Answer 500, not 404, when the IP lookup cannot read the database (closes #109)

A failed database read for an address was listed in the answer's errors
as if the address had no route, so the lookup answered 404, or 200 next
to a routed address. Only a missing route or an invalid address is
listed now; any other read error is logged and answers 500 with the JSON
error body, as the AS and prefix JSON routes do.

Model: opus-5-5

internal/server/handlers_internal_test.go

@@ -806,8 +806,7 @@ func (failingDB) GetPrefixDetailsContext(
 // the health check with a store whose reads fail with the driver's error text,
 // and a prefix that does not parse, and checks that no answer carries the
 // driver's or the prefix parser's text. Before the fix the answers sent it to
-// the client (https://git.eeqj.de/sneak/routewatch/issues/108). The IP lookup
-// answers 404, as it does whenever no address could be looked up.
+// the client (https://git.eeqj.de/sneak/routewatch/issues/108).
 func TestJSONRoutesDoNotSendErrorDetails(t *testing.T) {
 	t.Parallel()
 
@@ -823,7 +822,7 @@ func TestJSONRoutesDoNotSendErrorDetails(t *testing.T) {
 		{statsPath, http.StatusInternalServerError},
 		{"/api/v1/as/64500", http.StatusInternalServerError},
 		{"/api/v1/prefix/192.0.2.0/24", http.StatusInternalServerError},
-		{"/api/v1/ip/192.0.2.1", http.StatusNotFound},
+		{"/api/v1/ip/192.0.2.1", http.StatusInternalServerError},
 		{"/api/v1/prefix/foo/24", http.StatusBadRequest},
 	}
 
@@ -846,6 +845,78 @@ func TestJSONRoutesDoNotSendErrorDetails(t *testing.T) {
 	}
 }
 
+// The addresses failingIPLookupDB fails the read of and finds a route for.
+const (
+	failingLookupIP = "192.0.2.1"
+	routedLookupIP  = "192.0.2.2"
+)
+
+// failingIPLookupDB embeds database.Store (left nil) and answers the IP lookup
+// with errDiskIO for failingLookupIP, a route for routedLookupIP, and no route
+// for any other address. Every other Store method is unused and would panic if
+// called.
+type failingIPLookupDB struct {
+	database.Store
+}
+
+func (failingIPLookupDB) GetIPInfoContext(
+	_ context.Context, ip string,
+) (*database.IPInfo, error) {
+	switch ip {
+	case failingLookupIP:
+		return nil, errDiskIO
+	case routedLookupIP:
+		return &database.IPInfo{IP: ip}, nil
+	default:
+		return nil, database.ErrNoRoute
+	}
+}
+
+// TestIPLookupAnswers500WhenDatabaseReadFails sends IP lookups through the
+// server's router with a store whose read of one address fails with the
+// driver's error. A lookup that asks for that address answers 500 with the
+// JSON error body, as the AS and prefix JSON routes do; an address with no
+// route still answers 404. Before the fix the failed read was reported as if
+// the address had no route: 404 for that address alone, and 200 beside a
+// routed address (https://git.eeqj.de/sneak/routewatch/issues/109).
+func TestIPLookupAnswers500WhenDatabaseReadFails(t *testing.T) {
+	t.Parallel()
+
+	s := New(failingIPLookupDB{}, streamer.New(logger.New(), metrics.New()),
+		logger.New(), &config.Config{})
+
+	tests := []struct {
+		path     string
+		wantCode int
+	}{
+		{
+			path:     "/api/v1/ip/" + failingLookupIP,
+			wantCode: http.StatusInternalServerError,
+		},
+		{
+			path:     "/api/v1/ip/" + failingLookupIP + "," + routedLookupIP,
+			wantCode: http.StatusInternalServerError,
+		},
+		{
+			path:     "/api/v1/ip/203.0.113.1",
+			wantCode: http.StatusNotFound,
+		},
+	}
+
+	for _, tt := range tests {
+		rec := httptest.NewRecorder()
+		s.router.ServeHTTP(rec, httptest.NewRequestWithContext(
+			t.Context(), http.MethodGet, tt.path, nil))
+
+		if rec.Code != tt.wantCode {
+			t.Errorf("%s: status %d, want %d; body %s",
+				tt.path, rec.Code, tt.wantCode, rec.Body)
+		}
+
+		checkJSONErrorCode(t, tt.path, rec, tt.wantCode)
+	}
+}
+
 // settledGoroutineCount lets transient goroutines finish, then reports the
 // current count.
 func settledGoroutineCount() int {