private MemoryPoolAssignmentsRequest updateAssignments(Iterable<QueryExecution> queries) {
    ClusterMemoryPool reservedPool = pools.get(RESERVED_POOL);
    ClusterMemoryPool generalPool = pools.get(GENERAL_POOL);
    long version = memoryPoolAssignmentsVersion.incrementAndGet();
    // Check that all previous assignments have propagated to the visible nodes. This doesn't
    // account for temporary network issues,
    // and is more of a safety check than a guarantee
    if (reservedPool != null && generalPool != null && allAssignmentsHavePropagated(queries)) {
      if (reservedPool.getQueries() == 0 && generalPool.getBlockedNodes() > 0) {
        QueryExecution biggestQuery = null;
        long maxMemory = -1;
        for (QueryExecution queryExecution : queries) {
          long bytesUsed = queryExecution.getTotalMemoryReservation();
          if (bytesUsed > maxMemory) {
            biggestQuery = queryExecution;
            maxMemory = bytesUsed;
          }
        }
        for (QueryExecution queryExecution : queries) {
          if (queryExecution.getQueryId().equals(biggestQuery.getQueryId())) {
            queryExecution.setMemoryPool(new VersionedMemoryPoolId(RESERVED_POOL, version));
          }
        }
      }
    }

    ImmutableList.Builder<MemoryPoolAssignment> assignments = ImmutableList.builder();
    for (QueryExecution queryExecution : queries) {
      assignments.add(
          new MemoryPoolAssignment(
              queryExecution.getQueryId(), queryExecution.getMemoryPool().getId()));
    }
    return new MemoryPoolAssignmentsRequest(coordinatorId, version, assignments.build());
  }
  public void process(Iterable<QueryExecution> queries) {
    if (!enabled) {
      return;
    }
    long totalBytes = 0;
    for (QueryExecution query : queries) {
      long bytes = query.getTotalMemoryReservation();
      DataSize sessionMaxQueryMemory = getQueryMaxMemory(query.getSession());
      long queryMemoryLimit = Math.min(maxQueryMemory.toBytes(), sessionMaxQueryMemory.toBytes());
      totalBytes += bytes;
      if (bytes > queryMemoryLimit) {
        query.fail(
            new ExceededMemoryLimitException(
                "Query", DataSize.succinctDataSize(queryMemoryLimit, Unit.BYTE)));
      }
    }
    clusterMemoryUsageBytes.set(totalBytes);

    Map<MemoryPoolId, Integer> countByPool = new HashMap<>();
    for (QueryExecution query : queries) {
      MemoryPoolId id = query.getMemoryPool().getId();
      countByPool.put(id, countByPool.getOrDefault(id, 0) + 1);
    }

    updatePools(countByPool);

    updateNodes(updateAssignments(queries));
  }
  public synchronized void process(Iterable<QueryExecution> queries) {
    if (!enabled) {
      return;
    }

    boolean outOfMemory = isClusterOutOfMemory();
    if (!outOfMemory) {
      lastTimeNotOutOfMemory = System.nanoTime();
    }

    boolean queryKilled = false;
    long totalBytes = 0;
    for (QueryExecution query : queries) {
      long bytes = query.getTotalMemoryReservation();
      DataSize sessionMaxQueryMemory = getQueryMaxMemory(query.getSession());
      long queryMemoryLimit = Math.min(maxQueryMemory.toBytes(), sessionMaxQueryMemory.toBytes());
      totalBytes += bytes;
      if (resourceOvercommit(query.getSession()) && outOfMemory) {
        // If a query has requested resource overcommit, only kill it if the cluster has run out of
        // memory
        DataSize memory = succinctBytes(bytes);
        query.fail(
            new PrestoException(
                CLUSTER_OUT_OF_MEMORY,
                format(
                    "The cluster is out of memory and %s=true, so this query was killed. It was using %s of memory",
                    RESOURCE_OVERCOMMIT, memory)));
        queryKilled = true;
      }
      if (!resourceOvercommit(query.getSession()) && bytes > queryMemoryLimit) {
        DataSize maxMemory = succinctBytes(queryMemoryLimit);
        query.fail(exceededGlobalLimit(maxMemory));
        queryKilled = true;
      }
    }
    clusterMemoryUsageBytes.set(totalBytes);

    if (killOnOutOfMemory) {
      boolean shouldKillQuery =
          nanosSince(lastTimeNotOutOfMemory).compareTo(killOnOutOfMemoryDelay) > 0 && outOfMemory;
      boolean lastKilledQueryIsGone = (lastKilledQuery == null);

      if (!lastKilledQueryIsGone) {
        ClusterMemoryPool generalPool = pools.get(GENERAL_POOL);
        if (generalPool != null) {
          lastKilledQueryIsGone =
              generalPool.getQueryMemoryReservations().containsKey(lastKilledQuery);
        }
      }

      if (shouldKillQuery && lastKilledQueryIsGone && !queryKilled) {
        // Kill the biggest query in the general pool
        QueryExecution biggestQuery = null;
        long maxMemory = -1;
        for (QueryExecution query : queries) {
          long bytesUsed = query.getTotalMemoryReservation();
          if (bytesUsed > maxMemory && query.getMemoryPool().getId().equals(GENERAL_POOL)) {
            biggestQuery = query;
            maxMemory = bytesUsed;
          }
        }
        if (biggestQuery != null) {
          biggestQuery.fail(
              new PrestoException(
                  CLUSTER_OUT_OF_MEMORY,
                  "The cluster is out of memory, and your query was killed. Please try again in a few minutes."));
          queriesKilledDueToOutOfMemory.incrementAndGet();
          lastKilledQuery = biggestQuery.getQueryId();
        }
      }
    }

    Map<MemoryPoolId, Integer> countByPool = new HashMap<>();
    for (QueryExecution query : queries) {
      MemoryPoolId id = query.getMemoryPool().getId();
      countByPool.put(id, countByPool.getOrDefault(id, 0) + 1);
    }

    updatePools(countByPool);

    updateNodes(updateAssignments(queries));

    // check if CPU usage is over limit
    for (QueryExecution query : queries) {
      Duration cpuTime = query.getTotalCpuTime();
      Duration sessionLimit = getQueryMaxCpuTime(query.getSession());
      Duration limit = maxQueryCpuTime.compareTo(sessionLimit) < 0 ? maxQueryCpuTime : sessionLimit;
      if (cpuTime.compareTo(limit) > 0) {
        query.fail(new ExceededCpuLimitException(limit));
      }
    }
  }