I want to handle the Server DisconnectException and terminate the application when the server DisconnectException occurs
how to catch this error and stop the application?
#KafkaListener(topics = { "${kafka.status-topic}", "${kafka.start-topic}" }, containerFactory = "kafkaListenerContainerFactory")
public void listen(#Payload final String message,
#Header(KafkaHeaders.RECEIVED_TOPIC) final String topic) {
log.debug("Received '{}'-message {} from Kafka", topic, message);
LinkedList<IMessageListener> topicListeners = listeners.get(topic);
for (final IMessageListener l : topicListeners) {
// call listeners in a separate thread
executor.execute(new Runnable() {
#Override
public void run() {
l.messageReceived(topic, message);
}
});
}
}
You can try catching the exception and then calling System.exit(0) inside catch block
Related
I have a gRPC client in a kafka application. This means the client will constantly open and close channels.
public class UserAgentClient {
protected final Logger logger = LoggerFactory.getLogger(getClass());
private static final Config uaparserConfig = ConfigFactory.load().getConfig(ua);
private final ManagedChannel channel;
private final UserAgentServiceGrpc.UserAgentServiceBlockingStub userAgentBlockingStub;
public UserAgentParserClient() {
this(ManagedChannelBuilder.forAddress(uaConfig.getString("host"), uaConfig.getInt("port")).usePlaintext());
}
public UserAgentClient(ManagedChannelBuilder<?> usePlaintext) {
channel = usePlaintext.build();
userAgentBlockingStub = UserAgentServiceGrpc.newBlockingStub(channel);
}
public UserAgentParseResponse getUserAgent(String userAgent ) {
UserAgentRequest request = UserAgentRequest.newBuilder().setUserAgent(userAgent).build();
UserAgentParseResponse response = null;
try {
response = userAgentBlockingStub.parseUserAgent(request);
} catch(Exception e) {
logger.warn("An exception has occurred during gRPC call to the user agent.", e.getMessage());
}
shutdown();
return response;
}
public void shutdown() {
try {
channel.shutdown();
} catch (InterruptedException ie) {
logger.warn("Interrupted exception during gRPC channel close", ie);
}
}
}
I was wondering if I can keep the channel open the whole time? Or do I have to open a channel every time I make a new call? I was wondering because I was testing the performance and it seems to improve drastically if I just keep the channel open. On the other hand is there something that I'm missing?
creating a new channel has huge overhead, you should keep the channel open as long as possible.
Since the opening and closing of channel is expensive I removed the channel = usePlaintext.build(); completely from my client
Instead I'm opening and closing it in my kafka Transformer. In my class UserAgentDataEnricher that implements Transformer.
public class UserAgentDataEnricher implements Transformer<byte[], EnrichedData, KeyValue<byte[], EnrichedData>> {
private UserAgentParserClient userAgentParserClient;
#Override
public void init(ProcessorContext context) {
this.context = context;
open();
// schedule a punctuate() method every 15 minutes
this.context.schedule(900000, PunctuationType.WALL_CLOCK_TIME, (timestamp) -> {
close();
open();
logger.info("Re-opening of user agent channel is initialized");
});
}
#Override
public void close() {
userAgentParserClient.shutdown();
}
private void open() {
channel = ManagedChannelBuilder.forAddress("localhost", 50051).usePlaintext().build();
userAgentClient = new UserAgentClient(channel);
}
...
}
and now I initialize my client like that:
public UserAgentClient(ManagedChannel channel) {
this.channel = channel;
userAgentBlockingStub = UserAgentServiceGrpc.newBlockingStub(channel);
}
I have task in my app, and i do not know how it works return from this task.
public class TimeManager extends Service<String> {
#Override
protected Task<String> createTask() {
return new Task<String>() {
#Override
protected String call() throws Exception {
String txt = null;
while (!isCancelled()) {
try {
txt = "some txt";
Thread.sleep(1000);
} catch (InterruptedException e) {
System.out.println(e.getMessage());
}
}
return txt;
}
};
}
And in Main Class:
TimeManager time = new TimeManager();
time.start();
time.getValue();
time allways return null. What do I have to do to return the value?
