Implement app logging when the per app routes limit is reached

[plamen-bardarov]

Proposed Change

As an operator,
I want to have a log entry that records a specific issue with route limitations in the following scenario:
An app was created but not started, routes were added, and then the app was requested to be started.

Problem Details

Theres an internal limitation of the size of the raw routes field when calling DesireDesiredLRP and UpdateDesireLRP(looks like its 128kb), which happens when starting an application. However nothing shows in the application logs in case this limitation is reached and the app stays is requested state: started but with no running instances.

Proposed Solution

Our proposal is to implement that logging in the BBS, where application logging is added for any validation errors in the request(not only for routes) for Desire and Update LRP endpoints.

For example, in the scenario where the routes validation of the DesiredLRP request fails, the application logs would look like this:

 2024-09-10T08:32:34.66+0000 [DIEGO-API/DIEGO-API] ERR Error parsing request for app with guid 58aeebf2-3f99-4302-b2e0-53205bc80000, InvalidRequest, Invalid field: route

For discussion we did a POC in this PR
cloudfoundry/bbs#103

It might also be a good idea to consider whether this change should be made in BBS or in Cloud Controller.

Acceptance criteria

Scenario: Creating and mapping ~1000 routes to an application
Given the organisation I'm using has enough quota for the rules I create
When I either start/restart/update an app with the new routes that reach the internal limit of 128kb
Then I see a log entry in the application logs that show an error

Related links

• https://github.com/cloudfoundry/bbs/blob/4b574f98c713f8e77467ec6a4ac953ab52ddc718/models/routes.go#L68
• Log desired LRP validation errors bbs#103