MCOL4841 dev port run large join without OOM

utils/threadpool/prioritythreadpool.h

@@ -34,8 +34,10 @@
 #include <boost/thread/condition.hpp>
 #include <boost/shared_ptr.hpp>
 #include <boost/function.hpp>
+#include <atomic>
 #include "../winport/winport.h"
 #include "primitives/primproc/umsocketselector.h"
+#include "atomicops.h"
 
 namespace threadpool
 {
@@ -72,7 +74,9 @@ class PriorityThreadPool
     LOW,
     MEDIUM,
     HIGH,
-    _COUNT
+    _COUNT,
+    EXTRA  // After _COUNT because _COUNT is for jobQueue size and EXTRA isn't a jobQueue. But we need EXTRA
+           // in places where Priority is used.
   };
 
   /*********************************************
@@ -95,6 +99,20 @@ class PriorityThreadPool
    */
   void dump();
 
+  // If a job is blocked, we want to temporarily increase the number of threads managed by the pool
+  // A problem can occur if all threads are running long or blocked for a single query. Other
+  // queries won't get serviced, even though there are cpu cycles available.
+  // These calls are currently protected by respondLock in sendThread(). If you call from other
+  // places, you need to consider atomicity.
+  void incBlockedThreads()
+  {
+    blockedThreads++;
+  }
+  void decBlockedThreads()
+  {
+    blockedThreads--;
+  }
+
  protected:
  private:
   struct ThreadHelper
@@ -127,6 +145,10 @@ class PriorityThreadPool
   bool _stop;
   uint32_t weightPerRun;
   volatile uint id;  // prevent it from being optimized out
+
+  std::atomic<uint32_t> blockedThreads;
+  std::atomic<uint32_t> extraThreads;
+  bool stopExtra;
 };
 
 }  // namespace threadpool