I'm working on a project where we are polling files from a sftp server and streaming it out into a object on the rabbitmq queue. Now when the rabbitmq is down it still polls and deletes the file from the server and losses the file while sending it on queue when rabbitmq is down. I'm using ExpressionEvaluatingRequestHandlerAdvice to remove the file on successful transformation. My code looks like this:
#Bean
public SessionFactory<ChannelSftp.LsEntry> sftpSessionFactory() {
DefaultSftpSessionFactory factory = new DefaultSftpSessionFactory(true);
factory.setHost(sftpProperties.getSftpHost());
factory.setPort(sftpProperties.getSftpPort());
factory.setUser(sftpProperties.getSftpPathUser());
factory.setPassword(sftpProperties.getSftpPathPassword());
factory.setAllowUnknownKeys(true);
return new CachingSessionFactory<>(factory);
}
#Bean
public SftpRemoteFileTemplate sftpRemoteFileTemplate() {
return new SftpRemoteFileTemplate(sftpSessionFactory());
}
#Bean
#InboundChannelAdapter(channel = TransformerChannel.TRANSFORMER_OUTPUT, autoStartup = "false",
poller = #Poller(value = "customPoller"))
public MessageSource<InputStream> sftpMessageSource() {
SftpStreamingMessageSource messageSource = new SftpStreamingMessageSource(sftpRemoteFileTemplate,
null);
messageSource.setRemoteDirectory(sftpProperties.getSftpDirPath());
messageSource.setFilter(new SftpPersistentAcceptOnceFileListFilter(new SimpleMetadataStore(),
"streaming"));
messageSource.setFilter(new SftpSimplePatternFileListFilter("*.txt"));
return messageSource;
}
#Bean
#Transformer(inputChannel = TransformerChannel.TRANSFORMER_OUTPUT,
outputChannel = SFTPOutputChannel.SFTP_OUTPUT,
adviceChain = "deleteAdvice")
public org.springframework.integration.transformer.Transformer transformer() {
return new SFTPTransformerService("UTF-8");
}
#Bean
public ExpressionEvaluatingRequestHandlerAdvice deleteAdvice() {
ExpressionEvaluatingRequestHandlerAdvice advice = new ExpressionEvaluatingRequestHandlerAdvice();
advice.setOnSuccessExpressionString(
"#sftpRemoteFileTemplate.remove(headers['file_remoteDirectory'] + headers['file_remoteFile'])");
advice.setPropagateEvaluationFailures(false);
return advice;
}
I don't want the files to get removed/polled from the remote sftp server when the rabbitmq server is down. How can i achieve this ?
UPDATE
Apologies for not mentioning that I'm using spring cloud stream rabbit binder. And here is the transformer service:
public class SFTPTransformerService extends StreamTransformer {
public SFTPTransformerService(String charset) {
super(charset);
}
#Override
protected Object doTransform(Message<?> message) throws Exception {
String fileName = message.getHeaders().get("file_remoteFile", String.class);
Object fileContents = super.doTransform(message);
return new customFileDTO(fileName, (String) fileContents);
}
}
UPDATE-2
I added TransactionSynchronizationFactory on the customPoller as suggested. Now it doesn't poll file when rabbit server is down, but when the server is up, it keeps on polling the same file over and over again!! I cannot figure it out why? I guess i cannot use PollerSpec cause im on 4.3.2 version.
