Add seed code for DMaaP plugin

Change-Id: I8c7a9c432badd3052a571ed87b9b580760b376e6
Issue-Id: CCSDK-65
Signed-off-by: Jack Lucas <jflucas@research.att.com>

2 files changed, 120 insertions, 0 deletions

diff --git a/dmaap/consulif/__init__.py b/dmaap/consulif/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/dmaap/consulif/__init__.py
diff --git a/dmaap/consulif/consulif.py b/dmaap/consulif/consulif.py
new file mode 100644
index 0000000..e742895
--- /dev/null
+++ b/dmaap/consulif/consulif.py
@@ -0,0 +1,120 @@
+# ============LICENSE_START====================================================
+# org.onap.ccsdk
+# =============================================================================
+# Copyright (c) 2017 AT&T Intellectual Property. All rights reserved.
+# =============================================================================
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+# ============LICENSE_END======================================================
+
+import consul
+import json
+from urlparse import urlparse
+
+class ConsulHandle(object):
+    '''
+    Provide access to Consul KV store and service discovery
+    '''
+
+    def __init__(self, api_url, user, password, logger):
+        '''
+        Constructor
+        '''
+        u = urlparse(api_url)
+        self.ch = consul.Consul(host=u.hostname, port=u.port, scheme=u.scheme)
+
+    def get_config(self, key):
+        '''
+        Get configuration information from Consul using the provided key.
+        It should be in JSON form.  Convert it to a dictionary
+        '''
+        (index, val) = self.ch.kv.get(key)
+        config = json.loads(val['Value'])        # will raise ValueError if not JSON, let it propagate
+        return config
+
+    def get_service(self,service_name):
+        '''
+        Look up the service named service_name in Consul.
+        Return the service address and port.
+        '''
+        (index, val) = self.ch.catalog.service(service_name)
+        if len(val) > 0:                # catalog.service returns an empty array if service not found
+            service = val[0]            # Could be multiple listings, but we take the first
+            if ('ServiceAddress' in service) and (len(service['ServiceAddress']) > 0):
+                service_address = service['ServiceAddress']    # Most services should have this
+            else:
+                service_address = service['Address']         # "External" services will have this only
+            service_port = service['ServicePort']
+        else:
+            raise Exception('Could not find service information for "{0}"'.format(service_name))
+
+        return service_address, service_port
+
+    def add_to_entry(self, key, add_name, add_value):
+        '''
+        Find 'key' in consul.
+        Treat its value as a JSON string representing a dict.
+        Extend the dict by adding an entry with key 'add_name' and value 'add_value'.
+        Turn the resulting extended dict into a JSON string.
+        Store the string back into Consul under 'key'.
+        Watch out for conflicting concurrent updates.
+
+        Example:
+        Key 'xyz:dmaap' has the value '{"feed00": {"feed_url" : "http://example.com/feeds/999"}}'
+        add_to_entry('xyz:dmaap', 'topic00', {'topic_url' : 'http://example.com/topics/1229'})
+        should result in the value for key 'xyz:dmaap' in consul being updated to
+        '{"feed00": {"feed_url" : "http://example.com/feeds/999"}, "topic00" : {"topic_url" : "http://example.com/topics/1229"}}'
+        '''
+
+        while True:     # do until update succeeds
+            (index, val) = self.ch.kv.get(key)     # index gives version of key retrieved
+
+            if val is None:     # no key yet
+                vstring = '{}'
+                mod_index = 0   # Use 0 as the cas index for initial insertion of the key
+            else:
+                vstring = val['Value']
+                mod_index = val['ModifyIndex']
+
+            # Build the updated dict
+            # Exceptions just propagate
+            v = json.loads(vstring)
+            v[add_name] = add_value
+            new_vstring = json.dumps(v)
+
+            updated = self.ch.kv.put(key, new_vstring, cas=mod_index)       # if the key has changed since retrieval, this will return false
+            if updated:
+                break
+
+
+    def delete_entry(self,entry_name):
+        '''
+        Delete an entire key-value entry whose key is 'entry_name' from the Consul KV store.
+
+        Note that the kv.delete() operation always returns True,
+        whether there's an entry with key 'entry_name' exists or not.  This doesn't seem like
+        a great design, but it means it's safe to try to delete the same entry repeatedly.
+
+        Note also in our application for this plugin, the uninstall workflow will always delete all of the topics and
+        feeds we've stored into the 'component_name:dmaap' entry.
+
+        Given the two foregoing notes, it is safe for this plugin to attempt to delete the entire
+        'component_name:dmaap' entry any time it performs an 'unlink' operation for a publishes or
+        subscribes relationship.   The first unlink will actually remove the entry, the subsequent ones
+        will harmlessly try to remove it again.
+
+        The 'correct' approach would be to have a delete_from_entry(self, key, delete_name) that fetches
+        the entry from Consul, removes only the topic or feed being unlinked, and then puts the resulting
+        entry back into Consul.  It would be very similar to add_from_entry.  When there's nothing left
+        in the entry, then the entire entry would be deleted.
+        '''
+        self.ch.kv.delete(entry_name)