I want to check and test the "replication_factor" and ONE consistency level from Cassandra DB.
And I defined a cluster: "MyCluster01" with three nodes in two data centers: DC1 (node1, node2) in RAC1, DC2 (node3) in RAC2 .
The structure shown below:
[root@localhost ~]
Datacenter: DC1
===============
Status=Up/Down |/ State=Normal/Leaving/Joining/Moving
-- Address Load Tokens Owns Host ID Rack
UN 10.0.0.62 409.11 KB 256 ? 59bf9a73-45cc-4f9b-a14a-a27de7b19246 RAC1
UN 10.0.0.61 408.93 KB 256 ? b0cdac31-ca73-452a-9cee-4ed9d9a20622 RAC1
Datacenter: DC2
===============
Status=Up/Down |/ State=Normal/Leaving/Joining/Moving
-- Address Load Tokens Owns Host ID Rack
UN 10.0.0.63 336.34 KB 256 ? 70537e0a-edff-4f48-b5db-44f623ec6066 RAC2
Then I created a key space and a table as shown below:
CREATE KEYSPACE my_check1 WITH replication = {'class': 'SimpleStrategy', 'replication_factor': '1'};
create table replica_test(id uuid PRIMARY KEY);
After I inserted one record into that table:
insert into replica_test(id) values (uuid());
select * from replica_test;
id
5e6050f1-8075-4bc9-a072-5ef24d5391e5
I got this entry.
But when I stopped node1 and again requested in node 2 and node 3, none of the requests failed.
select * from replica_test;
Traceback (most recent call last): File "/usr/bin/cqlsh", line 997,
in perform_simple_statement
rows = self.session.execute(statement, trace=self.tracing_enabled) File
"/usr/share/cassandra/lib/cassandra-driver-internal-only-2.1.3.post.zip/cassandra-driver-2.1.3.post/cassandra/cluster.py",
line 1337, in execute
result = future.result(timeout) File "/usr/share/cassandra/lib/cassandra-driver-internal-only-2.1.3.post.zip/cassandra-driver-2.1.3.post/cassandra/cluster.py",
line 2861, in result
raise self._final_exception Unavailable: code=1000 [Unavailable exception] message="Cannot achieve consistency level ONE"
info={'required_replicas': 1, 'alive_replicas': 0, 'consistency':
'ONE'}
While the "nodetool status" command returns:
UN 10.0.0.62 409.11 KB 256 ? 59bf9a73-45cc-4f9b-a14a-a27de7b19246 RAC1
DN 10.0.0.61 408.93 KB 256 ? b0cdac31-ca73-452a-9cee-4ed9d9a20622 RAC1
UN 10.0.0.63 336.34 KB 256 ? 70537e0a-edff-4f48-b5db-44f623ec6066 RAC2
And when I tried to stop node 2, leaving node 1 and 3 alive; or stop node 3, keeping node 1 and 2 alive; An error has occurred.
, , ?