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From: Eric Wong <BOFH@YHBT.net>
To: unicorn-public@yhbt.net
Subject: [PATCH] http_server: detect disk-full when writing PID file
Date: Sat,  1 Oct 2022 22:57:40 +0000
Message-Id: <20221001225740.831378-1-BOFH@YHBT.net>
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List-Id: <unicorn-public.yhbt.net>

While unlikely, it's possible for write(2) to return a truncated
value or ENOSPC error if the device is full when writing a tiny
PID file.

As optimism has no place in engineering, use IO#write instead of
IO#syswrite since the former will retry on truncation and raise
a exception on ENOSPC.
---
 lib/unicorn/http_server.rb | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/unicorn/http_server.rb b/lib/unicorn/http_server.rb
index 21f2a05a..3416808f 100644
--- a/lib/unicorn/http_server.rb
+++ b/lib/unicorn/http_server.rb
@@ -187,7 +187,8 @@ def clobber_pid(path)
       rescue Errno::EEXIST
         retry
       end
-      fp.syswrite("#$$\n")
+      fp.sync = true
+      fp.write("#$$\n")
       File.rename(fp.path, path)
       fp.close
     end