How to use sling thread pool in CQ/AEM

Use Case: You are designing an application where you might need to delegate Job to a separate thread and you want to control this using thread pool so that your application itself does not run out of threads.

Prerequisite: Knowledge of Java Threads and basic Knowledge of thread pool. Note that there is Java Level thread pool as well that you can use. Check http://docs.oracle.com/javase/7/docs/api/java/util/concurrent/package-summary.html for that.

Reference: https://sling.apache.org/documentation/bundles/apache-sling-commons-thread-pool.html

Implementation Example:
Step 1: Create your Thread class
public YourThreadClass implements Runnable {
public void run() {
//Your custom logic
}}

Step 2: Main class to use a sling Thread pool
import java.util.Map;
import org.apache.felix.scr.annotations.Activate;
import org.apache.felix.scr.annotations.Component;
import org.apache.felix.scr.annotations.Properties;
import org.apache.felix.scr.annotations.Property;
import org.apache.felix.scr.annotations.Reference;
import org.apache.felix.scr.annotations.Service;
import org.apache.sling.api.SlingHttpServletRequest;
import org.apache.sling.api.SlingHttpServletResponse;
import org.apache.sling.commons.osgi.OsgiUtil;
import org.apache.sling.commons.threads.ModifiableThreadPoolConfig;
import org.apache.sling.commons.threads.ThreadPool;
import org.apache.sling.commons.threads.ThreadPoolConfig.ThreadPriority;
import org.apache.sling.commons.threads.ThreadPoolManager;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

@Component
@Service
public class YourTestClassService {
private static final Logger LOGGER = LoggerFactory.getLogger(YourTestClassService.class);

@Reference
private ThreadPoolManager threadPoolManager;

/** your thread pool */
private ThreadPool threadPool;

@Property(label = "minThreadPoolSize", description="Minium Thread pool size", intValue=5)
private static final String MINIMUM_THREAD_POOL_SIZE = "minThreadPoolSize";
private int minThreadPoolSize;

@Property(label = "maxThreadPoolSize", description="Max Thread pool size", intValue=10)
private static final String MAXUIMUM_THREAD_POOL_SIZE = "maxThreadPoolSize";
private int maxThreadPoolSize;

@Activate
protected final void activate(final Map<Object, Object> config) {
this.minThreadPoolSize = OsgiUtil.toInteger(config.get(MINIMUM_THREAD_POOL_SIZE), 5);
this.maxThreadPoolSize = OsgiUtil.toInteger(config.get(MAXUIMUM_THREAD_POOL_SIZE), 10);
ModifiableThreadPoolConfig threadPoolConfig = new ModifiableThreadPoolConfig();
if(threadPoolConfig.getMinPoolSize()<this.minThreadPoolSize) {
threadPoolConfig.setMinPoolSize(this.minThreadPoolSize);
}
if(threadPoolConfig.getMaxPoolSize()<this.maxThreadPoolSize) {
threadPoolConfig.setMaxPoolSize(this.maxThreadPoolSize);
}
//You can make this configurable as well
threadPoolConfig.setPriority(ThreadPriority.NORM);
this.threadPool = threadPoolManager.create(threadPoolConfig);
if(threadPool == null) {
throw new IllegalStateException("Could not get a ThreadPool");
}
}

@Deactivate
protected void deactivate(ComponentContext ctx) throws Exception {
if(threadPool != null) {
threadPoolManager.release(threadPool);
threadPoolManager = null;
threadPool = null;
}
}

public void yourMethod(){
YourThreadClass your_thread_class = new YourThreadClass();
Runnable YOUR_CUSTOM_THREAD = new Thread(your_thread_class);
this.threadPool.execute(YOUR_CUSTOM_THREAD);
}

}

Use CQ dependency finder to find what dependency you need for the above code in your pom.xml