Replaced all fixed thread pools with cached thread pools. The cached

thread pools will flush their cached (dead) threads after 60 seconds.
This will cause that YaCy now runs constantly withl about 50 threads,
about 100 at peak times. Previously, about 400 threads had been cached
and kept in a hibernation state, which caused that the numproc counter
in /proc/user_beancounters (exists only in VM-hosted linux) was as high
as the cached number of threads. This caused that VM supervisors
terminated whole VM sessions if a limit was reached. Many VM providers
have limits of numproc=96 which made it virtually impossible to run YaCy
on such machines. With this change, it will be possible to run many YaCy
instances even on VM hosts.

source/net/yacy/cora/protocol/Domains.java

@@ -803,7 +803,7 @@ public class Domains {
         cacheHit_Insert++;
     }
 
-    final private static TimeLimiter timeLimiter = new SimpleTimeLimiter(Executors.newFixedThreadPool(20));
+    final private static TimeLimiter timeLimiter = new SimpleTimeLimiter(Executors.newCachedThreadPool());
 
     /**
      * strip off any parts of an url, address string (containing host/ip:port) or raw IPs/Hosts,

source/net/yacy/cora/protocol/http/HTTPClient.java

@@ -117,7 +117,7 @@ public class HTTPClient {
 	private long upbytes = 0L;
 	private String host = null;
 	private final long timeout;
-	private static ExecutorService executor = Executors.newFixedThreadPool(200);
+	private static ExecutorService executor = Executors.newCachedThreadPool();
 
     public HTTPClient(final ClientIdentification.Agent agent) {
         super();

source/net/yacy/document/importer/MediawikiImporter.java

@@ -175,7 +175,7 @@ public class MediawikiImporter extends Thread implements Importer {
             final int threads = Math.max(2, Runtime.getRuntime().availableProcessors() - 1);
             final BlockingQueue<wikiparserrecord> in = new ArrayBlockingQueue<wikiparserrecord>(threads * 10);
             final BlockingQueue<wikiparserrecord> out = new ArrayBlockingQueue<wikiparserrecord>(threads * 10);
-            final ExecutorService service = Executors.newFixedThreadPool(threads + 1);
+            final ExecutorService service = Executors.newCachedThreadPool();
             final convertConsumer[] consumers = new convertConsumer[threads];
             final Future<?>[] consumerResults = (Future<?>[]) Array.newInstance(Future.class, threads);
             for (int i = 0; i < threads; i++) {
@@ -325,7 +325,7 @@ public class MediawikiImporter extends Thread implements Importer {
         final PositionAwareReader in = new PositionAwareReader(dumpFile);
         final indexProducer producer = new indexProducer(100, idxFromMediawikiXML(dumpFile));
         final wikiConsumer consumer = new wikiConsumer(100, producer);
-        final ExecutorService service = Executors.newFixedThreadPool(2);
+        final ExecutorService service = Executors.newCachedThreadPool();
         final Future<Integer> producerResult = service.submit(consumer);
         final Future<Integer> consumerResult = service.submit(producer);
         service.shutdown();

source/net/yacy/kelondro/blob/ArrayStack.java

@@ -879,7 +879,7 @@ public class ArrayStack implements BLOB {
         assert mem() <= m : "m = " + m + ", mem() = " + mem();
     }
 
-    private static final ExecutorService DELETE_EXECUTOR = Executors.newFixedThreadPool(128);
+    private static final ExecutorService DELETE_EXECUTOR = Executors.newCachedThreadPool();
 
     /**
      * close the BLOB