Define idrac Hardware Type Support of Redfish Interfaces

https://storyboard.openstack.org/#!/story/2004592

Operators need the ability to configure Ironic to use Redfish to manage Dell EMC bare metal servers, and be assured it:

  • offers a means of incrementally increasing the use of Redfish as Ironic’s support, the standard, and Dell EMC service implementations evolve,

  • delivers management protocol choice among those supported by Dell EMC – Intelligent Platform Management Interface (IPMI), Redfish, and Web Services Management (WS-Man),

  • provides all the idrac hardware type functionality they have relied on,

  • works and will continue to,

  • is supported by the vendor and community, and

  • can offer Dell EMC value added.

This specification suggests the idrac hardware type provides that.

Problem description

Use cases

Expanding on what the introductory paragraph describes above, several use cases can be envisioned. While this specification enables them, it may turn out only some will find practical use among operators. That could be driven by many factors, including an existing versus greenfield deployment, operator comfort level with Redfish versus WS-Man, maturity of the protocol implementations, availability of needed functionality across Redfish and WS-Man, requirement for vendor value added, operational plans and schedules, among others.

Here they are. Note that except for the first two, they can be used in combination to configure a single Dell EMC bare metal server.

  • An Admin User has a Dell EMC bare metal server and uses only WS-Man to manage it.

  • An Admin User has a Dell EMC bare metal server and uses only Redfish to manage it.

  • An Admin User has a Dell EMC bare metal server and uses both Redfish and WS-Man to manage it. When both offer the needed functionality, either is used.

  • An Admin User has a Dell EMC bare metal server and uses both Redfish and WS-Man to manage it. Ironic’s ability to manage the server is maximized.

  • An Admin User has a Dell EMC bare metal server and uses both Redfish and WS-Man to manage it. Vendor value added, which is available from only one or both, is used.

Proposed change

Background

The idrac hardware type is the Ironic driver intended for use with Dell EMC bare metal servers equipped with an integrated Dell Remote Access Controller (iDRAC) baseboard management controller (BMC). To date, all the out-of-band (OOB) management protocol-dependent interface implementations idrac has supported use the WS-Man protocol to interact with the iDRAC. Those implement the inspect, management, power, raid, and vendor hardware interfaces. Like the hardware type, they are named idrac. They rely on python-dracclient’s WS-Man client.

Operators also have the option to use the generic, vendor-independent redfish hardware type with Dell EMC bare metal servers that have an iDRAC that supports the Redfish protocol. redfish’s supported OOB protocol-dependent interface implementations use the Redfish protocol to interact with the BMC. Those implement the bios, inspect, management, and power hardware interfaces. Again, like the hardware type, they are named redfish. They rely on sushy’s Redfish client. Importantly, while some of those work with the iDRAC, including management and power, not all of them do.

The redfish hardware type enables managing servers compliant with the Redfish protocol. However, it is relatively new, and the protocol standard has been evolving, along with its implementations by hardware vendors such as Dell EMC. As is common among standards, there is a difference between compliance and interoperability. For example, the Redfish bios interface implementation has not worked with the iDRAC because of client and server protocol implementation incompatibility.

While there is much functional overlap between the interface implementations supported by the idrac and redfish hardware types, it is not complete. Only idrac supports a raid interface implementation and only redfish supports bios. Also, the optional hardware interface functionality available in the idrac and redfish interface implementations can differ. For example, while the redfish implementation of the management hardware interface first introduced optional boot mode functionality, idrac does not offer that, yet. Therefore, those two hardware types are not perfect substitutes for one another.

Dell EMC wants to be able to offer its customers vendor value added as supported by the Redfish standard, like it has done through WS-Man. That benefits operators by making available features and functionality that has not yet been standardized. Dell EMC can be more responsive to its customers’ needs and differentiate itself in the market.

Goal

With this specification, we are going to achieve the goal of promoting and accelerating the adoption of Redfish by operators with Dell EMC bare metal servers.

Non-goals

The following is considered outside the scope of this specification:

  • Support a node configuration with a mix of Redfish and WS-Man management and power interface implementations. The legacy idrac implementations of the management and power hardware interfaces interact to set the boot device. It is not clear there is a compelling need to accommodate that in a mixed Redfish and WS-Man configuration.

