public void offer(SyncFuture syncFuture) {
    // It is ok to overwrite an existing mapping.
    syncFutureCache.asMap().put(syncFuture.getThread(), syncFuture);
  }
Offers the sync future back to the cache for reuse.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/wal/SyncFutureCache.java