#Bean(name = "customPoller")
public PollerMetadata pollerMetadataDTX(StartStopTrigger startStopTrigger,
CustomTriggerAdvice customTriggerAdvice) {
PollerMetadata pollerMetadata = new PollerMetadata();
pollerMetadata.setAdviceChain(Collections.singletonList(customTriggerAdvice));
pollerMetadata.setTrigger(startStopTrigger);
pollerMetadata.setMaxMessagesPerPoll(Long.valueOf(sftpProperties.getMaxMessagePoll()));
ExpressionEvaluatingTransactionSynchronizationProcessor syncProcessor =
new ExpressionEvaluatingTransactionSynchronizationProcessor();
syncProcessor.setBeanFactory(applicationContext.getAutowireCapableBeanFactory());
syncProcessor.setBeforeCommitChannel(
applicationContext.getBean(TransformerChannel.TRANSFORMER_OUTPUT, MessageChannel.class));
syncProcessor
.setAfterCommitChannel(
applicationContext.getBean(SFTPOutputChannel.SFTP_OUTPUT, MessageChannel.class));
syncProcessor.setAfterCommitExpression(new SpelExpressionParser().parseExpression(
"#sftpRemoteFileTemplate.remove(headers['file_remoteDirectory'] + headers['file_remoteFile'])"));
DefaultTransactionSynchronizationFactory defaultTransactionSynchronizationFactory =
new DefaultTransactionSynchronizationFactory(syncProcessor);
pollerMetadata.setTransactionSynchronizationFactory(defaultTransactionSynchronizationFactory);
return pollerMetadata;
}
I don't know if you need this info but my CustomTriggerAdvice and StartStopTrigger looks like this :
#Component
public class CustomTriggerAdvice extends AbstractMessageSourceAdvice {
#Autowired private StartStopTrigger startStopTrigger;
#Override
public boolean beforeReceive(MessageSource<?> source) {
return true;
}
#Override
public Message<?> afterReceive(Message<?> result, MessageSource<?> source) {
if (result == null) {
if (startStopTrigger.getStart()) {
startStopTrigger.stop();
}
} else {
if (!startStopTrigger.getStart()) {
startStopTrigger.stop();
}
}
return result;
}
}
public class StartStopTrigger implements Trigger {
private PeriodicTrigger startTrigger;
private boolean start;
public StartStopTrigger(PeriodicTrigger startTrigger, boolean start) {
this.startTrigger = startTrigger;
this.start = start;
}
#Override
public Date nextExecutionTime(TriggerContext triggerContext) {
if (!start) {
return null;
}
start = true;
return startTrigger.nextExecutionTime(triggerContext);
}
public void stop() {
start = false;
}
public void start() {
start = true;
}
public boolean getStart() {
return this.start;
}
}
Well, would be great to see what your SFTPTransformerService and determine how it is possible to perform an onSuccessExpression when there should be an exception in case of down broker.
You also should not only throw an exception do not perform delete, but consider to add a RequestHandlerRetryAdvice to re-send the file to the RabbitMQ: https://docs.spring.io/spring-integration/docs/5.0.6.RELEASE/reference/html/messaging-endpoints-chapter.html#retry-advice
UPDATE
So, well, since Gary guessed that you use Spring Cloud Stream to send message to the Rabbit Binder after your internal process (very sad that you didn't share that information originally), you need to take a look to the Binder error handling on the matter: https://docs.spring.io/spring-cloud-stream/docs/Elmhurst.RELEASE/reference/htmlsingle/#_retry_with_the_rabbitmq_binder
And that is true that ExpressionEvaluatingRequestHandlerAdvice is applied only for the SFTPTransformerService and nothing more. The downstream error (in the Binder) is not included in this process already.
UPDATE 2
Yeah... I think Gary is right, and we don't have choice unless configure a TransactionSynchronizationFactory on the customPoller level instead of that ExpressionEvaluatingRequestHandlerAdvice: ExpressionEvaluatingRequestHandlerAdvice .
The DefaultTransactionSynchronizationFactory can be configured with the ExpressionEvaluatingTransactionSynchronizationProcessor, which has similar goal as the mentioned ExpressionEvaluatingRequestHandlerAdvice, but on the transaction level which will include your process starting with the SFTP Channel Adapter and ending on the Rabbit Binder level with the send to AMQP attempts.
See Reference Manual for more information: https://docs.spring.io/spring-integration/reference/html/transactions.html#transaction-synchronization.
The point with the ExpressionEvaluatingRequestHandlerAdvice (and any AbstractRequestHandlerAdvice) that they have a boundary only around handleRequestMessage() method, therefore only during the component they are declared.
