Adding support for JSON service discovery config

utils/service_discovery/config_stores.py

@@ -9,8 +9,9 @@
 from utils.service_discovery.etcd_config_store import EtcdStore
 from utils.service_discovery.consul_config_store import ConsulStore
 from utils.service_discovery.zookeeper_config_store import ZookeeperStore
+from utils.service_discovery.json_file_config_store import JsonStore
 
-SD_CONFIG_BACKENDS = ['etcd', 'consul', 'zk']  # noqa: used somewhere else
+SD_CONFIG_BACKENDS = ['etcd', 'consul', 'zk', 'json']  # noqa: used somewhere else
 SD_TEMPLATE_DIR = '/datadog/check_configs'
 
 
@@ -21,6 +22,8 @@ def get_config_store(agentConfig):
         return ConsulStore(agentConfig)
     elif agentConfig.get('sd_config_backend') == 'zk':
         return ZookeeperStore(agentConfig)
+    elif agentConfig.get('sd_config_backend') == 'json':
+        return JsonStore(agentConfig)
     else:
         return StubStore(agentConfig)
 

utils/service_discovery/json_file_config_store.py

@@ -0,0 +1,70 @@
+# (C) Datadog, Inc. 2010-2016
+# All rights reserved
+# Licensed under Simplified BSD License (see LICENSE)
+
+# std
+import logging
+import simplejson as json
+
+# project
+from utils.service_discovery.abstract_config_store import AbstractConfigStore, KeyNotFound
+
+DEFAULT_FILE_PATH = '/etc/dd-agent/sd.json'
+log = logging.getLogger(__name__)
+
+class JsonStore(AbstractConfigStore):
+    """Implementation of a config store client for flat json files"""
+    def _extract_settings(self, config):
+        """Extract settings from a config object"""
+        settings = {
+            'file_path': config.get('sd_json_file_path', DEFAULT_FILE_PATH),
+        }
+        return settings
+
+    def get_client(self, reset=False):
+        """Return a file client, create it if needed"""
+        if self.client is None or reset is True:
+            with open(self.settings.get('file_path')) as f:
+                self.client = json.load(f)
+        return self.client
+
+    def client_read(self, path, **kwargs):
+        """Retrieve a value from the json dict."""
+        if kwargs.get('watch', False):
+            # json file never reloads
+            return 0
+
+        if kwargs.get('all', False):
+            # This wants a list of tuples with the first element of the tuple
+            # being the path and the second element of the tuple being json.
+            # This is 2 levels past the depth of the sd_template_dir
+            return self._get_as_path_items(self.client, len(self.sd_template_dir.split("/")) + 2)
+        else:
+            res = self._get_nested_path(self.client, path)
+            if res is not None:
+                return json.dumps(res)
+            else:
+                raise KeyNotFound("The key %s was not found in the json file" % path)
+
+    def _get_as_path_items(self, data, depth, prefix = ""):
+        results = []
+        if depth == 1:
+            for key in data.iterkeys():
+                keystr = prefix.lstrip("/") + "/" + key
+                results.append((keystr, json.dumps(data[key])))
+        else:
+            for key in data.iterkeys():
+                prefix = prefix + "/" + key
+                results.extend(self._get_as_path_items(data[key], depth - 1, prefix))
+
+        return results
+
+    def _get_nested_path(self, data, path):
+        path_elements = path.split('/')
+        if data is None:
+            return None
+        elif len(path_elements) > 1:
+            first_element = path_elements[0]
+            return self._get_nested_path(data.get(first_element), "/".join(path_elements[1:]))
+        else:
+            return data.get(path_elements[0])