Handle dcrd disconnect properly

cmd/dcrdata/internal/api/apiroutes.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2018-2022, The Decred developers
+// Copyright (c) 2018-2025, The Decred developers
 // Copyright (c) 2017, The dcrdata developers
 // See LICENSE for details.
 
@@ -46,6 +46,11 @@ import (
 // once.
 const maxBlockRangeCount = 1000
 
+// noConnectionError is the error message returned by updateNodeConnections when
+// there are no connection to a dcrd node. This error means dcrdata has to be
+// restarted because auto reconnect has been disabled at the time of writing.
+var noConnectionError = errors.New("failed to get connection count")
+
 // DataSource specifies an interface for advanced data collection using the
 // auxiliary DB (e.g. PostgreSQL).
 type DataSource interface {
@@ -169,9 +174,10 @@ func NewContext(cfg *AppContextConfig) *appContext {
 func (c *appContext) updateNodeConnections() error {
 	nodeConnections, err := c.nodeClient.GetConnectionCount(context.TODO())
 	if err != nil {
-		// Assume there arr no connections if RPC had an error.
+		// Assume there are no connections if RPC had an error.
+		c.Status.SetReady(false)
 		c.Status.SetConnections(0)
-		return fmt.Errorf("failed to get connection count: %v", err)
+		return fmt.Errorf("%w: %v", noConnectionError, err)
 	}
 
 	// Before updating connections, get the previous connection count.
@@ -223,7 +229,14 @@ out:
 		case <-rpcCheckTicker.C:
 			if err := c.updateNodeConnections(); err != nil {
 				log.Warn("updateNodeConnections: ", err)
-				break keepon
+
+				if !errors.Is(err, noConnectionError) {
+					break keepon
+				}
+
+				log.Warn("Exiting block connected handler for STATUS monitor.")
+				rpcCheckTicker.Stop()
+				break out
 			}
 
 		case height, ok := <-wireHeightChan:

cmd/dcrdata/internal/explorer/explorer.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2018-2024, The Decred developers
+// Copyright (c) 2018-2025, The Decred developers
 // Copyright (c) 2017, The dcrdata developers
 // See LICENSE for details.
 
@@ -28,6 +28,7 @@ import (
 	"github.com/decred/dcrdata/exchanges/v3"
 	"github.com/decred/dcrdata/gov/v6/agendas"
 	pitypes "github.com/decred/dcrdata/gov/v6/politeia/types"
+	apitypes "github.com/decred/dcrdata/v8/api/types"
 	"github.com/decred/dcrdata/v8/blockdata"
 	"github.com/decred/dcrdata/v8/db/dbtypes"
 	"github.com/decred/dcrdata/v8/explorer/types"
@@ -228,6 +229,7 @@ type explorerUI struct {
 	invsMtx sync.RWMutex
 	invs    *types.MempoolInfo
 	premine int64
+	status  *apitypes.Status
 }
 
 // AreDBsSyncing is a thread-safe way to fetch the boolean in dbsSyncing.
@@ -276,6 +278,12 @@ func (exp *explorerUI) StopWebsocketHub() {
 	close(exp.xcDone)
 }
 
+// SetStatus updates exp.status and MUST not be used in a goroutine to avoid
+// data races.
+func (exp *explorerUI) SetStatus(status *apitypes.Status) {
+	exp.status = status
+}
+
 // ExplorerConfig is the configuration settings for explorerUI.
 type ExplorerConfig struct {
 	DataSource    explorerDataSource

cmd/dcrdata/internal/explorer/explorermiddleware.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2018-2021, The Decred developers
+// Copyright (c) 2018-2025, The Decred developers
 // Copyright (c) 2017, The dcrdata developers
 // See LICENSE for details.
 
@@ -146,39 +146,54 @@ func (exp *explorerUI) BlockHashPathOrIndexCtx(next http.Handler) http.Handler {
 	})
 }
 
-// SyncStatusPageIntercept serves only the syncing status page until it is
-// deactivated when ShowingSyncStatusPage is set to false. This page is served
-// for all the possible routes supported until the background syncing is done.
-func (exp *explorerUI) SyncStatusPageIntercept(next http.Handler) http.Handler {
+// StatusPageIntercept serves the syncing status page when
+// exp.ShowingSyncStatusPage is set to true until when exp.ShowingSyncStatusPage
+// is set to false. This page is served for all the possible routes supported
+// until the background syncing is done. If exp.Ready is false, an error
+// StatusPage is served.
+func (exp *explorerUI) StatusPageIntercept(next http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		if exp.ShowingSyncStatusPage() {
 			exp.StatusPage(w, "Database Update Running. Please Wait.",
 				"Blockchain sync is running. Please wait.", "", ExpStatusSyncing)
 			return
 		}
+
+		if !exp.status.Ready() {
+			exp.StatusPage(w, defaultErrorCode, "Uh Oh. Something unexpected happened, try again later. If you see this error message, please reach out to us via matrix or other communication channel.", "", ExpStatusError)
+			return
+		}
+
 		// Otherwise, proceed to the next http handler.
 		next.ServeHTTP(w, r)
 	})
 }
 
