If while executing one rest method, at the same time came next request also so I need to prevent the second request and respond back "One person is already using". How to achieve this in spring boot? I tried the code below given. But it's not request rejected. Its added into a queue, after first request second one will execute.
#RestController
class TestController {
private static ReentrantLock lock = new ReentrantLock();
#GetMapping("tests")
public String get() {
System.err.println("----------------------------------------1 " + lock.isLocked());
if (!lock.tryLock()) {
System.err.println("--------------------------------------2 " + lock.isLocked());
return "failed";
}
try {
System.err.println("Application Locked");
Thread.sleep(10000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
lock.unlock();
}
return "success";
}
Related
I would like to add custom behavior before my method annoted with #KafkaListener is called.
Actually I'm using an abstract class and the final class is using
#KafkaListener(topics = ....)
public void onMessages(List<ConsumerRecord> records) {
super.onMessages(records);
}
#Override
public void process(ConsumerRecord record) {
// Called by abstract class to really process the message (one by one)
}
But I also need to configure the abstract class in a #PostConstruct.
What would be the best approach ?
I would prefer just decorate the default container and use it with something like that :
#MyCustomKafkaLister(topics = ....)
public void onMessage(ConsumerRecord record) {
// Just handle the message
}
Or by customizing the MessageListenerFactory to create a CustomMessageListener inherited from the default one which will call my method annoted by #KafkaListener after some custom behavior.
But I don't know how.
Edit 1
I want my abstract processing to do the following :
public void process(List<ConsumerRecord> records) {
for (ConsumerRecord<K, V> record : records) {
// Check message
try {
if (record.value() == null) {
checkDeser(record, ErrorHandlingDeserializer2.VALUE_DESERIALIZER_EXCEPTION_HEADER);
}
if (record.key() == null) {
checkDeser(record, ErrorHandlingDeserializer2.KEY_DESERIALIZER_EXCEPTION_HEADER);
}
} catch (DeserializationException ex) {
this.deadLetterPublishingRecoverer.accept(record, ex);
LOGGER.error("Deserialization error recovered to DLT.", ex);
}
// Process message
try {
// Here I'm calling the original #KafkaListener aka the subclass
myRealListenerObject.processOneByOne(record);
} catch (Exception ex) {
LOGGER.warn("Exception while processing record. Key : {}", record.key(), ex);
handleException(record, ex);
}
}
}
This is calling "myRealListenerObject.processOneByOne(record);" which should be my listener implementation using #KafkaListener (or #CustomKafkaListener)
Edit 2
I would like my listeners to be like
#CustomKafkaListeners(topics = "myTopic", ...)
public void process(ConsumerRecord record) {
// Do my stuff
}
rather than having something like that for every listeners :
#KafkaListeners(topics = "myTopic", ...)
public void process(List<ConsumerRecord> records) {
for (ConsumerRecord record : records) {
try {
if (record.value() == null) {
checkDeser(record, ErrorHandlingDeserializer2.VALUE_DESERIALIZER_EXCEPTION_HEADER);
}
if (record.key() == null) {
checkDeser(record, ErrorHandlingDeserializer2.KEY_DESERIALIZER_EXCEPTION_HEADER);
}
} catch (DeserializationException ex) {
this.deadLetterPublishingRecoverer.accept(record, ex);
LOGGER.error("Deserialization error recovered to DLT.", ex);
}
// Process message
try {
// Do my stuff
} catch (Exception ex) {
LOGGER.warn("Exception while processing record. Key : {}", record.key(), ex);
MyExceptionHandler.handleException(record, ex);
}
}
}
You can perform that logic using a FilteringBatchMessageListenerAdapter with a custom RecordFilterStrategy to check for the deserialization exceptions.
Simply add the adapter to the listener container factory.
I am setting up java based graphQl App and find graphql-java-tools really convenient the problem though while itis pretty straight forward
With graphql-java to make field resolvers Async I couldn't Find a way to do it using graphql-java-tools
I tried
#Bean
public ExecutionStrategy executionStrategy() {
return new AsyncExecutionStrategy();
}
Here resolvers I use in order to test
#Component
public class VideoResolver implements GraphQLResolver<Video> {
public Episode getEpisode(Video video){
Episode result = new Episode();
result.setTitle("episodeTitle");
result.setUuid("EpisodeUuid");
result.setBrand("episodeBrand");
try {
Thread.sleep(2000L);
System.out.println(Thread.currentThread().getName());
} catch (InterruptedException e) {
e.printStackTrace();
}
return result;
}
public List<Images> getImages(Video video){
Images image = new Images();
image.setFileName("Image FileName1");
List<Images> imageList = new ArrayList<>();
imageList.add(image);
try {
Thread.sleep(2000L);
System.out.println(Thread.currentThread().getName());
} catch (InterruptedException e) {
System.out.println("Exxxxxxxxxx");
}
return imageList;
}
}
Was assuming this should run in about 2 seconds and print two different streams but no it takes 4
and print it is all in one same stream
I've been trying to make a simple backend for user login.
