解决秒级并发达到700万时，出现生成跟不上消费异常

src/main/java/com/baidu/fsg/uid/buffer/BufferPaddingExecutor.java

@@ -147,6 +147,27 @@ public void paddingBuffer() {
         }
 
         // fill the rest slots until to catch the cursor
+        putBuffer();
+    }
+    /**
+     * Padding buffer fill the slots until to catch the cursor
+     */
+    public Boolean booleanPaddingBuffer() {
+        LOGGER.info("Ready to padding buffer lastSecond:{}. {}", lastSecond.get(), ringBuffer);
+
+        // is still running
+        if (!running.compareAndSet(false, true)) {
+            LOGGER.info("Padding buffer is still running. {}", ringBuffer);
+            return false;
+        }
+
+        // fill the rest slots until to catch the cursor
+        putBuffer();
+        return  true;
+    }
+
+    private void putBuffer() {
+
         boolean isFullRingBuffer = false;
         while (!isFullRingBuffer) {
             List<Long> uidList = uidProvider.provide(lastSecond.incrementAndGet());

src/main/java/com/baidu/fsg/uid/buffer/RingBuffer.java

@@ -166,9 +166,16 @@ public long take() {
 
         // cursor catch the tail, means that there is no more available UID to take
         if (nextCursor == currentCursor) {
-            rejectedTakeHandler.rejectTakeBuffer(this);
+            Boolean running = false;
+            while (!running) {
+                running = bufferPaddingExecutor.booleanPaddingBuffer();
+            }
+            nextCursor = cursor.updateAndGet(old -> old == tail.get() ? old : old + 1);
+
+            if (nextCursor == currentCursor) {
+                rejectedTakeHandler.rejectTakeBuffer(this);
+            }
         }
-
         // 1. check next slot flag is CAN_TAKE_FLAG
         int nextCursorIndex = calSlotIndex(nextCursor);
         Assert.isTrue(flags[nextCursorIndex].get() == CAN_TAKE_FLAG, "Curosr not in can take status");