X-Git-Url: https://git.phdru.name/?a=blobdiff_plain;f=m_librarian%2Fweb%2Futils.py;h=8804f3b327df81831fbd707af57def93e965a8e9;hb=054ce4ecc6c93d0289864c80677c7dd8bf8b1962;hp=2efe724a6bdf8fcfb10a9e7e1c4ce9d0ca877de8;hpb=2d76928b93c208d27f942b9a9eb649df1d5b2192;p=m_librarian.git

diff --git a/m_librarian/web/utils.py b/m_librarian/web/utils.py
index 2efe724..8804f3b 100644
--- a/m_librarian/web/utils.py
+++ b/m_librarian/web/utils.py
@@ -1,7 +1,57 @@
+from fcntl import flock, LOCK_EX, LOCK_UN, LOCK_NB
+from tempfile import gettempdir
+import os
+import socket
+
+
+if os.access('/var/run/lock', os.W_OK):
+    lock_dir = '/var/run/lock'
+else:
+    lock_dir = gettempdir()
+
+if hasattr(os, 'getuid'):
+    suffix = '-%d' % os.getuid()
+else:
+    suffix = ''
+
+lock_fname = os.path.join(lock_dir, 'm_librarian%s.lock' % suffix)
+
+
+def get_lock(port):
+    try:
+        lock_file = open(lock_fname, 'r')
+    except IOError:  # no lock file
+        pass
+    else:
+        try:
+            flock(lock_file, LOCK_EX | LOCK_NB)
+        except IOError:  # locked
+            port = int(lock_file.readline())
+            lock_file.close()
+            return None, port
+        else:
+            flock(lock_file, LOCK_UN)
+            lock_file.close()
+
+    lock_file = open(lock_fname, 'w')
+    lock_file.write(str(port))
+    lock_file.close()
+    lock_file = open(lock_fname, 'r')
+    flock(lock_file, LOCK_EX | LOCK_NB)
+    return lock_file, None
+
+
+def close_lock(lock_file):
+    flock(lock_file, LOCK_UN)
+    lock_file.close()
+    lock_file = open(lock_fname, 'w')
+    lock_file.write('')
+    lock_file.close()
+    os.remove(lock_fname)
+
 
 def get_open_port():
     # https://stackoverflow.com/a/2838309/7976758
-    import socket
     s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
     s.bind(("", 0))
     # s.listen(1)