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Slow tcp connection causes my app to stall

I have found a class that handles TCP connections and I am using it to communicate with a gaming service. All was working fine until I realized that my application was stalling if the connection speed was slower. I have a thread polling let's say every 30 seconds.
I got the TCPClient class I use from this thread Java TCP sending first message, then infinite wait
This service requires 2 steps to verify a request. You first send a hash and you receive and acknowledge. Then you send the the actual request and you receive the response.
public byte[] getResponse(byte[] hash, byte[] request) throws Exception{
if(client == null || client.socket.isClosed() || !client.socket.isConnected()
|| client.socket.isInputShutdown() || client.socket.isOutputShutdown(){
client = new TCPClient(this.host, this.port);
}
client.SendToServer(hash);
byte[] ack = client.ReceiveFromServer();
if(checkAck(ack, getAckForRequest(request))){
client.SendToServer(request);
byte[] response = client.ReceiveFromServer();
return response;
}
}
My code looks something like this. I simplified it a bit to make it more readable.
I am using this function inside a try/catch block and when it throws an exception I store the request in a MySQL database.
Is there a way to avoid blocking my main thread if the connection is slow and do the same stuff?

Is there a way to avoid blocking my main thread if the connection is slow and do the same stuff?
Yes. One can call setSoTimeout() on a Socket.
The Oracle documentation:
https://docs.oracle.com/javase/8/docs/api/java/net/Socket.html#setSoTimeout-int-
Enable/disable SO_TIMEOUT with the specified timeout, in milliseconds. With this option set to a non-zero timeout, a read() call on the InputStream associated with this Socket will block for only this amount of time. If the timeout expires, a java.net.SocketTimeoutException is raised, though the Socket is still valid. The option must be enabled prior to entering the blocking operation to have effect. The timeout must be > 0. A timeout of zero is interpreted as an infinite timeout.
If you just want to close the connection and give up it works well. If you want to resume the action later you have to keep track of the bytes already read which means just having more threads is usually an easier option.

Apache HttpClient: setConnectTimeout() vs. setConnectionTimeToLive() vs. setSocketTimeout()

Can someone please explain what is the difference between these two:
client = HttpClientBuilder.create()
.setConnectionTimeToLive(1, TimeUnit.MINUTES)
.build();
and
RequestConfig requestConfig = RequestConfig.custom().setConnectTimeout(30 * 1000).build();
client = HttpClientBuilder
.create()
.setDefaultRequestConfig(requestConfig)
.build();
Is it better to use setSocketTimeout()?

A ConnectTimeout determines the maximum time to wait for the other side to answer "yes, I'm here, let's talk" when creating a new connection (ConnectTimeout eventually calls socket.connect(address, timeout). The wait-time is usually less than a second, unless the other side is really busy with just accepting new incoming connections or you have to go through the great firewall of China. In the latter cases it can be a minute (or more) before the new connection is created. If the connection is not established within the ConnectTimeout, you get an error (1).
setSocketTimeout eventually calls socket.setSoTimeout which is explained in this answer.
The ConnectionTimeToLive determines the maximum age of a connection (after which it will be closed), regardless of when the connection was last used. Normally, there is an "idle timeout" to cleanup connections, i.e. you or the other side will close a connection that is not used for a while. Typically, you will close an idle connection before the other side does to prevent errors. But there are two other cases I can think of where a maximum age for a connection is useful:
Bad network components: count yourself lucky if you have not met them. Some bad routers, firewalls, proxies, etc. will just drop (actively being used) connections after something like 30 minutes. Since you and the other side may not even be aware that a connection was dropped, you can get "connection reset" errors for no obvious reason at weird times.
Cached meta-data: most systems keep some meta-data about a connection in some sort of cache. Some systems manage this cache badly - cache size just grows with the age of the connection.
A note about the ConnectionTimeToLive implementation in Apache HttpClient 4.5.4: I think you must use the PoolingHttpClientConnectionManager for the option to work (it eventually all comes down to a call to this isExpired method). If you do not use this connection manager, test the option to make sure it really works.
(1) Interesting comment from EJP user207421 on this related answer

