diff --git a/TODO.md b/TODO.md
index 3312404f..403fd06c 100644
--- a/TODO.md
+++ b/TODO.md
@@ -355,5 +355,3 @@ make django admin taskstate uncollapse fucking traceback, ( if exists ?)
 # backend.context and backned.instance provided when an action is called? like forms.cleaned_data: do it on manager.generation(backend.context = backend.get_context()) or in backend.__getattr__ ? also backend.head,tail,content switching on manager.generate()?
 
 # replace return_code by exit_code everywhere
-
-# plan.rate registry
diff --git a/orchestra/contrib/orchestration/manager.py b/orchestra/contrib/orchestration/manager.py
index 92506be2..fc980c16 100644
--- a/orchestra/contrib/orchestration/manager.py
+++ b/orchestra/contrib/orchestration/manager.py
@@ -105,7 +105,7 @@ def execute(scripts, serialize=False, async=None):
     async: do not join threads (overrides route.async)
     """
     if settings.ORCHESTRATION_DISABLE_EXECUTION:
-        logger.info('Orchestration execution is dissabled by ORCHESTRATION_DISABLE_EXECUTION settings.')
+        logger.info('Orchestration execution is dissabled by ORCHESTRATION_DISABLE_EXECUTION.')
         return []
     # Execute scripts on each server
     executions = []
@@ -122,6 +122,7 @@ def execute(scripts, serialize=False, async=None):
         kwargs = {
             'async': async,
         }
+        # we clone the connection just in case we are isolated inside a transaction
         with db.clone(model=BackendLog) as handle:
             log = backend.create_log(*args, using=handle.target)
             log._state.db = handle.origin
diff --git a/orchestra/contrib/plans/admin.py b/orchestra/contrib/plans/admin.py
index 1ae7de53..16d08931 100644
--- a/orchestra/contrib/plans/admin.py
+++ b/orchestra/contrib/plans/admin.py
@@ -30,6 +30,7 @@ class ContractedPlanAdmin(AccountAdminMixin, admin.ModelAdmin):
     list_select_related = ('plan', 'account')
     search_fields = ('account__username', 'plan__name', 'id')
 
+
 admin.site.register(Plan, PlanAdmin)
 admin.site.register(ContractedPlan, ContractedPlanAdmin)
 
diff --git a/orchestra/contrib/plans/models.py b/orchestra/contrib/plans/models.py
index 4e5d68f0..b083a570 100644
--- a/orchestra/contrib/plans/models.py
+++ b/orchestra/contrib/plans/models.py
@@ -6,8 +6,10 @@ from django.utils.translation import ugettext_lazy as _
 
 from orchestra.core.validators import validate_name
 from orchestra.models import queryset
+from orchestra.utils.functional import cached
+from orchestra.utils.python import import_class
 
-from . import rating
+from . import settings
 
 
 class Plan(models.Model):
@@ -66,15 +68,6 @@ class RateQuerySet(models.QuerySet):
 
 
 class Rate(models.Model):
-    STEP_PRICE = 'STEP_PRICE'
-    MATCH_PRICE = 'MATCH_PRICE'
-    BEST_PRICE = 'BEST_PRICE'
-    RATE_METHODS = {
-        STEP_PRICE: rating.step_price,
-        MATCH_PRICE: rating.match_price,
-        BEST_PRICE: rating.best_price,
-    }
-    
     service = models.ForeignKey('services.Service', verbose_name=_("service"),
         related_name='rates')
     plan = models.ForeignKey(Plan, verbose_name=_("plan"), related_name='rates')
@@ -91,12 +84,18 @@ class Rate(models.Model):
         return "{}-{}".format(str(self.price), self.quantity)
     
     @classmethod
+    @cached
     def get_methods(cls):
-        return cls.RATE_METHODS
+        return dict((method, import_class(method)) for method in settings.PLANS_RATE_METHODS)
     
