[GitHub] [incubator-doris] wangbo commented on issue #5308: Compaction producer hang and none compaction consumer works

[GitBox <gi...@apache.org>]

wangbo commented on issue #5308:
URL: https://github.com/apache/incubator-doris/issues/5308#issuecomment-768783162


   code version: master
   ```
   bool CompactionPermitLimiter::request(int64_t permits) {
       DorisMetrics::instance()->compaction_waitting_permits->set_value(permits);
       if (permits > config::total_permits_for_compaction_score) {
           // when tablet's compaction score is larger than "config::total_permits_for_compaction_score",
           // it's necessary to do compaction for this tablet because this tablet will not get "permits"
           // anyway. otherwise, compaction task for this tablet will not be executed forever.
           std::unique_lock<std::mutex> lock(_permits_mutex);
           _permits_cv.wait(lock, [=] {
               return _used_permits == 0 ||
                      _used_permits + permits <= config::total_permits_for_compaction_score;
           });
       } else {
           if (_used_permits + permits > config::total_permits_for_compaction_score) {
               std::unique_lock<std::mutex> lock(_permits_mutex);
               _permits_cv.wait(lock, [=] {
                   return _used_permits + permits <= config::total_permits_for_compaction_score;
               });
           }
       }
       _used_permits += permits;  // here _used_permits is updated out of lock, Does this have concurrency issues ?
       DorisMetrics::instance()->compaction_waitting_permits->set_value(0);
       DorisMetrics::instance()->compaction_used_permits->set_value(_used_permits);
       return true;
   }
   ```
   I have a question as in the comment above.
   


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