Allow ServiceInsight to connect to scaled out instances of ServiceControl

[adamralph]

Info

Paging

SC generates Link header which contains up to 4 links: next, prev, first and last. These are used, instead of generating the links in SI, to page through the data.

The main benefit is making SI not dependent on the actual paging URL format of SC. The SI only needs to know how to initiate the search.

The actual goal is to be able to insert an intermediary between SI and SC. That intermediary could aggregate the results from multiple instances of SC without SI even knowing about its existence.

Page count

As part of the TF work of extending SC with the multi instance mode for audits we discovered that the page count is not possible to determine upfront by doing a simple calculation based on the assumed page size. Since we went from a simplified paging approach in contrast to keep the offsets per SC instance each page can return up to numberOfInstance * page_size worth of data. Audits cannot be assumed to be uniformly distributed. Based on that we figured having a page size visible at all time makes no sense. The ability to page through the data is more important than knowing how many pages there are.

Known endpoints

Previously ServiceInsight was using /endpoints which is essentially a mixture of multiple concerns. For example, the data structure returned there contains information like whether monitoring of the endpoint is on which is not relevant for SI. With the known endpoints API there are two distinct endpoints now. One for SI which contains only the SI relevant information and one for SP.

Plan of attack

• Switch to link based paging - Link based paging and and removal of page count for scaled out ServiceControl #775
• Remove page count - Link based paging and and removal of page count for scaled out ServiceControl #775
• Supply instance ID for retries - Supply instance ID to scaled out ServiceControl for retries #771
• [ ] Supply instance ID for body fetching No longer required since SC will return the instance id in the provided body URL
• Use endpoints/known when service is discovered - Prefer KnownEndpointsUrl, to EndpointsUrl, to local default #778
• Async UI for better responsiveness - Async Handling of ServiceControl communication #781

[adamralph]

Async UI for better responsiveness - #781

PR merged and PoA item checked.

[adamralph]

Use endpoints/known when service is discovered - #778

PR merged and last PoA item checked. Closing.