CassandraActor

The CassandraActor is a Coral Actor that enables communication with a Cassandra database. The actor receives queries in the trigger field and emits the results. All valid CQL queries can be executed, including creating keyspaces and inserting, deleting and updating values.

NOTE: Currently, the CassandraActor cannot be included directly in your runtime. It is meant as a supporting actor to be used by the Coral platform itself. In the future, it might be possible to use the Cassandra Actor to perform queries through a collect procedure.

Creating a CassandraActor

The params value is a JSON object with the following fields:

field	type	required	description
`seeds`	List[String]	yes	A JSON list of the IP addresses of seed nodes.
`keyspace`	String	yes	The name of the keyspace to connect to initially.
`port`	Int	no	The port to connect to, when omitted default Cassandra port 9042 is used.
`user`	String	no	The user name to connect to Cassandra.
`password`	String	no	The password to connect to Cassandra.

The CassandraActor can process any valid CQL query. The keyspace will be connected to initially, but it can later be changed by sending the CassandraActor a “use keyspace” statement:

{
  "query": "use keyspace otherKeyspace;"
}

Creation example

{
  "type": "cassandra",
  "params": {
    "seeds": ["192.168.0.2", "192.168.0.3"],
    "keyspace": "coral",
    "port": 9042,
    "user": "admin",
    "password": "admin"
  }
}

This will create a CassandraActor connecting to seed nodes 192.168.0.2 and 192.168.0.3 on port 9042, to keyspace “coral”, using user “admin” and password “admin”.

Trigger

The CassandraActor receives the CQL statement in the query field of the trigger JSON.

Example

{
    "query":"select * from testkeyspace.test1"
}

Emit

The CassandraActor does not emit its result to other actors, but instead should return the answer only to the caller. Thus, the CassandraActor can only be used with a collect procedure.

The answer that the CassandraActor returns is JSON, and looks as follows:

{
  "seeds" : [ "192.168.0.1" ],
  "query" : "select * from keyspace.table",
  "success" : true,
  "data" : [ {
    "field1" : "66d61c3e-a1a0-46e4-b567-a84a8a052a2d",
    "field2" : true,
    "field3" : 42,
    "field4": 26.73
  }]
}

The CassandraActor automatically converts the result of the query into a JSON object. It converts each Cassandra data type to a JSON type as in the following table:

Cassandra type	JSON type
`ascii`	JString
`bigint`	JInt
`boolean`	JBool
`int`	JInt
`decimal`	JDecimal
`double`	JDouble
`float`	JDouble
`text`	JString
`varchar`	JString
`varint`	JInt
`timestamp`	JInt
`uuid`	JString

An example of each of these data types is given below:

{
  "seeds" : [ "192.168.0.1" ],
  "query" : "select * from keyspace.datatypes",
  "success": true,
  "data": [{
    "ascii": "some text",
    "bigint": 156395834234098,
    "boolean": true,
    "int": 42,
    "decimal": 5634.34,
    "double": 5634.34,
    "float": 5634.34,
    "text": "some text",
    "varchar": "some text",
    "varint": 42,
    "timestamp": 1451746530,
    "uuid": "f0223bb6-dfed-489d-8923-54a250aafe21"
  }]
}

State

The CassandraActor returns its state as follows:

field	type	description
`connected`	boolean	Whether there is still an active connection to the Cassandra database at the time of collecting the state.
`keyspace`	String	The name of the keyspace the actor is currently connected to.
`schema`	Array	A JSON representation of the schema of the keyspace currently connected to.

An example of a schema is as follows:

{
  "connected": true,
  "keyspace": "keyspacename",
  "schema": [{
    "table1": [
     { "column1": "text" },
     { "column2": "int" },
     { "column3": "float" }], 
    "table2": [
     { "col1": "float" },
     { "col2": "int" }]
  }]
}

Collect

The CassandraActor does not collect state from other actors.

Timer

The CassandraActor does not provide timer actions.

Overview

Getting started

Documentation