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| public final class StreamAllocation {
// 地址
public final Address address;
private RouteSelector.Selection routeSelection;
private Route route;
private final ConnectionPool connectionPool;
public final Call call;
public final EventListener eventListener;
private final Object callStackTrace;
// State guarded by connectionPool.
private final RouteSelector routeSelector;
private int refusedStreamCount;
private RealConnection connection;
private boolean reportedAcquired;
private boolean released;
private boolean canceled;
private HttpCodec codec;
// 在RetryAndFollowUpInterceptor中调用构造方法初始化
public StreamAllocation(ConnectionPool connectionPool, Address address, Call call,
EventListener eventListener, Object callStackTrace) {
this.connectionPool = connectionPool;
this.address = address;
this.call = call;
this.eventListener = eventListener;
this.routeSelector = new RouteSelector(address, routeDatabase(), call, eventListener);
this.callStackTrace = callStackTrace;
}
/**
* 在ConnectInterceptor中调用
* 创建新的流，返回HttpCodec
* 注意⚠️：doExtensiveHealthChecks 如果不是GET请求就是true
*/
public HttpCodec newStream(
OkHttpClient client, Interceptor.Chain chain, boolean doExtensiveHealthChecks) {
int connectTimeout = chain.connectTimeoutMillis();
int readTimeout = chain.readTimeoutMillis();
int writeTimeout = chain.writeTimeoutMillis();
int pingIntervalMillis = client.pingIntervalMillis();
boolean connectionRetryEnabled = client.retryOnConnectionFailure();
try {
// 找到一个健康的连接
RealConnection resultConnection = findHealthyConnection(connectTimeout, readTimeout,
writeTimeout, pingIntervalMillis, connectionRetryEnabled, doExtensiveHealthChecks);
// 初始化 HttpCodec
HttpCodec resultCodec = resultConnection.newCodec(client, chain, this);
synchronized (connectionPool) {
codec = resultCodec;
return resultCodec;
}
} catch (IOException e) {
throw new RouteException(e);
}
}
/**
* 找到一个健康的连接，如果没有就创建个健康的
*/
private RealConnection findHealthyConnection(int connectTimeout, int readTimeout,
int writeTimeout, int pingIntervalMillis, boolean connectionRetryEnabled,
boolean doExtensiveHealthChecks) throws IOException {
// 注意这个永动机
while (true) {
// 从连接池中拿出一个连接
RealConnection candidate = findConnection(connectTimeout, readTimeout, writeTimeout,
pingIntervalMillis, connectionRetryEnabled);
// 所谓「健康」的连接，就是successCount为0
synchronized (connectionPool) {
if (candidate.successCount == 0) {
return candidate;
}
}
// 如果没有健康的连接，就继续循环去等
if (!candidate.isHealthy(doExtensiveHealthChecks)) {
noNewStreams();
continue;
}
return candidate;
}
}
// 返回一个连接，优先返回连接池中已经存在的，没有则创建
private RealConnection findConnection(int connectTimeout, int readTimeout, int writeTimeout,
int pingIntervalMillis, boolean connectionRetryEnabled) throws IOException {
boolean foundPooledConnection = false;
RealConnection result = null;
Route selectedRoute = null;
Connection releasedConnection;
Socket toClose;
//锁加到了连接池上
synchronized (connectionPool) {
if (released) throw new IllegalStateException("released");
if (codec != null) throw new IllegalStateException("codec != null");
if (canceled) throw new IOException("Canceled");
// 尝试使用已分配的连接。我们需要小心，因为我们的「已分配」连接可能已被限制创建新流。
releasedConnection = this.connection;
// 关闭连接，回收socket
toClose = releaseIfNoNewStreams();
// 复用this.connection
if (this.connection != null) {
result = this.connection;
releasedConnection = null;
}
if (!reportedAcquired) {
// If the connection was never reported acquired, don't report it as released!
releasedConnection = null;
}
if (result == null) {
// 从连接池中拿出一个连接，这块有点麻烦，我记得Internal.instance是在client中初始化了一个匿名类，回头再看一下去
Internal.instance.get(connectionPool, address, this, null);
if (connection != null) {
foundPooledConnection = true;
result = connection;
} else {
selectedRoute = route;
}
}
}
// 关闭Socket
closeQuietly(toClose);
if (releasedConnection != null) {
eventListener.connectionReleased(call, releasedConnection);
}
if (foundPooledConnection) {
eventListener.connectionAcquired(call, result);
}
if (result != null) {
// If we found an already-allocated or pooled connection, we're done.
return result;
}
// If we need a route selection, make one. This is a blocking operation.
boolean newRouteSelection = false;
if (selectedRoute == null && (routeSelection == null || !routeSelection.hasNext())) {
newRouteSelection = true;
routeSelection = routeSelector.next();
}
synchronized (connectionPool) {
if (canceled) throw new IOException("Canceled");
if (newRouteSelection) {
// Now that we have a set of IP addresses, make another attempt at getting a connection from
// the pool. This could match due to connection coalescing.