Thread works good and I can send data from the thread to the application
Your task does not publish intermediate updates. Furthermore Service is used to run tasks in background threads to avoid blocking the JavaFX application thread. For this reason the value is likely to not be assigned if you access it directly after starting the service. It would be better to use a binding or a listener to the value property to retrieve the data when it's assigned.
public class TimeManager extends Service<String> {
#Override
protected Task<String> createTask() {
return new Task<String>() {
int i = 0;
#Override
protected String call() throws Exception {
String txt = null;
while (!isCancelled()) {
txt = Integer.toString(++i);
updateValue(txt); // publish new value
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
System.out.println(e.getMessage());
}
}
return txt;
}
};
}
}
TimeManager time = new TimeManager();
label.textProperty().bind(time.valueProperty());
time.start();
Note that in this case a service may not be required since you're running only a single task. Running the Task instance using new Thread(task).start() may actually suffice.
Furthermore there are better options for scheduling fast repeating updates of the GUI, see JavaFX periodic background task
I managed to setup an Hystrix Command to be called from an Undertow HTTP Handler:
public void handleRequest(HttpServerExchange exchange) throws Exception {
if (exchange.isInIoThread()) {
exchange.dispatch(this);
return;
}
RpcClient rpcClient = new RpcClient(/* ... */);
try {
byte[] response = new RpcCommand(rpcClient).execute();
// send the response
} catch (Exception e) {
// send an error
}
}
This works nice. But now, I would like to use the observable feature of Hystrix, calling observe instead of execute, making the code non-blocking.
public void handleRequest(HttpServerExchange exchange) throws Exception {
RpcClient rpcClient = new RpcClient(/* ... */);
new RpcCommand(rpcClient).observe().subscribe(new Observer<byte[]>(){
#Override
public void onCompleted() {
}
#Override
public void onError(Throwable throwable) {
exchange.setStatusCode(StatusCodes.INTERNAL_SERVER_ERROR);
exchange.endExchange();
}
#Override
public void onNext(byte[] body) {
exchange.getResponseHeaders().add(Headers.CONTENT_TYPE, "text/plain");
exchange.getResponseSender().send(ByteBuffer.wrap(body));
}
});
}
As expected (reading the doc), the handler returns immediately and as a consequence, the exchange is ended; when the onNext callback is executed, it fails with an exception:
Caused by: java.lang.IllegalStateException: UT000127: Response has already been sent
at io.undertow.io.AsyncSenderImpl.send(AsyncSenderImpl.java:122)
at io.undertow.io.AsyncSenderImpl.send(AsyncSenderImpl.java:272)
at com.xxx.poc.undertow.DiyServerBootstrap$1$1.onNext(DiyServerBootstrap.java:141)
at com.xxx.poc.undertow.DiyServerBootstrap$1$1.onNext(DiyServerBootstrap.java:115)
at rx.internal.util.ObserverSubscriber.onNext(ObserverSubscriber.java:34)
Is there a way to tell Undertow that the handler is doing IO asynchronously? I expect to use a lot of non-blocking code to access database and other services.
Thanks in advance!
You should dispatch() a Runnable to have the exchange not end when the handleRequest method returns. Since the creation of the client and subscription are pretty simple tasks, you can do it on the same thread with SameThreadExecutor.INSTANCE like this:
public void handleRequest(HttpServerExchange exchange) throws Exception {
exchange.dispatch(SameThreadExecutor.INSTANCE, () -> {
RpcClient rpcClient = new RpcClient(/* ... */);
new RpcCommand(rpcClient).observe().subscribe(new Observer<byte[]>(){
//...
});
});
}
(If you do not pass an executor to dispatch(), it will dispatch it to the XNIO worker thread pool. If you wish to do the client creation and subscription on your own executor, then you should pass that instead.)