-// SyncStatusAPIIntercept returns a json response back instead of a web page
-// when display sync status is active for the api endpoints supported.
-func (exp *explorerUI) SyncStatusAPIIntercept(next http.Handler) http.Handler {
+// APIStatusIntercept returns a json response back instead of a web page for the
+// api endpoints supported when display sync status is active or explore is not
+// ready.
+func (exp *explorerUI) APIStatusIntercept(next http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		if exp.ShowingSyncStatusPage() {
 			exp.HandleApiRequestsOnSync(w, r)
 			return
 		}
+
+		if !exp.status.Ready() {
+			exp.HandleAPiRequestWhenNotReady(w)
+			return
+		}
+
 		// Otherwise, proceed to the next http handler.
 		next.ServeHTTP(w, r)
 	})
 }
 
-// SyncStatusFileIntercept triggers an HTTP error if a file is requested for
-// download before the DB is synced.
-func (exp *explorerUI) SyncStatusFileIntercept(next http.Handler) http.Handler {
+// ExplorerStatusFileIntercept triggers an HTTP error if a file is requested for
+// download before the DB is synced or when explorer is not ready.
+func (exp *explorerUI) ExplorerStatusFileIntercept(next http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		if exp.ShowingSyncStatusPage() {
+		if exp.ShowingSyncStatusPage() || !exp.status.Ready() {
 			http.Error(w, http.StatusText(http.StatusServiceUnavailable), http.StatusServiceUnavailable)
 			return
 		}

cmd/dcrdata/internal/explorer/explorerroutes.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2018-2024, The Decred developers
+// Copyright (c) 2018-2025, The Decred developers
 // Copyright (c) 2017, The dcrdata developers
 // See LICENSE for details.
 
@@ -73,6 +73,7 @@ type CommonPageData struct {
 	BaseURL       string // scheme + "://" + "host"
 	Path          string
 	RequestURI    string // path?query
+	Ready         bool
 }
 
 // FullURL constructs the page's complete URL.
@@ -2458,6 +2459,14 @@ func (exp *explorerUI) HandleApiRequestsOnSync(w http.ResponseWriter, r *http.Re
 	io.WriteString(w, str)
 }
 
+// HandleAPiRequestWhenNotReady handles all API request when the explorer is not
+// ready.
+func (exp *explorerUI) HandleAPiRequestWhenNotReady(w http.ResponseWriter) {
+	w.Header().Set("Content-Type", "application/json")
+	w.WriteHeader(http.StatusServiceUnavailable)
+	io.WriteString(w, `{"message": "Something went wrong, explorer is not ready. Please try again later."}`)
+}
+
 // MarketPage is the page handler for the "/market" path.
 func (exp *explorerUI) MarketPage(w http.ResponseWriter, r *http.Request) {
 	str, err := exp.templates.exec("market", struct {
@@ -2519,6 +2528,7 @@ func (exp *explorerUI) commonData(r *http.Request) *CommonPageData {
 		BaseURL:    baseURL,
 		Path:       r.URL.Path,
 		RequestURI: r.URL.RequestURI(),
+		Ready:      exp.status.Ready() || exp.ShowingSyncStatusPage(),
 	}
 }
 

cmd/dcrdata/internal/explorer/explorerroutes_test.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/decred/dcrd/chaincfg/v3"
 	"github.com/decred/dcrdata/db/dcrpg/v8"
+	apitypes "github.com/decred/dcrdata/v8/api/types"
 	"github.com/decred/dcrdata/v8/explorer/types"
 )
 
@@ -71,6 +72,8 @@ func TestStatusPageResponseCodes(t *testing.T) {
 		TestnetLink:   "/",
 	})
 
+	exp.SetStatus(new(apitypes.Status))
+
 	// handler := http.HandlerFunc()
 	// handler.ServeHTTP(rr, req)
 

cmd/dcrdata/internal/explorer/templates.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2018-2024, The Decred developers
+// Copyright (c) 2018-2025, The Decred developers
 // Copyright (c) 2017, The dcrdata developers
 // See LICENSE for details.
 
