public void notifyAndBecomePrimary() {
    synchronized (primaryLock) {
      setIsPrimary(true);
      notifyPrimaryLock();
    }
  }
Find out if this sender is the eldest in the DS. Returns true if: 1. No other sender is running
2. At least one sender is running in the system apart from this sender AND this sender's start
time is lesser of all (i.e. this sender is oldest)

@return boolean true if this eldest sender; false otherwise
geode-core/src/main/java/org/apache/geode/internal/cache/wan/GatewaySenderAdvisor.java