Make kannel channel paused when we get Queued message in response

handlers/kannel/handler.go

@@ -2,6 +2,7 @@ package kannel
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"net/http"
 	"net/url"
@@ -200,10 +201,22 @@ func (h *handler) Send(ctx context.Context, msg courier.MsgOut, clog *courier.Ch
 	}
 
 	var resp *http.Response
+	var respBody []byte
 	if verifySSL {
-		resp, _, err = h.RequestHTTP(req, clog)
+		resp, respBody, err = h.RequestHTTP(req, clog)
 	} else {
-		resp, _, err = h.RequestHTTPInsecure(req, clog)
+		resp, respBody, err = h.RequestHTTPInsecure(req, clog)
+	}
+
+	if strings.Contains(string(respBody), "Queued") {
+		rc := h.Backend().RedisPool().Get()
+		defer rc.Close()
+		rateLimitKey := fmt.Sprintf("rate_limit:%s", msg.Channel().UUID())
+		rc.Do("SET", rateLimitKey, "engaged")
+
+		// We pause sending 30 seconds so the connection to the SMSC is reset
+		rc.Do("EXPIRE", rateLimitKey, 30)
+		return nil, errors.New("received Queued response from kannel, we'll pause sending to empty the queue")
 	}
 
 	status := h.Backend().NewStatusUpdate(msg.Channel(), msg.ID(), courier.MsgStatusErrored, clog)