The definition of label in YARN-796 is pretty clear, * Node Label label that describes a node. Node can have multiple labels
* Label expression logical combination of labels (using && and, || or, ! not) With this definition (without considering the implementation), a node label could be treated as a Boolean type attribute of a node. Assuming the administrator define label1, label2, label3 in the system, and associate node1 with "label1, label2", this means the value of attribute label1 and label2 for node1 is true, while the value of attribute label3 will be false for node1. In current Yarn implementation, seems the resource partitioning has been treated as the primary use case for node label, and some design/implementation of node label mainly consider on the partitioning case, even the multiple label support has been disabled in YARN-2694. To cover the workload resource request use case, YARN-3409 was proposed while the description/example of constraint node label in YARN-3409 seems more like a String type attribute for a node instead of Boolean type anymore. I got confused about node label. >From my view, node label is one attribute of a node, and it could be used for >different scheduling scenarios. No matter resource partitioning or job >scheduling constraints, a node label is just a label on a node. For >partitioning, we can have one object calling partition or resource group >representing the group of nodes with certain label; for workload scheduling >constraints purpose, we may want to extend the current application level >constraint to be container level constraint, for one application, the master >may request one type of resource while the slave request another type of >resource. Comments? Lei Guo Senior Architect, Huawei Canada Research Centre
