Cassandra queries not having any effect - cassandra

Question

I'm running a bunch of queries one after the other but It seems like some queries are not having any effect even though no errors are thrown UNLESS I restart the session after each query. I'm using datastax cassandra driver for this.
Here are the queries, which I'm storing in a file seperated by ###.
DROP KEYSPACE if exists test_space;
####
CREATE KEYSPACE test_space WITH replication = {'class': 'NetworkTopologyStrategy','0':'2'};
####
CREATE TABLE test_space.fr_core (
frid text PRIMARY KEY,
attributes text,
pk1 text,
pk2 text,
pk3 text,
pk4 text,
pk5 text,
pk6 text
);
####
Here's the code for executing the above statements :
public class CassandraKeyspaceDelete {
public static void main(String[] args) {
try {
new CassandraKeyspaceDelete().run();
} catch (Exception e) {
e.printStackTrace();
}
}
public void run() {
// Get file from resources folder
ClassLoader classloader = Thread.currentThread().getContextClassLoader();
InputStream is = classloader.getResourceAsStream("create_keyspace.txt");
BufferedReader reader = new BufferedReader(new InputStreamReader(is));
StringBuilder out = new StringBuilder();
String line;
try {
while ((line = reader.readLine()) != null) {
out.append(line);
}
// read from input stream
reader.close();
} catch (Exception e) {
System.out.println("Error reading kespace creation script.");
return;
}
// System.out.println();
com.datastax.driver.core.Session readSession = CassandraManager.connect("12.10.1.122", "", "READ");
String selectStmnts[] = out.toString().split("####");// { };
for (String selectStmnt : selectStmnts) {
System.out.println("" + selectStmnt.trim());
if (selectStmnt.trim().length() > 0) {
ResultSet res = readSession.execute(selectStmnt.trim());
}
// readSession.close();
if (readSession.isClosed()) {
readSession = CassandraManager.connect("12.10.1.122", "", "READ");
}
}
System.out.println("Done");
return;
}
}
Here's the CassandraManager class :
public class CassandraManager {
static Cluster cluster;
public static Session session;
static PreparedStatement statement;
static BoundStatement boundStatement;
public static HashMap<String, Session> sessionStore = new HashMap<String, Session>();
public static Session connect(String ip, String keySpace,String type) {
PoolingOptions poolingOpts = new PoolingOptions();
poolingOpts.setCoreConnectionsPerHost(HostDistance.REMOTE, 2);
poolingOpts.setMaxConnectionsPerHost(HostDistance.REMOTE, 400);
poolingOpts.setMaxSimultaneousRequestsPerConnectionThreshold(HostDistance.REMOTE, 128);
poolingOpts.setMinSimultaneousRequestsPerConnectionThreshold(HostDistance.REMOTE, 2);
cluster = Cluster
.builder()
.withPoolingOptions( poolingOpts )
.addContactPoint(ip)
.withRetryPolicy( DowngradingConsistencyRetryPolicy.INSTANCE )
.withReconnectionPolicy( new ConstantReconnectionPolicy( 100L ) ).build();
Session s = cluster.connect();
return s;
}
}
When I run this, the first two CQL queries run without errors. When the third one runs, I get an error saying Keyspace test_space doesn't exist.
If I uncomment out readSession.close(), all the queries execute though each time the session is closed and then opened resulting in slow execution.
Why aren't the queries working unless session is restarted after each query ?

Answer 1

I created a new project and tried your code in my Cassandra sandbox. It worked with four changes:
My datacenter is defined as "DC1", so the replication factor I used for the test_space keyspace was {'class': 'NetworkTopologyStrategy','DC1':'1'};
My sandbox instance is secured, so I had to use .withCredentials in the Cluster.builder
I couldn't get getResourceAsStream to work, so I replaced that with a FileInputStream instead.
I moved readSession.close(); outside of the for loop.
Based on the fact that it worked on mine, I can't speak to the behavour that you are seeing, so I will offer a few observations:
Is your datacenter really named 0? Your keyspace replication factor {'class': 'NetworkTopologyStrategy','0':'2'} is telling Cassandra to put two replicas in the 0 datacenter. If that really is the case, you should make your datacenter name something a little more intuitive.
None of the statements in your text file return a result set. So doing this ResultSet res = readSession.execute(selectStmnt.trim()); really doesn't get you anything.
Given the name of your keyspace, I can only assume that you are testing some things out. So how do you know that you need all of these options on your cluster builder? My advice to you, is to start simple. Don't add the other options unless you know that you need them, and more importantly, what they do.
cluster = Cluster.builder()
.addContactPoint(ip)
.build();
Session s = cluster.connect();
Make sure that your readSession.close(); is outside of your for loop.
Something else that might help you, is to read through Things You Should Be Doing When Using Cassandra Drivers by DataStax's Rebecca Mills.