Add in exponential backoff for downloadResource()

kyleady · May 29, 2020 · 0a42034 · 0a42034
1 parent 82efbc4
commit 0a42034
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Showing 2 changed files with 18 additions and 10 deletions.
diff --git a/manifest.json b/manifest.json
@@ -1,6 +1,6 @@
 {
 	"name": "R20Exporter",
-	"version": "0.7",
+	"version": "0.7.1",
 	"manifest_version": 2,
 	"description": "Export a Roll20 Campaign with all its assets to a ZIP file.",
 	"permissions": [
@@ -30,4 +30,4 @@
       "run_at": "document_idle"
 		}
 	]
-}
+}
diff --git a/src/R20Exporter.js b/src/R20Exporter.js
@@ -541,7 +541,7 @@ class R20Exporter {
         return result
     }
 
-    
+
     jsonToBlob(obj) {
         return new Blob([JSON.stringify(obj, undefined, 4)], { "type": 'text/json' })
     }
@@ -588,8 +588,8 @@ class R20Exporter {
         img.src = url
     }
 
-    downloadResource(url, cb, errorCB = null) {
-        const id = this.newPendingOperation()
+    downloadResource(url, cb, errorCB = null, retryId = undefined, expBackoff = 1) {
+        const id = retryId || this.newPendingOperation()
 
         // Security in Chrome prevents getting http urls entirely.
         if (window.location.protocol === "https:" && url.startsWith("http:"))
@@ -598,6 +598,8 @@ class R20Exporter {
         fetch(url).then((response) => {
             if (response.status == 200 || response.status == 0) {
                 return Promise.resolve(response.blob())
+            } else if (response.status == 404 || response.status == 403) {
+                return Promise.reject(new Error("DO_NOT_RETRY"))
             } else {
                 return Promise.reject(new Error(response.statusText))
             }
@@ -608,9 +610,15 @@ class R20Exporter {
                 cb(blob)
         }
         ).catch((error) => {
-            this.completedOperation(id)
-            if (errorCB)
-                errorCB()
+            if (expBackoff < 30 && error.message != "DO_NOT_RETRY") {
+                setTimeout(() => {
+                    this.downloadResource(url, cb, errorCB, id, expBackoff * (1.5 + Math.random()))
+                }, expBackoff * 1000)
+            } else {
+                this.completedOperation(id)
+                if (errorCB)
+                    errorCB()
+            }
         }
         )
     }
@@ -1034,7 +1042,7 @@ class ModalWindow {
                 background-color: rgb(0,0,0); /* Fallback color */
                 background-color: rgba(0,0,0,0.4); /* Black w/ opacity */
             }
-            
+
             /* Modal Content */
             .modal-content {
                 background-color: #fefefe;
@@ -1231,4 +1239,4 @@ function addExportButton() {
 if (window.$ !== undefined)
     addExportButton()
 else
-    window.addEventListener("DOMContentLoaded", addExportButton)
+    window.addEventListener("DOMContentLoaded", addExportButton)