configuration backend simpler to choose different ones

conf/stolos-env.sh

@@ -8,19 +8,20 @@ if [ -z "$DIR" ] ; then DIR='.' ; fi
 export STOLOS_JOB_ID_DEFAULT_TEMPLATE="{date}_{client_id}_{collection_name}"
 export STOLOS_JOB_ID_VALIDATIONS="stolos.examples.job_id_validations"
 
-# you can specify a different configuration backend.  the default is json
-unset STOLOS_CONFIGURATION_BACKEND
+# Queue Backend:
+export STOLOS_ZOOKEEPER_HOSTS="localhost:2181"
+
+# Configuration backend.  the default is json
 
 # JSON configuration backend
-# export STOLOS_CONFIGURATION_BACKEND="stolos.configuration_backend.json_config.JSONConfig"
+# export STOLOS_CONFIGURATION_BACKEND="json"  # enabled by default
 export STOLOS_TASKS_JSON="$DIR/stolos/examples/tasks.json"
 
-# Zookeeper configuration backend
-export STOLOS_ZOOKEEPER_HOSTS="localhost:2181"
-
-
 # Redis configuration backend
-# export STOLOS_CONFIGURATION_BACKEND="stolos.configuration_backend.redis_config.RedisMapping"
+# export STOLOS_CONFIGURATION_BACKEND="redis"
 # export STOLOS_REDIS_DB=3
 # export STOLOS_REDIS_PORT=6379
 # export STOLOS_REDIS_HOST='localhost'
+
+# You can define your own custom configuration backend
+# export STOLOS_CONFIGURATION_BACKEND="mymodule.myconfiguration_backend"

stolos/configuration_backend/__init__.py

@@ -13,21 +13,44 @@
 from stolos import argparse_shared as at
 from stolos.util import load_obj_from_path as _load_obj_from_path
 
-# expose the configuration backend base class for developers
+# expose the base class to other configuration backend modules
 from .tasks_config_base import TasksConfigBaseMapping, TasksConfigBaseSequence
 
 
+_PREFIX = "stolos.configuration_backend"
+# a lookup table that we can alias a particular
+# configuration backend's full python import path to.
+_KNOWN_DEFAULT_BACKENDS = {
+    "json": "%s.%s" % (_PREFIX, "json_config.JSONMapping"),
+    "redis": "%s.%s" % (_PREFIX, "redis_config.RedisMapping"),
+}
+
+
+def _load_backend(inpt):
+    _cb = _KNOWN_DEFAULT_BACKENDS.get(inpt, inpt)
+    try:
+        cb = _load_obj_from_path(
+            _cb, dict(key='configuration_backend', configuration_backend=_cb))
+    except:
+        log.error(
+            "Could not load configuration backend",
+            extra=dict(configuration_backend=_cb))
+        raise
+    return cb
+
+
 build_arg_parser = at.build_arg_parser([at.group(
-    # TODO: inherit from the configuration backend choice somehow?
     "Application Dependency Configuration",
     at.add_argument(
         '--configuration_backend',
-        default='stolos.configuration_backend.json_config.JSONMapping', help=(
+        default='json', type=_load_backend, help=(
             "Where do you store the application dependency data?"
-            ' This options defines which backend to use to access'
+            ' This option defines which backend to use to access'
             ' application dependency configuration.'
-            ' Stolos supports a couple options.'
-            ' See conf/stolos-env.sh for an example')),
+            ' See conf/stolos-env.sh for an example. '
+            ' You can supply your own configuration backend or choose from the'
+            ' following supported options: %s'
+            ) % list(_KNOWN_DEFAULT_BACKENDS.keys())),
 )])
 
 
@@ -55,13 +78,4 @@ def get_tasks_config():
     configuration backend.
     """
     ns = stolos.get_NS()
-    try:
-        cb = _load_obj_from_path(
-            ns.configuration_backend,
-            dict(key='configuration_backend',
-                 configuration_backend=ns.configuration_backend)
-        )
-    except:
-        log.error("Could not load configuration backend")
-        raise
-    return cb()
+    return ns.configuration_backend()

stolos/configuration_backend/redis_config.py

@@ -68,10 +68,10 @@ class RedisMapping(_RedisConfig, TasksConfigBaseMapping):
     """
     def __init__(self, data=None):
         NS = get_NS()
-        self.db = NS.db
+        self.db = NS.redis_db
         self.redis_key_prefix = NS.redis_key_prefix
         self.cli = redis.StrictRedis(
-            db=NS.db, port=NS.port, host=NS.host)
+            db=NS.redis_db, port=NS.redis_port, host=NS.redis_host)
         if data is None:
             self.cache = {}
         elif isinstance(data, self.__class__):

stolos/initializer.py

@@ -38,14 +38,12 @@ def _get_parent_parsers(objects):
         yield p
 
 
-def initialize_configuration_backend(choice, parser, add_help):
+def initialize_configuration_backend(cbackend, parser, add_help):
     """
     get options for the chosen configuration_backend.
     ensure they don't conflict with previously defined ones
     """
-    cb = importlib.import_module(
-        util.load_obj_from_path(choice).__module__)\
-        .build_arg_parser()
+    cb = importlib.import_module(cbackend.__module__).build_arg_parser()
     newparser = at.build_arg_parser(parents=[parser, cb], add_help=add_help)
     return newparser