It works fine if I don't use threads, but when I try to implement multi-threading it breaks for some reason.
For now, I'm just trying to do something as simple as retrieving all users' info from the User table in JSON format. The problem is that the Rest controller returns nothing to Postman even though dbActions.getAll() returns the correct List.
There's no error, no exception, nothing. I could really use some help. The parts of my code I'm trying to get to work are below.
Rest controller:
#Async
#RequestMapping(value="/view", method =RequestMethod.GET)
public List<User> viewAll() {
try {
List<User> list = new ArrayList<>();
list = dbActions.getAll();
return list;
}catch(Exception e) {
e.printStackTrace();
return null;
}
}
dbActions service:
public List<User> getAll() {
List<User> results = new ArrayList<>();
CompletableFuture<Void> future;
try {
future = CompletableFuture.runAsync(new Runnable() {
public void run() {
userRepo.findAll().forEach(results::add);
}
});
future.get();
return results;
} catch (Exception e) {
e.printStackTrace();
return results;
}
}
Try removing the #Async annotation from your viewAll() method
I have been trying to do load testing(500 request in 1 second) with gatling for following three request handlers created with spring boot. Inspired by http://callistaenterprise.se/blogg/teknik/2014/04/22/c10k-developing-non-blocking-rest-services-with-spring-mvc/
but i received reverse output. "getUser" -BLOCKING request handler was able to handle 500 request in 1 second(but launched more then 200 threads).
"getUser2" and "getUser3" which are NONBLOCKING resulted in 503 error after handling around 10 request out of 500 request.
screen shot of gatling output: https://ibb.co/ePEEBk
Can somebody please explain me the reason or what I am doing wrong.
#RequestMapping("/getUser2")
public CompletionStage<Object> getUser2() {
return CompletableFuture.supplyAsync(()-> {
try {
logger.info("");
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
return "result";
});
}
#RequestMapping("getUser3")
public DeferredResult<String> getUser3() {
DeferredResult<String> def = new DeferredResult<String>();
CompletableFuture.runAsync(()-> {
logger.info("");
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}).whenCompleteAsync((res,err)-> {
def.setResult("result");
});
return def;
}
#RequestMapping("getUser")
public String getUser() {
try {
logger.info("");
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
return "result";
}
I am not sure if you have got the answer.
But for getUser3(), it seems your REST api is timed out. By default it will use the default timeout from the Spring MVC.
One thing you can do is to create a DeferredResult with a timeout value.
DeferredResult(java.lang.Long timeout)
See this constructor for further information https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/context/request/async/DeferredResult.html#DeferredResult-java.lang.Long-
For getUser, it should be the same, you probably need a longer timeout to fix it
I am processing three transaction inside a single method in stateless container managed bean .i want to persist three transaction while if one throws exception other two should complete their respective transaction ,error is that if first or any one is throwing exception other two are to executing please give some helpful suggestion
public void allocateSubjectToStudent(SubjectAllocatedToStudentDto dto)throws Exception {
logger.info("allocateSubjectToStudent method entry :");
List<Subject> coreList=dto.getCoreList();
Iterator<Subject> iterator=coreList.iterator();
while(iterator.hasNext()){
logger.info("inside while :");
SubjectAllocatedToStudentBo bo=new SubjectAllocatedToStudentBo();
bo.setBacthId(dto.getBacthId());
bo.setSemester(dto.getSemester());
bo.setStudentId(dto.getStudentId());
Subject subject=iterator.next();
bo.setSubjectName(subject.getSubjectName());
bo.setSubjectType(subject.getAbbreviation());
try{
manager.persist(bo);
}
catch(javax.persistence.PersistenceException e){
Throwable t = e.getCause();
while ((t != null) && !(t instanceof org.hibernate.exception.ConstraintViolationException)) {
t = t.getCause();
}//while
if (t instanceof org.hibernate.exception.ConstraintViolationException) {
throw new Exception("Core subject already allocated to student");
} //end of if
}//end of catch
}//end of while
List<Subject> departmentallist=dto.getDepartmentList();
