same file not picked up by multiple hosts - spring-integration

Question

I have an app hosted multiple hosts listening to single remote SFTP location. How should i make sure same file is not picked by an host which is already picked up by other? I am pretty new to spring integration. Appreciate someone can share examples
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EDIT:
Here is my integration flow getting file from sftp and placing in local directory and performing business logic in transformer and returning file and send it to remote sftp.
#Bean
public SessionFactory<ChannelSftp.LsEntry> sftpSessionFactory() {
LOGGER.debug(" Creating SFTP Session Factory -Start");
DefaultSftpSessionFactory factory = new DefaultSftpSessionFactory(true);
factory.setHost(sftpHost);
factory.setUser(sftpUser);
factory.setPort(port);
factory.setPassword(sftpPassword);
factory.setAllowUnknownKeys(true);
return new CachingSessionFactory<>(factory);
}
#Bean
public SftpInboundFileSynchronizer sftpInboundFileSynchronizer() {
SftpInboundFileSynchronizer fileSynchronizer = new SftpInboundFileSynchronizer(sftpSessionFactory());
fileSynchronizer.setDeleteRemoteFiles(true);
fileSynchronizer.setRemoteDirectory(sftpInboundDirectory);
fileSynchronizer.setFilter(new SftpPersistentAcceptOnceFileListFilter(store(), "*.json"));
return fileSynchronizer;
}
#Bean(name = PollerMetadata.DEFAULT_POLLER)
public PollerMetadata defaultPoller() {
PollerMetadata pollerMetadata = new PollerMetadata();
pollerMetadata.setTrigger(new PeriodicTrigger(5000));
return pollerMetadata;
}
#Bean
#InboundChannelAdapter(channel = "fileInputChannel", poller = #Poller(fixedDelay = "5000"))
public MessageSource<File> sftpMessageSource() {
SftpInboundFileSynchronizingMessageSource source =
new SftpInboundFileSynchronizingMessageSource(sftpInboundFileSynchronizer());
source.setLocalDirectory(localDirectory);
source.setAutoCreateLocalDirectory(true);
source.setLocalFilter(new AcceptOnceFileListFilter<File>());
source.setMaxFetchSize(1);
return source;
}
#Bean
IntegrationFlow integrationFlow() {
return IntegrationFlows.from(this.sftpMessageSource()).channel(fileInputChannel()).
transform(this::messageTransformer).channel(fileOutputChannel()).
handle(orderOutMessageHandler()).get();
}
#Bean
#ServiceActivator(inputChannel = "fileOutputChannel")
public SftpMessageHandler orderOutMessageHandler() {
SftpMessageHandler handler = new SftpMessageHandler(sftpSessionFactory());
LOGGER.debug(" Creating SFTP MessageHandler - Start ");
handler.setRemoteDirectoryExpression(new LiteralExpression(sftpOutboundDirectory));
handler.setFileNameGenerator(new FileNameGenerator() {
#Override
public String generateFileName(Message<?> message) {
if (message.getPayload() instanceof File) {
return ((File) message.getPayload()).getName();
} else {
throw new IllegalArgumentException("Expected Input is File.");
}
}
});
LOGGER.debug(" Creating SFTP MessageHandler - End ");
return handler;
}
#Bean
#org.springframework.integration.annotation.Transformer(inputChannel = "fileInputChannel", outputChannel = "fileOutputChannel")
public Transformer messageTransformer() {
return message -> {
File file=orderTransformer.transformInboundMessage(message);
return (Message<?>) file;
};
}
#Bean
public ConcurrentMetadataStore store() {
return new SimpleMetadataStore(hazelcastInstance().getMap("idempotentReceiverMetadataStore"));
}
#Bean
public HazelcastInstance hazelcastInstance() {
return Hazelcast.newHazelcastInstance(new Config().setProperty("hazelcast.logging.type", "slf4j"));

Answer 1

See SftpPersistentAcceptOnceFileListFilter to be injected into the SFTP Inbound Channel Adapter. This one has to be supplied with a MetadataStore based on the shared database.
See more info in the docs:
https://docs.spring.io/spring-integration/docs/current/reference/html/system-management.html#metadata-store
https://docs.spring.io/spring-integration/docs/current/reference/html/sftp.html#sftp-inbound