Related
I have this flow that I am trying to test but nothing works as expected. The flow itself works well but testing seems a bit tricky.
This is my flow:
#Configuration
#RequiredArgsConstructor
public class FileInboundFlow {
private final ThreadPoolTaskExecutor threadPoolTaskExecutor;
private String filePath;
#Bean
public IntegrationFlow fileReaderFlow() {
return IntegrationFlows.from(Files.inboundAdapter(new File(this.filePath))
.filterFunction(...)
.preventDuplicates(false),
endpointConfigurer -> endpointConfigurer.poller(
Pollers.fixedDelay(500)
.taskExecutor(this.threadPoolTaskExecutor)
.maxMessagesPerPoll(15)))
.transform(new UnZipTransformer())
.enrichHeaders(this::headersEnricher)
.transform(Message.class, this::modifyMessagePayload)
.route(Map.class, this::channelsRouter)
.get();
}
private String channelsRouter(Map<String, File> payload) {
boolean isZip = payload.values()
.stream()
.anyMatch(file -> isZipFile(file));
return isZip ? ZIP_CHANNEL : XML_CHANNEL; // ZIP_CHANNEL and XML_CHANNEL are PublishSubscribeChannel
}
#Bean
public SubscribableChannel xmlChannel() {
var channel = new PublishSubscribeChannel(this.threadPoolTaskExecutor);
channel.setBeanName(XML_CHANNEL);
return channel;
}
#Bean
public SubscribableChannel zipChannel() {
var channel = new PublishSubscribeChannel(this.threadPoolTaskExecutor);
channel.setBeanName(ZIP_CHANNEL);
return channel;
}
//There is a #ServiceActivator on each channel
#ServiceActivator(inputChannel = XML_CHANNEL)
public void handleXml(Message<Map<String, File>> message) {
...
}
#ServiceActivator(inputChannel = ZIP_CHANNEL)
public void handleZip(Message<Map<String, File>> message) {
...
}
//Plus an #Transformer on the XML_CHANNEL
#Transformer(inputChannel = XML_CHANNEL, outputChannel = BUS_CHANNEL)
private List<BusData> xmlFileToIngestionMessagePayload(Map<String, File> xmlFilesByName) {
return xmlFilesByName.values()
.stream()
.map(...)
.collect(Collectors.toList());
}
}
I would like to test multiple cases, the first one is checking the message payload published on each channel after the end of fileReaderFlow.
So I defined this test classe:
#SpringBootTest
#SpringIntegrationTest
#ExtendWith(SpringExtension.class)
class FileInboundFlowTest {
#Autowired
private MockIntegrationContext mockIntegrationContext;
#TempDir
static Path localWorkDir;
#BeforeEach
void setUp() {
copyFileToTheFlowDir(); // here I copy a file to trigger the flow
}
#Test
void checkXmlChannelPayloadTest() throws InterruptedException {
Thread.sleep(1000); //waiting for the flow execution
PublishSubscribeChannel xmlChannel = this.getBean(XML_CHANNEL, PublishSubscribeChannel.class); // I extract the channel to listen to the message sent to it.
xmlChannel.subscribe(message -> {
assertThat(message.getPayload()).isInstanceOf(Map.class); // This is never executed
});
}
}
As expected that test does not work because the assertThat(message.getPayload()).isInstanceOf(Map.class); is never executed.
After reading the documentation I didn't find any hint to help me solved that issue. Any help would be appreciated! Thanks a lot
First of all that channel.setBeanName(XML_CHANNEL); does not effect the target bean. You do this on the bean creation phase and dependency injection container knows nothing about this setting: it just does not consult with it. If you really would like to dictate an XML_CHANNEL for bean name, you'd better look into the #Bean(name) attribute.
The problem in the test that you are missing the fact of async logic of the flow. That Files.inboundAdapter() works if fully different thread and emits messages outside of your test method. So, even if you could subscribe to the channel in time, before any message is emitted to it, that doesn't mean your test will work correctly: the assertThat() will be performed on a different thread. Therefore no real JUnit report for your test method context.