Connection Timeout:
It is the timeout until a connection with the server is established.
Socket Timeout:
this is the time of inactivity to wait for packets[data] to receive.
setConnectionRequestTimeout:
However it is specific for configuring the connection manager. It is the time to fetch a connection from the connection pool.
It returns the timeout in milliseconds used when requesting a connection from the connection manager. 0(zero) is used for an infinite timeout.
setConnectionTimeToLive
public final HttpClientBuilder setConnectionTimeToLive(long connTimeToLive, TimeUnit connTimeToLiveTimeUnit)
Sets maximum time to live for persistent connections
Please note this value can be overridden by the setConnectionManager(org.apache.http.conn.HttpClientConnectionManager) method.
Since:
4.4
Example: HttpClientStarter.java
#Override
public boolean start() {
RegistryBuilder<ConnectionSocketFactory> r = RegistryBuilder.<ConnectionSocketFactory> create();
// Register http and his plain socket factory
final SocketFactory ss = getLevel().find(SocketFactory.class);
ConnectionSocketFactory plainsf = new PlainConnectionSocketFactory() {
#Override
public Socket createSocket(HttpContext context) throws IOException {
return ss.createSocket();
}
};
r.register("http", plainsf);
// Register https
ConnectionSocketFactory sslfactory = getSSLSocketFactory();
if (sslfactory != null) {
r.register("https", getSSLSocketFactory());
} else {
log(Level.WARN, "ssl factory not found, won't manage https");
}
HttpClientBuilder builder = HttpClientBuilder.create();
builder.setUserAgent(USERAGENT);
builder.setConnectionTimeToLive(timeout, TimeUnit.SECONDS);
builder.evictIdleConnections((long) timeout, TimeUnit.SECONDS);
PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager(r.build());
cm.setMaxTotal(maxConnect * 2);
cm.setDefaultMaxPerRoute(2);
cm.setValidateAfterInactivity(timeout * 1000);
builder.setConnectionManager(cm);
RequestConfig rc = RequestConfig.custom()
.setConnectionRequestTimeout(timeout * 1000)
.setConnectTimeout(timeout * 1000)
.setSocketTimeout(timeout * 1000)
.build();
builder.setDefaultRequestConfig(rc);
client = builder.build();
return true;
}
Resource Link:
HttpClientStarter.java
HttpClient 4.x
Timeout
The HTTP specification does not determine how long a persistent connection may or should remain active. Some HTTP servers use a non-standard header, Keep-Alive, to tell clients the number of seconds they want to stay connected on the server side. HttClient will take advantage of this if this information is available. If the header information Keep-Alive does not exist in the response, HttpClient assumes the connection remains active indefinitely. However, many real-world HTTP servers are configured to discard persistent connections after certain periods of inactivity to conserve system resources, often without notification to the client.
Here you can rewrite one, here is set to 5 seconds
ConnectionKeepAliveStrategy keepAliveStrategy = new DefaultConnectionKeepAliveStrategy() {
#Override
public long getKeepAliveDuration(final HttpResponse response, final HttpContext context) {
long keepAlive = super.getKeepAliveDuration(response, context);
if (keepAlive == -1) {
keepAlive = 5000;
}
return keepAlive;
}
};
Connection eviction policy
The main disadvantage of a classic blocking I/O model is that network
sockets respond to I/O events only when I/O operations are blocked.
When a connection is released back to the manager, it can be kept
alive without monitoring the status of the socket and responding to
any I/O events. If the connection is closed on the server side, then
the client connection can not detect changes in the connection status
and shut down the local socket to respond properly.
HttpClient tries to alleviate this problem by testing if the connection is outdated, which is no longer valid as it is already closed on the server side before using the connection that made the HTTP request. Outdated connection check is not 100% stable, but instead requires 10 to 30 milliseconds for each request execution. The only workable socket model thread solution that does not involve every free connection is to use a dedicated monitoring thread to reclaim the connection that is considered expired because of prolonged inactivity. Monitoring thread can periodically call ClientConnectionManager#closeExpiredConnections() method to close all expired connections, withdraw from the connection pool closed connection. It can also optionally call the ClientConnectionManager#closeIdleConnections() method to close all connections that have been idle for more than a given period of time.
Resource Link:
http://dev.dafan.info/detail/513285

