PutAll() with Transactions is slow

Question

Hi Guys,
I am looking into using transactions, but they seem to be really slow - perhaps I am doing something silly. I've written a simple test to measure the time taken by putAll() with and without transactions and putAll() with transactions takes nearly 4-5 times longer than without transactions.
Results:
Average time taken to insert without transactions 210ms
Average time taken to insert WITH transactions 1210ms
Test code:
public class TestCoherenceTransactions {
     private static final int MAP_SIZE = 5000;
     private static final int LIST_SIZE = 15;
     private static final int NO_OF_ITERATIONS = 50;
     public static void main (String[] args) {
          NamedCache cache = CacheFactory.getCache("dist-cache");          
          Map dataToInsert = new HashMap();
          for (int i=0;i < MAP_SIZE; i++) {
               List value = new ArrayList();
               for (int j = 0; j < LIST_SIZE; j++) {
                    value.add(j+"QWERTYU");     
               dataToInsert.put(i,value);
          long timeTaken = 0;
          long startTime = 0;
          for (int i = 0; i < NO_OF_ITERATIONS; i++) {     
               cache.clear();     
               startTime = System.currentTimeMillis();
               cache.putAll(dataToInsert);
               timeTaken += System.currentTimeMillis() - startTime;     
          System.out.println("Average time taken to insert without transactions " + timeTaken/NO_OF_ITERATIONS );
          timeTaken = 0;
          for (int i = 0; i < NO_OF_ITERATIONS; i++) {
               cache.clear();     
               startTime = System.currentTimeMillis();
               TransactionMap mapTx = CacheFactory.getLocalTransaction(cache);
               mapTx.setTransactionIsolation(TransactionMap.TRANSACTION_REPEATABLE_GET);
               mapTx.setConcurrency(TransactionMap.CONCUR_PESSIMISTIC);
               Collection txnCollection = Collections.singleton(mapTx);
               mapTx.begin();
               mapTx.putAll(dataToInsert);
               CacheFactory.commitTransactionCollection(txnCollection, 1);
               timeTaken += System.currentTimeMillis() - startTime;     
          System.out.println("Average time taken to insert WITH transactions " + timeTaken/NO_OF_ITERATIONS);
          System.out.println("cache size " + cache.size());
Am I misssing something obvious?? Can't understand why transactions are really slow. Any pointers would be very much appreciated.
Thanks
K

Answer 1

Hi,
TransactionMap is this slow because it locks and unlocks all entries (one by one as there is no lock-many funcitonality) you modify (or even read if you used at least REPEATABLE_READ isolation level) during the lifetime of the transaction if you are using CONCUR_PESSIMISTIC or CONCUR_OPTIMISTIC. Since each lock and unlock operation needs a network call (and that network call needs to be backed up from the primary node to the backup node in a distributed cache), the more entries you need to lock/unlock, the more latency is introduced due to this locking unlocking.
Best regards,
Robert