So, what I'd suggest to do is:
Have Files.inboundAdapter() stopped in the beginning of the test before any setup you'd like to do in the test. Or at least don't place files into that filePath, so the channel adapter doesn't emit messages.
Take the channel from the application context and if you wish subscribe or use a ChannelInterceptor.
Have an async barrier, e.g. CountDownLatch to pass to that subscriber.
Start the channel adapter or put file into the dir for scanning.
Wait for the async barrier before verifying some value or state.
In project,I verify the app_key is valid by pass redis.
I use ReactiveRedisTemplate to access redis data，and in filter I verify the app_key is valid.if the app_key is valid,then jump to next filter,else output to client the exception.
Actually：if redis connection timeout，ex should be runnig.but when the redis running normal ,the program is not exec verfiy app_key ,It direct jump to next filter.
Please tell me how do,Thanks!
#Resource
private AppKeyProvider appKeyProvider;
public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
try {
String app_key =exchange.getRequest().getQueryParams().getFirst("app_key"));
//app_key verify
Flux.just(app_key).flatMap(key -> appKeyProvider.getAppKey(key)).subscribe(
appKey -> {
if (appKey == null) {
//app_key is not valid
throw new AppException(ErrorCode.ILLEGAL_APP_KEY);
}else{
//do... jump to next filter
}
},
ex -> {
throw new AppException(ErrorCode.SERVICE_BASIC_ERROR, ex);
}
);
} catch (AppException ex) {
exchange.getResponse().setStatusCode(HttpStatus.BAD_REQUEST);
exchange.getResponse().getHeaders().setContentType(MediaType.APPLICATION_JSON);
String result = RestHelper.build(ex, exchange).toString();
return exchange.getResponse().writeWith(Mono.just(exchange.getResponse().bufferFactory().wrap(result.getBytes(Charsets.UTF_8))));
}
return chain.filter(exchange);
}
AppKeyProvider.java
#Component
public class AppKeyProvider {
#Resource
private ReactiveRedisTemplate reactiveRedisTemplate;
private final static Logger logger = LoggerFactory.getLogger(AppKeyProvider.class);
private final static AppKeyProvider instance = new AppKeyProvider();
private static ConcurrentHashMap<String, Api> apiMap = new ConcurrentHashMap<String, Api>();
private final static Lock lock = new ReentrantLock(true);
/**
* Get AppKey
*
* #param app_key
* #return
*/
public Mono<AppKey> getAppKey(String app_key) {
ReactiveValueOperations<String, AppKey> operations = reactiveRedisTemplate.opsForValue();
Mono<AppKey> appKey = operations.get(RedisKeypPrefix.APP_KEY + app_key);
return appKey;
}
}
This happens because you've manually subscribed to the key lookup part. Doing so decouples the main filter processing from that operation, meaning they can happen concurrently in different threads - so they can't track each others' result.
Also, in reactive programming errors happen within the pipeline and should be dealt with operators; try/catch blocks won't work in this case.
Here's an attempt at fixing this code snippet:
public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
String app_key = exchange.getRequest().getQueryParams().getFirst("app_key"));
return appKeyProvider.getAppKey(app_key)
.switchOnEmpty(Mono.error(new AppException(ErrorCode.ILLEGAL_APP_KEY)))
.flatMap(key -> chain.filter(exchange))
.onErrorResume(AppException.class, exc -> {
exchange.getResponse().setStatusCode(HttpStatus.BAD_REQUEST);
exchange.getResponse().getHeaders().setContentType(MediaType.APPLICATION_JSON);
String result = RestHelper.build(ex, exchange).toString();
return exchange.getResponse().writeWith(Mono.just(exchange.getResponse().bufferFactory().wrap(result.getBytes(Charsets.UTF_8))));
});
}
I have a web app that uses a request/response message in Masstransit.
This works on out test environment, no problem.
