[YARN-10780] Optimise retrieval of configured node labels in CS queues

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.4.0
• Fix Version/s: 3.4.0
• Component/s: capacity scheduler
• Target Version/s: 3.4.0
• Hadoop Flags: Reviewed
• Assignee: Andras Gyori
• Reporter: Andras Gyori
• Created: 20/May/21 14:27
• Updated: 12/Feb/24 06:05
• Resolved: 24/Jun/21 18:16

Description

CapacitySchedulerConfiguration#getConfiguredNodeLabels scales poorly with respect to queue numbers (its O(n*m), where n is the number of queues and m is the number of properties set by each queue). During CS reinit, the node labels are often queried, however looking at the code:

for (Entry<String, String> stringStringEntry : this) {
      e = stringStringEntry;
      String key = e.getKey();

      if (key.startsWith(getQueuePrefix(queuePath) + ACCESSIBLE_NODE_LABELS
          + DOT)) {
        // Find <label-name> in
        // <queue-path>.accessible-node-labels.<label-name>.property
        int labelStartIdx =
            key.indexOf(ACCESSIBLE_NODE_LABELS)
                + ACCESSIBLE_NODE_LABELS.length() + 1;
        int labelEndIndx = key.indexOf('.', labelStartIdx);
        String labelName = key.substring(labelStartIdx, labelEndIndx);
        configuredNodeLabels.add(labelName);
      }
    }

 This method iterates through ALL properties set in the configuration. For example in case of initialising 2500 queues, each having at least 2 properties:

2500 * 5000 ~= over 12 million iteration + additional properties

There are some ways to resolve this issue while keeping backward compatibility:

1. Create a property like the original accessible-node-labels, which contains predefined labels. If it is set, then getConfiguredNodeLabels get the value of this property, otherwise it falls back to the old logic. I think accessible-node-labels are not used for this purpose (though I have a feeling that it should have been).
2. Collect node labels for all queues at the beginning of parseQueue and only iterate through the properties once. This will increase the space complexity in exchange of not requiring intervention from user's perspective. 

Issue Links

• blocks: YARN-10813 Set default capacity of root for node labels