List<Route> routes = routeSelection.getAll();
for (int i = 0, size = routes.size(); i < size; i++) {
Route route = routes.get(i);
Internal.instance.get(connectionPool, address, this, route);
if (connection != null) {
foundPooledConnection = true;
result = connection;
this.route = route;
break;
}
}
}
if (!foundPooledConnection) {
if (selectedRoute == null) {
selectedRoute = routeSelection.next();
}
// Create a connection and assign it to this allocation immediately. This makes it possible
// for an asynchronous cancel() to interrupt the handshake we're about to do.
route = selectedRoute;
refusedStreamCount = 0;
result = new RealConnection(connectionPool, selectedRoute);
acquire(result, false);
}
}
// If we found a pooled connection on the 2nd time around, we're done.
if (foundPooledConnection) {
eventListener.connectionAcquired(call, result);
return result;
}
// 开始 TCP + TLS 握手，全程阻塞
result.connect(connectTimeout, readTimeout, writeTimeout, pingIntervalMillis,
connectionRetryEnabled, call, eventListener);
routeDatabase().connected(result.route());
Socket socket = null;
synchronized (connectionPool) {
reportedAcquired = true;
// Pool the connection.
Internal.instance.put(connectionPool, result);
// If another multiplexed connection to the same address was created concurrently, then
// release this connection and acquire that one.
if (result.isMultiplexed()) {
socket = Internal.instance.deduplicate(connectionPool, address, this);
result = connection;
}
}
closeQuietly(socket);
eventListener.connectionAcquired(call, result);
return result;
}
// 如果保持的连接限制创建新流，则释放当前保持的连接并返回一个套接字以关闭。
// 那么，什么连接会限制创建新流呢？http1.0只支持单连接，且不可复用；htpp2.0也是单路复用，所以不能创建新流。
private Socket releaseIfNoNewStreams() {
// 断言连接池持有监视器锁synchornized
assert (Thread.holdsLock(connectionPool));
RealConnection allocatedConnection = this.connection;
// 注意noNewStreams在什么时候被赋值还需要看一下
if (allocatedConnection != null && allocatedConnection.noNewStreams) {
// 释放资源
return deallocate(false, false, true);
}
return null;
}
public void streamFinished(boolean noNewStreams, HttpCodec codec, long bytesRead, IOException e) {
eventListener.responseBodyEnd(call, bytesRead);
Socket socket;
Connection releasedConnection;
boolean callEnd;
synchronized (connectionPool) {
if (codec == null || codec != this.codec) {
throw new IllegalStateException("expected " + this.codec + " but was " + codec);
}
if (!noNewStreams) {
connection.successCount++;
}
releasedConnection = connection;
socket = deallocate(noNewStreams, false, true);
if (connection != null) releasedConnection = null;
callEnd = this.released;
}
closeQuietly(socket);
if (releasedConnection != null) {
eventListener.connectionReleased(call, releasedConnection);
}
if (e != null) {
eventListener.callFailed(call, e);
} else if (callEnd) {
eventListener.callEnd(call);
}
}
public HttpCodec codec() {
synchronized (connectionPool) {
return codec;
}
}
private RouteDatabase routeDatabase() {
return Internal.instance.routeDatabase(connectionPool);
}
public Route route() {
return route;
}
public synchronized RealConnection connection() {
return connection;
}
public void release() {
Socket socket;
Connection releasedConnection;
synchronized (connectionPool) {
releasedConnection = connection;
socket = deallocate(false, true, false);
if (connection != null) releasedConnection = null;
}
closeQuietly(socket);
if (releasedConnection != null) {
eventListener.connectionReleased(call, releasedConnection);
}
}
// 我暂时理解为关闭数据流
public void noNewStreams() {
Socket socket;
Connection releasedConnection;
synchronized (connectionPool) {
releasedConnection = connection;
socket = deallocate(true, false, false);
if (connection != null) releasedConnection = null;
}
closeQuietly(socket);
if (releasedConnection != null) {
eventListener.connectionReleased(call, releasedConnection);
}
}
//解除分配，释放此分配持有的资源。 如果分配了足够的资源，连接将被分离或关闭。 调用者必须在连接池上同步。返回一个Util.closeQuietly ，调用者应在同步块完成后传递给Util.closeQuietly 。 （在连接池上同步时我们不进行 I/O。）
private Socket deallocate(boolean noNewStreams, boolean released, boolean streamFinished) {
assert (Thread.holdsLock(connectionPool));
if (streamFinished) {
this.codec = null;
}
if (released) {
this.released = true;
}
Socket socket = null;
if (connection != null) {
if (noNewStreams) {
// 擦，在这里就赋值了
connection.noNewStreams = true;
}
if (this.codec == null && (this.released || connection.noNewStreams)) {
