httpclient staleConnectionCheckEnabled获取连接流程解析
作者：codecraft
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本文主要研究一下httpclient的staleConnectionCheckEnabled
staleConnectionCheckEnabled
org/apache/http/client/config/RequestConfig.java
public class RequestConfig implements Cloneable {
public static final RequestConfig DEFAULT = new Builder().build();
private final boolean expectContinueEnabled;
private final HttpHost proxy;
private final InetAddress localAddress;
private final boolean staleConnectionCheckEnabled;
//......
/**
* Determines whether stale connection check is to be used. The stale
* connection check can cause up to 30 millisecond overhead per request and
* should be used only when appropriate. For performance critical
* operations this check should be disabled.
* <p>
* Default: {@code false} since 4.4
* </p>
*
* @deprecated (4.4) Use {@link
* org.apache.http.impl.conn.PoolingHttpClientConnectionManager#getValidateAfterInactivity()}
*/
@Deprecated
public boolean isStaleConnectionCheckEnabled() {
return staleConnectionCheckEnabled;
}
public static class Builder {
private boolean expectContinueEnabled;
private HttpHost proxy;
private InetAddress localAddress;
private boolean staleConnectionCheckEnabled;
//......
Builder() {
super();
this.staleConnectionCheckEnabled = false;
this.redirectsEnabled = true;
this.maxRedirects = 50;
this.relativeRedirectsAllowed = true;
this.authenticationEnabled = true;
this.connectionRequestTimeout = -1;
this.connectTimeout = -1;
this.socketTimeout = -1;
this.contentCompressionEnabled = true;
this.normalizeUri = true;
}
/**
* @deprecated (4.4) Use {@link
* org.apache.http.impl.conn.PoolingHttpClientConnectionManager#setValidateAfterInactivity(int)}
*/
@Deprecated
public Builder setStaleConnectionCheckEnabled(final boolean staleConnectionCheckEnabled) {
this.staleConnectionCheckEnabled = staleConnectionCheckEnabled;
return this;
}
//......
}
}RequestConfig定义了staleConnectionCheckEnabled属性，在4.4版本废弃了，默认为false，替换设置是org.apache.http.impl.conn.PoolingHttpClientConnectionManager.setValidateAfterInactivity(int)；Builder方法也提供了setStaleConnectionCheckEnabled方法
MainClientExec
org/apache/http/impl/execchain/MainClientExec.java
public CloseableHttpResponse execute(
final HttpRoute route,
final HttpRequestWrapper request,
final HttpClientContext context,
final HttpExecutionAware execAware) throws IOException, HttpException {
Args.notNull(route, "HTTP route");
Args.notNull(request, "HTTP request");
Args.notNull(context, "HTTP context");
AuthState targetAuthState = context.getTargetAuthState();
if (targetAuthState == null) {
targetAuthState = new AuthState();
context.setAttribute(HttpClientContext.TARGET_AUTH_STATE, targetAuthState);
}
AuthState proxyAuthState = context.getProxyAuthState();
if (proxyAuthState == null) {
proxyAuthState = new AuthState();
context.setAttribute(HttpClientContext.PROXY_AUTH_STATE, proxyAuthState);
}
if (request instanceof HttpEntityEnclosingRequest) {
RequestEntityProxy.enhance((HttpEntityEnclosingRequest) request);
}
Object userToken = context.getUserToken();
final ConnectionRequest connRequest = connManager.requestConnection(route, userToken);
if (execAware != null) {
if (execAware.isAborted()) {
connRequest.cancel();
throw new RequestAbortedException("Request aborted");
}
execAware.setCancellable(connRequest);
}
final RequestConfig config = context.getRequestConfig();
final HttpClientConnection managedConn;
try {
