The mechanism for executing multiple requests in the Load Balancer v3 API is improved.

To illustrate this, the following sections compare the v2 and v3 API mechanism through an example:

Enqueued process mechanism in v2

Device 123456 exists under account 1111.
When a user executes a POST or PUT request, it returns the status 200 OK, with the following response body:

{  
	"data": {  
		"status": "PROCESSING",  
		"eventId": "",  
		"resource": "POOL-172.16.1.106-80",  
		"timestamp": "2021-01-14T06:58:17.7277401Z",  
		"eventRef": "/events/"  
	}  
}

If the user re-executes the request before the first one completes, the request goes into ENQUEUED_PROCESSING:

{
    "data": [
        {
            "event_id": "",
            "status": 200,
            "message": "ENQUEUED_PREPROCESSING",
            "entrytimestamp": "2021-01-14T06:35:35",
            "modifiedtimestamp": "2021-01-14T06:35:35"
        }
    ]
}

The process might get dead-locked, so the user keeps re-executing the request thinking they’re not running. All of these requests get queued on the server awaiting execution.

The user has no idea why the requests never finish, so v3 has a lock mechanism on the device to avoid this issue.

Lock mechanism in v3

Device 123456 exists under account 1111.
When the user executes a POST or PUT request, the returned status is 200 OK, with the following response body:

{  
    "data": {  
        "eventId": "",  
        "status": "PROCESSING",  
        "timestamp": "2021-01-14T07:11:49.885096Z",  
        "resource": "POOL-172.16.1.109-80",  
        "eventRef": "/events/"  
    }  
}

If the user executes another the request before the first one completes, the returned response code is 423 Locked with the following repose body:

{  
    "request_url": "",  
    "details": "Another event already scheduled to launch on Device 535908",  
    "statusCode": 423,  
    "title": "423 Locked",  
    "transactionId": ""  
}

This process avoids any chance of deadlock, and as soon as the request gets completed, the device goes out of lock.

This mechanism lets the user know what is happening on the back-end. Even if a request doesn’t complete, the system removes the device from lock after a set length of time to avoid inconvenience for the user.