void acquireReadLock() {
    // TODO should this be interruptible?
    readLock.lock();
  }
Acquires the read Lock for the non blocking class. This method is overridden in the
BlockingHARegionQueue class which acquires the lock on a ReentrantLock instead of
ReentrantReadWriteLock of this class. A read lock is aquired by a non blocking peek while
operating on the idsAvailable LinkedHashSet without structurally modifying it.

All invocations of this method must have {@link #releaseReadLock()} in a matching finally
block.

<p>
author Asif
geode-core/src/main/java/org/apache/geode/internal/cache/ha/HARegionQueue.java