Timeout for UnknownHostException with established connection but no internet

I have an interesting issue.
I have an application where inside of it, I'm trying to account for the condition where the phone is connected to a router, but that router is not connected to the internet.
I've tried multiple methods of establishing the connection, but NONE of the timeouts account for this condition.
I've tried:
HttpParams httpParameters = new BasicHttpParams();
int timeoutSocket = 1000;
HttpConnectionParams.setSoTimeout(httpParameters, timeoutSocket);
HttpConnectionParams.setConnectionTimeout(httpParameters, timeoutSocket);
I've also tried:
HttpURLConnection huc = (HttpURLConnection)serverAddress.openConnection();
huc.setDoOutput(true);
huc.setRequestMethod("PUT"); // For amazon
//huc.setRequestMethod("POST"); // For regular server.
huc.setRequestProperty("Content-Type", "text/plain");
huc.setRequestProperty("Content-Length", String.valueOf(bytes));
huc.setFixedLengthStreamingMode(bytes);
huc.setConnectTimeout(1000); // Establishing connection timeout
huc.setReadTimeout(1000);
But in BOTH cases, when I execute/ get the output stream, it takes about 20 seconds to receive an UnknownHostException error.
I would like that reduced to a maximum of 5 seconds before reaching that conclusion.
Is there any way to do this?
Cheers

Through lots of searching and through the help of this link I've found a solid solution that seams to be working so far.
My understanding of the conclusion is that when I use methods like:
DataOutputStream wr = new DataOutputStream(huc.getOutputStream());
or
InputStream is = ucon.getInputStream();
BufferedInputStream bis = new BufferedInputStream(is);
(uploading or downloading)
There is a lot of things happening under the hood. Including a DNS lookup call. With no-connectivity, but while connected to a router, this is taking about 20 seconds to finally reach a UnknownHostException.
However, if I add this line of code first before the above code is executed:
InetAddress iAddr = InetAddress.getByName("myserverName.com");
Then it will give me the proper SocketTimeOutException and responds exactly how I would hope/expect it to. The above line of code apparently caches the DNS Lookup, and the timeouts work as expected.
Also, something to note: that once the failure is cached, executing the code above will take as long to fail as the other previous code. (Can't tell you exactly what will trigger this) But if you connect to the internet again, and then enter the connected but no connectivity state again, the earlier success will be cached and the timeouts will again work properly.
This wasn't particularly easy to find or figure out, so I hope this helps somebody.
Cheers,

You could implement a CountDownTimer that has a limit of 5000ms see this http://dewful.com/?p=3

Client thread hang emulation blocks server from accepting any I/O for the time client is set to wait

As the topic suggests I have a server and some clients.
The server accepts I/O connections concurrently (no queueing in socket connections) but I have this troubling issue and I do not know how to bypass it!
If I force a client to throw an I/O Exception the server detects it and terminates the client thread correctly (verified from Task Manager (Windows) and System Monitor (Ubuntu) ). But If I emulate an I/O that is "hanging" like i.e. Thread.sleep(60*1000);or
private static Object lock = new Object();
synchronized(lock) {
while (true) {
try {
lock.wait();
} catch (InterruptedException e) {
/* Foo */
}
}
}
then all subsequent I/O operations (connection & data transfer) seem to block or wait until the "hanging" client is terminated. The applications makes use of the ExecutorService so if the "hanging" client does not complete the operations in the suggested time limit then the task will time out and the client is forced to exit. The subsequent "blocked" I/Os will resume but I wonder why the server doesn't accept any I/O connections or performs any I/O operations when a client "hangs"?
NOTE:The client threading takes place in the server main like this:
while (true) {
accept client connection;
submit client task;
||
\ /
\/
// ExecutorService here in the form
// spService.submit(new Callable<Tuple<String[], BigDecimal[]>>() {
// ... code ... }}).get(taskTimeout, taskTimeUnit);
check task result & perform cleanup if result is null;
otherwise continue;
}

