The thrift_handler class' methods need storage service. This
patch makes sure this class has sharded storage service
reference on board.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Some .cc files over the code include the storage service
for no real need. Drop the header and include (in some)
what's really needed.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
This commit adds admission control in the form of passing
service permits to the Thrift server.
The support is partial, because Thrift also supports running CQL
queries, and for that purpose a query_state object is kept
in the Thrift handler. However, the handler is generally created
once per connection, not once per query, and the query_state object
is supposed to keep the state of a single query only.
In order to keep this series simpler, the CQL-on-top-of-Thrift
layer is not touched and is left as TODO.
Moreover, the Thrift layer does not make it easy to pass custom
per-query context (like service_permit), so the implementation
uses a trick: the service permit is created on the server
and then passed as reference to its connections and their respective
Thrift handlers. Then, each time a query is read from the socket,
this service permit is overwritten and then read back from the Thrift
handler. This mechanism heavily relies on the fact that there are
zero preemption points between overwriting the service permit
and reading it back by the handler. Otherwise, races may occur.
This assumption was verified by code inspection + empirical tests,
but if somebody is aware that it may not always hold, please speak up.
Remove the on-storage_service instance and make everybody use
th standalone one.
Stopping the thrift is done by registering the controller in
client service shutdown hooks. This automatically wires the
stopping into drain, decommission and isolation codes.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
