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This tutorial will guide you on how to expose data stored in Cassandra as a data service. Also, see the samples in Data Integration Samples.

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Prerequisites

Set up the Cassandra server with a keyspace and table for this tutorial:

Installing and starting Cassandra

A Cassandra server of version 3.0 should be already running in the default port. For instructions, go to Apache Cassandra Documentation.

Creating a

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Now, let's start creating the data service from scratch:

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Enter the following data service name.

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Connecting to the datasource

Click Add New Datasource. and enter the following details:

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keyspace and a table

Execute the SQL commands as given below.

• Create the keyspace named UsersKS:

  Code Block
  CREATE KEYSPACE UsersKS WITH replication = {'class':'SimpleStrategy', 'replication_factor':3}

• Create the table named Users in the UsersKS keyspace:

  Code Block
  CREATE TABLE UsersKS.Users (id uuid, name text, country text, age int, PRIMARY KEY (id))

Creating a data service

Now, let's start creating the data service from scratch:

1. Log in to the management console of ESB profile of WSO2 EI using the following URL on your browser:  "https://localhost:9443/carbon/".
2. Click Create under the Data Service menu to open the Create Data Service window.

3. Enter the following data service name.

   Data Service Name	CassandraDataService

4. Leave the default values for the other fields.
5. Click Next to go to the Datasources screen

Connecting to the datasource

Creating a query to add a table to the Keyspace

Follow the steps given below.

Click Add New Query and enter the following details:

Query IDEnter createTable as the query ID.DatasourceSelect the datasource for which you are going to write a query. Select the Cassandra datasource that you created previously.SQL

In this field, enter the SQL statement describing the keyspace.

Code Block
CREATE TABLE UsersKS.Users (id uuid, name text, country text, age int, PRIMARY KEY (id))

Save the query

1. Click Add New Datasource. and enter the following details:

   Datasource ID	Cassandra
   Datasource Type	Select Cassandra as the datasource.
   Cassandra Server	Enter localhost.

   The rest of the datasource properties are optional. See the descriptions given below.

   Expand
   title Properties for a Cassandra datasource
   The following describes the properties supported by the Cassandra datasource.  Data Source Property Description Cassandra Servers* Host names of Cassandra servers in a comma-separated list. Keyspace The default key space used by the Cassandra session. Port The port of Cassandra servers. Cluster Name The Cassandra cluster name. Compression Compression used in communication. User Name The authenticating user's username. Password The authenticating user's password. Load Balancing Policy The client load balancing policy on how calls should be made to the provided servers. Enable JMX Reporting Enable JMX statistics for the connector. Enable Metrics Enable metrics for the connector. Local Core Connections Per Host Connection pooling: Local core connections per server host. Remote Core Connections Per Host Connection pooling: Remote core connections per server host. Anchor Max_Con_Loc_Host Max_Con_Loc_Host Local Max.Connections Per Host Connection pooling: Maximum local connections per server host. Anchor Rem_Max_Con_Host Rem_Max_Con_Host Remote Max.Connections Per Host Connection pooling: Remote max connections per server host. Local New Connection Threshold This property determines the threshold in the connection pool, which will trigger the creation of a new connection when the connection pool has not reached the maximum capacity for local hosts. Generally, it will not be required to change the default value for this parameter. Remote New Connection Threshold This property determines the threshold in the connection pool, which will trigger the creation of a new connection when the connection pool has not reached the maximum capacity for remote hosts. Generally, it will not be required to change the default value for this parameter. Local Max Requests Per Connection This property allows you to throttle the number of concurrent requests per connection for local hosts. Remote Max Requests Per Connection This property allows you to throttle the number of concurrent requests per connection for remote hosts. Protocol Version The native protocol version to use. By default, it auto connects. "2" for Cassandra versions 2.0 and upwards, and "1" for Cassandra version 1.2.x. Consistency Level The consistency level used for queries. Fetch Size Fetch size used by queries. Serial Consistency Level The serial consistency level used for queries. Reconnection Policy The reconnection policy used for the cluster. Constant Reconnection Policy Delay If "ConstantReconnectionPolicy" is used for Reconnection Policy, this represents the constant wait time between reconnection attempts in milliseconds. Exponential Reconnection Policy Base Delay If "ExponentialReconnectionPolicy" is used for Reconnection Policy, this represents the base delay in milliseconds. Exponential Reconnection Policy Max. Delay If "ExponentialReconnectionPolicy" is used for Reconnection Policy, this represents the maximum delay in milliseconds. Retry Policy Configured the retry policy in this cluster. Connection Timeout The socket connection timeout in milliseconds. Keep Alive Set if socket keeps alive. Read Timeout Set per host socket read timeout in milliseconds. Receive Buffer Size The socket receive buffer size. Send Buffer Size Thesocketsendbuffersize. Reuse Address The socket re-use address. So Linger The socket linger on value. TCP no Delay Set socket TCP to no delay. Enable SSL Enable SSL. Enable OData In WSO2 EI OData protocol version 4 (OASIS standards) is supported, which mainly provides support for CRUD operations. You can easily expose databases as an odata service by selecting this check box. Currently, Odata service feature support is available for RDBMS datasources and Cassandra datasources. If you have enabled Odata for your data service, you can complete the data service creation process. That is, you are not required to define queries or operations for the service. This Odata service will now be accessible from the following endpoints: For super tenant: http://localhost:<port>/odata/{dataserviceName}/{datasourceId}/ For normal tenants: http://localhost:<port>/odata/t/{tenantId}/{dataserviceName}/{datasourceId}/ Disable Native Batch Requests Disables native Cassandrabatchrequests,and reverts to emulated batch requests. * Mandatory fields.