Iterator<Subject> iterator1=departmentallist.iterator();
while(iterator1.hasNext()){
logger.info("inside while :");
SubjectAllocatedToStudentBo bo=new SubjectAllocatedToStudentBo();
bo.setBacthId(dto.getBacthId());
bo.setSemester(dto.getSemester());
bo.setStudentId(dto.getStudentId());
Subject subject=iterator1.next();
bo.setSubjectName(subject.getSubjectName());
bo.setSubjectType(subject.getAbbreviation());
try{
manager.persist(bo);
}
catch(javax.persistence.PersistenceException e){
Throwable t = e.getCause();
while ((t != null) && !(t instanceof org.hibernate.exception.ConstraintViolationException)) {
t = t.getCause();
}//while
if (t instanceof org.hibernate.exception.ConstraintViolationException) {
throw new Exception("InterDepartmental subject already allocated to student");
} //end of if
}//end of catch
}//end of while
List<Subject> electiveList=dto.getElectiveList();
Iterator<Subject> iterator2=electiveList.iterator();
while(iterator2.hasNext()){
logger.info("inside while :");
SubjectAllocatedToStudentBo bo=new SubjectAllocatedToStudentBo();
bo.setBacthId(dto.getBacthId());
bo.setSemester(dto.getSemester());
bo.setStudentId(dto.getStudentId());
Subject subject=iterator2.next();
bo.setSubjectName(subject.getSubjectName());
bo.setSubjectType(subject.getAbbreviation());
try{
manager.persist(bo);
}
catch(javax.persistence.PersistenceException e){
Throwable t = e.getCause();
while ((t != null) && !(t instanceof org.hibernate.exception.ConstraintViolationException)) {
t = t.getCause();
}//while
if (t instanceof org.hibernate.exception.ConstraintViolationException) {
throw new Exception("Elective subject already allocated to student");
} //end of if
}//end of catch
}//end of while
logger.info("allocateSubjectToStudent method exit :");
} //end of method
create three different method all with TranscationAttributeType REQUIRES_NEW
Please find below code snippet for EJB3 Bean
public void doYourWork()
{
a();
b();
c();
}
#TransactionAttribute(TransactionAttributeType.REQUIRES_NEW)
public void a()
{
try
{
//Do the first transaction here
}catch(Exception e)
{
}
}
#TransactionAttribute(TransactionAttributeType.REQUIRES_NEW)
public void b()
{
try
{
//Do the second transaction here
}catch(Exception e)
{
}
}
#TransactionAttribute(TransactionAttributeType.REQUIRES_NEW)
public void c()
{
try
{
//Do the third transaction here
}catch(Exception e)
{
}
}
Within a single method invocation there is only a single transaction active. To achieve what you want, you must perform the three operations in different transactions. This would require one more level of abstracttion.
public class MyFreshTransaction {
#TransactionAttribute(REQUIRES_NEW)
public void updateO() {
//do something
}
#TransactionAttribute(REQUIRES_NEW)
public void update1() {
//do something
}
#TransactionAttribute(REQUIRES_NEW)
public void update2() {
//do something
}
}
#Stateless
public class MyTransactionProcessor {
#EJB
private MyFreshTransaction freshTransaction;
public void processTransaction() {
try {
//The current transaction context will be suspended, and a new one invoked
//if the new one fails and is rollback, the current one is not affected.
//you can then handle the exception, by rethrowing the exception,in which case
//the current transaction will also be rolled back, or continue based on your logic.
freshTransaction.update0();
} catch (Exception ex ) {//handle}
try {
//The current transaction context will be suspended, and a new one invoked
//if the new one fails and is rollback, the current one is not affected.
//you can then handle the exception, by rethrowing the exception,in which case
//the current transaction will also be rolled back, or continue based on your logic.
freshTransaction.update1();
} catch (Exception ex ) {//handle}
try {
//The current transaction context will be suspended, and a new one invoked
//if the new one fails and is rollback, the current one is not affected.
//you can then handle the exception, by rethrowing the exception,in which case
//the current transaction will also be rolled back, or continue based on your logic.
freshTransaction.update2();
} catch (Exception ex ) {//handle}
}
}
Note that if any of the update transaction was successful, and the the parent transaction is rolled back, it will not affect the status of the 'child' transactions, as they had already been committed and their effects (if DB effects) will be committed too.
Read on Java EE Transactions Java EE Transactions