     @classmethod
+    @cached
     def get_choices(cls):
         choices = []
-        for name, method in cls.RATE_METHODS.items():
+        for name, method in cls.get_methods().items():
             choices.append((name, method.verbose_name))
         return choices
+    
+    @classmethod
+    def get_default(cls):
+        return settings.PLANS_DEFAULT_RATE_METHOD
diff --git a/orchestra/contrib/plans/settings.py b/orchestra/contrib/plans/settings.py
new file mode 100644
index 00000000..f787b86d
--- /dev/null
+++ b/orchestra/contrib/plans/settings.py
@@ -0,0 +1,15 @@
+from orchestra.contrib.settings import Setting
+
+
+PLANS_RATE_METHODS = Setting('PLANS_RATE_METHODS',
+    (
+        'orchestra.contrib.plans.rating.step_price',
+        'orchestra.contrib.plans.rating.match_price',
+        'orchestra.contrib.plans.rating.best_price',
+    )
+)
+
+
+PLANS_DEFAULT_RATE_METHOD = Setting('PLANS_DEFAULT_RATE_METHOD',
+    'orchestra.contrib.plans.rating.step_price',
+)
diff --git a/orchestra/contrib/services/migrations/0002_auto_20150509_1501.py b/orchestra/contrib/services/migrations/0002_auto_20150509_1501.py
new file mode 100644
index 00000000..26e2d632
--- /dev/null
+++ b/orchestra/contrib/services/migrations/0002_auto_20150509_1501.py
@@ -0,0 +1,24 @@
+# -*- coding: utf-8 -*-
+from __future__ import unicode_literals
+
+from django.db import models, migrations
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('services', '0001_initial'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='service',
+            name='rate_algorithm',
+            field=models.CharField(choices=[('orchestra.contrib.plans.rating.best_price', 'Best price'), ('orchestra.contrib.plans.rating.step_price', 'Step price'), ('orchestra.contrib.plans.rating.match_price', 'Match price')], help_text='Algorithm used to interprete the rating table.<br>&nbsp;&nbsp;Best price: Produces the best possible price given all active rating lines.<br>&nbsp;&nbsp;Step price: All rates with a quantity lower than the metric are applied. Nominal price will be used when initial block is missing.<br>&nbsp;&nbsp;Match price: Only <b>the rate</b> with a) inmediate inferior metric and b) lower price is applied. Nominal price will be used when initial block is missing.', max_length=64, verbose_name='rate algorithm', default='orchestra.contrib.plans.rating.step_price'),
+        ),
+        migrations.AlterField(
+            model_name='service',
+            name='tax',
+            field=models.PositiveIntegerField(choices=[(0, 'Duty free'), (21, '21%')], verbose_name='tax', default=21),
+        ),
+    ]
diff --git a/orchestra/contrib/services/models.py b/orchestra/contrib/services/models.py
index 862f026d..fdca42ef 100644
--- a/orchestra/contrib/services/models.py
+++ b/orchestra/contrib/services/models.py
@@ -127,11 +127,13 @@ class Service(models.Model):
             (ANUAL, _("Anual data")),
         ),
         default=BILLING_PERIOD)
-    rate_algorithm = models.CharField(_("rate algorithm"), max_length=16,
+    rate_algorithm = models.CharField(_("rate algorithm"), max_length=64,
+        choices=rate_class.get_choices(),
+        default=rate_class.get_default(),
         help_text=string_concat(_("Algorithm used to interprete the rating table."), *[
             string_concat('<br>&nbsp;&nbsp;', method.verbose_name, ': ', method.help_text)
                 for name, method in rate_class.get_methods().items()
-        ]), choices=rate_class.get_choices(), default=rate_class.get_choices()[0][0])
+        ]))
     on_cancel = models.CharField(_("on cancel"), max_length=16,
         help_text=_("Defines the cancellation behaviour of this service."),
         choices=(
diff --git a/orchestra/contrib/tasks/decorators.py b/orchestra/contrib/tasks/decorators.py
index c42ad824..4a662d69 100644
--- a/orchestra/contrib/tasks/decorators.py
+++ b/orchestra/contrib/tasks/decorators.py
@@ -1,3 +1,4 @@
+import logging
 import traceback
 from functools import partial, wraps, update_wrapper
 from multiprocessing import Process
@@ -15,6 +16,9 @@ from orchestra.utils.python import AttrDict, OrderedSet
 from .utils import get_name, get_id
 
 
+logger = logging.getLogger(__name__)
+
+
 def keep_state(fn):
     """ logs task on djcelery's TaskState model """
     @wraps(fn)
@@ -30,14 +34,14 @@ def keep_state(fn):
         try:
             result = fn(*args, **kwargs)
         except:
+            trace = traceback.format_exc()
+            subject = 'EXCEPTION executing task %s(args=%s, kwargs=%s)' % (_name, str(args), str(kwargs))
+            logger.error(subject)
+            logger.error(trace)
             state.state = states.FAILURE
             state.traceback = trace
             state.runtime = (timezone.now()-now).total_seconds()
             state.save()
-            subject = 'EXCEPTION executing task %s(args=%s, kwargs=%s)' % (name, str(args), str(kwargs))
-            trace = traceback.format_exc()
-            logger.error(subject)
-            logger.error(trace)
             mail_admins(subject, trace)
             raise
         else:
diff --git a/orchestra/utils/sys.py b/orchestra/utils/sys.py
index d17ea275..29dbed56 100644
--- a/orchestra/utils/sys.py
+++ b/orchestra/utils/sys.py
@@ -6,6 +6,7 @@ import re
 import select
 import subprocess
 import sys
+import time
 
 from django.core.management.base import CommandError
 
@@ -165,6 +166,10 @@ def touch(fname, mode=0o666, dir_fd=None, **kwargs):
             dir_fd=None if os.supports_fd else dir_fd, **kwargs)
 
 
+class OperationLocked(Exception):
+    pass
+
+
 class LockFile(object):
     """ File-based lock mechanism used for preventing concurrency problems """
     def __init__(self, lockfile, expire=5*60, unlocked=False):
@@ -188,8 +193,8 @@ class LockFile(object):
     def __enter__(self):
         if not self.unlocked:
             if not self.acquire():
-                raise OperationLocked('%s lock file exists and its mtime is less '
-                    'than %s seconds' % (self.lockfile, self.expire))
+                raise OperationLocked("%s lock file exists and its mtime is less than %s seconds" %
+                    (self.lockfile, self.expire))
         return True
     
     def __exit__(self, type, value, traceback):