release(connection);
if (connection.allocations.isEmpty()) {
connection.idleAtNanos = System.nanoTime();
if (Internal.instance.connectionBecameIdle(connectionPool, connection)) {
socket = connection.socket();
}
}
connection = null;
}
}
return socket;
}
public void cancel() {
HttpCodec codecToCancel;
RealConnection connectionToCancel;
synchronized (connectionPool) {
canceled = true;
codecToCancel = codec;
connectionToCancel = connection;
}
if (codecToCancel != null) {
codecToCancel.cancel();
} else if (connectionToCancel != null) {
connectionToCancel.cancel();
}
}
public void streamFailed(IOException e) {
Socket socket;
Connection releasedConnection;
boolean noNewStreams = false;
synchronized (connectionPool) {
if (e instanceof StreamResetException) {
StreamResetException streamResetException = (StreamResetException) e;
if (streamResetException.errorCode == ErrorCode.REFUSED_STREAM) {
refusedStreamCount++;
}
// On HTTP/2 stream errors, retry REFUSED_STREAM errors once on the same connection. All
// other errors must be retried on a new connection.
if (streamResetException.errorCode != ErrorCode.REFUSED_STREAM || refusedStreamCount > 1) {
noNewStreams = true;
route = null;
}
} else if (connection != null
&& (!connection.isMultiplexed() || e instanceof ConnectionShutdownException)) {
noNewStreams = true;
// If this route hasn't completed a call, avoid it for new connections.
if (connection.successCount == 0) {
if (route != null && e != null) {
routeSelector.connectFailed(route, e);
}
route = null;
}
}
releasedConnection = connection;
socket = deallocate(noNewStreams, false, true);
if (connection != null || !reportedAcquired) releasedConnection = null;
}
closeQuietly(socket);
if (releasedConnection != null) {
eventListener.connectionReleased(call, releasedConnection);
}
}
/**
* Use this allocation to hold {@code connection}. Each call to this must be paired with a call to
* {@link #release} on the same connection.
*/
public void acquire(RealConnection connection, boolean reportedAcquired) {
assert (Thread.holdsLock(connectionPool));
if (this.connection != null) throw new IllegalStateException();
this.connection = connection;
this.reportedAcquired = reportedAcquired;
connection.allocations.add(new StreamAllocationReference(this, callStackTrace));
}
/** Remove this allocation from the connection's list of allocations. */
private void release(RealConnection connection) {
for (int i = 0, size = connection.allocations.size(); i < size; i++) {
Reference<StreamAllocation> reference = connection.allocations.get(i);
if (reference.get() == this) {
connection.allocations.remove(i);
return;
}
}
throw new IllegalStateException();
}
/**
* Release the connection held by this connection and acquire {@code newConnection} instead. It is
* only safe to call this if the held connection is newly connected but duplicated by {@code
* newConnection}. Typically this occurs when concurrently connecting to an HTTP/2 webserver.
*
* <p>Returns a closeable that the caller should pass to {@link Util#closeQuietly} upon completion
* of the synchronized block. (We don't do I/O while synchronized on the connection pool.)
*/
public Socket releaseAndAcquire(RealConnection newConnection) {
assert (Thread.holdsLock(connectionPool));
if (codec != null || connection.allocations.size() != 1) throw new IllegalStateException();
// Release the old connection.
Reference<StreamAllocation> onlyAllocation = connection.allocations.get(0);
Socket socket = deallocate(true, false, false);
// Acquire the new connection.
this.connection = newConnection;
newConnection.allocations.add(onlyAllocation);
return socket;
}
public boolean hasMoreRoutes() {
return route != null
|| (routeSelection != null && routeSelection.hasNext())
|| routeSelector.hasNext();
}
@Override public String toString() {
RealConnection connection = connection();
return connection != null ? connection.toString() : address.toString();
}
public static final class StreamAllocationReference extends WeakReference<StreamAllocation> {
/**
* Captures the stack trace at the time the Call is executed or enqueued. This is helpful for
* identifying the origin of connection leaks.
*/
public final Object callStackTrace;
StreamAllocationReference(StreamAllocation referent, Object callStackTrace) {
super(referent);
this.callStackTrace = callStackTrace;
}
}
}
|