The Problem :
This may very well indicate that your server ACCEPTS client connections concurrently, however, it only handles these connections synchronously. That means that even if a million clients connect, successfully, at any given time, if anyone of them takes a long time (or hangs), it will hold up the others.
The TEST:
To verify this : I would toggle the amount of time a client takes to connect by adding Thread.sleep statments(1000) in your clients.
Expected result :
I believe you will see that even adding a single Thread.sleep(1000) statement in your client delays all other connecting clients by 1000.

I think I have found the source of my problems!
I do use one thread-per-client model but I run my tests locally i.e. in the same machine which means all of them have the same IP! So each client is assigned the same IP with the server! I guess that this leaves server and clients to differ only in port number but since each client is mapped to a different localport for each server connection then the server shouldn't block. I have confirmed that each client and server use different I/Os (compared references) and I wrap their sockets using <Input/Output>Streams to BufferedReaders & PrintWriters but still when a client hangs all other clients hang too (so maybe the I/O channels are indeed the same???)!I will test this on another machine and check the results back with you! :)
EDIT: Confirmed the erratic behaviour. It seems that even with remote clients if one hangs the other clients seem to hang too! :/
Don't know but I am determined to fix this. It's just that it's pretty weird since I am pretty sure I use one thread-per-client (I/Os differ, client sockets differ, IPs seem to be not a problem, I even map each client in the server to a localport of my choice ...)
May be I'll switch to NIO if I don't find a solution soon enough.
SOLUTION: Solved the problem! It seemed that the ExecutorService had to be run in a seperate thread otherwise if an I/O in a client blocked, all I/Os would block! That's strange given the fact that I've tried both an Executors.newFixedThreadPool(<nThreads>); and Executors.newCachedThreadPool(); and the client actions (aka I/Os) should take place in a new Thread for each client.
In any case, I used a method and wrapped the calls so each client instace would use a final ExecutorService baseWorker = Executors.newSingleThreadExecutor(); and created a new Thread explicitly each time using <Thread instance>.start(); so each thread would run in the background :)

How to make the HTTP connection timeout/disconnected after a time interval?

I am new in Apache HttpClient, I used the following code to get the HTTP connection timeout (disconnected) after certain time interval:
PostMethod method = new PostMethod(authURL);
HttpClient client = new HttpClient();
HttpClientParams params= new HttpClientParams();
params.setParameter(params.CONNECTION_MANAGER_TIMEOUT, 10); //10 Nano second
client.executeMethod(method);
but it wait for more than one minute without any hope to timeout/disconnect? Where can the problem be?

There are 2 timeouts involved in HTTPClient, try to set both,
client.getHttpConnectionManager().
getParams().setConnectionTimeout(5000);
client.getHttpConnectionManager().
getParams().setSoTimeout(5000);
However, the values will be ignored if the connection is stuck in a native socket call. So you might have to run the request in a different thread so you can time it out. See my answer to this question on how to do that,
java native Process timeout

The connection manager timeout triggers when the act of trying to get a connection from your connection manager takes too long. This is not the same as the timeout for the http connection itself. Use HttpClientParams.setSoTimeout() instead.
http://hc.apache.org/httpclient-3.x/apidocs/org/apache/commons/httpclient/params/HttpMethodParams.html#setSoTimeout%28int%29

Have you looked at setting SO_TIMEOUT ?
Sets the socket timeout (SO_TIMEOUT)
in milliseconds to be used when
executing the method. A timeout value
of zero is interpreted as an infinite
timeout.