Mule 4 Cassandra Database Connector, in its current version of 3.10, has made significant improvements over the previous version. It is fairly straightforward to set up an integration with a Cassandra Database using the connector. This article is an introduction to using the Cassandra Connector to create connectivity with a Cassandra cluster.

I have created a two-node cluster as shown in the following diagram. The details on how to set up the Cassandra clustering will be covered in another post. Basically, I opened the native transport port 9042, which is the default value on both nodes.

We also need some initial setup using cqlsh   by running the following command:

$ cqlsh -u cassandra -p cassandra
cassandra@cqlsh> create keyspace if not exists dev_keyspace with replication = {'class' : 'SimpleStrategy', 'replication_factor' : 2};

The above command will create a keyspace, namely  dev_keyspace . We can query the keyspaces by the following command:

cassandra@cqlsh> desc keyspaces;

You should see the following:

system_schema  system      system_distributed
system_auth    dev_keyspace  system_traces

The next step is to create the emp  table by the following command:

cassandra@cqlsh> create table emp (empid int primary key, emp_first varchar, emp_last varchar, emp_dept varchar);

And insert a row:

create table emp (empid int primary key, emp_first varchar, emp_last varchar, emp_dept varchar);
insert into emp (empid, emp_first, emp_last, emp_dept) values (1, 'Gary','liu','consulting');

That is all, and we are ready to do the integration.

Add Cassandra Connector

First, we need to search the Exchange and add the Cassandra Connection, as shown in the following snapshot:

Create CassandraDB Config

Create a mule configuration, namely,  global-config.xml . Then create CassandraDB Config as the following:

Enter the General setting as the following. Note: Leave the Host empty, as we use cluster configuration.

Now, click the "Advanced Settings" tab and enter the information as follows:

As you can see, we can enter the IP addresses separated by a comma. In this way, we can achieve high availability from the client side. Now, we test the connectivity. If port 9042 is exposed correctly, it should work fine. I will explain more in my next article on how to make sure we expose the native transport port correctly.

Create Integration Flows

Read Flow

The read flow is very straightforward. The cassandra-db:select   operation uses payload as the whole query. We just need to set up the payload. In this case, it is " select * from emp; ":

<flow name="select-objecsFlow" doc:id="8bdcc4fe-cf4e-49be-b2f9-2dfacbddaf4b" >
  <http:listener doc:name="Listener" doc:id="ab57d8ab-2623-468b-b635-a0c6efd6c829" config-ref="HTTP_Listener_config" path="/cassandra/emp"/>
  <set-payload value="select * from emp;" doc:name="Set Payload"  />
  <cassandra-db:select doc:name="Select"  config-ref="CassandraDB_Config_cluster" />
  <ee:transform doc:name="Transform Message"  >
   <ee:message >
    <ee:set-payload ><![CDATA[%dw 2.0
output application/json
---
payload]]></ee:set-payload>
   </ee:message>
  </ee:transform>
  <logger level="INFO" doc:name="Logger" doc:id="e6097436-1909-4d8b-8c81-27be82c11714" message="#[payload]" />
 </flow>

</mule>

Insert A Row

To insert a row, we need to use an insert operation as follows:

<flow name="insert-objecsFlow" doc:id="8bdcc4fe-cf4e-49be-b2f9-2dfacbddaf4b" >
  <http:listener doc:name="Listener" doc:id="ab57d8ab-2623-468b-b635-a0c6efd6c829" config-ref="HTTP_Listener_config" path="/cassandra/emp/create"/>
  <ee:transform doc:name="Transform Message" doc:id="0d484493-fa23-4a56-9547-58f0bb54dbd1" >
   <ee:message >
    <ee:set-payload ><![CDATA[%dw 2.0
output application/java
---
payload]]></ee:set-payload>
   </ee:message>
  </ee:transform>
  <cassandra-db:insert table="emp" doc:name="Insert" doc:id="71cb7584-981a-4475-a839-ea82ed3b9832" config-ref="CassandraDB_Config_vm1" keyspaceName="rogers_dev"/>
  <ee:transform doc:name="Transform Message"  >
   <ee:message >
    <ee:set-payload ><![CDATA[%dw 2.0
output application/json
---
payload]]></ee:set-payload>
   </ee:message>
  </ee:transform>
  <logger level="INFO" doc:name="Logger" doc:id="e6097436-1909-4d8b-8c81-27be82c11714" message="#[payload]" />

 </flow>

Currently, we can only insert one row at a time. To insert multiple rows, we can use a for loop or use batch processes for large volumes.

About CassandraDB Connector

Detailed information can be found at the following Mulesoft document:

https://docs.mulesoft.com/connectors/cassandra/cassandra-connector

Important Cassandra Information

When you using cqlsh to connect Cassandra cluster, you should notice the following:

cqlsh -u cassandra -p cassandra
Connected to DevelopmentCluster at 127.0.0.1:9042.
[cqlsh 5.0.1 | Cassandra 3.11.3 | CQL spec 3.4.4 | Native protocol v4]

The v4 is the current native protocol version, which is required to configure the connector.