I have a function which connect server and login account:
Observabe<Response> loginAccount();
Most of the time, it can login success:
loginAccount().subscribe(new Subscriber<Response>() {
#Override
public void onCompleted() {
System.out.println("success");
}
#Override
public void onError(Throwable e) {
e.printStackTrace();
}
#Override
public void onNext(Response authenticationResponseResult) {
System.out.println(authenticationResponseResult,toString());
}
});
However, there are serveral times there is an SocketTimeoutException.
I only want to retry on SocketTimeoutException and at most retry twice.
How can I implement?
I know probably I can use retryWhen, but I don't know how to use it only when the exception is SocketTimeoutException and how to retry at most twice.
Use the 2-parameter overload of retry:
loginAccount()
.retry((throwable, count) -> count < 2 && (throwable instanceof SocketTimeoutException))
.subscribe(....);
I'm trying to implement Asynchronous Avro calls by using its NettyServer implementation. After digging the source code, I found an example on how to use NettyServer from TestNettyServerWithCallbacks.java
When running a few test, I realize that NettyServer never calls hello(Callback) method, instead it keeps calling the synchronous hello() method. The client program prints out "Hello" but I'm expecting "Hello-ASYNC" as a result. I really have no clue what's going on.
I hope someone can shine some light on me and perhaps point out the mistake. Below are the codes I use to perform a simple asynchronous avro test.
AvroClient.java - Client code.
public class AvroClient {
public static void main(String[] args) throws InterruptedException, ExecutionException, TimeoutException {
try {
NettyTransceiver transceiver = new NettyTransceiver(new InetSocketAddress(6666));
Chat.Callback client = SpecificRequestor.getClient(Chat.Callback.class, transceiver);
final CallFuture<CharSequence> future1 = new CallFuture<CharSequence>();
client.hello(future1);
System.out.println(future1.get());
transceiver.close();
} catch (IOException ex) {
System.err.println(ex);
}
}
}
AvroNetty.java - The Server Code
public class AvroNetty {
public static void main(String[] args) {
Index indexImpl = new AsyncIndexImpl();
Chat chatImpl = new ChatImpl();
Server server = new NettyServer(new SpecificResponder(Chat.class, chatImpl), new InetSocketAddress(6666));
server.start();
System.out.println("Server is listening at port " + server.getPort());
}
}
ChatImpl.java
public class ChatImpl implements Chat.Callback {
#Override
public void hello(org.apache.avro.ipc.Callback<CharSequence> callback) throws IOException {
callback.handleResult("Hello-ASYNC");
}
#Override
public CharSequence hello() throws AvroRemoteException {
return new Utf8("Hello");
}
}
This interface is auto-generated by avro-tool
Chat.java
#SuppressWarnings("all")
public interface Chat {
public static final org.apache.avro.Protocol PROTOCOL = org.apache.avro.Protocol.parse("{\"protocol\":\"Chat\",\"namespace\":\"avro.test\",\"types\":[],\"messages\":{\"hello\":{\"request\":[],\"response\":\"string\"}}}");
java.lang.CharSequence hello() throws org.apache.avro.AvroRemoteException;
#SuppressWarnings("all")
public interface Callback extends Chat {
public static final org.apache.avro.Protocol PROTOCOL = avro.test.Chat.PROTOCOL;
void hello(org.apache.avro.ipc.Callback<java.lang.CharSequence> callback) throws java.io.IOException;
}
}
Here is the Avro Schema
{
"namespace": "avro.test",
"protocol": "Chat",
"types" : [],
"messages": {
"hello": {
"request": [],
"response": "string"
}
}
}
The NettyServer implementation actually doesn't implement the Async style at all. It is a deficiency in the library. Instead you need to specify an asynchronous execution handler rather than try and chain services together through callbacks. Here is what I use to setup my NettyServer to allow for this:
ExecutorService es = Executors.newCachedThreadPool();
OrderedMemoryAwareThreadPoolExecutor executor = new OrderedMemoryAwareThreadPoolExecutor(Runtime.getRuntime().availableProcessors(), 0, 0);
ExecutionHandler executionHandler = new ExecutionHandler(executor);
final NettyServer server = new NettyServer(responder, addr, new NioServerSocketChannelFactory(es, es), executionHandler);