  • The following TripleO command can be used to register and configure nodes for their deployment with Ironic:

    openstack overcloud node import instackenv.json

    See the TripleO register nodes documentation. It sets properties in a node’s driver_info field which are required by its driver. Presently, when the node’s driver is idrac, those are the properties – drac_address, drac_username, and drac_password – needed by the WS-Man interface implementations idrac has supported. See the iDRAC driver documentation.

    The Redfish interface implementations need similar, but different, properties in the driver_info field, including redfish_address, redfish_system_id, redfish_username, and redfish_password. See the Redfish driver documentation.

    Changing that TripleO command to set both the Redfish and WS-Man properties in a node’s driver_info field when its driver is idrac is beyond the scope of this specification. That will be addressed by a TripleO project blueprint.

  • Define idrac hardware type support of IPMI interface implementations. That could be done as a follow-on to this.

Solution

This specification proposes to solve the problem it describes by changing the idrac hardware type. Since the Ironic Driver composition reform, we have been allowed to have “one vendor driver with options configurable per node instead of many drivers for every vendor.” [1] The reform’s goals include [2]:

* Make vendors in charge of defining a set of supported interface
  implementations in priority order

* Allow vendors to guarantee that unsupported interface implementations will
  not be used with hardware types they define. This is done by having a
  hardware type list all interfaces it supports.

Implementing the solution in the idrac hardware type contributes toward making it the one Dell EMC driver for its bare metal servers with iDRACs and their value added implementations of the IPMI, Redfish, and WS-Man management protocols. It also aligns with the goals of the reform. That is what operators have come to expect.

Here are the details of the proposal.

  • Define two new groups of interface implementations with entrypoints named idrac-redfish and idrac-wsman. The idrac-redfish entrypoints refer to Redfish interface implementations which are compatible with the iDRAC, presently those of the management and power hardware interfaces. The idrac-wsman entrypoints are new names for the legacy idrac entrypoints. The legacy idrac entrypoints are left unchanged. For example:

    ironic.hardware.interfaces.management =
    ...
    idrac = ironic.drivers.modules.drac.management:DracManagement
    idrac-redfish = ironic.drivers.modules.drac.management:DracRedfishManagement
    idrac-wsman = ironic.drivers.modules.drac.management:DracWSManManagement
    ...
    redfish = ironic.drivers.modules.redfish.management:RedfishManagement

  • Declare idrac hardware type support for the idrac, idrac-redfish, and idrac-wsman interface implementations. idrac continues to have the highest priority by being first in its supported_<INTERFACE>_interfaces lists. Here <INTERFACE> is a type of hardware interface: inspect, management, power, etc. For example:

    class IDRACHardware(generic.GenericHardware):
    ...
    @property
    def supported_management_interfaces(self):
        return [management.DracManagement, management.DracWSManManagement,
            management.DracRedfishManagement]
    ...

Note

The property uses classes, not instances nor entrypoint names. The example assumes the required modules are imported.

  • New idrac-redfish entrypoints are defined by new Python classes, because using the generic, vendor-independent Redfish classes would make the redfish entrypoints synonyms for idrac-redfish and supported. A later requirement to change the name of an entrypoint’s Python class to resolve a Dell EMC-specific incompatibility or introduce vendor value added, which would eliminate support for redfish, could be a breaking change. The new Python classes are derived from the generic, vendor-independent Redfish classes.

  • New idrac-wsman entrypoints are defined by new Python classes. Those classes are created by renaming the classes for the legacy idrac entrypoints from Drac<INTERFACE> to DracWSMan<INTERFACE>. Here <INTERFACE> refers to a type of hardware interface: Inspect, Management, Power, etc.

    The legacy Drac<INTERFACE> classes are redefined by simply deriving them from the new DracWSMan<INTERFACE> classes. For example:

    class DracManagement(DracWSManManagement):
    pass

    That makes the legacy Drac<INTERFACE> classes aliases for the new DracWSMan<INTERFACE> classes. Any bug fixes or features added to the WS-Man interface implementations are available from both the idrac and idrac-wsman entrypoints. Having separate classes for the two groups of entrypoints makes it possible to subsequently add logic that implements deprecation of the legacy idrac entrypoints by emitting a log message and similar.

