Fix concurrent retry-request

Sometimes it happens that the expired signal is received while the
there's a new request in flight.
This happens in cases such as:

1) We send a request (A)
2) We get disconnected from the mailserver
3) We connect to a new mailserver
4) We send a request (B)
5) We receive an expired signal for A

In such cases the request should not be retried or counted as a failure.

Signed-off-by: Igor Mandrigin <i@mandrigin.ru>

src/status_im/events.cljs

@@ -434,6 +434,11 @@
  (fn [cofx [_ error]]
    (mailserver/handle-request-error cofx error)))
 
+(handlers/register-handler-fx
+ :mailserver.callback/request-success
+ (fn [cofx [_ request-id]]
+   (mailserver/handle-request-success cofx request-id)))
+
 ;; network module
 
 (handlers/register-handler-fx

src/status_im/mailserver/core.cljs

@@ -262,6 +262,10 @@
     (log/debug "Adjusting mailserver request" "from:" from "adjusted-from:" adjusted-from)
     adjusted-from))
 
+(fx/defn handle-request-success [{:keys [db]} request-id]
+  (when (:mailserver/current-request db)
+    {:db (assoc-in db [:mailserver/current-request :request-id] request-id)}))
+
 (defn request-messages! [web3 {:keys [sym-key-id address]} {:keys [topics cursor to from] :as request}]
   ;; Add some room to from, unless we break day boundaries so that messages that have
   ;; been received after the last request are also fetched
@@ -288,10 +292,12 @@
                                 :to             to})
                       (fn [error request-id]
                         (if-not error
+                          (do
                             (log/info "mailserver: messages request success for topic " topics "from" from "to" to)
+                            (re-frame/dispatch [:mailserver.callback/request-success {:request-id request-id}]))
                           (do
                             (log/error "mailserver: messages request error for topic " topics ": " error)
-                            (utils/set-timeout #(re-frame/dispatch [:mailserver.callback/resend-request {:request-id "failed-request"}])
+                            (utils/set-timeout #(re-frame/dispatch [:mailserver.callback/resend-request {:request-id nil}])
                                                backoff-interval-ms)))))))
 
 (re-frame/reg-fx
@@ -575,14 +581,25 @@
 
 (fx/defn resend-request
   [{:keys [db] :as cofx} {:keys [request-id]}]
-  (if (and (:mailserver/current-request db)
+  (let [current-request (:mailserver/current-request db)]
-           (<= maximum-number-of-attempts
+    ;; no inflight request, do nothing
-               (get-in db [:mailserver/current-request :attempts])))
+    (when (and current-request
+               ;; the request was never successful
+               (or (nil? request-id)
+                   ;; we haven't received the request-id yet, but has expired,
+                   ;; so we retry even though we are not sure it's the current
+                   ;; request that failed
+                   (nil? (:request-id current-request))
+                   ;; this is the same request that we are currently processing
+                   (= request-id (:request-id current-request))))
+
+      (if            (<= maximum-number-of-attempts
+                         (:attempts current-request))
         (fx/merge cofx
                   {:db (update db :mailserver/current-request dissoc :attempts)}
                   (change-mailserver))
         (if-let [mailserver (get-mailserver-when-ready cofx)]
-      (let [{:keys [topics from to cursor limit] :as request} (get db :mailserver/current-request)
+          (let [{:keys [topics from to cursor limit] :as request} current-request
                 web3 (:web3 db)]
             (log/info "mailserver: message request " request-id "expired for mailserver topic" topics "from" from "to" to "cursor" cursor "limit" (decrease-limit))
             {:db (update-in db [:mailserver/current-request :attempts] inc)
@@ -590,7 +607,7 @@
              :mailserver/request-messages {:web3 web3
                                            :mailserver mailserver
                                            :request (assoc request :limit (decrease-limit))}})
-      {:mailserver/set-limit (decrease-limit)})))
+          {:mailserver/set-limit (decrease-limit)})))))
 
 (fx/defn initialize-mailserver
   [cofx custom-mailservers]

test/cljs/status_im/test/mailserver/core.cljs

@@ -339,6 +339,42 @@
                                      [{:id "mailserver-id" :enode "enode://mailserver-id@ip"}]
                                      [])))
 
+(deftest test-resend-request
+  (testing "there's no current request"
+    (is (not (mailserver/resend-request {:db {}} {}))))
+  (testing "there's a current request"
+    (testing "it reached the maximum number of attempts"
+      (testing "it changes mailserver"
+        (is (= :connecting
+               (get-in (mailserver/resend-request
+                        {:db {:mailserver/current-request
+                              {:attempts mailserver/maximum-number-of-attempts}}}
+                        {})
+                       [:db :mailserver/state])))))
+    (testing "it did not reach the maximum number of attempts"
+      (testing "it reached the maximum number of attempts"
+        (testing "it decrease the limit")
+        (is (= {:mailserver/set-limit 1000} (mailserver/resend-request {:db {:mailserver/current-request
+                                                                             {}}}
+                                                                       {})))))))
+
+(deftest test-resend-request-request-id
+  (testing "request-id passed is nil"
+    (testing "it resends the request"
+      (is (mailserver/resend-request {:db {:mailserver/current-request {}}} {}))))
+  (testing "request-id is nil in db"
+    (testing "it resends the request"
+      (is (mailserver/resend-request {:db {:mailserver/current-request {}}}
+                                     {:request-id "a"}))))
+  (testing "request id matches"
+    (testing "it resends the request"
+      (is (mailserver/resend-request {:db {:mailserver/current-request {:request-id "a"}}}
+                                     {:request-id "a"}))))
+  (testing "request id does not match"
+    (testing "it does not resend the request"
+      (is (not (mailserver/resend-request {:db {:mailserver/current-request {:request-id "a"}}}
+                                          {:request-id "b"}))))))
+
 (deftest peers-summary-change
   (testing "Mailserver added, sym-key doesn't exist"
     (let [result (peers-summary-change-result false true false)]