However on the customer deployment we face a problem. At the customer site we do have two network segments A and B. The component doing the database call is in segment A, the web app and the RabbitMq server in segment B.
Due to security restrictions the component in segment A has to go through a loadbalancer with a given address. The component itself can connect to RabbitMQ with Masstransit. So far so good.
The web component on segment B however uses the direct address for the RabbitMq server. When the web component now is starting the request/response call, I can see that the message arrives at the component in segment A.
However I see that the consumer tries to call the RabbitMQ server on the "wrong" address. It uses the address the web component uses to issue the request. However the component in segment A should reply on the "loadbalancer" address.
Is there a way to configure or tell the RespondAsync call to use the connection address configured for that component?
Of course the easiest would be to have the web component also connect through the loadbalancer, but due to the network segments/security setup the loadbalancer is only reachable from segment A.
Any input/help is appreciated.
I had a similar problem with rabbitmq federation. Here's what I did.
ResponseAddressSendObserver
class ResponseAddressSendObserver : ISendObserver
{
private readonly string _hostUriString;
public ResponseAddressSendObserver(string hostUriString)
{
_hostUriString = hostUriString;
}
public Task PreSend<T>(SendContext<T> context)
where T : class
{
if (context.ResponseAddress != null)
{
// Send relative response address alongside the message
context.Headers.Set("RelativeResponseAddress",
context.ResponseAddress.AbsoluteUri.Substring(_hostUriString.Length));
}
return Task.CompletedTask;
}
...
}
ResponseAddressConsumeFilter
class ResponseAddressConsumeFilter : IFilter<ConsumeContext>
{
private readonly string _hostUriString;
public ResponseAddressConsumeFilter(string hostUriString)
{
_hostUriString = hostUriString;
}
public Task Send(ConsumeContext context, IPipe<ConsumeContext> next)
{
var responseAddressOverride = GetResponseAddress(_hostUriString, context);
return next.Send(new ResponseAddressConsumeContext(responseAddressOverride, context));
}
public void Probe(ProbeContext context){}
private static Uri GetResponseAddress(string host, ConsumeContext context)
{
if (context.ResponseAddress == null)
return context.ResponseAddress;
object relativeResponseAddress;
if (!context.Headers.TryGetHeader("RelativeResponseAddress", out relativeResponseAddress) || !(relativeResponseAddress is string))
throw new InvalidOperationException("Message has ResponseAddress but doen't have RelativeResponseAddress header");
return new Uri(host + relativeResponseAddress);
}
}
ResponseAddressConsumeContext
class ResponseAddressConsumeContext : BaseConsumeContext
{
private readonly ConsumeContext _context;
public ResponseAddressConsumeContext(Uri responseAddressOverride, ConsumeContext context)
: base(context.ReceiveContext)
{
_context = context;
ResponseAddress = responseAddressOverride;
}
public override Uri ResponseAddress { get; }
public override bool TryGetMessage<T>(out ConsumeContext<T> consumeContext)
{
ConsumeContext<T> context;
if (_context.TryGetMessage(out context))
{
// the most hackish part in the whole arrangement
consumeContext = new MessageConsumeContext<T>(this, context.Message);
return true;
}
else
{
consumeContext = null;
return false;
}
}
// all other members just delegate to _context
}
And when configuring the bus
var result = MassTransit.Bus.Factory.CreateUsingRabbitMq(cfg =>
{
var host = cfg.Host(new Uri(hostAddress), h =>
{
h.Username(...);
h.Password(...);
});
cfg.UseFilter(new ResponseAddressConsumeFilter(hostAddress));
...
});
result.ConnectSendObserver(new ResponseAddressSendObserver(hostAddress));
So now relative response addresses are sent with the messages and used on the receiving side.
Using observers to modify anything is not recommended by the documentation, but should be fine in this case.
Maybe three is a better solution, but I haven't found one. HTH
Hi I am new to Storm and Kafka.
I am using storm 1.0.1 and kafka 0.10.0
we have a kafkaspout that would receive java bean from kafka topic.
