Merge pull request #46 from MaxIV-KitsControls/change-consistency-level

Make cassandra consistency level configurable.

hdbpp.py

@@ -112,7 +112,7 @@ class HDBPlusPlusConnection(object):
     "A very simple direct interface to the HDB++ cassandra backend"
 
     def __init__(self, nodes=None, keyspace="hdb", address_map=None,
-                 fetch_size=50000, cache_size=1e9):
+                 fetch_size=50000, cache_size=1e9, consistency_level="ONE"):
         self.nodes = nodes if nodes else ["localhost"]
         if address_map:
             translator = LocalNetworkAdressTranslator(address_map)
@@ -121,9 +121,7 @@ def __init__(self, nodes=None, keyspace="hdb", address_map=None,
             self.cluster = Cluster(self.nodes)
 
         s = self.cluster.connect(keyspace)
-        # TODO: Might be useful to be able to set the consistency
-        # level in the configuration
-        s.default_consistency_level = ConsistencyLevel.LOCAL_QUORUM
+        s.default_consistency_level = getattr(ConsistencyLevel, consistency_level)
         self.session = aiosession(s)  # asyncio wrapper
         self.session.default_fetch_size = fetch_size
 

hdbppviewer.conf

@@ -15,6 +15,10 @@ data_cache_size=1000000000
 nodes=b-kirk13-cas-3,b-kirk13-cas-4,b-kirk13-cas-5,b-picard13-cas-0,b-picard13-cas-1,b-picard13-cas-2
 # name of the keyspace to use
 keyspace=hdb
+# Consistency level for reading data. Must be one of the levels listed on
+# https://docs.datastax.com/en/cassandra-oss/3.0/cassandra/dml/dmlConfigConsistency.html
+# Defaults to ONE
+consistency_level=ONE
 
 # [hdbpp:cassandra_address_translation]
 # # This is a driver feature which allows a mapping between cassandra

server.py

@@ -235,8 +235,9 @@ async def post_raw_search(hdbpp, request):
     config = configparser.RawConfigParser()
     config.read(args.config)
     PORT = config.getint("server", "port")
-    CASSANDRA_NODES = config.get("hdbpp:cassandra", "nodes").split(",")
-    CASSANDRA_KEYSPACE = config.get("hdbpp:cassandra", "keyspace")
+    CASSANDRA_NODES = config["hdbpp:cassandra"].get("nodes").split(",")
+    CASSANDRA_KEYSPACE = config["hdbpp:cassandra"].get("keyspace")
+    CASSANDRA_CONSISTENCY_LEVEL = config["hdbpp:cassandra"].get("consistency_level", "ONE")
     if config.has_section("hdbpp:cassandra_address_translation"):
         CASSANDRA_ADDRESS_TRANSLATION = dict(
             config.items("hdbpp:cassandra_address_translation"))
@@ -253,7 +254,8 @@ async def post_raw_search(hdbpp, request):
     hdbpp = HDBPlusPlusConnection(nodes=CASSANDRA_NODES,
                                   keyspace=CASSANDRA_KEYSPACE,
                                   address_map=CASSANDRA_ADDRESS_TRANSLATION,
-                                  cache_size=DATA_CACHE_SIZE)
+                                  cache_size=DATA_CACHE_SIZE,
+                                  consistency_level=CASSANDRA_CONSISTENCY_LEVEL)
 
     app.router.add_route('GET', '/controlsystems',
                          partial(get_controlsystems, hdbpp))