* MM-24972: make GetHubForUserId lock-less and zero-alloc
The hubs aren't meant to be modified after the server starts up.
But the key problem was the SetHubs method which would zero out
the underlying hubs slice.
This wasn't ideally necessary because an hub would only be stopped
once during server shutdown. However, this was required by a test
which would shutdown the hub twice. And since the hub shutdown isn't
idempotent, zeroing the slice would just skip over shutting down the hub again.
To improve the overall situation, we apply several optimizations.
- We use the new hash/maphash package which exposes Go runtime's
internal hash algorithms to be used as a package. This is much faster
than hash/fnv.
- We move around the initialization of the hub to happen before
the metrics server starts. This allows us to initialize the hub
before any of the hub elements are being accessed.
- To make the test run successfully, we do not call th.TearDown.
This is fine for a test, because anyways the test process would eventually stop
and relinquish the resources to the OS.
This allows us to completely remove any mutexes and thereby
we can remove all the methods and any edge-case checks related to
index being out of bounds. As a result, the fast path becomes
very straightforward and zero-alloc.
name old time/op new time/op delta
GetHubForUserId-8 116ns ± 1% 38ns ± 7% -67.22% (p=0.000 n=10+10)
name old alloc/op new alloc/op delta
GetHubForUserId-8 36.0B ± 0% 0.0B -100.00% (p=0.000 n=10+10)
name old allocs/op new allocs/op delta
GetHubForUserId-8 2.00 ± 0% 0.00 -100.00% (p=0.000 n=10+10)
Manually tested with some load testing and running Hub tests in -race mode.
* remove mutex
* incorporate review comments
* Removing some other fake apps
* More FakeApp removed
* Removing entirely FakeApp
* Fixing some tests
* Fixing get Cluster id from get plugin status
* Fixing failing tests
* Fixing tests
* Fixing test initialization for web
* Fixing InitServer for server tests
* Fixing InitServer for server tests
* Reverting go.sum and go.mod
* Removing unneded HTMLTemplates function in App layer
* Moving back some functions to its old place to easy the review
* Moving back some functions to its old place to easy the review
* Using the last struct2interface version
* Generating store layers
* Fixing merge problems
* Addressing PR comments
* Small fix
* Fixing app tests build
* Fixing tests
* fixing tests
* Fix tests
* Fixing tests
* Fixing tests
* Fixing tests
* Moving license to server struct
* Adding some fixes to the test compilation
* Fixing cluster and some jobs initialization
* Fixing some license tests compilation problems
* Fixing recursive cache invalidation
* Regenerating app layers
* Fix test compilation
Co-authored-by: mattermod <mattermod@users.noreply.github.com>
* Consistent license message for all the go files
* Fixing the last set of unconsistencies with the license headers
* Addressing PR review comments
* Fixing busy.go and busy_test.go license header
