rpc: Strip down the base RPC client interface. (#6971)

* rpc: Strip down the base RPC client interface.

Prior to this change, the RPC client interface requires implementing the entire
Service interface, but most of the methods of Service are not needed by the
concrete clients. Dissociate the Client interface from the Service interface.

- Extract only those methods of Service that are necessary to make the existing
  clients work.

- Update the clients to combine Start/Onstart and Stop/OnStop. This does not
  change what the clients do to start or stop. Only the websocket clients make
  use of this functionality anyway.

  The websocket implementation uses some plumbing from the BaseService helper.
  We should be able to excising that entirely, but the current interface
  dependencies among the clients would require a much larger change, and one
  that leaks into other (non-RPC) packages.

  As a less-invasive intermediate step, preserve the existing client behaviour
  (and tests) by extracting the necessary subset of the BaseService
  functionality to an analogous RunState helper for clients. I plan to obsolete
  that type in a future PR, but for now this makes a useful waypoint.

Related:
- Clean up client implementations.
- Update mocks.

rpc/jsonrpc/server/ws_handler.go

@@ -13,7 +13,7 @@ import (
 	"github.com/gorilla/websocket"
 
 	"github.com/tendermint/tendermint/libs/log"
-	"github.com/tendermint/tendermint/libs/service"
+	"github.com/tendermint/tendermint/rpc/client"
 	ctypes "github.com/tendermint/tendermint/rpc/coretypes"
 	types "github.com/tendermint/tendermint/rpc/jsonrpc/types"
 )
@@ -86,8 +86,8 @@ func (wm *WebsocketManager) WebsocketHandler(w http.ResponseWriter, r *http.Requ
 	}()
 
 	// register connection
-	con := newWSConnection(wsConn, wm.funcMap, wm.wsConnOptions...)
-	con.SetLogger(wm.logger.With("remote", wsConn.RemoteAddr()))
+	logger := wm.logger.With("remote", wsConn.RemoteAddr())
+	con := newWSConnection(wsConn, wm.funcMap, logger, wm.wsConnOptions...)
 	wm.logger.Info("New websocket connection", "remote", con.remoteAddr)
 	err = con.Start() // BLOCKING
 	if err != nil {
@@ -106,7 +106,7 @@ func (wm *WebsocketManager) WebsocketHandler(w http.ResponseWriter, r *http.Requ
 //
 // In case of an error, the connection is stopped.
 type wsConnection struct {
-	service.BaseService
+	*client.RunState
 
 	remoteAddr string
 	baseConn   *websocket.Conn
@@ -150,9 +150,11 @@ type wsConnection struct {
 func newWSConnection(
 	baseConn *websocket.Conn,
 	funcMap map[string]*RPCFunc,
+	logger log.Logger,
 	options ...func(*wsConnection),
 ) *wsConnection {
 	wsc := &wsConnection{
+		RunState:          client.NewRunState("wsConnection", logger),
 		remoteAddr:        baseConn.RemoteAddr().String(),
 		baseConn:          baseConn,
 		funcMap:           funcMap,
@@ -166,7 +168,6 @@ func newWSConnection(
 		option(wsc)
 	}
 	wsc.baseConn.SetReadLimit(wsc.readLimit)
-	wsc.BaseService = *service.NewBaseService(nil, "wsConnection", wsc)
 	return wsc
 }
 
@@ -218,9 +219,11 @@ func ReadLimit(readLimit int64) func(*wsConnection) {
 	}
 }
 
-// OnStart implements service.Service by starting the read and write routines. It
-// blocks until there's some error.
-func (wsc *wsConnection) OnStart() error {
+// Start starts the client service routines and blocks until there is an error.
+func (wsc *wsConnection) Start() error {
+	if err := wsc.RunState.Start(); err != nil {
+		return err
+	}
 	wsc.writeChan = make(chan types.RPCResponse, wsc.writeChanCapacity)
 
 	// Read subscriptions/unsubscriptions to events
@@ -231,16 +234,18 @@ func (wsc *wsConnection) OnStart() error {
 	return nil
 }
 
-// OnStop implements service.Service by unsubscribing remoteAddr from all
-// subscriptions.
-func (wsc *wsConnection) OnStop() {
+// Stop unsubscribes the remote from all subscriptions.
+func (wsc *wsConnection) Stop() error {
+	if err := wsc.RunState.Stop(); err != nil {
+		return err
+	}
 	if wsc.onDisconnect != nil {
 		wsc.onDisconnect(wsc.remoteAddr)
 	}
-
 	if wsc.ctx != nil {
 		wsc.cancel()
 	}
+	return nil
 }
 
 // GetRemoteAddr returns the remote address of the underlying connection.