This commit introduces several key changes to
Teleport backend and API infrastructure
in order to achieve scalability improvements
on 10K+ node deployments.
Events and plain keyspace
--------------------------
New backend interface supports events,
pagination and range queries
and moves away from buckets to
plain keyspace, what better aligns
with DynamoDB and Etcd featuring similar
interfaces.
All backend implementations are
exposing Events API, allowing
multiple subscribers to consume the same
event stream and avoid polling database.
Replacing BoltDB, Dir with SQLite
-------------------------------
BoltDB backend does not support
having two processes access the database at the
same time. This prevented Teleport
using BoltDB backend to be live reloaded.
SQLite supports reads/writes by multiple
processes and makes Dir backend obsolete
as SQLite is more efficient on larger collections,
supports transactions and can detect data
corruption.
Teleport automatically migrates data from
Bolt and Dir backends into SQLite.
GRPC API and protobuf resources
-------------------------------
GRPC API has been introduced for
the auth server. The auth server now serves both GRPC
and JSON-HTTP API on the same TLS socket and uses
the same client certificate authentication.
All future API methods should use GRPC and HTTP-JSON
API is considered obsolete.
In addition to that some resources like
Server and CertificateAuthority are now
generated from protobuf service specifications in
a way that is fully backward compatible with
original JSON spec and schema, so the same resource
can be encoded and decoded from JSON, YAML
and protobuf.
All models should be refactored
into new proto specification over time.
Streaming presence service
--------------------------
In order to cut bandwidth, nodes
are sending full updates only when changes
to labels or spec have occured, otherwise
new light-weight GRPC keep alive updates are sent
over to the presence service, reducing
bandwidth usage on multi-node deployments.
In addition to that nodes are no longer polling
auth server for certificate authority rotation
updates, instead they subscribe to event updates
to detect updates as soon as they happen.
This is a new API, so the errors are inevitable,
that's why polling is still done, but
on a way slower rate.
control how often the server sends keep-alive messages to clients and
after how many missed keep-alive replies the server tears down the
connection to the client.