I have spent several hours digging to find the right approach for that.
Found few articles which are useful but none of the approaches worked for me so far.
Following is my codes:
StormTopology:
public class StormTopology {
public static void main(String[] args) throws Exception {
//Topo test /zkroot test
if (args.length == 4) {
System.out.println("started");
BrokerHosts hosts = new ZkHosts("localhost:2181");
SpoutConfig kafkaConf1 = new SpoutConfig(hosts, args[1], args[2],
args[3]);
kafkaConf1.zkRoot = args[2];
kafkaConf1.useStartOffsetTimeIfOffsetOutOfRange = true;
kafkaConf1.startOffsetTime = kafka.api.OffsetRequest.LatestTime();
kafkaConf1.scheme = new SchemeAsMultiScheme(new KryoScheme());
KafkaSpout kafkaSpout1 = new KafkaSpout(kafkaConf1);
System.out.println("started");
ShuffleBolt shuffleBolt = new ShuffleBolt(args[1]);
AnalysisBolt analysisBolt = new AnalysisBolt(args[1]);
TopologyBuilder topologyBuilder = new TopologyBuilder();
topologyBuilder.setSpout("kafkaspout", kafkaSpout1, 1);
//builder.setBolt("counterbolt2", countbolt2, 3).shuffleGrouping("kafkaspout");
//This is for field grouping in bolt we need two bolt for field grouping or it wont work
topologyBuilder.setBolt("shuffleBolt", shuffleBolt, 3).shuffleGrouping("kafkaspout");
topologyBuilder.setBolt("analysisBolt", analysisBolt, 5).fieldsGrouping("shuffleBolt", new Fields("trip"));
Config config = new Config();
config.registerSerialization(VehicleTrip.class, VehicleTripKyroSerializer.class);
config.setDebug(true);
config.setNumWorkers(1);
LocalCluster cluster = new LocalCluster();
cluster.submitTopology(args[0], config, topologyBuilder.createTopology());
// StormSubmitter.submitTopology(args[0], config,
// builder.createTopology());
} else {
System.out
.println("Insufficent Arguements - topologyName kafkaTopic ZKRoot ID");
}
}
}
I am serializing the data at kafka using kryo
KafkaProducer:
public class StreamKafkaProducer {
private static Producer producer;
private final Properties props = new Properties();
private static final StreamKafkaProducer KAFKA_PRODUCER = new StreamKafkaProducer();
private StreamKafkaProducer(){
props.put("bootstrap.servers", "localhost:9092");
props.put("acks", "all");
props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
props.put("value.serializer", "com.abc.serializer.MySerializer");
producer = new org.apache.kafka.clients.producer.KafkaProducer(props);
}
public static StreamKafkaProducer getStreamKafkaProducer(){
return KAFKA_PRODUCER;
}
public void produce(String topic, VehicleTrip vehicleTrip){
ProducerRecord<String,VehicleTrip> producerRecord = new ProducerRecord<>(topic,vehicleTrip);
producer.send(producerRecord);
//producer.close();
}
public static void closeProducer(){
producer.close();
}
}
Kyro Serializer:
public class DataKyroSerializer extends Serializer<Data> implements Serializable {
#Override
public void write(Kryo kryo, Output output, VehicleTrip vehicleTrip) {
output.writeLong(data.getStartedOn().getTime());
output.writeLong(data.getEndedOn().getTime());
}
#Override
public Data read(Kryo kryo, Input input, Class<VehicleTrip> aClass) {
Data data = new Data();
data.setStartedOn(new Date(input.readLong()));
data.setEndedOn(new Date(input.readLong()));
return data;
}
I need to get the data back to the Data bean.
