server: Report payment interval in payment challenges

doc/live-runner.md

@@ -391,7 +391,9 @@ parameters. The client retries the same request with `Livepeer-Payment` and
 `Livepeer-Segment`, then periodically refreshes payment at
 `POST /apps/{runner_id}/session/{session_id}/payment`. The orchestrator accounts
 usage on its configured payment interval and releases the session if payment
-fails. If the payment unit is `fixed` then payment is only processed once.
+fails. The challenge response reports that interval as `payment_interval_ms` so
+clients can size and time payments to keep the session balance funded. If the
+payment unit is `fixed` then payment is only processed once.
 
 Offchain runners do not issue payment challenges. For the underlying ticket
 protocol, see [Payments](payments.md).

server/ai_http.go

@@ -185,6 +185,8 @@ type liveRunnerPaymentChallengeResponse struct {
 	// Keep the URL in top-level JSON so clients do not need to parse the protobuf just to route payment.
 	Orchestrator string `json:"orchestrator"`
 	ManifestID   string `json:"manifest_id"`
+	// Interval at which the orchestrator debits the session balance.
+	PaymentIntervalMs int64 `json:"payment_interval_ms"`
 }
 
 type liveRunnerTrickleChannelRequest struct {
@@ -402,7 +404,7 @@ func (h *lphttp) runnerChallenge(w http.ResponseWriter, r *http.Request, priceIn
 		respondWithError(w, err.Error(), http.StatusInternalServerError)
 		return
 	}
-	data, err := marshalLivePaymentChallengeResponse(oInfo)
+	data, err := marshalLivePaymentChallengeResponse(oInfo, h.node.LivePaymentInterval)
 	if err != nil {
 		respondWithError(w, err.Error(), http.StatusInternalServerError)
 		return
@@ -427,7 +429,7 @@ func (h *lphttp) scopePaymentChallenge(w http.ResponseWriter, r *http.Request) (
 	if err != nil {
 		return false, err
 	}
-	data, err := marshalLivePaymentChallengeResponse(oInfo)
+	data, err := marshalLivePaymentChallengeResponse(oInfo, h.node.LivePaymentInterval)
 	if err != nil {
 		return false, err
 	}
@@ -437,15 +439,16 @@ func (h *lphttp) scopePaymentChallenge(w http.ResponseWriter, r *http.Request) (
 	return true, nil
 }
 
-func marshalLivePaymentChallengeResponse(oInfo *lpnet.OrchestratorInfo) ([]byte, error) {
+func marshalLivePaymentChallengeResponse(oInfo *lpnet.OrchestratorInfo, paymentInterval time.Duration) ([]byte, error) {
 	buf, err := proto.Marshal(oInfo)
 	if err != nil {
 		return nil, err
 	}
 	return json.Marshal(liveRunnerPaymentChallengeResponse{
-		PaymentParams: base64.StdEncoding.EncodeToString(buf),
-		Orchestrator:  oInfo.GetTranscoder(),
-		ManifestID:    oInfo.GetAuthToken().GetSessionId(),
+		PaymentParams:     base64.StdEncoding.EncodeToString(buf),
+		Orchestrator:      oInfo.GetTranscoder(),
+		ManifestID:        oInfo.GetAuthToken().GetSessionId(),
+		PaymentIntervalMs: paymentInterval.Milliseconds(),
 	})
 }
 

server/ai_http_test.go

@@ -664,6 +664,7 @@ func TestLiveRunnerReserveSessionOnchainReturnsPaymentChallenge(t *testing.T) {
 	require.NotEmpty(t, challenge.PaymentParams)
 	require.Equal(t, lp.orchestrator.ServiceURI().String(), challenge.Orchestrator)
 	require.NotEmpty(t, challenge.ManifestID)
+	require.Equal(t, int64(5000), challenge.PaymentIntervalMs)
 	require.Equal(t, challenge.ManifestID, oInfo.GetAuthToken().GetSessionId())
 	require.NotNil(t, oInfo.GetTicketParams())
 	require.NotNil(t, oInfo.GetPriceInfo())

server/rpc.go

@@ -496,7 +496,7 @@ func (h *lphttp) RefreshPayment(w http.ResponseWriter, r *http.Request) {
 	}
 
 	w.Header().Set("Content-Type", "application/json")
-	data, err := marshalLivePaymentChallengeResponse(oInfo)
+	data, err := marshalLivePaymentChallengeResponse(oInfo, h.node.LivePaymentInterval)
 	if err != nil {
 		respondJsonError(ctx, w, err, http.StatusInternalServerError)
 		return