multithreading - Java Fork Join Pool getting stuck -

i have data migration service reads stuff 1 database in chunks migrates database.

to work through 'chunks' of data- trying use recursiveaction , fork join pool. there reason work execute work on these "chunks" in parallel, chunk, execute, chunk, etc.

what's happening process stops. see no exceptions in logs, , see no deadlocked threads. code below, questions are:

• am missing in worker? need return value or call method free resource?
• is dumb me using recursiveaction here? should using different parallelize chunks of work?
• i have 1 worker thread in thread dump seems waiting- normal or indicator of problem?

forkjoinpool-1-worker-18 id=12191 state=waiting - waiting on <0x1b5ca93e> (a java.util.concurrent.forkjoinpool) - locked <0x1b5ca93e> (a java.util.concurrent.forkjoinpool) @ sun.misc.unsafe.park(native method) @ java.util.concurrent.locks.locksupport.park(locksupport.java:186) @ java.util.concurrent.forkjoinpool.tryawaitwork(forkjoinpool.java:864) @ java.util.concurrent.forkjoinpool.work(forkjoinpool.java:647) @ java.util.concurrent.forkjoinworkerthread.run(forkjoinworkerthread.java:398)

code:

@component public class bulkmigrationservice {  final forkjoinpool pool = new forkjoinpool();  private static final logger log = loggerfactory.getlogger(bulkmigrationservice.class);  private sourcedataapi api; private final migrator migrator; private metadataservice metadataservice;  @autowired public bulkmigrationservice(sourcedataapi api, migrator migrator, metadataservice metadataservice) {     this.api = api;     this.migrator = migrator;     this.metadataservice = metadataservice; }  public void migrate(integer batchsize, long max) throws migrationexception {      long currentcount = 0l;     integer currentindex = 0;      while (currentcount < max) {         list<string> itemstomigrate = api.finditemrange(currentindex, currentindex + batchsize);          if (assetstomigrate.size() > 0) {             migrateforkedworker starter = new migrateforkedworker(assetstomigrate);             pool.invoke(starter);         }          currentcount += assetstomigrate.size();         currentindex += batchsize - 1;         if (log.isdebugenabled()) {             log.debug("migrated " + currentcount + " items.");         }     }  }  public class migrateforkedworker extends recursiveaction {      private int max = 10;     private list<string> allitems;      public migrateforkedworker(list<string> allitems) {         this.allitems = allitems;      }      @override     protected void compute() {         if (allitems.size() <= max) {             (string iteminfo : allitems) {                  try {                     migrator.migrateasset(iteminfo);                  }                 catch (migrationexception e) {                     e.printstacktrace();                 }             }         }         else {             int targetsize = allitems.size() % 2 == 0 ? allitems.size() / 2 : (allitems.size() + 1) / 2;             list<list<string>> splits = lists.partition(allitems, targetsize);             migrateforkedworker migrateforkedworkerone = new migrateforkedworker(splits.get(0));             migrateforkedworker migrateforkedworkertwo = new migrateforkedworker(splits.get(1));              invokeall(migrateforkedworkerone, migrateforkedworkertwo);         }     } }  } 

your first problem using invokeall(). submits new requests pool , waits them complete. follow example in javadoc: use fork() migrateforkedworkerone.fork(); migrateforkedworkertwo.compute(); migrateforkedworkerone.join();