Server responds with 403 error code instead of 503 when Event Subscription limit exceeds

[adathatri]

After exceeding maximum subscription limit of 20, BMC server responds with 403 error code instead of the expected 503 error code.

Steps to reproduce:

1. Create 20 Push style subscriptions in BMC using RedfishEventListener_v1.py script.
2. Try to subscribe for the 21st time and BMC responds with 403 instead of the expected 503 error code.

Error response obtained for 21st subscription from RedfishEventListener_v1.py:

Method = POST, status = 403, expected status = [200, 201, 204] ---> Error code is 403 instead of 503
{'Date': 'Tue, 08 Sep 2020 14:12:11 GMT', 'Cache-Control': 'no-Store,no-Cache', 'Content-Length': '770', 'X-XSS-Protection': '1; mode=block', 'Strict-Transport-Security': 'max-age=31536000; includeSubdomains; preload', 'Content-Security-Policy': "default-src 'none'; img-src 'self' data:; font-src 'self'; style-src 'self'; script-src 'self'; connect-src 'self' wss:", 'Pragma': 'no-cache', 'Content-Type': 'application/json', 'X-Frame-Options': 'DENY', 'X-Content-Type-Options': 'nosniff', 'Server': 'bmcweb'}
{
"error": {
"@Message.ExtendedInfo": [
{
"@odata.type": "#Message.v1_0_0.Message",
"Message": "The event subscription failed due to the number of simultaneous subscriptions exceeding the limit of the implementation.",
"MessageArgs": [],
"MessageId": "Base.1.4.0.EventSubscriptionLimitExceeded",
"Resolution": "Reduce the number of other subscriptions before trying to establish the event subscription or increase the limit of simultaneous subscriptions (if supported).",
"Severity": "Critical"
}
],
"code": "Base.1.4.0.EventSubscriptionLimitExceeded",
"message": "The event subscription failed due to the number of simultaneous subscriptions exceeding the limit of the implementation."
}
}

@apuli1 @feistjj @ratagupt

[edtanous]

@adathatri Can you please retest with: https://gerrit.openbmc-project.xyz/c/openbmc/bmcweb/+/37230

And see if it resolves your issue?

[adathatri]

@edtanous Retested with https://gerrit.openbmc-project.xyz/c/openbmc/bmcweb/+/37230. I am seeing 503 as the response code now. Thanks!

Method = POST, status = 503, expected status = [200, 201, 204]
{
  "error": {
    "@Message.ExtendedInfo": [
      {
        "@odata.type": "#Message.v1_0_0.Message",
        "Message": "The event subscription failed due to the number of simultaneous subscriptions exceeding the limit of the implementation.",
        "MessageArgs": [],
        "MessageId": "Base.1.8.1.EventSubscriptionLimitExceeded",
        "MessageSeverity": "Critical",
        "Resolution": "Reduce the number of other subscriptions before trying to establish the event subscription or increase the limit of simultaneous subscriptions upported)."
      }
    ],
    "code": "Base.1.8.1.EventSubscriptionLimitExceeded",
    "message": "The event subscription failed due to the number of simultaneous subscriptions exceeding the limit of the implementation."
  }
}