allow parallel sessions

app.R

@@ -97,8 +97,12 @@ server <- function(input, output, session) {
   event_reload <- reactiveVal(val = 0)
   observeEvent(event_reload(), ignoreNULL=FALSE, {
     
-    # the model is already loaded, nothing to do
-    if (!is.null(sess$is_loaded) && sess$is_loaded) return()
+    # the model is already loaded, we just make sure the send button is enabled
+    if (!is.null(sess$is_loaded) && sess$is_loaded) {
+      shinyjs::enable("send")
+      updateActionButton(inputId = "send", label = "Send")
+      return()
+    } 
     
     # the model isn't loaded, this we disable the send button and
     # show that we are loading the model
@@ -111,12 +115,16 @@ server <- function(input, output, session) {
       cat("Started loading model ....", "\n")
       model_loaded(sess$load_model(repo))
       sess$is_loaded <- FALSE # not yet loaded, but loading
+    } else {
+      # the model is loading, but this is handled by another session. We should
+      # come back to this observer later to enable the send button once model
+      # is loaded.
+      invalidateLater(5000, session)
+      return()
     }
     
-    # this runs for the cases where sess$is_loaded was NULL or if 
-    # sess$is_loaded = FALSE ie (another connection already tried)
-    # to load the model.
-    
+    # this runs for the cases where sess$is_loaded was NULL
+    # ie there was no model currently loading.
     cat("Loading model:",sess$sess$poll_process(), "\n")
     m <- model_loaded() %>% 
       promises::then(onFulfilled = function(x) {