[YARN-7561] Why hasContainerForNode() return false directly when there is no request of ANY locality without considering NODE_LOCAL and RACK_LOCAL?

• Type: Task
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 2.7.3, 3.1.0
• Component/s: fairscheduler
• Assignee: Unassigned
• Reporter: wuchang
• Created: 27/Nov/17 05:19
• Updated: 03/Jan/18 19:15

Description

I am studying the FairScheduler source cod of yarn 2.7.3.
By the code of class FSAppAttempt:

  public boolean hasContainerForNode(Priority prio, FSSchedulerNode node) {

    ResourceRequest anyRequest = getResourceRequest(prio, ResourceRequest.ANY);  
    ResourceRequest rackRequest = getResourceRequest(prio, node.getRackName()); 
    ResourceRequest nodeRequest = getResourceRequest(prio, node.getNodeName()); 
    
    return
        // There must be outstanding requests at the given priority:
        anyRequest != null && anyRequest.getNumContainers() > 0 &&
            // If locality relaxation is turned off at *-level, there must be a
            // non-zero request for the node's rack:
            (anyRequest.getRelaxLocality() ||
                (rackRequest != null && rackRequest.getNumContainers() > 0)) &&
            // If locality relaxation is turned off at rack-level, there must be a
            // non-zero request at the node:
            (rackRequest == null || rackRequest.getRelaxLocality() ||
                (nodeRequest != null && nodeRequest.getNumContainers() > 0)) &&
            // The requested container must be able to fit on the node:
            Resources.lessThanOrEqual(RESOURCE_CALCULATOR, null,
                anyRequest.getCapability(), node.getRMNode().getTotalCapability());
}

I really cannot understand why when there is no anyRequest , hasContainerForNode() return false directly without considering whether there is NODE_LOCAL or RACK_LOCAL requests.
And , AppSchedulingInfo.allocateNodeLocal() and AppSchedulingInfo.allocateRackLocal() will also decrease the number of containers for ResourceRequest.ANY, this is another place where I feel confused.

Really thanks for some prompt.