As per few articles I need to provide with a custom scheme and make it part of topology but till now I have no luck
Code for Bolt and Scheme
Scheme:
public class KryoScheme implements Scheme {
private ThreadLocal<Kryo> kryos = new ThreadLocal<Kryo>() {
protected Kryo initialValue() {
Kryo kryo = new Kryo();
kryo.addDefaultSerializer(Data.class, new DataKyroSerializer());
return kryo;
};
};
#Override
public List<Object> deserialize(ByteBuffer ser) {
return Utils.tuple(kryos.get().readObject(new ByteBufferInput(ser.array()), Data.class));
}
#Override
public Fields getOutputFields( ) {
return new Fields( "data" );
}
}
and bolt:
public class AnalysisBolt implements IBasicBolt {
/**
*
*/
private static final long serialVersionUID = 1L;
private String topicname = null;
public AnalysisBolt(String topicname) {
this.topicname = topicname;
}
public void prepare(Map stormConf, TopologyContext topologyContext) {
System.out.println("prepare");
}
public void execute(Tuple input, BasicOutputCollector collector) {
System.out.println("execute");
Fields fields = input.getFields();
try {
JSONObject eventJson = (JSONObject) JSONSerializer.toJSON((String) input
.getValueByField(fields.get(1)));
String StartTime = (String) eventJson.get("startedOn");
String EndTime = (String) eventJson.get("endedOn");
String Oid = (String) eventJson.get("_id");
int V_id = (Integer) eventJson.get("vehicleId");
//call method getEventForVehicleWithinTime(Long vehicleId, Date startTime, Date endTime)
System.out.println("==========="+Oid+"| "+V_id+"| "+StartTime+"| "+EndTime);
} catch (Exception e) {
e.printStackTrace();
}
}
but if I submit the storm topology i am getting error:
java.lang.IllegalStateException: Spout 'kafkaspout' contains a
non-serializable field of type com.abc.topology.KryoScheme$1, which
was instantiated prior to topology creation.
com.minda.iconnect.topology.KryoScheme$1 should be instantiated within
the prepare method of 'kafkaspout at the earliest.
Appreciate help to debug the issue and guide to right path.
Thanks
Your ThreadLocal is not Serializable. The preferable solution would be to make your serializer both Serializable and threadsafe. If this is not possible, then I see 2 alternatives since there is no prepare method as you would get in a bolt.
Declare it as static, which is inherently transient.
Declare it transient and access it via a private get method. Then you can initialize the variable on first access.
Within the Storm lifecycle, the topology is instantiated and then serialized to byte format to be stored in ZooKeeper, prior to the topology being executed. Within this step, if a spout or bolt within the topology has an initialized unserializable property, serialization will fail.
If there is a need for a field that is unserializable, initialize it within the bolt or spout's prepare method, which is run after the topology is delivered to the worker.
Source: Best Practices for implementing Apache Storm
I am learning about Spring-Integration and have a basic understanding about Gateway and Service-Activators. I love the concept of Gateway. Spring Integration generates the proxy for gateway at run-time. This proxy hides all the messaging details from the consumer of the gateway. In addition, the generated proxy might also be co-relating request and reply.
With the objective of learning, I set out to implement request and reply correlation using raw Spring Integration features and not using Gateway. I am able to set the correlation identifier in the request header, but not able to specify correlation identifier while receiving reply for the channel. The following (at the end of the question) is the code snippet for the same. Also how does the correlation stuff works against a message broker (e.g. RabbitMQ)? Does RabbitMQ provides an ability to retrieve a message with a specific header (correlation identifier) in it?
public class RemoteProxyCalculatorService implements CalculatorService
{
public int Square(int n)
{
UUID uuid = SendRequest(n, "squareRequestChannel");
int squareOfn = ReceiveReply("squareReplyChannel", uuid);
return squareOfn;
}
private <T> UUID SendRequest(T payload, String requestChannel)
{
UUID requestID = UUID.randomUUID();
Message<T> inputMessage = MessageBuilder.withPayload(payload)
.setCorrelationId(requestID)
.build();
MessageChannel channel = (MessageChannel)context.getBean(requestChannel, MessageChannel.class);
channel.send(inputMessage);
return requestID;
}
#SuppressWarnings("unchecked")
private <T> T ReceiveReply(String replyChannel, UUID requestID)
{
//How to consume requestID so as to receive only the reply related to the request posted by this thread
PollableChannel channel = (PollableChannel)context.getBean(replyChannel);
Message<?> groupMessage = channel.receive();
return (T)groupMessage.getPayload();
}
private ClassPathXmlApplicationContext context;
}
Thanks.
