inspect: add inspect mode for debugging crashed tendermint node (#6785)

EDIT: Updated, see [comment below]( https://github.com/tendermint/tendermint/pull/6785#issuecomment-897793175)

This change adds a sketch of the `Debug` mode. 

This change adds a `Debug` struct to the node package. This `Debug` struct is intended to be created and started by a command in the `cmd` directory. The `Debug` struct runs the RPC server on the data directories: both the state store and the block store.

This change required a good deal of refactoring. Namely, a new `rpc.go` file was added to the `node` package. This file encapsulates functions for starting RPC servers used by nodes. A potential additional change is to further factor this code into shared code _in_ the `rpc` package. 

Minor API tweaks were also made that seemed appropriate such as the mechanism for fetching routes from the `rpc/core` package.

Additional work is required to register the `Debug` service as a command in the `cmd` directory but I am looking for feedback on if this direction seems appropriate before diving much further.

closes: #5908

state/indexer/indexer_service.go

@@ -51,43 +51,47 @@ func (is *Service) OnStart() error {
 
 	go func() {
 		for {
-			msg := <-blockHeadersSub.Out()
+			select {
+			case <-blockHeadersSub.Canceled():
+				return
+			case msg := <-blockHeadersSub.Out():
 
-			eventDataHeader := msg.Data().(types.EventDataNewBlockHeader)
-			height := eventDataHeader.Header.Height
-			batch := NewBatch(eventDataHeader.NumTxs)
+				eventDataHeader := msg.Data().(types.EventDataNewBlockHeader)
+				height := eventDataHeader.Header.Height
+				batch := NewBatch(eventDataHeader.NumTxs)
 
-			for i := int64(0); i < eventDataHeader.NumTxs; i++ {
-				msg2 := <-txsSub.Out()
-				txResult := msg2.Data().(types.EventDataTx).TxResult
+				for i := int64(0); i < eventDataHeader.NumTxs; i++ {
+					msg2 := <-txsSub.Out()
+					txResult := msg2.Data().(types.EventDataTx).TxResult
 
-				if err = batch.Add(&txResult); err != nil {
-					is.Logger.Error(
-						"failed to add tx to batch",
-						"height", height,
-						"index", txResult.Index,
-						"err", err,
-					)
-				}
-			}
-
-			if !IndexingEnabled(is.eventSinks) {
-				continue
-			}
-
-			for _, sink := range is.eventSinks {
-				if err := sink.IndexBlockEvents(eventDataHeader); err != nil {
-					is.Logger.Error("failed to index block", "height", height, "err", err)
-				} else {
-					is.Logger.Debug("indexed block", "height", height, "sink", sink.Type())
+					if err = batch.Add(&txResult); err != nil {
+						is.Logger.Error(
+							"failed to add tx to batch",
+							"height", height,
+							"index", txResult.Index,
+							"err", err,
+						)
+					}
 				}
 
-				if len(batch.Ops) > 0 {
-					err := sink.IndexTxEvents(batch.Ops)
-					if err != nil {
-						is.Logger.Error("failed to index block txs", "height", height, "err", err)
+				if !IndexingEnabled(is.eventSinks) {
+					continue
+				}
+
+				for _, sink := range is.eventSinks {
+					if err := sink.IndexBlockEvents(eventDataHeader); err != nil {
+						is.Logger.Error("failed to index block", "height", height, "err", err)
 					} else {
-						is.Logger.Debug("indexed txs", "height", height, "sink", sink.Type())
+						is.Logger.Debug("indexed block", "height", height, "sink", sink.Type())
+					}
+
+					if len(batch.Ops) > 0 {
+						err := sink.IndexTxEvents(batch.Ops)
+						if err != nil {
+							is.Logger.Error("failed to index block txs", "height", height, "err", err)
+						} else {
+							is.Logger.Debug("indexed txs", "height", height, "sink", sink.Type())
+						}
 					}
 				}
 			}

state/indexer/sink/sink.go

@@ -0,0 +1,65 @@
+package sink
+
+import (
+	"errors"
+	"strings"
+
+	"github.com/tendermint/tendermint/config"
+	"github.com/tendermint/tendermint/state/indexer"
+	"github.com/tendermint/tendermint/state/indexer/sink/kv"
+	"github.com/tendermint/tendermint/state/indexer/sink/null"
+	"github.com/tendermint/tendermint/state/indexer/sink/psql"
+)
+
+// EventSinksFromConfig constructs a slice of indexer.EventSink using the provided
+// configuration.
+//
+//nolint:lll
+func EventSinksFromConfig(cfg *config.Config, dbProvider config.DBProvider, chainID string) ([]indexer.EventSink, error) {
+	if len(cfg.TxIndex.Indexer) == 0 {
+		return []indexer.EventSink{null.NewEventSink()}, nil
+	}
+
+	// check for duplicated sinks
+	sinks := map[string]struct{}{}
+	for _, s := range cfg.TxIndex.Indexer {
+		sl := strings.ToLower(s)
+		if _, ok := sinks[sl]; ok {
+			return nil, errors.New("found duplicated sinks, please check the tx-index section in the config.toml")
+		}
+		sinks[sl] = struct{}{}
+	}
+	eventSinks := []indexer.EventSink{}
+	for k := range sinks {
+		switch indexer.EventSinkType(k) {
+		case indexer.NULL:
+			// When we see null in the config, the eventsinks will be reset with the
+			// nullEventSink.
+			return []indexer.EventSink{null.NewEventSink()}, nil
+
+		case indexer.KV:
+			store, err := dbProvider(&config.DBContext{ID: "tx_index", Config: cfg})
+			if err != nil {
+				return nil, err
+			}
+
+			eventSinks = append(eventSinks, kv.NewEventSink(store))
+
+		case indexer.PSQL:
+			conn := cfg.TxIndex.PsqlConn
+			if conn == "" {
+				return nil, errors.New("the psql connection settings cannot be empty")
+			}
+
+			es, _, err := psql.NewEventSink(conn, chainID)
+			if err != nil {
+				return nil, err
+			}
+			eventSinks = append(eventSinks, es)
+		default:
+			return nil, errors.New("unsupported event sink type")
+		}
+	}
+	return eventSinks, nil
+
+}