* feat(server): reduce server refreshes of the repository
Previously each source would refresh itself from the repository
very frequently to determine the upcoming snapshot time. This change
refactors source manager so it does not own the repository connection
on its own but instead delegates all policy reads through the server.
Also introduces a new server scheduler that is responsible for
centrally managing the snapshot schedule and triggering snapshots
when they are due.
* Update cli/command_server_start.go
Co-authored-by: Shikhar Mall <mall.shikhar.in@gmail.com>
* Update internal/server/server.go
Co-authored-by: Shikhar Mall <mall.shikhar.in@gmail.com>
* Update internal/server/server_maintenance.go
Co-authored-by: Shikhar Mall <mall.shikhar.in@gmail.com>
* pr feedback
---------
Co-authored-by: Shikhar Mall <mall.shikhar.in@gmail.com>
This removes big shared lock held for for the duration of each request
and replaces it with trivially short lock to capture the current
state of the server/repository before passing it to handlers.
Handlers are now limited to only accessing a small subset of Server
functionality to be able to better reason about them.
* cli: refactored snapshot list
* cli: show range tags in snapshot list
For example if N snapshots are coalesced together because they
have identical roots we may emit now:
```
2021-03-31 23:09:27 PDT ked3400debc7dd61baffab070bafd59cd (monthly-10)
2021-04-30 06:12:53 PDT kd0576d212e55a831b7ff1636f90a7233 (monthly-4..9)
+ 5 identical snapshots until 2021-09-30 23:00:19 PDT
2021-10-31 23:22:25 PDT k846bf22aa2863d27f05e820f840b14f8 (monthly-3)
2021-11-08 21:29:31 PST k5793ddcd61ef27b93c75ab74a5828176 (latest-1..3,hourly-1..13,daily-1..7,weekly-1..4,monthly-1..2,annual-1)
+ 18 identical snapshots until 2021-12-04 10:09:54 PST
```
* server: server-side coalescing of snapshot
* ui: added coalescing of retention tags
Added policy.Definition which allows us to precisely report where
each piece of policy came from.
Fixed a one-off bug with "noParent", which prevented merging of parent
policies one level too soon.
Added a whole bunch of merging helpers and generic reflection-based
test that ensures every single merge is tested.
CreateSnapshotSource API for ensuring source exists
Upload - starts upload on a given source or matching sources
Cancel - cancels upload on a given source or matching sources
