groovy thread for urls - groovy

Question

I wrote logic for testing urls using threads.
This works good for less number of urls and failing with more than 400 urls to check .
class URL extends Thread{
def valid
def url
URL( url ) {
this.url = url
}
void run() {
try {
def connection = url.toURL().openConnection()
connection.setConnectTimeout(10000)
if(connection.responseCode == 200 ){
valid = Boolean.TRUE
}else{
valid = Boolean.FALSE
}
} catch ( Exception e ) {
valid = Boolean.FALSE
}
}
}
def threads = [];
urls.each { ur ->
def reader = new URL(ur)
reader.start()
threads.add(reader);
}
while (threads.size() > 0) {
for(int i =0; i < threads.size();i++) {
def tr = threads.get(i);
if (!tr.isAlive()) {
if(tr.valid == true){
threads.remove(i);
i--;
}else{
threads.remove(i);
i--;
}
}
}
Could any one please tell me how to optimize the logic and where i was going wrong .
thanks in advance.

Answer 1

Have you considered using the java.util.concurrent helpers? It allows multithreaded programming at a higher level of abstraction. There's a simple interface to run parallel tasks in a thread pool, which is easier to manage and tune than just creating n threads for n tasks and hoping for the best.
Your code then ends up looking something like this, where you can tune nThreads until you get the best performance:
import java.util.concurrent.*
def nThreads = 1000
def pool = Executors.newFixedThreadPool(nThreads)
urls.each { url ->
pool.submit(url)
}
def timeout = 60
pool.awaitTermination(timeout, TimeUnit.SECONDS)

Answer 2

Using ataylor's suggestion, and your code, I got to this:
import java.util.concurrent.Executors
import java.util.concurrent.TimeUnit
class MyURL implements Runnable {
def valid
def url
void run() {
try {
url.toURL().openConnection().with {
connectTimeout = 10000
if( responseCode == 200 ) {
valid = true
}
else {
valid = false
}
disconnect()
}
}
catch( e ) {
valid = false
}
}
}
// A list of URLs to check
def urls = [ 'http://www.google.com',
'http://stackoverflow.com/questions/2720325/groovy-thread-for-urls',
'http://www.nonexistanturlfortesting.co.ch/whatever' ]
// How many threads to kick off
def nThreads = 3
def pool = Executors.newFixedThreadPool( nThreads )
// Construct a list of the URL objects we're running, submitted to the pool
def results = urls.inject( [] ) { list, url ->
def u = new MyURL( url:url )
pool.submit u
list << u
}
// Wait for the poolclose when all threads are completed
def timeout = 10
pool.shutdown()
pool.awaitTermination( timeout, TimeUnit.SECONDS )
// Print our results
results.each {
println "$it.url : $it.valid"
}
Which prints out this:
http://www.google.com : true
http://stackoverflow.com/questions/2720325/groovy-thread-for-urls : true
http://www.nonexistanturlfortesting.co.ch/whatever : false
I changed the classname to MyURL rather than URL as you had it, as it will more likely avoid problems when you start using the java.net.URL class