@@ -78,14 +78,14 @@ func (t *templates) reloadTemplates() error {
 	if errorStrings == nil {
 		return nil
 	}
-	return fmt.Errorf(strings.Join(errorStrings, " | "))
+	return fmt.Errorf("%s", strings.Join(errorStrings, " | "))
 }
 
 // execTemplateToString executes the associated input template using the
 // supplied data, and writes the result into a string. If the template fails to
 // execute or isn't found, a non-nil error will be returned. Check it before
-// writing to theclient, otherwise you might as well execute directly into
-// your response writer instead of the internal buffer of this function.
+// writing to the client, otherwise you might as well execute directly into your
+// response writer instead of the internal buffer of this function.
 func (t *templates) execTemplateToString(name string, data interface{}) (string, error) {
 	temp, ok := t.templates[name]
 	if !ok {

cmd/dcrdata/main.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2018-2024, The Decred developers
+// Copyright (c) 2018-2025, The Decred developers
 // Copyright (c) 2017, Jonathan Chappelow
 // See LICENSE for details.
 
@@ -651,6 +651,10 @@ func _main(ctx context.Context) error {
 		chainDB.SignalHeight(uint32(chainDBHeight))
 	}
 
+	// Set explore status. This will enable tracking whether or not we are still
+	// connected to a node.
+	explore.SetStatus(app.Status)
+
 	// Configure the URL path to http handler router for the API.
 	apiMux := api.NewAPIRouter(app, cfg.IndentJSON, cfg.UseRealIP, cfg.CompressAPI)
 
@@ -688,7 +692,7 @@ func _main(ctx context.Context) error {
 		webMux.Use(explorer.AllowedHosts(cfg.AllowedHosts))
 	}
 
-	webMux.With(explore.SyncStatusPageIntercept).Group(func(r chi.Router) {
+	webMux.With(explore.StatusPageIntercept).Group(func(r chi.Router) {
 		r.Get("/", explore.Home)
 		r.Get("/visualblocks", explore.VisualBlocks)
 	})
@@ -724,9 +728,8 @@ func _main(ctx context.Context) error {
 		webMux.Mount(profPath, http.StripPrefix(profPath, http.DefaultServeMux))
 	}
 
-	// SyncStatusAPIIntercept returns a json response if the sync status page is
-	// enabled (no the full explorer while syncing).
-	webMux.With(explore.SyncStatusAPIIntercept).Group(func(r chi.Router) {
+	// APIStatusIntercept returns a json response if the status page if enabled.
+	webMux.With(explore.APIStatusIntercept).Group(func(r chi.Router) {
 		// Mount the dcrdata's REST API.
 		r.Mount("/api", apiMux.Mux)
 		// Setup and mount the Insight API.
@@ -743,11 +746,11 @@ func _main(ctx context.Context) error {
 	})
 
 	// HTTP Error 503 StatusServiceUnavailable for file requests before sync.
-	webMux.With(explore.SyncStatusFileIntercept).Group(func(r chi.Router) {
+	webMux.With(explore.ExplorerStatusFileIntercept).Group(func(r chi.Router) {
 		r.Mount("/download", fileMux.Mux)
 	})
 
-	webMux.With(explore.SyncStatusPageIntercept).Group(func(r chi.Router) {
+	webMux.With(explore.StatusPageIntercept).Group(func(r chi.Router) {
 		r.NotFound(explore.NotFound)
 
 		r.Mount("/explorer", explore.Mux) // legacy

cmd/dcrdata/views/extras.tmpl

@@ -176,6 +176,7 @@
 				rel="noopener noreferrer"
 			>© {{currentYear}} The Decred developers (ISC)</a>
 		</span>
+		{{if .Ready }}
 		<span
 			id="connection"
 			class="text-nowrap align-items-center clickable d-inline-block"
@@ -186,6 +187,11 @@
 			title="While connected, you will receive live page updates and, if enabled, desktop notifications (click to enable)."
 			><span class="d-none d-sm-inline" data-connection-target="status">Connecting <span class="d-none d-md-inline-block">to WebSocket...</span></span><div></div>
 		</span>
+		{{else}}
+		<span class="text-nowrap align-items-center d-inline-block">
+			Not ready...
+		</span>
+		{{end}}
 	</div>
 	<script
 		src="/dist/js/4.06b06a4759f2b4ad.bundle.js"