limit number of /subscribe clients and queries per client (#3269)

* limit number of /subscribe clients and queries per client

Add the following config variables (under [rpc] section):
  * max_subscription_clients
  * max_subscriptions_per_client
  * timeout_broadcast_tx_commit

Fixes #2826

new HTTPClient interface for subscriptions

finalize HTTPClient events interface

remove EventSubscriber

fix data race

```
WARNING: DATA RACE
Read at 0x00c000a36060 by goroutine 129:
  github.com/tendermint/tendermint/rpc/client.(*Local).Subscribe.func1()
      /go/src/github.com/tendermint/tendermint/rpc/client/localclient.go:168 +0x1f0

Previous write at 0x00c000a36060 by goroutine 132:
  github.com/tendermint/tendermint/rpc/client.(*Local).Subscribe()
      /go/src/github.com/tendermint/tendermint/rpc/client/localclient.go:191 +0x4e0
  github.com/tendermint/tendermint/rpc/client.WaitForOneEvent()
      /go/src/github.com/tendermint/tendermint/rpc/client/helpers.go:64 +0x178
  github.com/tendermint/tendermint/rpc/client_test.TestTxEventsSentWithBroadcastTxSync.func1()
      /go/src/github.com/tendermint/tendermint/rpc/client/event_test.go:139 +0x298
  testing.tRunner()
      /usr/local/go/src/testing/testing.go:827 +0x162

Goroutine 129 (running) created at:
  github.com/tendermint/tendermint/rpc/client.(*Local).Subscribe()
      /go/src/github.com/tendermint/tendermint/rpc/client/localclient.go:164 +0x4b7
  github.com/tendermint/tendermint/rpc/client.WaitForOneEvent()
      /go/src/github.com/tendermint/tendermint/rpc/client/helpers.go:64 +0x178
  github.com/tendermint/tendermint/rpc/client_test.TestTxEventsSentWithBroadcastTxSync.func1()
      /go/src/github.com/tendermint/tendermint/rpc/client/event_test.go:139 +0x298
  testing.tRunner()
      /usr/local/go/src/testing/testing.go:827 +0x162

Goroutine 132 (running) created at:
  testing.(*T).Run()
      /usr/local/go/src/testing/testing.go:878 +0x659
  github.com/tendermint/tendermint/rpc/client_test.TestTxEventsSentWithBroadcastTxSync()
      /go/src/github.com/tendermint/tendermint/rpc/client/event_test.go:119 +0x186
  testing.tRunner()
      /usr/local/go/src/testing/testing.go:827 +0x162
==================
```

lite client works (tested manually)

godoc comments

httpclient: do not close the out channel

use TimeoutBroadcastTxCommit

no timeout for unsubscribe

but 1s Local (5s HTTP) timeout for resubscribe

format code

change Subscribe#out cap to 1

and replace config vars with RPCConfig

TimeoutBroadcastTxCommit can't be greater than rpcserver.WriteTimeout

rpc: Context as first parameter to all functions

reformat code

fixes after my own review

fixes after Ethan's review

add test stubs

fix config.toml

* fixes after manual testing

- rpc: do not recommend to use BroadcastTxCommit because it's slow and wastes
Tendermint resources (pubsub)
- rpc: better error in Subscribe and BroadcastTxCommit
- HTTPClient: do not resubscribe if err = ErrAlreadySubscribed

* fixes after Ismail's review

* Update rpc/grpc/grpc_test.go

Co-Authored-By: melekes <anton.kalyaev@gmail.com>

rpc/lib/types/types.go

@@ -1,18 +1,15 @@
 package rpctypes
 
 import (
-	"context"
 	"encoding/json"
 	"fmt"
+	"net/http"
 	"reflect"
 	"strings"
 
 	"github.com/pkg/errors"
 
 	amino "github.com/tendermint/go-amino"
-
-	tmpubsub "github.com/tendermint/tendermint/libs/pubsub"
-	tmtypes "github.com/tendermint/tendermint/types"
 )
 
 // a wrapper to emulate a sum type: jsonrpcid = string | int
@@ -236,30 +233,47 @@ func RPCServerError(id jsonrpcid, err error) RPCResponse {
 
 //----------------------------------------
 
-// *wsConnection implements this interface.
+// WSRPCConnection represents a websocket connection.
 type WSRPCConnection interface {
+	// GetRemoteAddr returns a remote address of the connection.
 	GetRemoteAddr() string
+	// WriteRPCResponse writes the resp onto connection (BLOCKING).
 	WriteRPCResponse(resp RPCResponse)
+	// TryWriteRPCResponse tries to write the resp onto connection (NON-BLOCKING).
 	TryWriteRPCResponse(resp RPCResponse) bool
-	GetEventSubscriber() EventSubscriber
+	// Codec returns an Amino codec used.
 	Codec() *amino.Codec
 }
 
-// websocket-only RPCFuncs take this as the first parameter.
-type WSRPCContext struct {
-	Request RPCRequest
-	WSRPCConnection
+// Context is the first parameter for all functions. It carries a json-rpc
+// request, http request and websocket connection.
+//
+// - JSONReq is non-nil when JSONRPC is called over websocket or HTTP.
+// - WSConn is non-nil when we're connected via a websocket.
+// - HTTPReq is non-nil when URI or JSONRPC is called over HTTP.
+type Context struct {
+	// json-rpc request
+	JSONReq *RPCRequest
+	// websocket connection
+	WSConn WSRPCConnection
+	// http request
+	HTTPReq *http.Request
 }
 
-// EventSubscriber mirrors tendermint/tendermint/types.EventBusSubscriber
-type EventSubscriber interface {
-	Subscribe(ctx context.Context, subscriber string, query tmpubsub.Query, outCapacity ...int) (tmtypes.Subscription, error)
-	Unsubscribe(ctx context.Context, subscriber string, query tmpubsub.Query) error
-	UnsubscribeAll(ctx context.Context, subscriber string) error
+// RemoteAddr returns either HTTPReq#RemoteAddr or result of the
+// WSConn#GetRemoteAddr().
+func (ctx *Context) RemoteAddr() string {
+	if ctx.HTTPReq != nil {
+		return ctx.HTTPReq.RemoteAddr
+	} else if ctx.WSConn != nil {
+		return ctx.WSConn.GetRemoteAddr()
+	}
+	return ""
 }
 
 //----------------------------------------
 // SOCKETS
+
 //
 // Determine if its a unix or tcp socket.
 // If tcp, must specify the port; `0.0.0.0` will return incorrectly as "unix" since there's no port