AtomicQueue example.

Tail.java

package com.github.junkdog.hallucinolog.component;

import lombok.ToString;

import org.apache.commons.io.input.Tailer;

import com.artemis.Component;
import com.badlogic.gdx.utils.AtomicQueue;

@ToString
public class Tail extends Component
{
        public String path;
        public transient Tailer tailer;
        // from an entity system, poll() until messages returns null.
        public transient AtomicQueue<String> messages = new AtomicQueue<String>(1024);
        public transient int consecutiveRuns;
        public transient int maxEmissionsPerTick = 1;
        
        public Tail() {}
        
        public Tail(String path)
        {
                this.path = path; 
        }
}

TailManager.java

package com.github.junkdog.hallucinolog.manager;

import java.io.File;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

import lombok.AllArgsConstructor;
import lombok.ArtemisManager;

import org.apache.commons.io.input.Tailer;
import org.apache.commons.io.input.TailerListener;

import com.artemis.Entity;
import com.artemis.Manager;
import com.badlogic.gdx.utils.Array;
import com.github.junkdog.hallucinolog.component.Tail;

@ArtemisManager(
        requires=Tail.class)
public class TailManager extends Manager
{
        private Array<Entity> active;
        private ExecutorService pool;
        
        @Override
        protected void initialize()
        {
                active = new Array<Entity>();
                pool = Executors.newCachedThreadPool();
        }
        
        @Override
        public void added(Entity e)
        {
                Tail tail = tailMapper.get(e);
                int delayMillis = 250;
                Tailer tailer = new Tailer(new File(tail.path), new TailListener(tail), delayMillis, true);
                tail.tailer = tailer;
                
                active.add(e);

                pool.submit(tailer);
        }
        
        @Override
        public void deleted(Entity e)
        {
                Tail tail = tailMapper.get(e);
                tail.tailer.stop();
                
                active.removeValue(e, true);
        }
        
        @AllArgsConstructor
        private static class TailListener implements TailerListener
        {
                private final Tail tail;
                
                @Override public void init(Tailer tailer) {}
                @Override public void fileRotated() {}

                @Override
                public void fileNotFound()
                {
                        System.err.println("missing file: " + tail.path);
                }

                @Override
                public void handle(String line)
                {
                        tail.messages.put(line);
                }

                @Override
                public void handle(Exception ex)
                {
                        ex.printStackTrace();
                }
        }
}