Creating a query to a Keyspace to Cassandra

Follow the steps given below.

Click Add New Query and enter the following details:

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CREATE KEYSPACE UsersKS WITH replication = {'class':'SimpleStrategy', 'replication_factor':3}

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1. {datasourceId}/ Disable Native Batch Requests Disables native Cassandrabatchrequests,and reverts to emulated batch requests. * Mandatory fields.

Creating a query to ADD user information

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1. Click Add New Query and enter the following details:

   Query ID	Enter getUsersbyID as the query ID.
   Datasource	Select the datasource for which you are going to write a query. Select the Cassandra datasource that you created previously.
   SQL	In this field, enter the SQL statement describing the data that should be retrieved from the Cassandra datasource. Code Block SELECT id, age, country, name FROM UsersKS.Users WHERE id = :id

2. Click Generate Input Mapping to create the input mapping. The id is the input as shown below.

   
   

3. Edit the id column and change the Type to UUID.
4. Save the mapping and click Main Configuration to return to the query.
   

5. Click Generate Response to create the output mapping. This defines how the employee details retrieved from the datasource will be presented in the result. Note that, by default, the output type is XML. 

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6. Save the query.
7. Click Next to open the Operations screen.

Creating SOAP operationa to invoke the queries

To invoke the query, you need to define an operation.

Click Add New Operation and enter the following information.


Operation NamecreateKSOpQuery IDcreateKS
1. Save the operation.

2. Click Add New Operation and enter the following information.
   

   Operation NamecreateTableOpQuery IDcreateTableSave the operation.

   . Note that, by default, the output type is XML. 

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3. Save the query.
4. Click Next to open the Operations screen.

Creating SOAP operationa to invoke the queries

1. Click Add New Operation and enter the following information.
   

   Operation Name	addUsersOp
   Query ID	addUsers

2. Save the operation.

3. Click Add New Operation and enter the following information.
   

   Operation Name	getUsersbyIDop
   Query ID	getUsersbyID

4. Save the operation.

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Creating a REST resource to invoke the query

Click Add New Resource and enter the following information.

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Now, let's create REST resources to invoke the query created above. Alternatively, you can create SOAP operations to invoke the queries. See the previous section for instructions.

Click Add New Resource and enter the following information.

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to invoke the queries. See the previous section for instructions.

1. Click Add New Resource and enter the following information.
   

   Resource Path	users
   Resource Method	POST
   Query ID	addUsers

2. Save the resource.

3. Click Add New Resource and enter the following information.
   

   Resource Path	users/{id}
   Resource Method	GET
   Query ID	getUsersbyID

4. Save the resource.
   

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curl -X GET http://localhost:8280/services/

CassandraDataService.HTTPEndpoint/

users/a05cdd7a-3d6a-11e8-b467-0ed5f89f718b