From 88ba140db9cd2701e0b9d247f124639a944a20f7 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Fri, 7 May 2021 07:22:51 +0530
Subject: [PATCH] Retry sending message after a sleep

Avoids spurious errors on multiple simultaneous calibre launches. Fixes #1927546 ["ERROR: Contacting calibre failed"](https://bugs.launchpad.net/calibre/+bug/1927546)
---
 src/calibre/gui2/main.py | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/src/calibre/gui2/main.py b/src/calibre/gui2/main.py
index 2bda7b4dd1..c90e8c4bb0 100644
--- a/src/calibre/gui2/main.py
+++ b/src/calibre/gui2/main.py
@@ -447,14 +447,18 @@ singleinstance_name = 'GUI'
 def send_message(msg):
     try:
         send_message_in_process(msg)
-    except Exception as err:
-        print(_('Failed to contact running instance of calibre'), file=sys.stderr, flush=True)
-        print(err, file=sys.stderr, flush=True)
-        if Application.instance():
-            error_dialog(None, _('Contacting calibre failed'), _(
-                'Failed to contact running instance of calibre, try restarting calibre'),
-                det_msg=str(err) + '\n\n' + repr(msg), show=True)
-        return False
+    except Exception:
+        time.sleep(2)
+        try:
+            send_message_in_process(msg)
+        except Exception as err:
+            print(_('Failed to contact running instance of calibre'), file=sys.stderr, flush=True)
+            print(err, file=sys.stderr, flush=True)
+            if Application.instance():
+                error_dialog(None, _('Contacting calibre failed'), _(
+                    'Failed to contact running instance of calibre, try restarting calibre'),
+                    det_msg=str(err) + '\n\n' + repr(msg), show=True)
+            return False
     return True