final int timeout = config.getConnectionRequestTimeout();
managedConn = connRequest.get(timeout > 0 ? timeout : 0, TimeUnit.MILLISECONDS);
} catch(final InterruptedException interrupted) {
Thread.currentThread().interrupt();
throw new RequestAbortedException("Request aborted", interrupted);
} catch(final ExecutionException ex) {
Throwable cause = ex.getCause();
if (cause == null) {
cause = ex;
}
throw new RequestAbortedException("Request execution failed", cause);
}
context.setAttribute(HttpCoreContext.HTTP_CONNECTION, managedConn);
if (config.isStaleConnectionCheckEnabled()) {
// validate connection
if (managedConn.isOpen()) {
this.log.debug("Stale connection check");
if (managedConn.isStale()) {
this.log.debug("Stale connection detected");
managedConn.close();
}
}
}
final ConnectionHolder connHolder = new ConnectionHolder(this.log, this.connManager, managedConn);
try {
if (execAware != null) {
execAware.setCancellable(connHolder);
}
HttpResponse response;
for (int execCount = 1;; execCount++) {
if (execCount > 1 && !RequestEntityProxy.isRepeatable(request)) {
throw new NonRepeatableRequestException("Cannot retry request " +
"with a non-repeatable request entity.");
}
if (execAware != null && execAware.isAborted()) {
throw new RequestAbortedException("Request aborted");
}
if (!managedConn.isOpen()) {
this.log.debug("Opening connection " + route);
try {
establishRoute(proxyAuthState, managedConn, route, request, context);
} catch (final TunnelRefusedException ex) {
if (this.log.isDebugEnabled()) {
this.log.debug(ex.getMessage());
}
response = ex.getResponse();
break;
}
}
context.setAttribute(HttpCoreContext.HTTP_REQUEST, request);
response = requestExecutor.execute(request, managedConn, context);
//......
}
}
//......
//......
}MainClientExec的execute先通过connManager.requestConnection获取ConnectionRequest，然后通过connRequest.get(timeout > 0 ? timeout : 0, TimeUnit.MILLISECONDS)获取managedConn，之后判断requestConfig的isStaleConnectionCheckEnabled，为true的话，会执行连接的校验，先判断是否open，再判断是否stale，为stale的话则执行close；在managedConn关闭的时候，会通过establishRoute再进行连接
establishRoute
org/apache/http/impl/execchain/MainClientExec.java
/**
* Establishes the target route.
*/
void establishRoute(
final AuthState proxyAuthState,
final HttpClientConnection managedConn,
final HttpRoute route,
final HttpRequest request,
final HttpClientContext context) throws HttpException, IOException {
final RequestConfig config = context.getRequestConfig();
final int timeout = config.getConnectTimeout();
final RouteTracker tracker = new RouteTracker(route);
int step;
do {
final HttpRoute fact = tracker.toRoute();
step = this.routeDirector.nextStep(route, fact);
switch (step) {
case HttpRouteDirector.CONNECT_TARGET:
this.connManager.connect(
managedConn,
route,
timeout > 0 ? timeout : 0,
context);
tracker.connectTarget(route.isSecure());
break;
case HttpRouteDirector.CONNECT_PROXY:
this.connManager.connect(
managedConn,
route,
timeout > 0 ? timeout : 0,
context);
final HttpHost proxy = route.getProxyHost();
tracker.connectProxy(proxy, route.isSecure() && !route.isTunnelled());
break;
case HttpRouteDirector.TUNNEL_TARGET: {
final boolean secure = createTunnelToTarget(
proxyAuthState, managedConn, route, request, context);
this.log.debug("Tunnel to target created.");
tracker.tunnelTarget(secure);
} break;
case HttpRouteDirector.TUNNEL_PROXY: {
// The most simple example for this case is a proxy chain
// of two proxies, where P1 must be tunnelled to P2.
