# HG changeset patch
# User Philippe Pepiot <philippe.pepiot@logilab.fr>
# Date 1540566746 -7200
# Node ID e385c9732f1ea2c29e0b996ad6c0b23c2cd5e7a3
# Parent  ed486562ba7e26a13e030e5665be7dfcb8c69a57
Make test database template creation concurrent

build_db_cache() is used in tests to create test database templates, i.e.
DEFAULT_EMPTY_DB_ID (which is __default_empty_db__) and custom template
database using CubicwebTC test_db_id/pre_setup_database API.

When running tests in parallel using multiple processes, build_db_cache() may
try to build the same database twice. Avoid this by adding synchronisation of
process by using a file lock.

So when two processes require the same template database, one build the
database and others wait it to be created.

Use filelock (https://github.com/benediktschmitt/py-filelock) library to have a
portable (unix / windows) way for handling locks.
Also filelock is packaged in debian: https://packages.debian.org/source/python-filelock

diff -r ed486562ba7e -r e385c9732f1e cubicweb/devtools/__init__.py
--- a/cubicweb/devtools/__init__.py	Fri Oct 26 17:00:05 2018 +0200
+++ b/cubicweb/devtools/__init__.py	Fri Oct 26 17:12:26 2018 +0200
@@ -32,6 +32,7 @@
 from os.path import abspath, join, exists, split, isdir, dirname
 from functools import partial
 
+import filelock
 from six import text_type
 from six.moves import cPickle as pickle
 
@@ -470,20 +471,23 @@
         ``pre_setup_func`` to setup the database.
 
         This function backup any database it build"""
-        if self.has_cache(test_db_id):
-            return  # test_db_id, 'already in cache'
-        if test_db_id is DEFAULT_EMPTY_DB_ID:
-            self.init_test_database()
-        else:
-            print('Building %s for database %s' % (test_db_id, self.dbname))
-            self.build_db_cache(DEFAULT_EMPTY_DB_ID)
-            self.restore_database(DEFAULT_EMPTY_DB_ID)
-            self.get_repo(startup=True)
-            cnx = self.get_cnx()
-            with cnx:
-                pre_setup_func(cnx, self.config)
-                cnx.commit()
-        self.backup_database(test_db_id)
+        lockfile = join(self._ensure_test_backup_db_dir(),
+                        '{}.lock'.format(test_db_id))
+        with filelock.FileLock(lockfile):
+            if self.has_cache(test_db_id):
+                return  # test_db_id, 'already in cache'
+            if test_db_id is DEFAULT_EMPTY_DB_ID:
+                self.init_test_database()
+            else:
+                print('Building %s for database %s' % (test_db_id, self.dbname))
+                self.build_db_cache(DEFAULT_EMPTY_DB_ID)
+                self.restore_database(DEFAULT_EMPTY_DB_ID)
+                self.get_repo(startup=True)
+                cnx = self.get_cnx()
+                with cnx:
+                    pre_setup_func(cnx, self.config)
+                    cnx.commit()
+            self.backup_database(test_db_id)
 
 
 class NoCreateDropDatabaseHandler(TestDataBaseHandler):
diff -r ed486562ba7e -r e385c9732f1e debian/control
--- a/debian/control	Fri Oct 26 17:00:05 2018 +0200
+++ b/debian/control	Fri Oct 26 17:12:26 2018 +0200
@@ -28,6 +28,7 @@
  python-passlib,
  python-repoze.lru,
  python-wsgicors,
+ python-filelock,
  sphinx-common,
 Standards-Version: 3.9.6
 Homepage: https://www.cubicweb.org
@@ -51,6 +52,7 @@
  python-passlib,
  python-tz,
  graphviz,
+ python-filelock,
  gettext,
 Recommends:
  cubicweb-ctl (= ${source:Version}),
diff -r ed486562ba7e -r e385c9732f1e setup.py
--- a/setup.py	Fri Oct 26 17:00:05 2018 +0200
+++ b/setup.py	Fri Oct 26 17:12:26 2018 +0200
@@ -74,6 +74,7 @@
         'pytz',
         'Markdown',
         'unittest2 >= 0.7.0',
+        'filelock',
     ],
     entry_points={
         'console_scripts': [