Alternatives

  • We could change the lowest layer of python-dracclient to support Redfish, in addition to WS-Man. However, we expect it would be challenging to provide python-dracclient APIs and workflows which abstract the very different Redfish and WS-Man technologies. Redfish’s interface is RESTful, while WS-Man is a Simple Object Access Protocol (SOAP). APIs and workflows would likely need to be changed or newly defined. That would require substantial modification of the existing idrac interface implementations.

  • We could maintain the status quo split of the idrac hardware type for WS-Man and redfish hardware type for Redfish. However, that would not promote and accelerate the use of Redfish among operators with Dell EMC bare metal servers today, because redfish does not offer everything idrac does. That also would not support resolving Dell EMC vendor-specific incompatibilities with the generic, vendor-independent redfish hardware type nor using Redfish to introduce vendor value added.

  • We could let the redfish interface implementations use Redfish OEM extensions to address vendor-specific incompatibilities and introduce vendor value added. However, that seems inconsistent with the intent that they be generic and vendor-independent.

Data model impact

None

State Machine Impact

None

REST API impact

None

Client (CLI) impact

“ironic” CLI

None

“openstack baremetal” CLI

None

RPC API impact

None

Driver API impact

None

Nova driver impact

None

Ramdisk impact

None

Security impact

None

Other end user impact

None

Scalability impact

None

Performance Impact

None

Other deployer impact

  • A deployer can add idrac-redfish to the enabled_management_interfaces and enabled_power_interfaces options to enable those new interface implementations.

  • A deployer can add idrac-wsman to the enabled_inspect_interfaces, enabled_management_interfaces, enabled_power_interfaces, enabled_raid_interfaces, and enabled_vendor_interfaces to enable those new interface implementations.

  • A deployer must specify properties in the node’s driver_info field that are needed by Redfish interface implementations, including redfish_address, redfish_system_id, redfish_username, and redfish_password, to use the idrac-redfish interface implementations. That is in addition to the legacy properties the idrac hardware type has needed in driver_info – drac_address, drac_username, and drac_password.

    openstack baremetal node create --driver idrac --driver-info \
  drac_address=1.2.3.4 --driver-info drac_username=admin --driver-info \
  drac_password=password --driver_info redfish_address=https://1.2.3.4 \
  --driver-info redfish_system_id=/redfish/v1/Systems/System.Embedded.1 \
  --driver-info redfish_username=admin --driver-info \
  redfish_password=password

    See the Redfish driver documentation, iDRAC driver documentation, and Non-goals.

  • A deployer can specify the new idrac-redfish and idrac-wsman interface implementations on node enrollment:

    openstack baremetal node create --driver idrac ... --management-interface \
  idrac-wsman --power-interface idrac-wsman ...

    They can also be set by the following command:

    openstack baremetal node set <NODE> --management-interface idrac-redfish \
  --power-interface idrac-redfish

    They must be enabled as described above.

Developer impact

None

Implementation

Assignee(s)

Primary assignee:

rpioso

Other contributors:

None

Work Items

  • Define two new groups of interface implementations with entrypoints named idrac-redfish and idrac-wsman.

  • Declare idrac hardware type support for the idrac, idrac-redfish, and idrac-wsman interface implementations.

  • Integration test the changes against Dell EMC bare metal servers.

  • Modify the Dell EMC Ironic third-party continuous integration (CI) to cover supported configurations added by this specification.

  • Update the iDRAC driver documentation.

Dependencies

This specification is related to the Driver composition reform.

It specifically targets Dell EMC bare metal servers equipped with an iDRAC and managed by the idrac hardware type.

Testing

This is not testable in the gate given current limitations on the availability of the specific hardware required.

The mitigation plan is to add coverage to the Dell EMC Ironic third-party CI for supported configurations added by this specification that we expect to be common.

Upgrades and Backwards Compatibility

This change is designed to be backwards compatible. The legacy idrac interface implementation entrypoints will be supported for at least some time. A separate story will cover their deprecation.

We will recommend switching to the appropriate new idrac-redfish and idrac-wsman interface implementation entrypoints as soon as it is possible.

Documentation Impact

The iDRAC driver documentation is updated to:

  • describe switching from the legacy idrac interface implementation entrypoints to the new idrac-redfish and idrac-wsman entrypoints,

  • reflect the changes to the supported interface implementations, and

  • inform that a node configuration with a mix of Redfish and WS-Man management and power interface implementations is not supported.

References

OpenStack software projects:
Related Ironic specifications:
Documentation:
Standards:

Footnotes