public void barrierAcquiredByMember(String member) {
    LOG.debug("member: '" + member + "' joining acquired barrier for procedure '" + procName
      + "' on coordinator");
    if (this.acquiringMembers.contains(member)) {
      synchronized (joinBarrierLock) {
        if (this.acquiringMembers.remove(member)) {
          this.inBarrierMembers.add(member);
          acquiredBarrierLatch.countDown();
        }
      }
      LOG.debug(
        "Waiting on: " + acquiredBarrierLatch + " remaining members to acquire global barrier");
    } else {
      LOG.warn("Member " + member + " joined barrier, but we weren't waiting on it to join."
        + " Continuing on.");
    }
  }
Call back triggered by an individual member upon successful local barrier acquisition
hbase-server/src/main/java/org/apache/hadoop/hbase/procedure/Procedure.java