hadoop-hdds/common/src/main/resources/network-topology-default.xml

<?xml version="1.0"?>
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<!--
This is the default for network topology configuration. It defines
level prefix key name, level default cost and max levels.
-->
<configuration>
    <!-- The version of network topology configuration file format, it must be an integer -->
    <layoutversion>1</layoutversion>
    <layers>
        <layer id="datacenter">
            <prefix></prefix>
            <cost>1</cost>
            <type>Root</type>
        </layer>
        <!-- layer id is only used as the reference internally in this document -->
        <layer id="rack">
            <!-- prefix of the name of this layer. For example, if the prefix is "dc", then every
            name in this layer should start with "dc", such as "dc1", "dc2", otherwise NetworkTopology
            class should report error when add a node path which does't follow this rule. This field
            is case insensitive. It is optional and can have empty or "" value, in all these cases
            prefix check will not be enforced.
            -->
            <prefix>rack</prefix>
            <!-- The default cost of this layer, an positive integer or 0. Can be override by the
            "${cost}" value in specific path. This field is also optional. When it's not defined,
            it's value is default "1".
            -->
            <cost>1</cost>
            <!-- Layer type, optional field, case insensitive, default value InnerNode.
            Current value range : {Root, InnerNode, Leaf}
            Leaf node can only appear in the end of the "path" field of the "topology" section.
            Root node is a special node. It doesn't have name. It's represented by "/" at the beginning of the path.
            -->
            <type>InnerNode</type>
            <!-- default name if this layer is missed. Only apply to InnerNode. Ignored for Leaf node and Root. -->
            <default>/default-rack</default>
        </layer>
        <layer id="node">
            <prefix></prefix>
            <cost>0</cost>
            <type>Leaf</type>
        </layer>
    </layers>
    <topology>
        <path>/datacenter/rack/node</path>
        <!-- When this field is true, each InnerNode layer should has its prefix defined with not empty value,
         otherwise the content is not valid. Default value is false.
         -->
        <enforceprefix>false</enforceprefix>
    </topology>
</configuration>