// route: Source -> P1 -> P2 -> Target (3 hops)
// fact: Source -> P1 -> Target (2 hops)
final int hop = fact.getHopCount()-1; // the hop to establish
final boolean secure = createTunnelToProxy(route, hop, context);
this.log.debug("Tunnel to proxy created.");
tracker.tunnelProxy(route.getHopTarget(hop), secure);
} break;
case HttpRouteDirector.LAYER_PROTOCOL:
this.connManager.upgrade(managedConn, route, context);
tracker.layerProtocol(route.isSecure());
break;
case HttpRouteDirector.UNREACHABLE:
throw new HttpException("Unable to establish route: " +
"planned = " + route + "; current = " + fact);
case HttpRouteDirector.COMPLETE:
this.connManager.routeComplete(managedConn, route, context);
break;
default:
throw new IllegalStateException("Unknown step indicator "
+ step + " from RouteDirector.");
}
} while (step > HttpRouteDirector.COMPLETE);
}establishRoute方法在循环里头通过connManager.connect建立连接
requestConnection
org/apache/http/impl/conn/PoolingHttpClientConnectionManager.java
public ConnectionRequest requestConnection(
final HttpRoute route,
final Object state) {
Args.notNull(route, "HTTP route");
if (this.log.isDebugEnabled()) {
this.log.debug("Connection request: " + format(route, state) + formatStats(route));
}
final Future<CPoolEntry> future = this.pool.lease(route, state, null);
return new ConnectionRequest() {
@Override
public boolean cancel() {
return future.cancel(true);
}
@Override
public HttpClientConnection get(
final long timeout,
final TimeUnit timeUnit) throws InterruptedException, ExecutionException, ConnectionPoolTimeoutException {
final HttpClientConnection conn = leaseConnection(future, timeout, timeUnit);
if (conn.isOpen()) {
final HttpHost host;
if (route.getProxyHost() != null) {
host = route.getProxyHost();
} else {
host = route.getTargetHost();
}
final SocketConfig socketConfig = resolveSocketConfig(host);
conn.setSocketTimeout(socketConfig.getSoTimeout());
}
return conn;
}
};
}PoolingHttpClientConnectionManager的requestConnection返回的ConnectionRequest的get方法是通过leaseConnection(future, timeout, timeUnit)来获取连接的，而leaseConnection依赖的是pool.lease(route, state, null)返回的future
lease
org/apache/http/pool/AbstractConnPool.java
/**
* {@inheritDoc}
* <p>
* Please note that this class does not maintain its own pool of execution
* {@link Thread}s. Therefore, one <b>must</b> call {@link Future#get()}
* or {@link Future#get(long, TimeUnit)} method on the {@link Future}
* returned by this method in order for the lease operation to complete.
*/
@Override
public Future<E> lease(final T route, final Object state, final FutureCallback<E> callback) {
Args.notNull(route, "Route");
Asserts.check(!this.isShutDown, "Connection pool shut down");
return new Future<E>() {
private final AtomicBoolean cancelled = new AtomicBoolean(false);
private final AtomicBoolean done = new AtomicBoolean(false);
private final AtomicReference<E> entryRef = new AtomicReference<E>(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返回的future的get(final long timeout, final TimeUnit timeUnit)方法在一个循环里头去获取连接，内部是通过getPoolEntryBlocking获取到leasedEntry，然后在validateAfterInactivity大于0的时候进行连接校验，在leasedEntry.getUpdated() + validateAfterInactivity <= System.currentTimeMillis()的时候进行validate，校验不成功的话进行关闭掉leasedEntry，然后release掉leasedEntry，然后继续循环获取下一个连接
小结
httpclient的RequestConfig提供了staleConnectionCheckEnabled属性用于在请求获取到连接的时候进行连接检测，不过这个属性在4.4版本被废弃了，并默认设置为false，替换设置是org.apache.http.impl.conn.PoolingHttpClientConnectionManager.setValidateAfterInactivity(int)，它是在ConnectionRequest的lease方法里头根据leasedEntry.getUpdated() + validateAfterInactivity判断是否需要校验连接，若需要且校验不通过则循环继续获取；而staleConnectionCheckEnabled则是在requestConnection之后根据RequestConfig的isStaleConnectionCheckEnabled来判断，然后进行连接校验，校验不通过则关闭managedConn，最后会在判断如果managedConn.isOpen()为false，则执行establishRoute，在循环里头通过connManager.connect来建立新连接。
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