File Tail Inbound Channel Adapter stderr and stdout - spring-integration

Question

I am trying to a tail file using spring integration and it is working as the code below but i have two questions
#Configuration
public class RootConfiguration {
#Bean(name = PollerMetadata.DEFAULT_POLLER)
public PollerMetadata defaultPoller() {
PollerMetadata pollerMetadata = new PollerMetadata();
pollerMetadata.setTrigger(new PeriodicTrigger(10));
return pollerMetadata;
}
#Bean
public MessageChannel input() {
return new QueueChannel(50);
}
#Bean
public FileTailInboundChannelAdapterFactoryBean tailInboundChannelAdapterParser() {
FileTailInboundChannelAdapterFactoryBean x = new FileTailInboundChannelAdapterFactoryBean();
x.setAutoStartup(true);
x.setOutputChannel(input());
x.setTaskExecutor(taskExecutor());
x.setNativeOptions("-F -n +0");
x.setFile(new File("/home/shahbour/Desktop/file.txt"));
return x;
}
#Bean
#ServiceActivator(inputChannel = "input")
public LoggingHandler loggingHandler() {
return new LoggingHandler("info");
}
#Bean
public TaskExecutor taskExecutor() {
ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();
taskExecutor.setCorePoolSize(4);
taskExecutor.afterPropertiesSet();
return taskExecutor;
}
}
Per below log i have 4 threads used for tailing the file. Do i need all of them or i can disable some. Why do i have a thread for Monitoring process java.lang.UNIXProcess#b37e761 , Reading stderr ,Reading stdout .
I am asking this because i am going to run the program on voip switch and i want to use the minimal resources possible.
2016-12-10 13:22:55.666 INFO 14862 --- [ taskExecutor-1] t.OSDelegatingFileTailingMessageProducer : Starting tail process
2016-12-10 13:22:55.665 INFO 14862 --- [ main] t.OSDelegatingFileTailingMessageProducer : started tailInboundChannelAdapterParser
2016-12-10 13:22:55.682 INFO 14862 --- [ main] o.s.i.endpoint.PollingConsumer : started rootConfiguration.loggingHandler.serviceActivator
2016-12-10 13:22:55.682 INFO 14862 --- [ main] o.s.c.support.DefaultLifecycleProcessor : Starting beans in phase 2147483647
2016-12-10 13:22:55.701 INFO 14862 --- [ main] c.t.SonusbrokerApplication : Started SonusbrokerApplication in 3.84 seconds (JVM running for 4.687)
2016-12-10 13:22:55.703 DEBUG 14862 --- [ taskExecutor-2] t.OSDelegatingFileTailingMessageProducer : Monitoring process java.lang.UNIXProcess#b37e761
2016-12-10 13:22:55.711 DEBUG 14862 --- [ taskExecutor-3] t.OSDelegatingFileTailingMessageProducer : Reading stderr
2016-12-10 13:22:55.711 DEBUG 14862 --- [ taskExecutor-4] t.OSDelegatingFileTailingMessageProducer : Reading stdout
My Second question is , is it possible to start reading the file from the begging and continue to tail , i was thinking in using native options for this -n 1000
note: the real code will be to monitor folder for new files as they are created and then start the tail process

Answer 1

The process monitor is needed to waitFor() the process - it doesn't use any resources except a bit of memory.
The stdout reader is needed to actually handle the data that is produced by the tail command.
The starting thread (in your case taskExecutor-1 exits after it has done its work of starting the other threads).
There is not currently an option to disable the stderr reader, but it would be easy for us to add one so there are only 2 threads at runtime.
Feel free to open a JIRA 'improvement' Issue and, of course, contributions are welcome.