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LittleProxy is a high performance HTTP proxy written in Java and using the Netty networking framework.
package org.littleshoot.proxy.impl;
import io.netty.util.concurrent.Future;
import io.netty.util.concurrent.GenericFutureListener;
import java.util.Queue;
import java.util.concurrent.ConcurrentLinkedQueue;
/**
* Coordinates the various steps involved in establishing a connection, such as
* establishing a socket connection, SSL handshaking, HTTP CONNECT request
* processing, and so on.
*/
class ConnectionFlow {
private Queue steps = new ConcurrentLinkedQueue();
private final ClientToProxyConnection clientConnection;
private final ProxyToServerConnection serverConnection;
private volatile ConnectionFlowStep currentStep;
private volatile boolean suppressInitialRequest = false;
private final Object connectLock;
/**
* Construct a new {@link ConnectionFlow} for the given client and server
* connections.
*
* @param clientConnection
* @param serverConnection
* @param connectLock
* an object that's shared by {@link ConnectionFlow} and
* {@link ProxyToServerConnection} and that is used for
* synchronizing the reader and writer threads that are both
* involved during the establishing of a connection.
*/
ConnectionFlow(
ClientToProxyConnection clientConnection,
ProxyToServerConnection serverConnection,
Object connectLock) {
super();
this.clientConnection = clientConnection;
this.serverConnection = serverConnection;
this.connectLock = connectLock;
}
/**
* Add a {@link ConnectionFlowStep} to this flow.
*
* @param step
* @return
*/
ConnectionFlow then(ConnectionFlowStep step) {
steps.add(step);
return this;
}
/**
* While we're in the process of connecting, any messages read by the
* {@link ProxyToServerConnection} are passed to this method, which passes
* it on to {@link ConnectionFlowStep#read(ConnectionFlow, Object)} for the
* current {@link ConnectionFlowStep}.
*
* @param msg
*/
void read(Object msg) {
if (this.currentStep != null) {
this.currentStep.read(this, msg);
}
}
/**
* Starts the connection flow, notifying the {@link ClientToProxyConnection}
* that we've started.
*/
void start() {
clientConnection.serverConnectionFlowStarted(serverConnection);
advance();
}
/**
*
* Advances the flow. {@link #advance()} will be called until we're either
* out of steps, or a step has failed.
*
*/
void advance() {
currentStep = steps.poll();
if (currentStep == null) {
succeed();
} else {
processCurrentStep();
}
}
/**
*
* Process the current {@link ConnectionFlowStep}. With each step, we:
*
*
*
* - Change the state of the associated {@link ProxyConnection} to the
* value of {@link ConnectionFlowStep#getState()}
* - Call {@link ConnectionFlowStep#execute()}
* - On completion of the {@link Future} returned by
* {@link ConnectionFlowStep#execute()}, check the success.
* - If successful, we call back into
* {@link ConnectionFlowStep#onSuccess(ConnectionFlow)}.
* - If unsuccessful, we call {@link #fail()}, stopping the connection
* flow
*
*/
private void processCurrentStep() {
final ProxyConnection connection = currentStep.getConnection();
final ProxyConnectionLogger LOG = connection.getLOG();
LOG.debug("Processing connection flow step: {}", currentStep);
connection.become(currentStep.getState());
suppressInitialRequest = suppressInitialRequest
|| currentStep.shouldSuppressInitialRequest();
if (currentStep.shouldExecuteOnEventLoop()) {
connection.ctx.executor().submit(new Runnable() {
@Override
public void run() {
doProcessCurrentStep(LOG);
}
});
} else {
doProcessCurrentStep(LOG);
}
}
/**
* Does the work of processing the current step, checking the result and
* handling success/failure.
*
* @param LOG
*/
@SuppressWarnings("unchecked")
private void doProcessCurrentStep(final ProxyConnectionLogger LOG) {
currentStep.execute().addListener(
new GenericFutureListener>() {
public void operationComplete(
io.netty.util.concurrent.Future future)
throws Exception {
synchronized (connectLock) {
if (future.isSuccess()) {
LOG.debug("ConnectionFlowStep succeeded");
currentStep
.onSuccess(ConnectionFlow.this);
} else {
LOG.debug("ConnectionFlowStep failed",
future.cause());
fail(future.cause());
}
}
};
});
}
/**
* Called when the flow is complete and successful. Notifies the
* {@link ProxyToServerConnection} that we succeeded.
*/
void succeed() {
synchronized (connectLock) {
serverConnection.getLOG().debug(
"Connection flow completed successfully: {}", currentStep);
serverConnection.connectionSucceeded(!suppressInitialRequest);
notifyThreadsWaitingForConnection();
}
}
/**
* Called when the flow fails at some {@link ConnectionFlowStep}.
* Disconnects the {@link ProxyToServerConnection} and informs the
* {@link ClientToProxyConnection} that our connection failed.
*/
@SuppressWarnings("unchecked")
void fail(final Throwable cause) {
final ConnectionState lastStateBeforeFailure = serverConnection
.getCurrentState();
serverConnection.disconnect().addListener(
new GenericFutureListener() {
@Override
public void operationComplete(Future future)
throws Exception {
synchronized (connectLock) {
if (!clientConnection.serverConnectionFailed(
serverConnection,
lastStateBeforeFailure,
cause)) {
// the connection to the server failed and we are not retrying, so transition to the
// DISCONNECTED state
serverConnection.become(ConnectionState.DISCONNECTED);
// We are not retrying our connection, let anyone waiting for a connection know that we're done
notifyThreadsWaitingForConnection();
}
}
}
});
}
/**
* Like {@link #fail(Throwable)} but with no cause.
*/
void fail() {
fail(null);
}
/**
* Once we've finished recording our connection and written our initial
* request, we can notify anyone who is waiting on the connection that it's
* okay to proceed.
*/
private void notifyThreadsWaitingForConnection() {
connectLock.notifyAll();
}
}