The simplest way to correlate within an app doesn't even require a correlationId header. Instead you can create a QueueChannel instance (that you don't share) and provide that as s the replyChannel header on the Message you send. Whatever downstream component ultimately responds, it will find that header in the Message.
Regarding RabbitMQ, our outbound-gateway simply applies a similar technique, but using the replyTo property of the AMQP Message.
Hope that helps.
-Mark
Problem is with common reply channel. The solution (Mark suggested the similar) will look like this.
public class RemoteProxyCalculatorService
{
public int Square(int n)
{
PollableChannel replyChannel = SendRequest(n, "squareRequestChannel");
int squareOfn = ReceiveReply(replyChannel);
return squareOfn;
}
private <T> PollableChannel SendRequest(T payload, String requestChannel)
{
UUID requestID = UUID.randomUUID();
QueueChannel replyQueueChannel = new QueueChannel();
Message<T> inputMessage = MessageBuilder.withPayload(payload)
.setCorrelationId(requestID)
.setReplyChannel(replyQueueChannel)
.build();
MessageChannel channel = context.getBean(requestChannel, MessageChannel.class);
channel.send(inputMessage);
return replyQueueChannel;
}
#SuppressWarnings("unchecked")
private <T> T ReceiveReply(PollableChannel replyChannel)
{
Message<?> groupMessage = replyChannel.receive();
return (T) groupMessage.getPayload();
}
private ClassPathXmlApplicationContext context;
}
If you want to use common reply channel then I think this is what you are looking for.
public class RemoteProxyCalculatorService
{
public int Square(int n)
{
PollableChannel replyChannel = SendRequest(n, "squareRequestChannel");
int squareOfn = ReceiveReply(replyChannel);
return squareOfn;
}
private <T> PollableChannel SendRequest(T payload, String requestChannel)
{
UUID requestID = UUID.randomUUID();
Message<T> inputMessage = MessageBuilder.withPayload(payload)
.setCorrelationId(requestID)
.setReplyChannel(myMessageHandler.getSubscribedChannel())
.build();
// Create a Pollable channel for two things
// 1. Pollable channel is where this thread should look for reply.
QueueChannel replyQueueChannel = new QueueChannel();
// 2. Message Handler will send reply to this Pollable channel once it receives the reply using correlation Id.
myMessageHandler.add(requestID, replyQueueChannel);
MessageChannel channel = context.getBean(requestChannel, MessageChannel.class);
channel.send(inputMessage);
return replyQueueChannel;
}
#SuppressWarnings("unchecked")
private <T> T ReceiveReply(PollableChannel replyChannel)
{
Message<?> groupMessage = replyChannel.receive();
return (T) groupMessage.getPayload();
}
private ClassPathXmlApplicationContext context;
#Autowired
private MyMessageHandler myMessageHandler;
}
/**
* Message Handler
*
*/
public class MyMessageHandler implements MessageHandler
{
private final Map<Object, MessageChannel> idChannelsMap = new TreeMap<>();
private final Object lock = new Object();
private final SubscribableChannel subscribedChannel;
public MyMessageHandler(SubscribableChannel subscribedChannel)
{
this.subscribedChannel = subscribedChannel;
}
#Override
public void handleMessage(Message<?> message) throws MessagingException
{
synchronized (lock)
{
this.idChannelsMap.get(message.getHeaders().getCorrelationId()).send(message);
this.idChannelsMap.remove(message.getHeaders().getCorrelationId());
}
}
public void add(Object correlationId, MessageChannel messageChannel)
{
synchronized (lock)
{
this.idChannelsMap.put(correlationId, messageChannel);
}
}
public SubscribableChannel getSubscribedChannel()
{
return subscribedChannel;
}
}