Guest RPC Ping Pong

Blueprint:

https://blueprints.launchpad.net/trove/+spec/guest-rpc-ping-pong

The proposal is to introduce a new Management API route that facilitates a lightweight ping/pong mechanism for determining whether RPC communication is working as expected.

Problem Description

Today, the only means of ascertaining whether direct or indirect RPC connectivity between the control-plane and the guest is functioning, via an API, is by using the ‘show’ operation in the Management API.

Although mgmt-show indirectly answers the question of “is the guest reachable?”, it is a relatively heavyweight call. Beyond consulting the filesystem for rudimentary information, mgmt-show sends ‘show’ requests to Nova and Cinder.

Use Cases

  • As a deployer, I want to be able to determine whether RPC connectivity between the control-plane and a specific guest is broken.

Proposed Change

Introduce:

GET HOST:8779/v1.0/<tenant_id>/mgmt/instances/<instance_id>/rpc_ping

Behavior

The request:

GET HOST:8779/v1.0/<tenant_id>/mgmt/instances/<instance_id>/rpc_ping

will result in the following if it’s successful:

HTTP/1.1 204 No Content
Content-Length: 0
Content-Type: application/json
Date: Thu, 02 Oct 2014 23:32:26 GMT

on the other hand, if trove-guest is shutdown, or the guest is generally not responding, the following will be returned:

HTTP/1.1 400 Bad Request
Content-Length: 237
Content-Type: application/json; charset=UTF-8
Date: Thu, 02 Oct 2014 23:32:59 GMT

{"badRequest": {"message": "An error occurred communicating
 with the guest: Timeout while waiting on RPC response -
 topic: \"guestagent.1e4099f1-7f8d-4564-bd83-0b9f66aa35b9\",
 RPC method: \"rpc_ping\" info: \"<unknown>\".", "code": 400}}

Configuration

No Configuration changes.

Database

No Database changes.

Public API

No public API changes.

Public API Security

No public API Security related changes.

Management API

Introduces:

GET HOST:8779/v1.0/<tenant_id>/mgmt/instances/<instance_id>/rpc_ping

Internal API

No internal API changes.

Guest Agent

No Guest Agent changes.

Alternatives

The current alternative is mgmt-show, but it’s too heavyweight of a call, and can fail to return meaningful information if the underlying compute and/or volume are unhealthy.

Implementation

Assignee(s)

Primary assignee:
Auston McReynolds (amcrn)

Milestones

Kilo-1

Dependencies

No dependencies.

Testing

Standard.

Documentation Impact

If the Management API is documented (which I don’t believe it is), then the addition of the ‘rpc_ping’ route is relevant.

References

None.