From f8c2c8f879fd3866d4375d94124f82c985ef340e Mon Sep 17 00:00:00 2001
From: Markus Unterwaditzer <markus@unterwaditzer.net>
Date: Sat, 19 Apr 2014 22:35:49 +0200
Subject: [PATCH 1/3] Use multiple connections when syncing.

---
 example.cfg       |  6 ++++++
 vdirsyncer/cli.py | 45 ++++++++++++++++++++++++++++++---------------
 2 files changed, 36 insertions(+), 15 deletions(-)

diff --git a/example.cfg b/example.cfg
index a5ba092..3e07ee8 100644
--- a/example.cfg
+++ b/example.cfg
@@ -5,6 +5,12 @@
 # A folder where vdirsyncer can store some metadata about each pair.
 status_path = ~/.vdirsyncer/status/
 
+# The amount of processes to use when synchronizing. If the CPU of your server
+# is the bottleneck (which is plausible for small homeservers), set this to the
+# number of cores * 2. Defaults to one process for each collection. The value
+# 0 will be ignored.
+#processes =
+
 # CONTACTS
 [pair bob_contacts]
 # Similar to accounts in OfflineIMAP.
diff --git a/vdirsyncer/cli.py b/vdirsyncer/cli.py
index f2128fa..1f1df37 100644
--- a/vdirsyncer/cli.py
+++ b/vdirsyncer/cli.py
@@ -190,23 +190,38 @@ def _main(env, file_cfg):
             config_a.update(all_storages[a_name])
             config_b = dict(storage_defaults)
             config_b.update(all_storages[b_name])
-            a = storage_instance_from_config(config_a)
-            b = storage_instance_from_config(config_b)
 
-            def x(a=a, b=b, pair_name=pair_name, collection=collection):
-                status_name = \
-                    '_'.join(filter(bool, (pair_name, collection)))
-                pair_description = \
-                    ' from '.join(filter(bool, (collection, pair_name)))
-                cli_logger.info('Syncing {}'.format(pair_description))
-                status = load_status(general['status_path'], status_name)
-                sync(a, b, status,
-                     pair_options.get('conflict_resolution', None))
-                save_status(general['status_path'], status_name, status)
-            actions.append(x)
 
-        for action in actions:
-            action()
+            actions.append({
+                'config_a': config_a,
+                'config_b': config_b,
+                'pair_name': pair_name,
+                'collection': collection,
+                'pair_options': pair_options,
+                'general': general
+            })
+
+        from multiprocessing import Pool
+        p = Pool(processes=general.get('processes', 0) or len(actions))
+        p.map(_sync_collection, actions)
 
     app.register_command('sync', sync_command)
     app()
+
+def _sync_collection(x):
+    return sync_collection(**x)
+
+def sync_collection(config_a, config_b, pair_name, collection, pair_options,
+                    general):
+    a = storage_instance_from_config(config_a)
+    b = storage_instance_from_config(config_b)
+
+    status_name = \
+            '_'.join(filter(bool, (pair_name, collection)))
+    pair_description = \
+            ' from '.join(filter(bool, (collection, pair_name)))
+    cli_logger.info('Syncing {}'.format(pair_description))
+    status = load_status(general['status_path'], status_name)
+    sync(a, b, status,
+         pair_options.get('conflict_resolution', None))
+    save_status(general['status_path'], status_name, status)

From 6c81fd6fc2f6f0fe27935a41b987794efff6c2f2 Mon Sep 17 00:00:00 2001
From: Markus Unterwaditzer <markus@unterwaditzer.net>
Date: Sat, 19 Apr 2014 23:59:35 +0200
Subject: [PATCH 2/3] Don't use multiprocessing when having one process

---
 vdirsyncer/cli.py | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/vdirsyncer/cli.py b/vdirsyncer/cli.py
index 1f1df37..2af91cf 100644
--- a/vdirsyncer/cli.py
+++ b/vdirsyncer/cli.py
@@ -201,9 +201,19 @@ def _main(env, file_cfg):
                 'general': general
             })
 
-        from multiprocessing import Pool
-        p = Pool(processes=general.get('processes', 0) or len(actions))
-        p.map(_sync_collection, actions)
+        processes = general.get('processes', 0) or len(actions)
+        cli_logger.debug('Using {} processes.'.format(processes))
+
+        if processes == 1:
+            cli_logger.debug('Not using multiprocessing.')
+            _map = map
+        else:
+            cli_logger.debug('Using multiprocessing.')
+            from multiprocessing import Pool
+            p = Pool(processes=general.get('processes', 0) or len(actions))
+            _map = p.map
+
+        _map(_sync_collection, actions)
 
     app.register_command('sync', sync_command)
     app()

From 15e9446bbea4cfe7ebfaef9a7368681d6b5184c3 Mon Sep 17 00:00:00 2001
From: Markus Unterwaditzer <markus@unterwaditzer.net>
Date: Sun, 20 Apr 2014 00:01:41 +0200
Subject: [PATCH 3/3] Update cfg about special case in multiprocessing

---
 example.cfg | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/example.cfg b/example.cfg
index 3e07ee8..0b12929 100644
--- a/example.cfg
+++ b/example.cfg
@@ -8,7 +8,7 @@ status_path = ~/.vdirsyncer/status/
 # The amount of processes to use when synchronizing. If the CPU of your server
 # is the bottleneck (which is plausible for small homeservers), set this to the
 # number of cores * 2. Defaults to one process for each collection. The value
-# 0 will be ignored.
+# 0 will be ignored, the value 1 disables multiprocessing.
 #processes =
 
 # CONTACTS