From 143379dad73bab96a8d94f768609a1c93b9a64c0 Mon Sep 17 00:00:00 2001
From: Katelyn Baker <katelyn.baker@r3.com>
Date: Fri, 13 Jul 2018 18:14:34 +0100
Subject: [PATCH] CORDA-1588 - Add an extra check in the attachment resolution
 flow to prevent duplicate attachment import if multiple transactions with the
 same attachment are being resolved at the same time. (#3599)

---
 .../main/kotlin/net/corda/core/internal/FetchDataFlow.kt  | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/core/src/main/kotlin/net/corda/core/internal/FetchDataFlow.kt b/core/src/main/kotlin/net/corda/core/internal/FetchDataFlow.kt
index 867a719949..5c82f5ea53 100644
--- a/core/src/main/kotlin/net/corda/core/internal/FetchDataFlow.kt
+++ b/core/src/main/kotlin/net/corda/core/internal/FetchDataFlow.kt
@@ -147,7 +147,13 @@ class FetchAttachmentsFlow(requests: Set<SecureHash>,
 
     override fun maybeWriteToDisk(downloaded: List<Attachment>) {
         for (attachment in downloaded) {
-            serviceHub.attachments.importAttachment(attachment.open(), "$P2P_UPLOADER:${otherSideSession.counterparty.name}", null)
+            with(serviceHub.attachments) {
+                if (!hasAttachment(attachment.id)) {
+                    importAttachment(attachment.open(), "$P2P_UPLOADER:${otherSideSession.counterparty.name}", null)
+                } else {
+                    logger.info("Attachment ${attachment.id} already exists, skipping.")
+                }
+            }
         }
     }