);
//......
}
AbstractConnPool声明实现ConnPool、ConnPoolControl接口，它定义E必须继承PoolEntry，同时定义了泛型C，表示connectionType
shutdown
public void shutdown() throws IOException {
if (this.isShutDown) {
return ;
}
this.isShutDown = true;
this.lock.lock();
try {
for (final E entry: this.available) {
entry.close();
}
for (final E entry: this.leased) {
entry.close();
}
for (final RouteSpecificPool pool: this.routeToPool.values()) {
pool.shutdown();
}
this.routeToPool.clear();
this.leased.clear();
this.available.clear();
} finally {
this.lock.unlock();
}
}
shutdown方法会遍历available、leased挨个执行close，然后遍历routeToPool挨个执行shutdown
lease方法
public Future lease(final T route, final Object state, final FutureCallback callback) {
Args.notNull(route, "Route");
Asserts.check(!this.isShutDown, "Connection pool shut down");
return new Future() {
private final AtomicBoolean cancelled = new AtomicBoolean(false);
private final AtomicBoolean done = new AtomicBoolean(false);
private final AtomicReference entryRef = new AtomicReference(null);
@Override
public boolean cancel(final boolean mayInterruptIfRunning) {
if (done.compareAndSet(false, true)) {
cancelled.set(true);
lock.lock();
try {
condition.signalAll();
} finally {
lock.unlock();
}
if (callback != null) {
callback.cancelled();
}
return true;
}
return false;
}
@Override
public boolean isCancelled() {
return cancelled.get();
}
@Override
public boolean isDone() {
return done.get();
}
@Override
public E get() throws InterruptedException, ExecutionException {
try {
return get(0L, TimeUnit.MILLISECONDS);
} catch (final TimeoutException ex) {
throw new ExecutionException(ex);
}
}
@Override
public E get(final long timeout, final TimeUnit timeUnit) throws InterruptedException, ExecutionException, TimeoutException {
for (;;) {
synchronized (this) {
try {
final E entry = entryRef.get();
if (entry != null) {
return entry;
}
if (done.get()) {
throw new ExecutionException(operationAborted());
}
final E leasedEntry = getPoolEntryBlocking(route, state, timeout, timeUnit, this);
if (validateAfterInactivity > 0) {
if (leasedEntry.getUpdated() + validateAfterInactivity <= System.currentTimeMillis()) {
if (!validate(leasedEntry)) {
leasedEntry.close();
release(leasedEntry, false);
continue;
}
}
}
if (done.compareAndSet(false, true)) {
entryRef.set(leasedEntry);
done.set(true);
onLease(leasedEntry);
if (callback != null) {
callback.completed(leasedEntry);
}
return leasedEntry;
} else {
release(leasedEntry, true);
throw new ExecutionException(operationAborted());
}
} catch (final IOException ex) {
if (done.compareAndSet(false, true)) {
if (callback != null) {
callback.failed(ex);
}
}
throw new ExecutionException(ex);
}
}
}
}
};
}
lease方法主要是get及cancel，其中get方法主要是执行getPoolEntryBlocking，对于validateAfterInactivity大于0的则根据判断是否需要validate，若需要且validate失败则执行leasedEntry.close()及release方法
getPoolEntryBlocking
org/apache/http/pool/AbstractConnPool.java
private E getPoolEntryBlocking(
final T route, final Object state,
final long timeout, final TimeUnit timeUnit,
final Future future) throws IOException, InterruptedException, ExecutionException, TimeoutException {
Date deadline = null;
if (timeout > 0) {
deadline = new Date (System.currentTimeMillis() + timeUnit.toMillis(timeout));
}
this.lock.lock();
try {
final RouteSpecificPool pool = getPool(route);
E entry;
for (;;) {
Asserts.check(!this.isShutDown, "Connection pool shut down");
if (future.isCancelled()) {
throw new ExecutionException(operationAborted());
}
for (;;) {
entry = pool.getFree(state);
if (entry == null) {
break;
}
if (entry.isExpired(System.currentTimeMillis())) {
entry.close();
}
if (entry.isClosed()) {
this.available.remove(entry);
pool.free(entry, false);
} else {
break;
}
}
if (entry != null) {
this.available.remove(entry);
this.leased.add(entry);
onReuse(entry);
return entry;
}
// New connection is needed
final int maxPerRoute = getMax(route);
// Shrink the pool prior to allocating a new connection
final int excess = Math.max(0, pool.getAllocatedCount() + 1 - maxPerRoute);
if (excess > 0) {
for (int i = 0; i < excess; i++) {
final E lastUsed = pool.getLastUsed();
if (lastUsed == null) {
break;
}
lastUsed.close();
this.available.remove(lastUsed);
pool.remove(lastUsed);
}
}
if (pool.getAllocatedCount() < maxPerRoute) {
final int totalUsed = this.leased.size();
final int freeCapacity = Math.max(this.maxTotal - totalUsed, 0);
if (freeCapacity > 0) {
final int totalAvailable = this.available.size();
if (totalAvailable > freeCapacity - 1) {
if (!this.available.isEmpty()) {
final E lastUsed = this.available.removeLast();
lastUsed.close();
final RouteSpecificPool otherpool = getPool(lastUsed.getRoute());
otherpool.remove(lastUsed);
}
}
final C conn = this.connFactory.create(route);
entry = pool.add(conn);
this.leased.add(entry);
return entry;
}
}
boolean success = false;
try {
pool.queue(future);
this.pending.add(future);
if (deadline != null) {
success = this.condition.awaitUntil(deadline);
} else {
this.condition.await();
success = true;
}
if (future.isCancelled()) {
throw new ExecutionException(operationAborted());
}
} finally {
// In case of 'success', we were woken up by the
// connection pool and should now have a connection
// waiting for us, or else we're shutting down.
