From 33aeb2c12a2f50141fa28eb6e235af594f740327 Mon Sep 17 00:00:00 2001
From: Oliver Sanders <oliver.sanders@metoffice.gov.uk>
Date: Fri, 28 Jun 2024 09:47:19 +0100
Subject: [PATCH] tui: prevent hang on shutdown

* Add a timeout on the updater shutdown to prevent any hanging operation
  stopping Tui from exiting.
---
 changes.d/fix.6178.md | 1 +
 cylc/flow/tui/app.py  | 5 ++++-
 2 files changed, 5 insertions(+), 1 deletion(-)
 create mode 100644 changes.d/fix.6178.md

diff --git a/changes.d/fix.6178.md b/changes.d/fix.6178.md
new file mode 100644
index 00000000000..7d1b9b0f3f6
--- /dev/null
+++ b/changes.d/fix.6178.md
@@ -0,0 +1 @@
+Fix an issue where Tui could hang when closing.
diff --git a/cylc/flow/tui/app.py b/cylc/flow/tui/app.py
index 783f1217cc8..eb9f8dec09c 100644
--- a/cylc/flow/tui/app.py
+++ b/cylc/flow/tui/app.py
@@ -216,7 +216,10 @@ def updater_subproc(filters, client_timeout):
         yield updater
     finally:
         updater.terminate()
-        p.join()
+        p.join(4)  # timeout of 4 seconds
+        if p.exitcode is None:
+            # updater did not exit within timeout -> kill it
+            p.terminate()
 
 
 class TuiApp: