Adding retry to id block store.

Change-Id: I274a928a13d2999ccfeb79fc45caf292dbb81f5b

@@ -13,6 +13,7 @@ import org.apache.felix.scr.annotations.Service;
 import org.onosproject.core.IdBlock;
 import org.onosproject.core.IdBlockStore;
 import org.onosproject.store.service.AtomicCounter;
+import org.onosproject.store.service.StorageException;
 import org.onosproject.store.service.StorageService;
 import org.slf4j.Logger;
 
@@ -25,6 +26,8 @@ import com.google.common.collect.Maps;
 @Service
 public class ConsistentIdBlockStore implements IdBlockStore {
 
+    private static final int MAX_TRIES = 3;
+
     private final Logger log = getLogger(getClass());
     private final Map<String, AtomicCounter> topicCounters = Maps.newConcurrentMap();
 
@@ -45,11 +48,23 @@ public class ConsistentIdBlockStore implements IdBlockStore {
 
     @Override
     public IdBlock getIdBlock(String topic) {
-        AtomicCounter counter = topicCounters.computeIfAbsent(topic,
+        AtomicCounter counter = topicCounters
+                .computeIfAbsent(topic,
                                  name -> storageService.atomicCounterBuilder()
                                          .withName(name)
                                          .build());
+        Throwable exc = null;
+        for (int i = 0; i < MAX_TRIES; i++) {
+            try {
                 Long blockBase = counter.getAndAdd(DEFAULT_BLOCK_SIZE);
                 return new IdBlock(blockBase, DEFAULT_BLOCK_SIZE);
+            } catch (StorageException e) {
+                log.warn("Unable to allocate ID block due to {}; retrying...",
+                         e.getMessage());
+                exc = e;
+            }
         }
+        throw new IllegalStateException("Unable to allocate ID block", exc);
+    }
+
 }