// Just continue in the loop, both cases are checked.
pool.unqueue(future);
this.pending.remove(future);
}
// check for spurious wakeup vs. timeout
if (!success && (deadline != null && deadline.getTime() <= System.currentTimeMillis())) {
break;
}
}
throw new TimeoutException("Timeout waiting for connection");
} finally {
this.lock.unlock();
}
}
getPoolEntryBlocking先根据route从routeToPool取出对应的RouteSpecificPool，然后pool.getFree(state)，之后判断是否过期，是否关闭，没问题则从available移除，添加到leased中，然后执行onReuse回调，如果entry为null则通过connFactory.create(route)来创建
release
@Override
public void release(final E entry, final boolean reusable) {
this.lock.lock();
try {
if (this.leased.remove(entry)) {
final RouteSpecificPool pool = getPool(entry.getRoute());
pool.free(entry, reusable);
if (reusable && !this.isShutDown) {
this.available.addFirst(entry);
} else {
entry.close();
}
onRelease(entry);
Future future = pool.nextPending();
if (future != null) {
this.pending.remove(future);
} else {
future = this.pending.poll();
}
if (future != null) {
this.condition.signalAll();
}
}
} finally {
this.lock.unlock();
}
}
release方法先获取RouteSpecificPool，然后执行pool.free(entry, reusable)
CPool
org/apache/http/impl/conn/CPool.java
@Contract(threading = ThreadingBehavior.SAFE)
class CPool extends AbstractConnPool {
private static final AtomicLong COUNTER = new AtomicLong();
private final Log log = LogFactory.getLog(CPool.class);
private final long timeToLive;
private final TimeUnit timeUnit;
public CPool(
final ConnFactory connFactory,
final int defaultMaxPerRoute, final int maxTotal,
final long timeToLive, final TimeUnit timeUnit) {
super(connFactory, defaultMaxPerRoute, maxTotal);
this.timeToLive = timeToLive;
this.timeUnit = timeUnit;
}
@Override
protected CPoolEntry createEntry(final HttpRoute route, final ManagedHttpClientConnection conn) {
final String id = Long.toString(COUNTER.getAndIncrement());
return new CPoolEntry(this.log, id, route, conn, this.timeToLive, this.timeUnit);
}
@Override
protected boolean validate(final CPoolEntry entry) {
return !entry.getConnection().isStale();
}
@Override
protected void enumAvailable(final PoolEntryCallback callback) {
super.enumAvailable(callback);
}
@Override
protected void enumLeased(final PoolEntryCallback callback) {
super.enumLeased(callback);
}
}
CPool继承了AbstractConnPool，其T为HttpRoute，C为ManagedHttpClientConnection，E为CPoolEntry；其createEntry方法创建CPoolEntry，validate则判断connect是不是stale
小结
ConnPool定义了lease及release方法，其中定义了两个泛型，T表示route，E表示poolEntry；AbstractConnPool声明实现ConnPool、ConnPoolControl接口，它定义E必须继承PoolEntry，同时定义了泛型C，表示connectionType；CPool继承了AbstractConnPool，其T为HttpRoute，C为ManagedHttpClientConnection，E为CPoolEntry。
AbstractConnPool的lease方法主要是get及cancel，其中get方法主要是执行getPoolEntryBlocking，对于validateAfterInactivity大于0的则根据判断是否需要validate，若需要且validate失败则执行leasedEntry.close()及release方法；release方法先获取RouteSpecificPool，然后执行pool.free(entry, reusable)