The Migrate method on the Backend interface was not implemented by any
backends.
Migration should be implemented in the New method of backends so they
can be sure migration happens before any background processes are
started.
This code is not caught by linters because it's exported and they assume
there's some external users.
Since teleport is relatively self-contained, we can tell for sure
whether something is called or not.
* Add resest for buffers to close watchers
and reset buffer the state.
* Add reconnect logic to DynamoDB
* Add tests for cache watchers, make sure
the errors of the cache internal watcher propagate to
external watchers.
This commit expands the usage of the caching layer
for auth server API:
* Introduces in-memory cache that is used to serve all
Auth server API requests. This is done to achieve scalability
on 10K+ node clusters, where each node fetches certificate authorities,
roles, users and join tokens. It is not possible to scale
DynamoDB backend or other backends on 10K reads per seconds
on a single shard or partition. The solution is to introduce
an in-memory cache of the backend state that is always used
for reads.
* In-memory cache has been expanded to support all resources
required by the auth server.
* Experimental `tctl top` command has been introduced to display
common single node metrics.
Replace SQLite Memory Backend with BTree
SQLite in memory backend was suffering from
high tail latencies under load (up to 8 seconds
in 99.9%-ile on load configurations).
This commit replaces the SQLite memory caching
backend with in-memory BTree backend that
brought down tail latencies to 2 seconds (99.9%-ile)
and brought overall performance improvement.
Jim Bishopp