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/client/ws_client.go

@@ -14,7 +14,7 @@ import (
 	metrics "github.com/rcrowley/go-metrics"
 
 	tmsync "github.com/tendermint/tendermint/internal/libs/sync"
-	"github.com/tendermint/tendermint/libs/service"
+	tmclient "github.com/tendermint/tendermint/rpc/client"
 	types "github.com/tendermint/tendermint/rpc/jsonrpc/types"
 )
 
@@ -41,6 +41,7 @@ func DefaultWSOptions() WSOptions {
 //
 // WSClient is safe for concurrent use by multiple goroutines.
 type WSClient struct { // nolint: maligned
+	*tmclient.RunState
 	conn *websocket.Conn
 
 	Address  string // IP:PORT or /path/to/socket
@@ -83,8 +84,6 @@ type WSClient struct { // nolint: maligned
 	// Send pings to server with this period. Must be less than readWait. If 0, no pings will be sent.
 	pingPeriod time.Duration
 
-	service.BaseService
-
 	// Time between sending a ping and receiving a pong. See
 	// https://godoc.org/github.com/rcrowley/go-metrics#Timer.
 	PingPongLatencyTimer metrics.Timer
@@ -114,6 +113,7 @@ func NewWSWithOptions(remoteAddr, endpoint string, opts WSOptions) (*WSClient, e
 	}
 
 	c := &WSClient{
+		RunState:             tmclient.NewRunState("WSClient", nil),
 		Address:              parsedURL.GetTrimmedHostWithPath(),
 		Dialer:               dialFn,
 		Endpoint:             endpoint,
@@ -127,7 +127,6 @@ func NewWSWithOptions(remoteAddr, endpoint string, opts WSOptions) (*WSClient, e
 
 		// sentIDs: make(map[types.JSONRPCIntID]bool),
 	}
-	c.BaseService = *service.NewBaseService(nil, "WSClient", c)
 	return c, nil
 }
 
@@ -143,9 +142,11 @@ func (c *WSClient) String() string {
 	return fmt.Sprintf("WSClient{%s (%s)}", c.Address, c.Endpoint)
 }
 
-// OnStart implements service.Service by dialing a server and creating read and
-// write routines.
-func (c *WSClient) OnStart() error {
+// Start dials the specified service address and starts the I/O routines.
+func (c *WSClient) Start() error {
+	if err := c.RunState.Start(); err != nil {
+		return err
+	}
 	err := c.dial()
 	if err != nil {
 		return err
@@ -167,10 +168,9 @@ func (c *WSClient) OnStart() error {
 	return nil
 }
 
-// Stop overrides service.Service#Stop. There is no other way to wait until Quit
-// channel is closed.
+// Stop shuts down the client.
 func (c *WSClient) Stop() error {
-	if err := c.BaseService.Stop(); err != nil {
+	if err := c.RunState.Stop(); err != nil {
 		return err
 	}
 	// only close user-facing channels when we can't write to them