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Logical Domains 1.2 Administration Guide

Request and Response Messages

The XML interface into LDoms has two different formats:

The two formats share many common XML structures, but are separated in this discussion for a better understanding of the differences between them. This document also contains an XML Schema which details the combined incoming and outgoing XML (See LDM_Event XML Schema).

Request Messages

An incoming XML request to the LDoms Manager at its most basic level includes a description of a single command, operating on a single object. More complicated requests can handle multiple commands and multiple objects per command. Following is the structure of a basic XML command.

Example 10–1 Format of a Single Command Operating on a Single Object


<LDM_interface version="1.0">
  <cmd>
    <action>Place command here</action>
    <option>Place options for certain commands here</option>
    <data version="3.0">
      <Envelope>
        <References/>
        <!-- Note a <Section> section can be here instead of <Content> -->
        <Content xsi:type="ovf:VirtualSystem_Type" id="Domain name">
          <Section xsi:type="ovf:ResourceAllocationSection_type">
            <Item>
              <rasd:OtherResourceType>LDom Resource Type</rasd:OtherResourceType>
              <gprop:GenericProperty
              key="Property name">Property Value</gprop:GenericProperty>
            </Item>
          </Section>
          <!-- Note: More Sections sections can be placed here -->
        </Content>
      </Envelope>
    </data>
    <!-- Note: More Data sections can be placed here -->
  </cmd>
  <!-- Note: More Commands sections can be placed here -->
</LDM_interface>

The <LDM_interface> Tag

All commands sent to the LDoms Manager must start with the <LDM_interface> tag. Any document sent into the LDoms Manager must have only one <LDM_interface> tag contained within it. The <LDM_interface> tag must include a version attribute as shown in Example 10–1.

The <cmd> Tag

Within the <LDM_interface> tag, the document must include at least one <cmd> tag. Each <cmd> section must have only one <action> tag. Use the <action> tag to describe the command to run. Each <cmd> tag must include at least one <data> tag to describe the objects on which the command is to operate.

The <cmd> tag can also have an <option> tag, which is used for options and flags that are associated with some commands. The following commands use options:

The <data> Tag

Each <data> section contains a description of an object pertinent to the command specified. The format of the data section is based on the XML schema portion of the Open Virtualization Format (OVF) draft specification. That schema defines an <Envelope> section which contains a <References> tag (unused by LDoms) and <Content> and <Section> sections.

For LDoms, the <Content> section is used to identify and describe a particular domain. The domain name in the id= attribute of the <Content> node identifies the domain. Within the <Content> section are one or more <Section> sections describing resources of the domain as needed by the particular command.

If you only need to identify a domain name, then you do not need to use any <Section> tags. Conversely, if no domain identifier is needed for the command, then you do need to provide a <Section> section, describing the resources needed for the command, outside of a <Content> section, but still within the <Envelope> section.

A <data> section does not need to contain an <Envelope> tag in cases where the object information can be inferred. This situation mainly applies to requests for monitoring all objects applicable to an action, and event registration and unregistration requests.

To allow use of the OVF specification's schema to properly define all types of objects, two additional OVF types have been defined:

The <gprop:GenericProperty> tag was defined to handle any object's property for which the OVF specification does not have a definition. The property name is defined in the key= attribute of the node and the value of the property is the contents of the node. The <binding> tag is used in the list-bindings subcommand output to define resources that are bound to other resources.

Response Messages

An outgoing XML response closely matches the structure of the incoming request in terms of the commands and objects included, with the addition of a <Response> section for each object and command specified, as well as an overall <Response> section for the request. The <Response> sections provide status and message information as described in Example 10–2. Following is the structure of a response to a basic XML request.

Example 10–2 Format of a Response to a Single Command Operating on a Single Object


<LDM_interface version="1.0">
  <cmd>
    <action>Place command here</action>
    <data version="3.0">
      <Envelope>
        <References/>
        <!-- Note a <Section> section can be here instead of <Content> -->
        <Content xsi:type="ovf:VirtualSystem_Type" id="Domain name">
          <Section xsi:type="ovf:ResourceAllocationSection_type">
            <Item>
              <rasd:OtherResourceType>
                LDom Resource Type
              </rasd:OtherResourceType>
              <gprop:GenericProperty
              key="Property name">
                Property Value
            </gprop:GenericProperty>
            </Item>
          </Section>
          <!-- Note: More <Section> sections can be placed here -->
        </Content>
      </Envelope>
      <response>
        <status>success or failure</status>
        <resp_msg>Reason for failure</resp_msg>
      </response>
    </data>
    <!-- Note: More Data sections can be placed here -->
    <response>
      <status>success or failure</status>
      <resp_msg>Reason for failure</resp_msg>
    </response>
  </cmd>
  <!-- Note: More Command sections can be placed here -->
  <response>
    <status>success or failure</status>
    <resp_msg>Reason for failure</resp_msg>
  </response>
</LDM_interface>

Overall Response

This <response> section, which is the direct child of the <LDM_interface> section, indicates overall success or failure of the entire request. Unless the incoming XML document is malformed, the <response> section includes only a <status> tag. If this response status indicates success, all commands on all objects have succeeded. If this response status is a failure and there is no <resp_msg> tag, then one of the commands included in the original request failed. The <resp_msg> tag is used only to describe some problem with the XML document itself.

Command Response

The <response> section under the <cmd> section alerts the user to success or failure of that particular command. The <status> tag shows if that command succeeds or fails. As with the overall response, if the command fails, the <response> section includes only a <resp_msg> tag if the contents of the <cmd> section of the request is malformed. Otherwise, the failed status means one of the objects the command ran against caused a failure.

Object Response

Finally, each <data> section in a <cmd> section also has a <response> section. This shows if the command being run on this particular object passes or fails. If the status of the response is SUCCESS, there is no <resp_msg> tag in the <response> section. If the status is FAILURE, there are one or more <resp_msg> tags in the <response> field, depending on the errors encountered when running the command against that object. Object errors can result from problems found when running the command, or a malformed or unknown object.

In addition to the <response> section, the <data> section can contain other information. This information is in the same format as an incoming <data> field, describing the object that caused a failure. See The <data> Tag. This additional information is especially useful in the following cases: