From a382f7005a23f557b25b03cc11d8e33669a85214 Mon Sep 17 00:00:00 2001
From: bko <bko@scireum.de>
Date: Fri, 19 Apr 2024 13:47:28 +0200
Subject: [PATCH] Retries resolving image if any exception occurred

In some cases, the image we want to resolve is not yet available. It is therefore important to try again after a short waiting time.

This is the case, for example, when we request a variant of an image that has not yet been created.

Fixes: SIRI-958
---
 .../pdf/AsyncLoadedImageElement.java          | 48 ++++++++++++++-----
 1 file changed, 37 insertions(+), 11 deletions(-)

diff --git a/src/main/java/sirius/web/templates/pdf/AsyncLoadedImageElement.java b/src/main/java/sirius/web/templates/pdf/AsyncLoadedImageElement.java
index 087f4f42e..5d443d111 100644
--- a/src/main/java/sirius/web/templates/pdf/AsyncLoadedImageElement.java
+++ b/src/main/java/sirius/web/templates/pdf/AsyncLoadedImageElement.java
@@ -16,6 +16,7 @@
 import org.xhtmlrenderer.render.RenderingContext;
 import sirius.kernel.async.CallContext;
 import sirius.kernel.commons.Tuple;
+import sirius.kernel.commons.Wait;
 import sirius.kernel.health.Exceptions;
 import sirius.web.security.ScopeInfo;
 import sirius.web.security.UserContext;
@@ -39,6 +40,7 @@
  */
 public final class AsyncLoadedImageElement implements ITextReplacedElement {
 
+    private static final int MAX_ATTEMPTS = 3;
     private final Thread resolvingThread;
     private final int cssWidth;
     private final int cssHeight;
@@ -62,20 +64,44 @@ public AsyncLoadedImageElement(PdfReplaceHandler handler, String uri, int cssWid
         ScopeInfo scopeInfo = UserContext.getCurrentScope();
         resolvingThread = Thread.startVirtualThread(() -> {
             UserContext.get().setCurrentScope(scopeInfo);
-            try {
-                semaphore.acquire();
-                image = handler.resolveUri(uri, null, cssWidth, cssHeight);
-            } catch (InterruptedException e) {
-                Thread.currentThread().interrupt();
-                Exceptions.handle(e);
-            } catch (Exception e) {
-                Exceptions.handle(e);
-            } finally {
-                semaphore.release();
-            }
+            startResolvingResource(uri, handler, semaphore, 1);
         });
     }
 
+    private void startResolvingResource(String uri, PdfReplaceHandler handler, Semaphore semaphore, int attempt) {
+        Exception exception = null;
+        try {
+            semaphore.acquire();
+            image = handler.resolveUri(uri, null, cssWidth, cssHeight);
+        } catch (InterruptedException e) {
+            Thread.currentThread().interrupt();
+            exception = e;
+        } catch (Exception e) {
+            exception = e;
+        } finally {
+            semaphore.release();
+            if (image == null || exception != null) {
+                retryOrFail(uri, handler, semaphore, attempt, exception);
+            }
+        }
+    }
+
+    private void retryOrFail(String uri, PdfReplaceHandler handler, Semaphore semaphore, int attempt, Exception exception) {
+        if (exception instanceof InterruptedException) {
+            // we should accept that the thread is interrupted and don't try again
+            Exceptions.handle(exception);
+            return;
+        }
+        if (attempt < MAX_ATTEMPTS) {
+            Wait.millis(500);
+            startResolvingResource(uri, handler, semaphore, attempt + 1);
+        } else if (exception != null) {
+            Exceptions.handle(exception);
+        } else {
+            Exceptions.handle().withSystemErrorMessage("Could not resolve image: %s", uri).handle();
+        }
+    }
+
     /**
      * Returns the resolved image.
      * <p>